Unit 3
Table of Contents
Biology in the News
Why Getting Healthy can seem worse than Getting Sick
Chapter 5
The skeletal system consist of connective tissue
Mature Bone Undergoes Remodeling and Repair
The Skeleton Protects, Supports, and Permits Movement
Joints form Connections between Bones
Chapter 6
Muscles Produce Movement or Generate Tension
Individual Muscle Cells Contract and Relax
Cardiac and Smooth Muscles have Special Features
Chapter 7
The Components and Functions of Blood
Hemostasis: Stopping Blood Loss
Human Blood Types
Chapter 8
Blood Vessels Transport Blood
The Heart Pumps Blood through the Vessels
Chapter 9
Pathogens cause Disease
The Lymphatic System defends the Body
Keeping Pathogens out:
The First Line of Defense
Nonspecific Defenses: The Second Line of Defense
Specific Defense Mechanisms: The Third Line of Defense
Immune Memory creates Immunity
Medical Assistance in the War against Pathogens
Inappropriate Immune System Activities causes Problems
Chapter 10
Respiration Takes Place throughout the Body
The Respiratory System Consists of Upper and Lower
Respiratory Tracts
The Process of Breathing Involves a Pressure Gradient
Gas Exchange and Transport occur passively
The Nervous System Regulates Breathing
Disorders of the Respiratory System
Biology in the
News
Why Getting Healthy can seem worse than Getting Sick
Science Daily March
20, 2012
An article published by Science
Daily tries to help explain why the immune system makes us feel worse while
trying to make us healthy. The new research
is showing a new prospective of the immune system. With many changes in blood protein levels,
metabolic functions, and how the body reacts to viruses or other foreign bodies
that invade the body. This puts cells
and tissue under extreme stress and is known as acute-phase response. This response can create stress in many
different ways. It can create stress by
raising body temperature, make you lose your appetite, and create anemia. Then oddly, at the same time key nurturance
are being pulled from the blood stream.
LeGrand interviewed by Science
Daily quotes, “In many ways, the acute-phase response reinforces the stress
inflicted on pathogens locally at the infection site.” Generally system stressors do more harm to
invaders than harm to healthy cells and tissue.
Sometimes this isn’t the case and the body is left venerable and at risk
for infection.
Chapter 5
The skeletal system consist of connective tissue
The human skeleton is made up of three types of connective
tissue. They are bone, ligaments, and cartilage. Bones are hard and can break. Ligaments hold bones together and are made of
dense fibers. Lastly cartilage is made
of collagen and a gel like fluid called ground substance.
Bone is made of non-living calcium minerals that make bones
feel hard. Surprisingly bone is also
made out of living tissues. There are
five important roles bones preform.
Three roles bones preformed can be grouped together they are support,
protection, and movement. Bones allow us
to have posture and protect many internal organs. The combination of muscle and bone allow us
to move and endure impact. The other two
important functions of bones are the development of blood cells and the storage
of certain minerals. Bones act like long
term storage units for both calcium and phosphate. An interesting fact I learned was that cells
located in certain bones are the only source for red and white blood
cells. They are also the only source for
blood platelets and without production a person would die within a few
months.
Bones that are longer than they are wide are called long
bones. The shaft and end of the long
bones contain yellow bone marrow (mostly fat) that can be used for energy. The most outer layer of bone is called the
periosteum and is a strong layer of connective tissue. When the epiphysis (knob on the end of bone)
forms a joint with another bone a smooth layer of cartilage reduces friction
between bones. Inside the epiphysis is a
spongy bone that is made up of living cells and calcium. The femur and humorous are filled with red
bone marrow in which stem cells are present.
The stem cells are responsible for all the red and white blood cell
production and platelets as well.
Mature Bone Undergoes Remodeling and Repair
Even though bones don’t continue to grow longer over time
they don’t stay the same. Bone tissue is
constantly being replaced, repaired, or remodeled. When bone repairs or remodels itself is
called osteoclast. The osteoclast can
cut through mature bone tissue removing osteoid matrix in their paths. As time goes on the actual shape of bone
can change through bone remodeling. With
regular exercise and the use of weight exercises bone mass and strength
increase. This is very important because
a condition called osteoporosis where bone loses mass can occur after years of
inconsistent inactivity. Hormones also
can affect bone cells. Everything in the
body needs to maintain balance but when there isn’t balance then bones can be affected. It is estimated that every year 10% of our
bones are replaced even though we don’t realize it has happened.
Sometimes we accidently fracture or break a bone. When a bone breaks a hematoma (blood clot)
forms accompanied with pain and swelling.
A few days later fibroblasts travel to the break/fracture and become
chondroblasts. Together they produce
callus (tough fibrocartilage bond) between the broken bones. Then osteoclasts start removing dead
fragments and blood cells of the hematoma.
Last osteoblasts arrive on the scene depositing an osteoid matrix and
converts callus into bone. The repair
process is very strong and so bones rarely break in the same place twice.
The Skeleton Protects, Supports, and Permits Movement
Bones can be categorized into four types based on if they
are long, short, flat, or irregular.
Long bones are longer than they are wide. Short bones are as wide as they are long
(approximately). Flat bones can be
curved but are flat and thin containing only a small amount of spongy
bone. Irregular bones come in many
different shapes and sizes. A few flat
and irregular bones have red bone marrow.
All four types of these bones make up the human skeleton. The human body is made of 206 bones and is
organized into either the axial or appendicular skeleton.
The axial skeleton consists of the skull, sternum, sacrum
and spine (vertebral column). The skull
is made of cranial bones that protect the brain; frontal bones that are the
bones of the forehead and the upper ridges of the eye sockets. The left and right sides of the skull are
comprised of parietal bones and the temporal bones. The temporal bones allow us to hear. Then
between the temporal bone and the frontal bone is the sphenoid bone forming the
back of the eye sockets. The ethmoid
bone supports the nose and contributes to the eye sockets as well. The nasal bones make up the nose. The mandible is the lower jaw and the
occipital bone is at the posterior base of the skull. Where the spinal column connects to the skull
the large opening is referred to as foramen magnum, Latin for “great
opening”. There are also facial and
cranial bones that are air spaces called sinuses. The sinuses make the skull lighter and give
our voices there uniqueness and tone.
All sinuses are lined with mucus that traps particles in the air before
we breathe them in. Sometimes sinuses
have inflammation called sinusitis that can cause sinus headaches.
The main axis of the body is the spine. The spine protects the spinal cord and
supports our head. The spinal column is
made up of 33 irregular shaped bones called vertebrae. They are then divided up into five more groups. Cervical vertebrae make up the neck area and
are made up of seven bones. The thoracic
vertebrae area is made up of twelve bones in the chest area. The lumbar vertebrae section is the lower
back and is made up of five bones.
Sacral region is the sacrum and are five vertebrae that are fused
together right below the lumbar vertebrae.
Last, the tailbone (coccygeal) is below the sacrum and is comprised of
four fused bones. When vertebrae have
two points of contact they are called articulations. Separating every vertebra is an
intervertebral disk that is made of a soft but tough fibrocartilage. The intervertebral disk acts like shock
absorbers from everyday activities.
Sometimes a disk gets herniated causing severe pain usually occurring in
the lumbar vertebrae.
The ribs and the sternums job is to protect the contents in
the chest cavity. Humans have 12 pairs
of ribs that connect to the sternum and vertebral column. All ribs connect this way except the bottom
two ribs that are considered free floating because they don’t attach to the
sternum but rather connect to another rib.
The rib cage protects the lungs and the heart.
The appendicular skeleton consists of our arms and legs called
appendages. Our arms and legs attach to
the axial skeleton. The arms and hands
are made up of 30 different bones.
Metacarpals make up the wrist and hand bones and the phalanges are the
finger and thumb bones. Something very
unique is the range of motion of our arms.
We can rotate our arms almost 360 degrees and has the greatest range of
motion in our body. Humans also have an
“opposable thumb” which is unique to humans.
This makes it so we can grip small objects and is due to evolution.
The pelvic girdle consists of two coxal bones, sacrum, coccyx,
and the vertebra column. The main
function of the pelvic girdle is to support the weight of the upper body
against the force of gravity and helps to hold all our organs in. During puberty women produce sex hormones
that trigger bone remodeling to prepare for pregnancy and childbirth. The pelvic girdle is also where the legs
attach. The femur bone is the longest
and strongest bone in the body connecting to the pelvis. When you run or jump the amount of force
exposed to your femur is several tons per square inch.
Joints form Connections between Bones
Between bones are joints.
Ligaments and tendons stabilize joints with connective tissue. There are three types of joints. Fibrous joints are immoveable joints. When a baby is born they have soft spots
called fontanels that allow a baby to pass through the birth canal. These joints also allow for brain growth
after birth. These fontanels harden in
childhood. Cartilaginous joints are
bones connected by slightly moveable hyaline cartilage. The most moveable joints are synovial joints
and are separated by a fluid. The bones of synovial joints are held together by
ligaments. The fluid cavity is lined
with a synovial membrane that secretes synovial fluid lubricating the
joint. One type of synovial joint is a
hinge joint found in elbows and knees.
The knee joint is very strong but still flexible. To reduce friction there are small disks of
cartilage on both sides of the knee called the meniscus. The knee joint also includes 13 small fluid
sacs called burae for padding and is then wrapped in strong ligaments. Another type of synovial joint is a ball in
socket joint that allow a large amount of range of motion. Your legs and arms are ball in socket joints
allowing you to rotate them. Synovial
joints take constant poundings and couldn’t withstand the wear and tear without
ligaments, tendons, and muscles. Tendons
stabilize joints with a tough connective tissue that join bones and
muscle. Ligaments and tendons have
collagen used for making them both strong and flexible. Muscles both contract and stabilize
joints.
Chapter 6
Muscles Produce Movement or Generate Tension
There are muscle cells in every part of the human body and
is about half of our body mass. There
are three different types of muscles: cardiac, smooth, and skeletal
muscles. They all respond to chemical
and electrical signals from other organ systems. All three muscles also contract (shorten) and
relax returning to abnormal. Muscles are
either voluntary or involuntary.
Voluntary muscles are controlled by conscious control. An example of voluntary muscles is the shown
in through the act of running. The heart
is an involuntary muscle and is beyond conscious control. You can’t make your heart stop beating by
thinking it. We know muscles contract
and relax but they also produce heat.
The contraction of skeletal muscles produces approximately ¾ of all heat
produced by the body. Since the
temperature outside is usually cooler than our bodies this is important in
maintaining homeostasis of our body temperature.
Skeletal muscles cause bones to move or not move. Through either contraction or relaxation
tasks like writing and shivering are performed. There are 600 different skeletal muscles
that are usually in pairs or groups. All
motion is controlled by nerves that perform by themselves or in groups. When muscles work together in groups to
accomplish one movement this is called synergistic muscles. Muscles that face each other are called
antagonistic muscles. Most all skeletal
muscles are attached to bone by tendons.
Very specific movements are made by how a muscle joins a bone. An organ is one end of a skeletal muscle
connected to bone. The other end of the
muscle is called its insertion and it attaches to another bone across a
joint. When a muscle contracts the
origin and insertion are pulled towards each other.
A whole muscle or single muscle is made up of a group of
individual muscle cells that all have the same origin, insertion, and have the
same function. In cross sections of
muscles there are bundles called fascicles.
Each muscle is enclosed in a casing of connective tissue. Each fascicle has between a few dozen to
thousands of muscle fibers. The outer
layers of a muscle are covered by many layers of fascia. Then fascia connects to the ends of the
muscle from tendons that attach to the bone.
Individual muscle cells are tubed shaped and longer than
most other muscle cells. Some muscle
cells are only a millimeter in length and other muscle cells can be thirty
centimeters. Individual muscle cells
have more than one nucleus. The nuclei
are right under the cell membrane because it is filled with long cylindrical
structures called myofibrils. One
myofibril in a bicep muscle has more than 100,000 sarcomeres. A sarcomere consists of two kinds of protein
filaments. One is myosin that is thick
filaments (fibers) made of proteins.
The other is a different protein called actin. Muscle contractions all depend on the interactions
of actin and myosin proteins.
Individual Muscle Cells Contract and Relax
Sarcomeres shorten when a muscle contracts and preform a
very powerful action. There are four
important facts to understanding what makes a muscle contract and relax 1.
Muscles must be activated by a nerve 2. Calcium concentrations in the same area
as contractile proteins increase nerve activation 3. Calcium has to be present
for muscle contraction 4. Muscle contraction ends when it isn’t stimulated by a
nerve. Motor neurons tell certain nerve
cells to contract muscle cells. This is
done by motor neurons secreting chemicals called acetylcholine that are
neurotransmitters. The connection
between motor neurons and (skeletal) muscles cells are called neuromuscular
junctions. Tube like extensions of the
cell membrane are called T (transverse) tubules that transmit electronic pulses
into the cell. This gets information
quickly from one place to another. The T
tubules are in close proximity with the sarcoplasmic reticulum (membrane
chambers). Sarcoplasmic reticulum and
endoplasmic reticulum are similar except for their shape. Inside muscle cells electrical impulses race
to T tubules and to the sarcoplasmic reticulum.
The electrical impulses trigger the release of calcium ions from the
sarcoplasmic reticulum. As muscles
contract sarcomeres shorten as thin filaments slide past each other. This process is called sliding filament
mechanism.
When nerve activity ends muscle cells relax. Without nerve activity calcium isn’t released
from the sarcoplasmic reticulum. The
calcium is crucial for muscle contraction.
When there are interferences in nerve activation muscle function can be
interrupted. A disorder called
myasthenia gravis that attaches and destroys the body’s immune system. The muscles fail to respond to weal nerve
impulses. An example of this is droopy
eye lids and double vision.
Muscle contractions require a lot of energy. Muscle cells use ATP as an energy
source. When calcium is present the APT
cycle of attachment, bending, and detachment is repeated over and over. Muscle cells store only about 10 seconds worth
of ATP. When the stored ATP is depleted
either more ATP has to be produced or energy from glycogen, glucose or fatty
acids has to be used. When a person dies
a process of rigor mortis (Latin for “rigid death”) occurs. In rigor mortis the body turns very stiff
from about four hours to many days. This
occurs because just after death calcium leaks from the sarcoplasmic reticulum
causing muscles to contract. Rigor
mortis eventually goes away after lasting many days.
Stored ATP combined with creatine phosphate process enough
energy for 30-40 seconds of heavy activity.
After that muscles must use stored glycogen. This supply of stored glycogen only lasts an
additional three to five minutes. After
the stored supply of glycogen is gone the long term source of energy is fatty
acids, glucose, and latic acid. Heavy
activity has the side effect of producing latic acid. This is the deep burning sensation you feel
after intense exercise. When long
distance runners start out they use stored energy but after a few minutes they
have to rely on aerobic metabolism.
Aerobatic metabolism occurs in the mitochondria and requires
oxygen. After a person has finished
exercising they still need to deep breath.
This is to compensate and replenish the body’s oxygen debt. Muscle fatigue is the decline in muscle
performance during exercise. This
happens when ATP is depleted or when the body’s energy is gone. Fatigue can also occur when a person physcs
themselves out.
Cardiac and Smooth Muscles have Special Features
Besides skeletal muscles there are also smooth and cardiac
muscles. These muscles are involuntary muscles because you can’t control them
because they lack stimulation from nerves.
Cardiac muscles have their own cycle of relaxation and contraction. In the cardiac muscles are pace maker cells
that have the fastest rhythm that the other cells follow. Cardiac muscle cells are connected by their
blunt ends by intercalated disks. The
disks have gap junctions that allow one cell to stimulate the next cell electrically. The pace maker cells dictate the pace of
contraction and relaxing of the entire heart.
Smooth muscles are also connected by gap joints that allow cells to
activate each other. This way the entire
tissue works together.
Skeletal muscles are
the fastest in regards to contraction and how fast and how a body sustains
them. Cardiac muscles are rhythmic and
smooth muscles stay partly contracted at all times. Smooth muscles play an important part in
regulating blood pressure because it maintains the size of blood vessels.
Chapter 7
The Components and Functions of Blood
The circulatory system is very important in giving the cells nutrients and removing waste. Blood is
a connective tissue that is made of cells, cell fragments, ions, and molecules
in a watery solution. Blood does three
very important jobs. Blood
transportation: blood transports everything that is needed throughout the
body. From oxygen to the heart to
providing nutrients or hormones, blood transport is essential. Blood also helps in the removal of waste from
the body. Blood regulation: Blood helps to regulate and maintain body
temperature, how much water is in the body, and maintaining a good pH level of
body fluids. Blood Defense: blood has specialized defense cells that
protect the body from illness and infection.
Blood can also clot preventing any major blood loss. The human body is composed of about 8%
blood. An old saying is true that blood
is thicker than water. This might be
because of all the nutrients and has such rich components. Two categories of blood are 1. Plasma: This
is the liquid component 2. Red cells, white cells, and platelets: cells and all formed elements. Plasma is the transportation for blood cells
and platelets. About 90% of plasma is
made of water and the rest is proteins, hormones, ions, and 100 different small
molecules. Almost 2/3 of plasma proteins
are albumins that maintain the balance of water between blood and interstitial
fluid. Albumins are made in the liver
and contribute in blood transportation.
Globulins job is to transport many substances in the blood. Globulins are also designed as either alpha,
beta, or gamma. Gamma globulins are part
of the body’s defense system and help protect from infection. Beta goblins bind to fat (lipid) molecules,
for instance cholesterol and when a protein attaches it is now a
lipoprotein. Doctors check for both high
and low lipoproteins. Low lipoproteins
are a sign of bad cholesterol because lipoproteins are associated with
cardiovascular health problems. High
lipoproteins show a healthy body without risk of cardiovascular disease. Another group of plasma proteins are clotting
proteins that are essential in blood clotting.
Half of the volume of blood consists of white cells, red
cells, and plasma. Mostly consisting of
f=red blood cells that carry oxygen and carbon dioxide through the body. For every cubic millimeter of blood there is
5 million red blood cells. Red blood
cells have a unique shape because they have to be able to bend when
needed. They are flat, small, and disk
shaped with the center being thinner than the outer edges. This design makes it so the cytoplasm isn’t far
from the cell surface enabling the gas exchange. Red blood cells are in the plasma membrane
with almost 300 million molecules of oxygen binding proteins called
hemoglobin. Hemoglobin is made of four
polypeptide chains each having a heme group.
A single red blood cell carries up to 1.2 billion oxygen molecules. Red blood cells don’t have mitochondria so
they don’t use any of the oxygen they are transporting. Hemoglobin binds oxygen the best when oxygen
levels are high and the pH level is low.
When body heat increases hemoglobin releases more oxygen. The percentage
of red blood cells in the body is called the hematocrit. Hematocrit is the measure of the oxygen
carrying capacity of blood. Normal range
for a man is between 43-49% and between 37-43% for women. When someone has a low hematocrit this may
show signs of anemia. High hematocrit
can be bad too because of the risk of blood clots due to too many red blood
cells making blood thicker than it should be.
All blood cells and platelets are made in red bone marrow of
certain bones. Stem cells divide and
reproduce for our entire lives. The stem
cells produce immature blood cells that develop into platelets, red and white
blood cells. Red blood cells don’t have
a nucleus so they can’t divide. They
rely in stem cells for reproduction and because red blood cells wear out fast
there is a lot of production. Red blood
cells live only approximately 120 days and during that time make almost 3,000
round trips every day. More than 2
million red blood cells are produced per second. The spleen and liver remove old and damaged
red blood cells from the body through large cells called macrophages (the
largest white blood cells). Certain
cells in the kidneys monitor the oxygen levels in the body. When oxygen levels get too low a hormone
called erythropoietin is secreted stimulating stem cells to produce more red
blood cells. When someone has kidney
disease they don’t make enough erythropoietin to regulate the right amount of
red blood cells produced.
Only about 1% of blood consists of white blood cells. They are bigger than red blood cells and are
much more diverse. White blood cells
have a nucleus but don’t have hemoglobin and are also translucent. For every 700 red blood cells there is only
one white blood cell. White blood cells
play important roles of defending the body against disease. There are two different categories of white
blood cells: granular leukocytes and
agranular leukocytes. Both have vesicles
in their cytoplasm and are filled with proteins and enzymes assisting in
defenses. Most granular leukocytes die
anywhere from a few hours to approximately 9 days after being made. This is mainly due to injuries from fighting
off microorganisms. The amount of white
blood cells increases when the body is threatened with viruses, bacteria, or
other health problems.
About 6% of white blood cells are called neutrophils. This is the first white blood cell that
attacks infections, bacteria, and some fungi.
Eosinophils are circulating white blood cells that account for only
2-4%. They have 2 important jobs of
defending the body against large parasites (worms) and releasing chemicals that
help with allergic reactions. The rarest
white blood cell is basophils that account for only 0.5% of white blood
cells. They contain histamine that
initiates the inflammatory response.
When the body is injured histamine releases plasma to the injured
area. Plasma brings the needed
nurturance, cells, and chemicals to begin repairing any damage. Inflammation is the body’s defense even
though it is uncomfortable. The largest
white blood cells are monocytes and make up 5% of circulating white blood
cells. These white blood cells are
unique because they can filter out of the blood stream and exist in tissues. They also stimulate lymphocytes to defend the
body. Monocytes are very active during
chronic infections and fight hard against viruses. Last, lymphocytes make up 30% of white blood
cells that are found in the bloodstream, tonsils, spleen, lymph nodes, and
thymus gland. They destroy specific
threats such as bacterias, viruses, and cancer cells. They play a crucial role in the body’s immune
system.
Blood platelets are derived from megakaryocytes (large
cells) made from stem cells. Only 1% of
blood is platelets. Megakaryocytes don’t circulate, staying in
bone marrow. Platelets aren’t living and
only last a maximum of nine days. When a
blood vessel is damaged and leaks, platelets help with clotting and limit any
tissue damage. After bleeding stops
platelets also help to repair damage by releasing proteins that promote blood
vessel growth and repair.
Hemostasis: Stopping Blood Loss
Hemostasis is the natural process of stopping blood flow or
blood loss. This happens in three
different stages: 1. intense contraction of blood vessels 2. Platelets make a
plug 3. Blood clotting happens (coagulation). Next tissue repair can begin.
Damaged blood vessels have spasms and contractions that
constrict vessels when they are damaged.
This immediately stops or slows blood flow. Next circulating platelets swell, clump
together, and develop spikey extensions.
They become sticky and adhere to the vessel wall creating a platelet
plug. The last stage in hemostasis is
the formation of a blood clot, in which blood becomes gel like. At least 12 substances help create the
reactions necessary for clotting. When
any steps in the process don’t happen the results can be deadly. People who have the inherited condition
hemophilia have one or more clotting deficiencies. Fifty years ago people with this condition
didn’t live past childhood but now with science there are treatments.
Medications like aspirin block platelet clumping and interfere with natural
hemostasis.
Human Blood Types
There are many different blood types and the success of
blood transfusions depends on blood matching.
Testing is done to determine your blood type. If you
receive blood from someone who doesn’t have a compatible blood type severe
reactions can occur.
Our cells have specific proteins that the immune system recognizes
as “self”. Foreign cells have different proteins
that the body knows are “nonself”. An
antigen is a nonself protein that stimulates the immune system of an organism
to defend. The immune system produces an
opposite protein called a antibody.
Antibodies float freely in the blood and lymph until they meet an
intruder with a matching antigen. Then
they bind and mark the foreign molecule for destruction. Antigen-antibodies often cause foreign cells
to clump together.
Red blood cells also have proteins that identify them as
“self” to the body. Almost everyone is
classified in one of four blood types.
Blood types: A, B, AB, and O. An
type A blood type has A antigens, type B blood has B antigens, type AB blood
has AB antigens, and type O blood has neither A or B antigens and is referred
to as zero. In addition blood also has
antibodies. Type B blood has A
antibodies, type A blood has B antibodies, type O blood has both A and B
antibodies, and type AB blood doesn’t have either antibodies. Antibodies appear early in life and it
doesn’t matter if someone has had a blood transfusion they naturally have the
antibodies. The antibodies attach red
blood cells with foreign antigens causing them to clump together. These clumps can block blood vessels that can
cause organ damage or even death.
There is another red blood cell antigen that is important in
blood transfusions called the Rh factor.
Approximately 85% of Americans are Rh positive. This means they carry the Rh antigen on their
blood cells. Only 15% do not have an Rh
antigen meaning they are Rh negative.
The Rh factor is mostly important with pregnant women. If a woman is Rh negative but is having an
Rh positive baby with an Rh positive man the maternal antibodies can cross the
placenta attaching to the babies red blood cells. This can result in mental retardation or
death of the infant.
Other wonderful uses of blood typing are used in criminal
investigations, paternity, and tracking of population migration. There are over 100 other blood antigens in
the human population that aren’t very common.
To make sure blood transfusions are safe medical labs do blood typing
and cross matching. This involves mixing
a donors blood with the blood of a receiver.
If agglutination does not occur then the bloods are considered to be a
good match.
Chapter 8
Blood Vessels Transport Blood
The heart and blood vessels make up the cardiovascular
system. The cardiovascular system is
crucial in supplying the body with the right amounts of blood and maintaining
homeostasis. Blood vessels transport
blood to all parts of the body. If we
were to lay out all the blood vessels in out body they would stretch 60,000
miles.
There are three major types of blood vessels in the
body. Thick arteries transport blood at
high pressure. Capillaries interchange
solutes and water with cells of the body.
Thin veins store and return blood back to the heart.
Arteries transport blood away from the heart. When the blood leaves the heart it does this
with very high pressure. Because of this
pressure the arteries have a thick muscle layer to withstand the pressure day
after day. Arteries continue branching
and the farther blood moves away from the heart the less pressure there is. They can stretch somewhat and are able to
store blood that is pumped into them with every heartbeat. Artery vessel walls are put together in three
layers that surround the lumen (interior hollow space). The inner layer is thin and is called the
endothelium. It is composed of flat,
squamish epithelial cells. This design
reduces friction and creating a slick surface so blood can flow smoothly. The middle layer is mainly made of smooth
muscle with interwoven connective tissue.
The center layer of the artery is generally the thickest layer. The outer layer of large and medium sized
arteries is made of a thick connective tissue, mainly made of collagen. This layer is helpful in protecting the
artery from injury. Since blood is being
pumped at such high pressure they are at some risk for injury. If the inner layer of a artery, the
endothelium, gets damaged blood can seep between the layers of an artery. This can cause an artery to split apart. This can balloon the artery wall creating an
aneurism. Sometimes aneurisms can cause
chest pain but sometimes there aren’t any symptoms until the artery blows out
creating internal bleeding and death. Aneurisms
of the aorta (the largest artery) kill approximately 25,000 Americans yearly. The
aorta is about 1 inch in diameter. Many aneurisms actually take years to develop. Doctors can detect some aneurisms with a
stethoscope or using a computerized tomography scan (CT) and surgically repair
them before they rupture. Eventually
blood reaches small arteries called arterioles.
Arterioles are about the diameter of a piece of thread. By the time blood reaches small arteries the
pressure is considerably reduced. The
arterioles don’t have the outer layer of connective tissue that large and
medium arteries have. Another difference
is that the smooth muscle isn’t thick and they help to regulate the blood flow
to each capillary. Where the arteriole
joins a capillary is a band of smooth muscle called pre capillary
sphincter. The pre capillary sphincter
controls the gates of blood flow to each capillary.
The smallest arteries are called arterioles that connect to
capillaries (smallest blood vessels).
Capillaries are not much wider than red blood cells and sometimes the
red bold cells have to squeeze through the narrow passageways. In every area of the body there are capillary
beds that have porous walls allowing oxygen and carbon dioxide exchange. They also facilitate the exchange of
nurturance and waste as well. Capillary
are composed of a single layer of squamish epithelial cells. There are microscopic pores that cells are
separated by. The capillaries function
is to strain and exchange material with the interstitial fluid. Most filtered fluid is reabsorbed into the
last part of the capillary before joining the vein.
Capillaries filter out plasma fluid and the amount that
isn’t reabsorbed is about two or three liters a day. The excess fluid is then picked up by the
lymphatic capillaries that are blind ended vessels. The lymphatic system also picks up objects that
are too big to diffuse by capillaries.
From the capillaries blood flows back to the heart through
small veins (venules) and veins. Vein
walls are made up of three layers of tissue just like arteries. The difference is that vein walls have a
larger diameter lumen (open space) than arteries. The two outer layers of veins are thinner
than they are in arteries. Veins are
able to stretch like balloons to house large volumes of blood that is presented
in low pressure. Almost 2/3 of our
blood is in your veins making its way back up to your heart. Veins serve as a reservoir for the cardiovascular
system. The force of gravity can
sometimes lead to problems bringing the blood back to the heart. People who spend a lot of time on their feet
can develop varicose veins. When this
happens veins become swollen and it usually occurs in the feet and legs. The veins appear to es solution in them
causing them to shrivel. This makes them
less noticeable and less painful. Three
things that help veins return blood back to the heart are the contraction of
skeletal muscles, valves that don’t let blood go backward, and by
breathing. When blood travels back
towards the heart, skeletal muscles are relaxing and contracting. This causes blood to be pushed towards the
heart. Then almost all veins have one
way valves that are inside the lumen.
This allows blood to only flow in one direction (to the heart). The name for the relationship between
skeletal muscles and valves is called the skeletal muscle pump. Next the blood flow assists in pressure
changes in the chest and abdominal cavity during breathing. Abdominal pressure increases and squeezes
abdominal veins as we inhale. At the same
time thoracic veins dilate due to decreased pressure in the thoracic
cavity.
The Heart Pumps Blood through the Vessels
The heart is a coned shaped organ that is slightly larger
than your fist. The heart is very
muscular and is located between the lungs and behind the sternum in the
thoracic cavity. The heart pumps without
stopping in a squeezing motion propelling blood through blood vessels. At rest your heart pumps approximately 75
times per minute never resting for more than 2/3 of a second. If you added up all the heart beats someone
has over 70 years the number is about 2.8 billion beats. Usually the brain tells the heart to pump but
the heart can also pump without the brain telling it to. The heart is placed in the chest cavity and
is enclosed in the pericardium, a tough fibrous sac. The pericardium anchors the heart, protects,
and prevents it from overfilling with blood.
The space that separates the pericardium from the heart is the
pericardial cavity. This cavity has a
lubricating fluid reducing friction and allowing the heart and pericardium to
slide against each other smoothly.
Inside the heart there are three layers: the epicardium, myocardium, and
endocardium. The outer most layer is the
epicardium and is composed of a thin layer of epithelial and connective
tissue. The center layer is myocardium
and is thick, and is mainly cardiac muscle and forms the majority of the
heart. The myocardium is the layer of
the heart that contracts every time the heart beats/pumps. An electrical signal from one cardiac muscle
cell can spread to neighboring other cells making the heart act as a unit. The inner layer of the heart is the
endocardium and a thin endothelial layer that rests on a connective tissue
layers. Sometimes one of the heart
layers becomes inflamed due to many different factors. Some factors include cancer, infection,
injury, and complications from surgery.
Depending on the cause of inflammation there are people who can be
treated with medications.
The heart is divided into four different section called
chambers. The two chambers on top are
called the atria and the two bottom chambers are called the ventricles. Then there is a muscular divider called the
septum divides the right and left sides of the heart. When blood returns to the heart it enters
through the right atrium. Then it goes
through a valve to the right ventricle.
The right ventricle is muscular because it pumps blood with high
pressure to the artery that enters the lungs.
After the blood has been oxygenated the blood enters the left atrium and
then goes through a valve to the left ventricle. Again the left ventricle is very muscular and
pumps blood into the aorta (largest artery).
From the aorta the blood travels through arteries (large and medium
arteries) to arterioles (small arteries), to capillaries, venules (small
veins), and veins back up to the atrium.
Pulmonary Circuit
The pulmonary circuit is when blood is being pumped through
the lungs. Blood enters the right atrium
after returning from veins. The blood
has dispersed all the oxygen and now carries carbon dioxide. Blood passes from right atrium to right
ventricle. Then the right ventricle pumps blood through the semilunar valve and
into the main pulmonary artery going to the lungs. The pulmonary artery supplies both the right
and left lungs. The pulmonary
capillaries assist in the exchange of carbon dioxide and oxygen. When we inhale a breath blood gets
oxygenated. This blood is then carried
back into the pulmonary veins leading to the heart. Next blood enters the left atrium and then
into the left ventricle. The part of the heart containing blood that is without
oxygen never mixes with the side of the heart that has oxygen.
Systemic Circuit
The other circuit is called the systematic circuit (rest of
cardiovascular system). From the left ventricle
blood is forcefully pumped into the large aorta artery. Then blood travels through branching arteries
to arterioles to capillaries the deliver oxygen and nurturance to the entire
body. Last blood flows from the
capillaries to venules, veins, and back up to the right atrium.
There are three major arteries and veins in the human
body. The iliac artery supplies blood to
the legs and the iliac vein returns blood back to the heart. The carotid artery supply blood to the head,
but the jugular vein returns the blood away from the head. The heart has its own set of blood vessels
called coronary arteries. Cardiac veins
collect blood from capillaries in the heart muscle and channel it back to the
right atrium.
Chapter 9
Pathogens cause Disease
The immune system is a complex group of cells, proteins,
lymphatic, and circulatory systems.
The
immune system does its best it can identifying abnormal cells or pathogens but
sometimes things slip through.
Pathogens
are defined as
an agent that causes disease,
especially a living microorganism such as a bacterium or fungus (http://www.thefreedictionary.com/pathogen, accessed 23 March 2012).
Bacteria
Bacteria:
Bacteria are single cells organisms that don’t have a nucleus. The DNA in bacteria has only one chromosome
and the outer surface is covered by a rigid cell wall giving bacteria
different, distinct shaped. Bacteria are
amazing because it’s one of the most successful organisms on earth. Most bacteria are smaller than most cells and
use its tiny size to its advantage. The
small size of bacteria makes it so there is a high surface to volume
ratio. The many things types of bacteria
can do are to decompose dead plants and animals, break down raw sewage, and get
nurturance from air and soil.
Researchers have also produced bacteria used in antibiotics, hormones,
vaccines, and in many different type of foods.
Oddly there are also a few bacteria’s that are pathogens. They get the energy they require from human
cells and damage or kill these cells in the process. Some of these bacteria can cause syphilis,
pneumonia, toxic shock syndrome, and many other diseases. But we need to remember that most bacteria
are helpful and not harmful at all. Luckily
bacterial infections can be treated with antibiotics most of the time
successfully.
Some Virus Types
Viruses: Viruses are so small. Remember how bacteria are about the size of a
human cell, well viruses are one- hundredth the size of bacterium. The structure of a virus has either only DNA
or RNA with a protein cover. Viruses
aren’t alive and can’t reproduce or grow on their own. The main way viruses infect human cells is by
being brought into the cell through the cytoplasm. When this happens the viral material joins
itself into the host cells genetic material.
Another way viruses enter the body is by is by attaching to the outer
cell surface and injecting the virus genetic material into the cell. When viral material enters a human cell it
makes the cell begin producing thousands of virus copies instead of doing the
role the cell usually preforms. Sometimes
cells become consumed with a virus and explode releasing the virus even further
in the body. Some diseases are very
serious and some are mild. A few
diseases caused by viruses are AIDS, hepatitis, rabies, the common cold, warts,
and even chickenpox.
Prion: A
prion is a misfolded form of a normal brain cell protein that triggers the
misfolding of nearby normal proteins.
Once a prion enters a nerve the process goes wild. Nerve cells die making someone have debilitating
neurological symptoms. Prions have no cure and are resistant to cooking,
freezing, and drying. When a person eats
beef from a cow that had mad cow disease called variant Creutzfeldt-Jakob
disease (vCJD). Researchers know that
prion is responsible for both mad cow disease and vCJD. Mad cow disease destroys nerve cells in an
animal’s brain and spinal cord. This
then causes the animal to jerk, stagger, and have other unusual behaviors. The disease vCJD in humans displays almost
the same signs as mad cow disease does.
Some
pathogens aren’t as dangerous to humans as other pathogens are. Things that make a pathogen threatening is how easy it can be
passed person to person, the way it is transmitted, and how detrimental the
disease is. Things like the common cold
are transmitted by fluids distributed by sneezing and coughing. Then there is the HIV virus that causes AIDS
which is also in fluids. The HIV virus
is found in semen, breast milk, blood, or vaginal secretions. The HIV virus is a super virus and at this
time doesn’t have a cure. In the past
there have been other diseases that have spread to deadly epidemics. A bacterial infection between 1348 and 1350
killed between 25-40% of the European population called the bubonic plague. The Ebola virus that arose in 1976 is still
present today in Africa. This virus can
kill 80% of an exposed population in less than two weeks.
The Lymphatic System defends the Body
The lymphatic system is closely linked with the
cardiovascular system. The three
functions the lymphatic system preforms are maintaining the blood volume in the
cardiovascular system, transporting fats and vitamins absorbed in the digestive
tract to the cardiovascular system, and to defend the body against
infection. The lymphatic system protects
the body from disease. Most immune
system cells are located in the lymphatic system. The lymph system is a large network of lymph
vessels, lymph nodes, the spleen, thymus gland, tonsils and adenoids.
Lymphatic System
Lymph capillaries are close to blood capillaries and
cells. They pick up materials that are
too big to be picked up by blood capillaries (including bacteria). The fluid in lymph capillaries is a milky
fluid that has white blood cells, proteins, fats, and sometimes bacteria and
viruses in it. The lymph capillaries
merge and create lymph vessels. Lymph
vessels have three layer walls and also have a one way valves preventing any
back flow. Skeletal muscle contractions
and relaxing also help the lymph flow.
The lymph vessels merge forming larger vessels and eventually they form
two major lymph ducts called right lymphatic duct and thoracic duct. These two major lymph ducts join the
subclavian veins near the shoulders and returns lymph to the cardiovascular
system.
Along the route there are lymph nodes that are along
lymphatic vessels. They collect debris
and remove abnormal cells before returning to the cardiovascular system. A person has hundreds of lymph nodes
clustered in the neck, armpits, groin, and digestive tract. Lymph nodes range in size from 1mm to 2.5 cm. Inside lymph nodes are connective tissue and two
types of white blood cells that identify microorganisms and removing them. Macrophages destroy foreign cells and
activate other defense mechanisms. Clean
lymph fluid flows out of the lymph node and continues to the veins.
The spleen is the largest lymph organ that is located in the
upper-left abdominal cavity. it is the
size of a fist and is soft. The two main
functions of the spleen are to help fight infection and remove old or damaged
red blood cells. Together the lymph
nodes and blood keep circulating body fluids free of damaged cells and microorganisms. Sometimes when it is necessary to remove a person’s
spleen they have a hard time fighting off infections.
The thymus gland
located behind the sternum, above the heart, and is in the lower neck. The thymus
Gland secretes two hormones that cause T lymphocytes to
mature and start defending the body. The
thymus gland is the largest during childhood and can completely disappear in
old age.
Tonsils are located near the throat entrance. They filter out many microorganisms that are
in air or even food. Even though we have
many tonsils in our body the ones in the throat are the biggest and most
popular. They often become infected and
are sometimes removed.
Keeping
Pathogens out: The First Line of Defense
The skin is considered the most important barrier for
keeping out pathogens. There are four
things that make the skin an effective barrier.
First the skins structure and many layers are great at keeping things out. Secondly, the skin is always being replaced. Third, healthy skins pH is 5 or 6 mainly due
to sweat. Lastly, a natural produced
antibiotic made by sweat glands called dermicidin, kills many harmful bacteria
before they enter the body. This is why
when someone gets 3rd degree burns on their body, the risk of
infection is so high. This is because
the body’s main barrier has been compromised and isn’t keeping pathogens out.
Pathogens are most
successful in entering the body where there isn’t skin. Some of these places include the moist mucus
membrane ling the digestive tract, urinary, respiratory, and reproductive
tracts. These places have their own
defenses to these pathogens as well.
Tears and saliva contain lysozyme that kills bacteria. Thick mucus secreted by cells restricts
access to the cells beneath it. Undiluted
digestive acid is strong enough on an empty stomach to kill all but one
pathogen. Helicobacter pylori are
bacteria that have evolved to love a very acidic environment. Vaginal secretions are also slightly
acidic. Through vomiting the body can
rid itself of toxins or infected stomach contents. Diarrhea can also rid the body of pathogens.
Nonspecific Defenses: The Second Line of Defense
With the slim chance that pathogens get past all the
barriers they begin damaging or killing cells.
The body immediately starts trying to find pathogens to get rid of
them. The body also begins repairing the
damaged area and cleans any injuries. When
pathogens enter the body a second a line of defense mechanisms called
nonspecific begins the process. Nonspecific
defenses include phagocytes, natural killer cells, inflammation, infrons, and
fever.
Phagocyte
Phagocytes are white blood cells that destroy foreign cells
through the process of phagocytosis.
First the phagocytes catch the bacterium with cytoplasmic extensions. Then it engulfs and encloses the
bacterium. Next powerful enzymes in the
lysosomes dissolve the bacterium membrane.
After the bacterium is destroyed then the waste is then discarded from
the cell.
The first white blood cells to respond are neutrophils. They digest and destroy bacterium in the
blood and tissue fluids. Monocytes are
other white blood cells that actually leave the cardiovascular system and
mature into macrophages. The
macrophages can engulf and digest large amounts of foreign calls including
viruses and bacteria. They clean up
debris and fragments. Another wonderful
function is that they release chemicals that stimulate the production of more
white blood cells.
Lastly another type of white blood cells called eosinophils
are brought in when foreign objects are too big for the phagocytosis. The eosinophils surround certain parasites
and surround them with large amounts of digestive enzymes killing them. Another process involves ingesting other proteins.
When any of the white blood cells are fighting off foreign
invaders the body must continuously make more white blood cells because so many
white blood cells are being destroyed in the fight. The destroyed white blood cells, tissue
fluids, microorganisms, and any other cellular debris grouped together to form
a substance we refer to as pus. Sometimes
pus is in an area in which it can’t drain.
When this occurs an abscess is formed.
Inflammation is swelling, redness, warmth, and pain. Inflammation is important in preventing any
damage from spreading. It also aids in getting
rid of pathogens and cellular debris, and prepares the body for healing and
repair. There is a formula that is
carried out when tissue becomes injured.
First chemicals are released from the injured area to alert the body of
a problem. Then chemicals stimulate mast
cells to release histamine. Next the
histamine support vasodilation of any close by small blood vessels. The definition of vasodilation is Widening of
blood vessels that results from relaxation of the muscular walls of the
vessels. What widens in vasodilation is actually the diameter of the interior
(lumen) of the vessel. (http://www.medterms.com/script/main/art.asp?articlekey=5965,
accessed 24 March 2012). Through
vasodilation more blood is brought to the injured area warming it up. The warmth promotes phagocytes activity. Swelling is caused by capillary walls
allowing more fluid in. Luckily the
fluids brought in carry lots of nutrients and oxygen. Last basophils of white blood cells also
secrete histamine. The pain felt with
inflammation is actually good because it makes the body rest and heal
faster.
Natural killer cells (NK) are a group of white blood cells
whose job is to destroy tumor cells and cells infected by viruses. Unlike other cells these natural killer
cells can identify changes in the plasma membrane of tumor cells. Natural killer cells release chemicals that
actually break down the cell membrane of the tumor or virus cell. Natural killer cells also secrete substances
that improve the inflammation response.
The complement system is made up of twenty plasma proteins
that are constantly help other defense mechanisms in any way they can. They are so effective because they cause a
chain reaction when activated. By
creating holes in the bacterium salt and other fluids leak into the bacterium
until it bursts.
When cells become infected by a virus the cells releases
proteins telling other cells to put up their defenses called interferon. This makes it harder for viruses to penetrate
other healthy cells. Interfrons are
actually being produced in pharmaceutical labs and is showing promise in
fighting certain viral diseases such as genital warts.
Many believe a fever is bad and must be brought down
immediately. Really mild fevers are
quite beneficial to the body. By raising
the body temperature pathogens aren’t as comfortable plus by raising the
temperature the metabolic rate increases.
This speeds up the repair process along with all defense
mechanisms. When the infection is gone macrophages stop
releasing pyrogens that originally told the brain to increase body
temperature. Everything then returns to
normal. Some fevers can be unsafe and you
should seek medical help if a fever rises above 100 degrees Fahrenheit or lasts
more than a couple days.
Specific Defense Mechanisms: The Third Line of Defense
If all other defenses fail then the immune system kicks
in. Together proteins, cells and lymph
systems work together to kill off any foreign or bad cells called the immune
response. The immune response recognizes
and attacks certain pathogens and foreign substances. Another thing the immune response does is
that it isn’t limited to a specific area but instead protects the entire
body. Plus it has the capability to
remember past infections or exposures allowing the body to react quickly.
The body is amazing in the way it can distinguish between
what is “self” and what is foreign.
Antigens are any substance that provokes an immune response. Most antigens are large proteins or
polysaccharide molecules. Every antigen
has a unique shape and every virus and bacterium has a different shape. The immune system starts producing antibodies
to attach and disarm the antigen with the cell carrying it. Once a virus has entered a cell the immune
system can no longer detect it. All
antigens are on the outside of the cell or virus. Self-markers are known as major histocompatibility
complex (MHC) proteins and are unique to each person through their unique set
of genes. Cancerous cells or abnormal
cells have a MHC protein that alerts the body it isn’t “self”. The immune system sets out to destroy all
antigens on pathogens and foreign cells.
Another line of defense is lymphocytes that are white blood cells. They have one nucleus that takes up almost
the entire cell. About 30% of white
blood cells in the body are lymphocytes.
Of these lymphocytes there are either B lymphocytes (B cells) or T
lymphocytes (T cells). B cells mature in
bone marrow and are responsible for all antibody-mediated immunity. B cells produce and release antibodies into
lymph, blood, and tissue fluids that circulate through the body. When B cells have the correct antigen its surface
receptor binds to the antigen. This
immediately activates the B cell to grow and multiply making exact copies
(clones) if that specific B cell. B
cells stay in the lymphatic system but there clones called plasma cells, start
secreting their antibodies into lymph plasma.
Then they ultimately end up in blood plasma. A blood plasma cell can typically make
antibody molecules at 2,000 per second.
This production maintains for a few days then the cell dies but the
antibodies remain. When antibodies meet
matching antigens they bind creating an antigen-antibody complex. This complex shows the body the antigen
attached to the foreign cell that needs to be destroyed. Some antibodies can inactivate pathogens by
making them agglutinate (clump) not allowing them to enter cells or cause
disease. Some cloned B cells become
memory cells that store information about a pathogen. If there was then a second exposure to that
pathogen the body would act quicker than it did the first time. Our memory cells create our long term
immunity.
The other type of lymphocyte called T cells is responsible
for cell-mediated immunity.
T cells
don’t produce antibodies but instead directly attack foreign cells that carry
antigens.
T cells release proteins that
help with other parts of the immune response.
Amazingly T cells can identify and kill infected human cells before the
cells have a chance to release new bacteria or viruses.
There is a process that has to happen before
T cells can do their job.
This is because
T cells can only respond to fragments of antigens.
Some of these cells that help in the process
activate B cells and antigen-presenting cells (APCs) can engulf foreign
particles, partially digest them, and then give the fragments to the T
cell.
Some T cells develop from stem
cells in bone marrow then mature in the thymus gland.
As they mature they develop to either CD4
surface protein or CD8 surface protein.
The proteins decide what type of T cell they will become.
CD4 cells become memory and helper cells and
CD8 cells become either cytotoxic and suppressor genes.
The definition of cytotoxic is defined as of,
relating to, or producing a toxic effect on cells (
http://education.yahoo.com/reference/dictionary/entry/cytotoxic,
accessed 27 March 2012).
When a CD4 cell
comes across an antigen-presenting cell with an antigen fragment the CD4
becomes a helper cell.
The new cell goes
through mitosis producing identical clones.
The clones begin secreting signaling molecules called cytokines that
activate T cell actions and support the development of other immune cells.
The cytokines that are released from helper T
cells encourage other immune cells like phagocytes, NK cells, and CD8 cells (T
cells).
They attract white blood cells when
necessary and can activate B cells.
There are five classes of antibodies that belong to blood
plasma proteins called gamma globulins.
They play an important part in creating immunity. The term immunoglobulin (Ig) is used when
referring to gamma globulins and each of the five classes have a designated
letter. IgG makes up 75% of immunoglobulin
and are in blood, lymph, intestines, and tissue fluids. This is the only antibody that can cross the
placenta during pregnancy to give the fetus the mother’s immunities. IgM antibodies make up 5-10% and are the
first released in an immune response.
They are in both blood and lymph and cause foreign cells to agglutinate
(clump). IgA antibodies make up 15% and neutralize
infectious pathogens. They are in a mother’s
milk and are passed to the baby. This is
why health professionals recommend mothers to nurse their baby. They are in areas of the body covered by
mucus membranes. IgD are antibodies located in blood, lymph, and B cells. They make up only 1% and there function is
unclear. IgE antibodies are the rarest
with only 0.1% contained. They activate
the inflammation response by triggering the release of histamine which causes
our allergies. Antigens provide all the
information the immune system needs to know about foreign substances. Through a lock and key system the immune
system can provide a key (antibody) for every lock (foreign invader).
Cytotoxic T cells job is to kill any abnormal or foreign
cell. When mature CD8 cells meet an
antigen-producing cell with a antigen fragment the T cells begin producing
clones of killer T cells. They are the
only T cell that directly attack and destroy other cells. Killer T cells circulate through the blood
and lymph. Once they are activated they
search for antigens they are familiar with.
They can also go to an infection site or to a tumor where they release
toxic chemicals. T cells that become
memory cells keep receptors off the antigen that originally stimulated its
production.
Sadly the reason AIDS has been so devastating is because the
virus that caused AIDS (HIV) destroys helper T cells. The body becomes susceptible to diseases and
weakens the body’s ability to mount a huge immune response. People with AIDS die from the disease the
body can’t fend off.
HIV Virus
Immune Memory creates Immunity
When your body is exposed to an antigen there are many
defense systems in place. One of those
defenses is your body’s immunity or memory.
Three to six days after antigens first appear the immune response kicks
in. B cells that are precise to the
antigen develop and multiply into plasma cells.
Between 10-12 days antibody concentrations that have been constantly
rising now level off. The memory cells
that create a person’s immunity from pathogens become present. So the next time that person is exposed to
the same pathogen the memory cells bind to the pathogen within hours. This is much faster that the first time the pathogen
was first introduced. Also antigen
concentrations rise much faster during the second exposure than the first exposure. Memory cells live a long time and can create
a second response to a pathogen over a person’s lifetime. Other memory cells are used for fighting
bacterial infections such as tetanus has to be revitalized every ten
years. It is easy to get the cold and
flu because there are over 100 different viruses that cause them. These viruses evolve quickly and are
constantly changing their antigen. Viruses
are constantly doing this to survive and are always evolving.
Immunity
Medical Assistance in the War against Pathogens
The way to help a body’s immunities is by immunizing which
involves giving a vaccine. Most vaccines
are made out of dead or weakened pathogens.
Other vaccines are made from genetically altered organisms that make a
specific antigen. When a vaccine has
pathogens that have been weakened there is the possibility that it could
actually cause the disease. It takes a
lot of time, money, and research to make vaccines. Also vaccines only offer immunity to one
specific pathogen so for every additional pathogen another vaccine is
needed. People who are immunized have a
better rounded immunity than those who aren’t immunized. Having a high immunity can be highly
beneficial because more than 50,000 Americans die yearly from infections that
could have been prevented.
When a person already has a pathogen a procedure called
passive immunization can help. A shot of
gamma globulin usually of IgG antibodies gives the person the antibodies that would
be produced if the person had immunity.
Passive immunization is very different than immunizing because it
doesn’t last a long time. This is
because the persons B cells were not activated so memory cells for that
pathogen never developed. Passive immunization
has been very beneficial in treating common viral infections, bacterial
infections, and Rh incompatibility of mother and fetus.
Antibodies made in laboratories from cloned offspring of B
cells are called monoclonal antibodies.
They have been useful in research, testing, and cancer treatment because
large amounts can be made inexpensively.
The technique for making monoclonal antibodies includes removing B cells
from a mouse’s spleen. This is done
after the mouse after a mouse is immunized with a specific antigen that
stimulates the production of B cells.
The B cells are then bonded with cancer cells (myeloma) to create hybrid
cancer cells (hybridoma). This creates
the sought after traits from both cells. The hybrid cancer cells are grown in cultural
dishes. Then the desired antibodies are
separated out, cloned, and then mass produced.
The antibodies are harvested and made into pure monoclonal antibodies. Test that use monoclonal antibodies are home
pregnancy tests, prostate cancer screening, testing on flu, hepatitis, and
HIV/AIDS.
The word antibiotic means “against life”. Antibiotics kill all good and bad bacteria
and restrict bacterial growth. They were
first made from molds and funguses but are now only made in labs. There
are many different types of antibiotics.
There are ones that are for specific bacteria and others that are called
broad-spectrum antibiotics that are used for many different types of
bacteria. Antibiotics will not do
anything to a virus because viruses can’t reproduce without a host. Due to over prescribing and people insisting
they need antibiotics, when they don’t bacteria’s have evolved and becoming
resistant to antibiotics.
Inappropriate Immune System Activities causes Problems
Approximately 10% of people living in North America suffer
from allergies. Some are mild and others
can be life threatening. An allergy is
caused by the body responding to what it thinks is a pathogen but is only
something causing an allergic reaction. An immune response is triggered causing B
cells to then produce IgE antibodies that bond to most mast cells and
basophils. The second time and all following
times, when an allergy is presented in the body the body has the same reaction
but also releases histamine. Histamine
causes the body to feel warmth, redness, itching, swelling, mucus production, and
pain. Allergens that are absorbed or
injected into the blood stream are quickly carried though the body. Some severe allergies cause it hard to
breath, cause stomach cramps, major swelling, and dropping of blood
pressure. When someone has any of these
symptoms they are in anaphylactic shock and needs immediate medical care. There are treatments a person with severe
allergies can take when they come in contact with an allergen. Allergy shots cause the body to produce IgG
antibodies that combine with the allergen blocking reaction.
Sometimes the body can’t distinguish between self and non
self. When this happens the immune
system produces antibodies and cytotoxic T cells that target the body’s “self”
cells. These conditions are called
autoimmune disorders. It is estimated
that 5%of adults in North America have and suffer from a type of autoimmune
disorder. Of the 5%, two-thirds of these
people are women. There are different
reasons and thoughts of what cause this to happen and in some cases an antigen
was never exposed to the immune system in fetal development. The antigens were never programmed as
“self”. Other times antibodies are
produced against foreign antigens cross react with a person’s own tissues. As of right now there isn’t a cure for
autoimmune disorders. Treatments for
autoimmune disorders include depressing the body’s defense mechanisms and
relieve symptoms. Diseases include multiple sclerosis that is an
advanced disorder of the central nervous system, type 1 diabetes that affects
the pancreas, Lupus that makes the body attack its own connective tissue, and
rheumatoid arthritis involves inflammation of synovial membrane of certain
joints. The inflammation ultimately
destroys joint cartilage and bone.
Chapter 10
Respiration Takes Place throughout the Body
Humans can live for many days without food and water but
will die within minutes without oxygen.
The respiratory systems job is to exchange oxygen and carbon
dioxide. When we take a breath, oxygen
is taken out of the air and when we exhale carbon dioxide is released. Some may wonder where oxygen comes from. Oxygen is produces by plants. Carbon dioxide is absorbed by plants and is
used in producing energy for the plant through a process of photosynthesis. The outcome of this process is the production
of oxygen. Sometimes people might forget
how important and vital plants really are to us.
Respiration is defined through different methods of
breathing. They are external respiration
( gas exchange between blood and oxygenated air), internal respiration (gas
exchange between blood and tissue fluids), and cellular respiration (uses
oxygen to produce APT in cells). The act
of breathing isn’t only done by the lungs.
Bones, muscles, and nerves also help with the breathing process. The respiratory system not only deals with
breathing but also with a person’s voice.
The ability to produce sound or vocalizations has helped cultural
development and the exchange of information which is essential in the survival
of humans.
The Respiratory System Consists of Upper and Lower
Respiratory Tracts
The respiratory system is a system of passageways that
transports air in and out of the lungs.
The
respiratory system is divided into upper and lower respiratory tracts.
The upper respiratory tract is made up of the
nose, nasal cavity, and pharynx.
The
definition of pharynx is the hollow tube that is about 5 inches long and starts
behind the nose and ends at the top of the trachea (windpipe) and esophagus.
The pharynx serves as a vestibule or entryway for the trachea and esophagus.(
http://www.medterms.com/script/main/art.asp?articlekey=4863,
accessed 5 April 2012).
The lower respiratory
tract begins with the larynx (voice box) and also contains the trachea, two
bronchi (branching from the trachea), and the lungs.
When you breath in through you nose not only do you receive
oxygen but your nose also allows you to smell, screens out partials in the air,
and helps to provide the tone of your voice.
The nasal cavity is divided into two sections by the nasal septum. As we breathe in nose hairs start filtering
out particles in the air. Next the air
flows to the nasal cavity that is lines with epithelial tissue and lots of
blood vessels. The blood vessels warm
the air and the epithelial tissue secretes mucus to humidify incoming air. The epithelial tissue is covered in cilia
(hair like). In cold temperatures cilia
slow down and because they slow down mucus pools making you have a runny
nose.
The sinuses are the air spaces in the skull that are lined
with tissue and secrete mucus. Sinuses
drain into the nasal cavity and when you cry your tear ducts not only release
tears but also drain into the nasal cavity.
This is the reason why your nose runs when you cry. Air enters the pharynx (throat) that connects
to the mouth and nasal cavity to the larynx or voice box. The upper pharynx stretches from the nasal
cavity to the roof of the mouth. The lower
pharynx is the passageway for both air and food. At this point food goes to the esophagus and
air travels to the lower respiratory tract.
Next let’s look at the components in a little more
detail. The larynx (voice box) expands
for approximately 2” below the pharynx.
The larynx has two important components the epiglottis and the vocal
cords. The epiglottis is a flexible flap
of cartilage that is located at the beginning of the larynx. The flap can close or remain open. It
closes whenever we eat or drink and remains open as we breathe. This flap routes everything where it needs to
go. The vocal cords are made up of two
folds if connective tissue that extend across the airway. Then surrounding that opening is the glottis. The vocal cords are supported by ligaments
and are encased in a cartilaginous structure called the Adams apple. The sounds we produce are mainly done by the
vocal cords but also by the tongue and teeth.
When we are not talking the vocal cords are open and relaxed. As soon as we begin talking the vocal cords
stretch tightly across the tracheal opening and vibrate (producing sound) as
air flows past. The tighter the vocal
cords are stretched the higher your tone is.
The pharynx, nose, and nasal sinuses amplify and enhance a person’s vocal
tone.
Next the trachea better known as the windpipe extends from
the larynx into the left and right bronchi.
The trachea is made of many C shaped cartilaginous incomplete rings that
are held together by muscle and connective tissue. The trachea is lined with cilia covered
epithelial tissue. The tissue secretes
mucus that helps trap partials and move them away from the lungs. If the trachea becomes blocked and isn’t
unblocked within a few minutes the person will die. When someone is choking the throat stimulates
a cough reflex in the attempt to dislodge the item in the trachea.
The bronchi are the left and right airways that branch from
the trachea. The bronchi divide and
divide into smaller bronchi. As the
airways get smaller the amounts of cartilage is reduced and are now called
bronchioles. The smallest bronchioles
are 1 millimeter or less in
diameter. Besides transporting air the
bronchi and bronchioles also clean and warm incoming air to body
temperature. They also humidify the air
before it reaches the lungs.
People who smoke have extra mucus production but cilia stop
working correctly due to the smoke.
Smokers cough is the constant coughing due to the body’s attempt to
dislodge mucus from the airways. The
constant amount of extra causes frequent infections because pathogens and irritants
stay in the respiratory tract. Smoking
also increases the risks of cancer, bronchitis, and emphysema.
Healthy Lungs Smokers
Lungs
Last the lungs are the organ that exchanges oxygen and
carbon dioxide. Each lung is enclosed in
the pleural membranes that are two thin epithelial membrane layers. The lungs consist of three lobes in the right
lung and two lungs in the left lung.
Each lobe is full of bronchioles and blood vessels. Lobes have the ability to function
independently of each other and in the case one lobe has to be removed
breathing wont usually be too impaired.
Inside the lungs are bronchioles and at the end of the bronchioles are
300 million air filled sacs called alveoli.
These sacs are at the end of every bronchiole. When looking at a single alveolus, you can
see it is made of a thin bubble of squamish epithelial cells that is only one
cell thick. The combined surface area is
an amazing 800 square feet.
Pulmonary arteries divide into smaller arteries, arterioles,
and end at the pulmonary capillaries.
The capillaries blood is in extremely close contact to the air and
alveoli. Because the air and blood
contact is so close researchers are developing medicines to be administered by
inhaling them. The hope is this method
would be a good alternative to delivering blood via the bloodstream.
The Process of Breathing Involves a Pressure Gradient
The act of breathing involves many different parts of the
body working together. One of those
important parts is a skeletal muscle named the diaphragm. The diaphragm is a sheet of muscle that
separated the thoracic and abdominal cavities from each other. The lungs are stretchable allowing
contracting and expanding. This is
assisted by the pleural cavity that is an air tight cavity. As the cavity expands it allows the lungs to
expand with it. When a person inhales
(inspiration) air is pulled into the lungs ans as a person exhales (expiration)
lung volume decreases and air is pushed out.
At a relaxed state both the diaphragm and intercostal muscles are
relaxed. At a relaxed state the
diaphragm is domed shaped but as soon as someone inhales the diaphragm
contracts abs is pulled flat. At the
same time the intercostal muscles poll the rib cage up and out to also
accommodate breathing. Then when a
person exhales the diaphragm and intercostal muscles return back to a relaxed
state. As this happens the lungs become
smaller due to pressure reduction within the lungs.
When a person is relaxed and breathing quietly no effort has
to be used with inhaling or exhaling. But when a person is exercising or
stressed the amount of breathes needed increases abs both inhaling and exhaling
requires extra effort. Also when a
person needs to cough or sneeze the abdominal muscles contract and the pressure
within the abdomen rises.
When relaxed a person takes approximately twelve breaths per
minute. This can be converted to tidal
volume that is used to measure a person’s lung capacity. Each breath is about a pint (500ML) of
air. With each new breath only about
350ML of air reached the alveoli exchanging oxygen and carbon dioxide. The remaining 150ML stays in the airway and
is called dead space volume. It doesn’t
matter how hard you try to get all the air out of your lungs because it is impossible
to get all the air out. Some air always
stays in the lungs. A spirometer is a
machine that measures a person’s lung capacity. All someone has to do is breathe normally
into the machine then they take a huge breath and blow the breath out as hard
as they can. When people have lung
diseases this device can be very useful in diagnosis.
Gas Exchange and Transport occur passively
The human body uses oxygen by cells to create energy. The earth is full of different types of
gasses. Nitrogen makes up 78% of the
earth’s atmosphere. The remaining
percentages of gasses in earth are 21% oxygen, 0.04% carbon dioxide, and all
the other gasses combined make up 1%.
Partial pressure is the percentage of gas composition of combined
gasses. Partial pressure is represented
by the letter P and like atmosphere pressure it is represented by mm Hg. The atmospheric pressure is all the partial
pressures at sea level combined.
When the body exchanges oxygen and carbon dioxide no energy
(ATP) is used. The body’s cells get the
oxygen they need from the surrounding interstitial fluid. Cells are always taking oxygen by diffusion
from the interstitial fluid. Now the
interstitial fluid partial pressure oxygen is lower than it is in arterial
blood. So when blood enters capillaries,
oxygen diffuses into the interstitial fluid which replenishes the oxygen used
by cells for energy. Then carbon dioxide
diffuses out of cells into interstitial fluid and into capillary blood. The goal is to have homeostasis of oxygen and
carbon dioxide throughout the body.
Oxygen is transported through the body by either being
attached to hemoglobin in red blood cells or by being dissolved in plasma. The most common way of transport is to have
the necessary hemoglobin present to transport oxygen. This is because oxygen is not soluble in
water. Only 2% of a body’s oxygen is
dissolved and transported by plasma.
Without hemoglobin the body wouldn’t receive enough oxygen to stay
alive. Hemoglobin binds oxygen the best
when the body’s pH level is neutral and in places that are cool. This is why the lungs are ideal for binding
the oxygen with the hemoglobin.
Once the body has used the oxygen it then needs to get rid
of the carbon dioxide (waste). This can
be done with either being dissolved in plasma, attached to hemoglobin, or in
bicarbonate form. Carbon dioxide is
transported by blood plasma 10% of the time, attached to hemoglobin 20% of the
time, and the remaining amount by converting and transported by
bicarbonate. Most bicarbonate is
diffused out by red blood cells and is transported by plasma to the lungs. Some hydrogen ions that were formed with the
bicarbonate bind to hemoglobin and remain in red blood cells. When this happens the attachment of oxygen
and hemoglobin weakens and cause more oxygen to be released.
The Nervous System Regulates Breathing
There are still more ways the body depends on for
breathing. The pattern is which we
inhale and exhale is established near the base of the brain called the medulla
oblongata. This area is considered the respiratory
center where a group of nerves generates electrically pulses every 4-5
seconds. The impulses travel along
nerves to the diaphragm and intercostal muscles telling the muscles to contract
(inhalation). Then the nerve impulses
tell the diaphragm and intercostal muscles to relax (exhalation). If there is a disorder that interferes with
the impulses then breathing will be affected.
Some people who develop certain breathing disorders die relatively soon
after diagnosis.
The body tries to maintain homeostasis and does well
adapting and correcting mishaps. Cells
in the medulla oblongata can detect carbon dioxide changes in the cerebrospinal
fluid around brain cells. Signals are
then transmitted to the respiratory center causing increased signals to
increase breathing. Other receptors the
measure oxygen is located in the carotid artery and aorta called the carotid
and aortic bodies. When oxygen levels
drop below a certain point the respiratory center increases inhalation to raise
oxygen levels back to normal.
Another way to control breathing is by conscious
control. This is done in the higher
brain centers (cortex) and gives the ability to do many things. With this function a person can hold their
breath or also hyperventilate.
Disorders of the Respiratory
System
When the body isn’t functioning at 100% respiratory
disorders may arise. Some reasons
include cancer, infections, diseases, heart failure, and genetic diseases.
Asthma is defined as a spasm contraction of the bronchial
muscle that is also associated with bronchial swelling and increased mucus
production. As asthma attack causes the
bronchi to partially close making it hard to breath. This disorder affects 17 million people just
in North America and is rising all over the world. Some symptoms include shortness of breath,
wheezing, chest tightness, and coughing during physical activity. Asthma is triggered by a range of things
including viruses, air particles, exercise, tobacco smoke, and a large range of
allergies. Most asthma attacks are
caused by a hyper active immune system.
There are drugs to open airways and reduce swelling but treatment is
mainly focused on prevention.
Emphysema is a chronic lung disorder that is caused by
damaged alveoli. It begins with the
destruction of connective tissue in small airways and results in the airway not
staying open correctly. High pressure within the lungs eventually
damage alveoli permanently. This reduces
the surface area that is needed for diffusion.
One form of emphysema is inherited but most forms are caused by inhaling
smoke or long term pollution exposure.
Bronchitis is inflammation of the bronchi. This disorder creates a persistent cough and
large amounts of phlegm. Sometimes it
can go away after a few days and sometimes it can continue over many
years. People who have bronchitis are
usually smokers or people who live in highly polluted areas. Infections caused by bacteria can be taken
care of with antibiotics. Other
solutions are also available if a doctor feels they are helpful.
Cystic fibrosis is an inherited disorder that is caused by a
single defective gene. The result is
mucus producing cells in the lungs that constantly produce thick, sticky
mucus. This disease can affect other
organs as well and cause frequent infections.
Physical therapy and drugs are used as treatment.
Microorganisms can also cause respiratory disorders and mainly
because the lungs are prone to infections.
The lungs are naturally moist, warm, and covered in a thin fluid layer creating
the perfect environment for microorganisms to flourish. Colds are caused by either the rhinovirus or
coronavirus family. Flu is caused by
viruses in the influenza family. No
medical treatment is available for either the cold or flu. The immune system has a hard time identifying
and fighting viral infections because they are constantly evolving. This makes them hard for the immune system to
recognize.
Pneumonia is when the lungs become inflamed due to an
infection. Some pneumonia is caused by
bacteria and is occasionally caused by viruses.
What happens is alveoli produce extra fluid when they become inflamed,
thus clogging the lungs. This makes the
exchange of oxygen and carbon dioxide difficult. Treatment depends on if it was caused by
bacteria, in which antibiotics are effective or a virus in which other things
are available to help recovery.
Pneumonia is ranked in the top ten for causes of death.
Tuberculosis (TB) is an infection caused by bacteria. People pass this on by spit that is coughed
or sneezed. The immune system fights
this infection well but has the side effect of lung scarring. In less than 5% of cases the bacteria spreads
into the bloodstream. Symptoms include
chest pain, fever, loss of appetite, weight loss, and coughing. A skin test can show if someone has been
exposed to TB. Some strains of TB are
beginning to be resistant to antibiotics.
Botulism is a type of poisoning if the body that is caused
by clostridium botulinum bacteria. Botulism can be found in foods that weren’t
correctly prepared or stored. The
bacteria blocks nerve signals to skeletal muscles. Someone who has botulism poisoning shows
symptoms within 8-36 hours after being infected. Someone who has been infected shows signs of impaired
speech, vomiting, nausea, and trouble swallowing. It can also be fatal is not treated when respiratory
muscles become paralyzed.
Cancer can weaken how air moves through the lungs and also
impairs the exchange of oxygen and carbon dioxide. Lung cancer can take years to develop and
occurs mostly with past and present smokers.
Some lung cancer symptoms include a chronic cough, wheezing, chest pain,
and coughing up blood. If lung cancer is
cough early enough it is possible to treat the cancer by removing the section
or lobe infected. Another treatment
possibility is done with radiation and/or chemotherapy treatment.
Pneumothorax is when one or more lobes in the lung
collapse. This can happen by the onset
of disease or by an injury. It can be
life threatening and can require medical attention. Atelectasis is defined as either a fluid
buildup in the lungs or a problem with exchanging oxygen and carbon dioxide
resulting from an alveolar collapse. This
can occur after someone has had surgery.
Because of the possibility of this happening patients are encouraged to
start walking, talking, and coughing as soon as they can to prevent atelectasis. Pressure form a ventilator can also help to
force alveoli open if necessary.
Congestive heart
failure is when the heart gradually stops working as effectively. Even though it directly affects the heart it
also impacts the lungs. This is because
fluid builds up in the lungs interstitial spaces between capillaries and
alveoli. This reduces the exchange of
oxygen and carbon dioxide. Treatment of
this is done by trying to improve the heart.
Once the heart improves the lung function will also improve.
