Download Class Notes - Gonzaga High School

UNIT 2.3 CIRCULATORY SYSTEM
Circulation


Transport system which links the cells of an organism with its environment
Unicellular organisms (e.g. bacteria) do not require a transport system
Two major types of circulatory systems:
1.
Open Circulatory System

Found in smaller organisms such as arthropods

Blood is contained in blood vessels for only part of the time

Blood bathes the internal organs directly
2.
Closed Circulatory System

Blood is always contained in blood vessels

Materials are exchanged between the blood and cells

Found in large complex organisms (e.g. humans)
Two separate transport systems:
1.
Blood
2.
Lymph
The major organs of the circulatory system are:
1.
2.
3.
Blood
Blood vessels
Heart
1.
Blood

An adult human has between 4 to 6 liters of blood
Functions:




Transport materials to and from the body cells
Distribute heat in the body
Provides defence against invading organisms
Serves as a regulator in the body (homeostasis)
1
Blood is composed of two major divisions:
A.
Plasma (55%) – solvent


This is the liquid component of the blood
A clear, straw-colored liquid
Composed of:
1)
Water (90%)
2)
Dissolved substances (10%)
Salts
Glucose
Amino acids
Fatty acids
Vitamins
Enzymes
Hormones
Wastes
Proteins









Three major forms of protein:
a)
b)
c)
B.
Fibrinogen – important in blood clotting
Globulin – body defence
Albumin – helps requlate water balance in the blood (osmotic balance)
Formed Elements (45%) – solute


Solid component of the blood
Consists of red blood cells (RBCs), white blood cells (WBCs), and platelets
1)
RBCs (Erythrocytes)







5 million/mm3
30 trillion/adult
produced in bone marrow
disc shaped possessing no nuclei
life span of 120 days
2 million destroyed per second. New ones are produced at the same rate
dead ones are removed from circulation by the liver and spleen
2


contain the protein hemoglobin which combines with oxygen to form
oxyhemoglobin. This occurs at the lungs
transports carbon dioxide from the body cells to the lungs. Does this in two ways:
a)
b)





2)
One disease associated with RBCs is anemia
Caused by either a lack of hemoglobin or too few RBCs
Symptoms include dizziness, weakness, and pale color
Sickle-cell anemia is a hereditary disorder caused by an abnormal form of
hemoglobin
The cells are sickle shaped and therefore carry little O2 and tend to become
clogged in the blood vessels
WBCs (Leukocytes)





8000/mm3
60 billion/adult
produced in the bone marrow and lymphatic tissue
larger than RBCs and contain a nucleus
defends body against disease by:
a)
b)





3)
CO2 combines with the hemoglobin to form carboxyhemoglobin
CO2 combines with water found inside the cell
engulf (eat) bacteria
produce antibodies
five different types
can move out of blood vessels into body tissue
increase in numbers at times of infection (30,000 or more per mm3)
one disease associated with the WBCs is leukemia
this is a cancer of the blood and is caused by abnormally high levels of WBCs
Platelets






300,000 per mm3
1.5 trillion per adult
produced from bone marrow when bits of cytoplasm pinch off from larger cells
within the marrow
called cell fragments
contain no nucleus
play a major role in blood clotting
3
Blood counts as a diagnostic tool



low RBC count (below 5 million per mm3) indicates anemia
high WBC count (30,000 per mm3) indicates infection in the body
abnormally high WBC with ever increasing numbers indicates leukemia
Blood Clotting


maintains homeostasis by preventing the loss of blood from torn or ruptured blood
vessels
major stages are as follows:
1.
blood platelets strike a rough surface such as that created by a torn blood vessel, breaks
apart and releases the protein thromboplastin
2.
thromboplastin in the presence of Ca2+ causes the protein prothrombin to change into
thrombin
3.
thrombin acts as an enzyme causing fibrinogen to form fibrin
4.
fibrin is insoluble and settles out as long strands trapping RBCs and platelets forming a
blood clot
Blood Typing





a person’s blood type depends upon the presence or absence of two special proteins,
called antigens A and B, on the surface of the red blood cell
an individual is born with antibodies against red blood cell antigens that his or her blood
does not have
antibodies are proteins formed within the blood that react with antigens
these special antibodies are called agglutinins
e.g. blood type A has antigen A on the RBC but contains anti-B antibodies or agglutinins
in the plasma
Major Blood Types
TYPE
A
B
AB
O
ANTIGEN
A
B
A and B
none
AGGLUTININ (ANTIBODIES)
Anti-B
Anti-A
none
Anti-A, Anti-B
4
Blood Transfusions


blood type is important in blood transfusions
if a person gets the wrong blood type the agglutin in his or her plasma will react with the
antigen on the RBC of the donor
the blood will agglutinate or clump
blood vessels may become block eventually leading to death


To see if agglutination will occur follow these steps:
1.
identify the recipient and the donor
2.
find the agglutinin of the recipient
3.
find the antigen of the donor
4.
if the agglutinin of the recipient and the antigen of the donor are the same, agglutination
will occur and therefore a transfusion cannot take place
To Clump or Not to Clump?
Donor Blood Type
A
B
O
Recipient Blood
Type
AB
O
A
B
AB
Universal Donor is blood type ________
Universal Recipient is blood type _________
Blood Transfusion Chart
Type
Antigen
Agglutinin
Receive from
A
B
AB
O
Rh Factor



a protein found on the RBC
first discovered in rhesus monkeys
~85% of humans have the Rh factor on their RBCs and are said to be Rh+
5
Give to

the other 15% lack the Rh factor and are said to be Rh-
Rh Factor & Blood Transfusions



A person with Rh+ blood can receive both Rh+ and Rh- blood
A person with Rh- blood can only receive Rh- blood
If given Rh+ blood the recipient’s blood plasma produces anti-Rh antibodies causing the
blood to agglutinate
Donor
Rh+
Recipient
Rh-
Rh+
Rh-
Rh Factor and Pregnancy






Can be a problem if a pregnant woman has Rh- blood and the baby is Rh+
Circulatory systems of mother and baby are usually independent of one another
There is sometimes a small mixing of blood during birth
The mother’s blood plasma will produce anti-Rh antibodies to fight the foreign Rh+
protein
Doesn’t happen during first pregnancy
On subsequent pregnancies the anti-Rh antibodies from the mother’s blood can enter the
baby’s blood and destroy its Rh+ blood cells
Treatment



Problem can be eliminated if the Rh- mother is given an injection of anti-Rh antibodies
called Rho Gam shortly after the birth of each Rh+ child
These antibodies destroy any Rh antigens on the baby’s blood cells that have entered the
mother’s circulatory system
The mother’s immune system does not have to produce anti-Rh antibodies and there is no
problem with the next Rh+ baby
Blood Vessels
Artery




Carry blood away from the heart
Branches as it enters organs
Smallest are arterioles
Made of thick muscular walls
6





Elastic and stretch and contract as the heart pushes blood through them. This is called a
pulse.
Located deep inside the body for protection
Carry blood rich in O2 with the exception of the pulmonary artery
Artheroschlerosis – arteries become hardened and lose their elasticity
Major cause of artheroschlerosis is a buildup of cholesterol on the walls of the arteries
Capillaries








Carry blood from arterioles to venules
Walls are one cell thick and very narrow
Site of all exchanges between the blood and body cells
Fitted with rings of muscle on the arteriole end to control blood flow through themselves
The opening and closing of the rings of muscle directs blood to where it is needed
Most numerous blood vessels in the body
Not all capillaries are open at the same time
Damaged capillaries will seep blood causing a bruise
Vein










Carry blood to the heart
Smallest veins found in the organs are venules
Walls are thinner and less elastic than arteries
Little pressure on them
Found closer to the surface than arteries
Carry blood poor in O2 with the exception of the pulmonary vein
Valves allow blood to flow in one direction – towards the heart
When a valve fails blood builds up in a vein
Walls become stretched and lose their elasticity
Condition is called varicose veins
Heart
Location


Found in the thoracic or chest cavity under the ribs and sternum between the two lungs
Surrounded by a protective sac called the pericardium
7
Structure



Composed mostly of cardiac tissue which consists of a branching, interlocking network
of individual cardiac muscle cells
Cells contain many mitochondria
Divided into four chambers:
a)
b)
c)
d)














Right atrium
Right ventricle
Left atrium
Left ventricle
Top chambers or atria (atrium) receive blood from circulation
Have thinner walls than ventricles
Bottom chambers or ventricles pump blood out into circulation
Have thick muscular cell walls
Divided into left and right hand sides by a muscle called the septum
Right side consists of right atrium and right ventricle
Carries deoxygenated blood into the lungs and is called pulmonary circulation
Left side consists of left atrium and left ventricle
Carries oxygenated blood out to the body organs and is called systemic circulation
Systemic system consists of a number of major branches:
1)
Coronary Circulation

Supplies blood, along with its nutrients and oxygen to the muscle cells of
the heart
2)
Hepatic-Portal Circulation

Carries blood from the digestive tract to the liver to maintain the balance
of nutrients (e.g. glucose) in the blood
3)
Renal Circulation

Carries blood to and from the kidneys so that wastes can be removed from
the blood and excreted by the kidneys
A four chambered heart is the most efficient heart possible since it completely separates
deoxygenated and oxygenated blood
Heart is often called a double pump
Valves are present in the heart
Control the direction of blood flow through the heart:
1)
Atrioventricular valves (A-V valves) – two types:
8
2)
a)
Tricuspid valve:
Found between the right atrium and right ventricle
b)
Bicuspid or Mitral valve:
Found between the left atrium and left ventricle
Semilunar valves – two types:
a)
Pulmonary artery semilunar valve
Located at the entrance of the pulmonary artery as blood exits the right
ventricle
b)
Aortic artery semilunar valve
located at the entrance to the aorta as blood exits the left ventricle
Defective Heart Valves


improper closing of heart valves causes a backflow of blood at certain times during the
heartbeat cycle
produces an abnormal heart sound known as a heart murmur
Blood Flow
Deoxygenated blood:
All throughout the body  superior vena cava/inferior vena cava  right atrium  tricuspid valve
 right ventricle  semilunar valve  pulmonary artery  lung
Oxygenated blood:
Pulmonary vein  left atrium  bicuspid valve  left ventricle  semilunar valve  aorta  body
organs
Heartbeat Cycle

Consists of two main periods:
1)
2)
Diastole
Systole
Diastole – a period of relaxation for the heart muscle


Right and left atria relax
Blood flows into the right atrium from the superior and inferior vena cava
9



Blood flows into the left atrium from the pulmonary veins
A-V valves open and blood flows from the atria into the ventricles
By the end of this stage the ventricles are about 70% filled
Systole – a period of contraction for heart muscle




Begins with contraction of the atria which forces more blood into the ventricles, filling
them
Ventricles contract causing the A-V valves to close and the semilunar valves to open
Blood is pushed into both the pulmonary artery and aorta
When the ventricles relax a new period of diastole begins and the cycle repeats
Control of Hearbeat





Cardiac fibers interlock forming a network or lattice
Causes the two atria to function as one unit and the two ventricles to function as another
unit
Cardiac muscle has a built in ability to contract
The heart as a whole must work as a unit
This is made possible by the sinoatrial node (S-A node) or pacemaker
Heartbeat is a two stage process:
1.
2.
A current originates in the S-A node, passes over the atria causing them to contract, and
arrives at a second bundle of tissue called the atrioventricular or A-V node
A current moves from the A-V node over the ventricles causing them to contract
Rate of Heartbeat




The rate of heartbeat is regulated by two pairs of nerves which run from the medulla
oblongata (part of the brain) to the S-A node
Right and left cardioaccelerator nerves -> speed up the S-A node
Right and left vagus nerves -> slow down the S-A node
The actual heartbeat observed at any given time is affected by any number of factors such
as:
1)
2)
3)
4)

Amount of O2 in the blood
Blood pressure
Amount of muscular activity
Body temperature
The average heartbeat rate is between 70-72 beats per minute
10
Blood Pressure

The pressure of blood against the walls of the blood vessels as it circulates around the
body
Two major factors affect blood pressure:
1)
2)
1)
Cardiac Output/Arteriole Resistance
Kidneys
Cardiac Output/Arteriole Resistance
Cardiac output consists of two factors:
A.
B.
Stroke Volume – the quantity of blood pumped per beat
Heart Rate – number of times the heart beats per minute


Special nerves involved with blood pressure
If pressure is too low, they signal the S-A node of the heart to increase cardiac
output and cause a constriction in the rings of muscle found on the arterioles
leading into the capillaries
Blood pressure rises
If blood pressure is too high, the nerves signal the S-A node to decrease cardiac
output and cause a dilation in the rings of muscle found on the arterioles leading
into the capillaries
Blood pressure decreases



2)
Kidneys


Regulate the water content of the blood
If blood pressure is too low, the kidney takes less water from the blood and allows blood
pressure to rise
If blood pressure is too high, the kidney takes more water from the blood and allows the
blood pressure to decrease

Measurement of Blood Pressure



Measured by a device called a sphygmomanomter
Measures blood pressure in terms of the height of a column of mercury in millimeters
Two parts to the measurement:
1)
2)
Systolic pressure – highest pressure when the ventricles contract
Diastolic pressure – lowest pressure created when ventricles relax
11





The pressure is recorded as systolic/diastolic
The normal blood pressure for an adult is 120/80
Blood pressure changes as blood moves away from the heart
It is highest in the arteries dropping as it passes into the arterioles and capillaries
It is lowest in the veins
Major Problems Associated with Blood Pressure
1)
Low blood pressure

Results in poor circulation
2)
High blood pressure (Hypertension)

A common and dangerous condition caused by factors such as smoking, obesity,
artheroschlerosis

Can lead to several serious problems:
a)
b)
Heart attack
Weaker arteries may eventually rupture. If this occurs in the brain it is
called a cerebral hemorrhage or a stroke
Lymphatic System











A secondary circulation system that parallels blood circulation
Collects lymph that has diffused from the blood at the arteriole end of a capillary but has
failed to be absorbed at the venous end of the capillary
Most lymph diffused from the arteriole end is absorbed into the venous end of the
capillary
System consists of blind-ended tubules that collect unabsorbed lymph and pass it to the
lymphatic vessels
Lymphatic vessels merge into the thoracic duct which puts lymph into the blood through
the subclavian vein
This restores the fluid portion of the blood lost at the capillaries
Lymph nodes are scattered throughout the body
They filter out bacteria and dead cells from the lymph
Destroyed by WBCs found in the blood
Lymphatic system has no pump
Circulation is the result of body movement
Disease and the Immune System
Disease: any change in the body, besides injury, that interferes with the normal functioning of
the body is called a disease
12
Two types of diseases:
1)
2)
Non-infectious
Infectious
1)
Non-infectious

Often called functional diseases

An organ does not work properly

E.g. cancer, heart disease
2)
Infectious

Caused by a disease producing microorganism called a pathogen

E.g. measles, colds, flus, AIDS
Defence – Immunity
The body’s defences against pathogens include:
1)
2)
Non specific defences
Specific defences
Non-Specific Defences



First line of defence against pathogens
Guard against all types of foreign organisms
Major forms of non-specific defences include:
A.
Physical and Chemical Barriers








Skin
Membrane linings
Sweat
Saliva
Stomach acid
Urine
Tears
Mucus
B.
Inflammatory Response


Causes redness, swelling, pain, and warmth in the area of infection
Cells damaged by the infection release chemicals that cause an increase in blood flow to
the infected area
13








Results in WBCs called phagocytes being transported to the site of infection
Phagocytes ingest the pathogens and damaged tissue via phagocytosis
Results in the formation of pus
Sometimes the infection gets into the lymphatic system and causes the lymph nodes to
swell
If the infection is serious more phagocytes will form
If this does not kill the infection, chemicals are released that increase body temperature
Called a fever
Two purposes of a fever:
a)
b)
Kills microorganisms that cannot survive higher temperatures
Slows down microorganisms, giving the WBCs a chance to destroy them
C.
Interferon



If the pathogen is a virus another defence system occurs
Interferon produced by cells that are infected by a virus
Causes non-infected cells to produce an enzyme that blocks reproduction of the virus
Specific Defences









Second line of defence
Immune system becomes active
Antibodies or specialized cells are produced to inactivate foreign substances or cells
Immune system includes all parts of the body that are involved in the recognition and
destruction of foreign materials
Body must be able to recognize its own substances (self) and foreign substances (nonself)
Antigen – any foreign substance that triggers a specific defence
Antigens are usually proteins but can be polysaccharides, lipids, or nucleic acids
Antigens are carried on the surface of bacteria, viruses, fungi, and other pathogens that
may enter the body
The response to an antigen is called an immune response
Types of Immune Responses
1.
Primary Immune Response


Occurs when an antigen enters the body for the first time
Takes up to 5 days for the body to recognize the antigen and start production of
antibodies
Takes another 10-15 days for the antibodies to build up

14
2.
Secondary Immune Response


Occurs only if an antigen that enters the body enters a second time
Shorter response time of only 1-2 days for antibody production
B Cells, T Cells and Immunity









T-Cells
lymphocytes that mature in the thymus
B-Cells
Lymphocytes that mature in the bone marrow
Produce antibodies
When a macrophage ingests a pathogen it displays the antigens on its surface
Helper T cells link to the antigen
Activates the production of killer T cells and B cells
Functions of killer T cells include:
a)
b)
c)
d)


B-cells begin producing antibodies
Antibodies function by:
a)
b)
c)
d)

Puncture holes in cell membrane of pathogen
Attacking cells infected with viruses
Destruction of mutated cells
Rejection of organ transplants
Combining with antigens on the pathogen to make it more recognizable to
macrophages
Preventing access to other cells
Preventing toxins from becoming attached to cell receptors
Preventing viruses from entering host cells
Once the pathogen is neutralized, suppressor T cells limit the activities of B cells and
other T cells
Immune System’s Memory


Special B and T cells called memory cells remain in the body after an attack
If the same antigen enters the body again memory B cells produce a large number of
antibodies to destroy the pathogen
Immunity – the ability to resist a specific disease
15
Types of Immunity
Two types:
1)
2)
Active Immunity
Passive Immunity
1.
Active Immunity



Body produces its own antibodies to attack a specific antigen
Long lasting
Develops in two ways:
a)
b)
When a person had the disease
By vaccination of a weakened or milder form of the pathogen
2.
Passive Immunity


Borrowed immunity
Person receives antibodies from another person or animal that has been infected with an
antigen
Temporary (about 30 days)
Faster acting
Most common example is between mother and baby



Immune System and Organ Transplants



Body recognizes transplanted organs as foreign to the body and tries to fight them as if
they were a pathogen
Results in destruction of the transplanted organ
Controlled in two ways:
a)
b)
Donor and recipient are closely matched
Recipient is given immunosuppressant drugs to suppress the immune system
AIDS – Acquired Immune Deficiency Syndrome



Caused by the human immunodeficiency virus (HIV)
Virus attacks helper T cells of the immune system
Virus enters the T cell and remains dormant within the cells for months of even years
without producing any signs or symptoms
16
Several significant properties:
1)
2)



Able to mutate giving it the ability to produce different strains e.g. HIV-1 was identified
in 1981, HIV-2 was identified in 1982.
Causes changes in the cell membrane of the helper T cell.

Helper T cells fuse together

Allows the virus to pass from cell to cell without entering the bloodstream and
becoming exposed to antibodies in the blood
When HIV becomes active the individual develops AIDS
The virus reproduces, spreads, and destroys helper T-cells
The T cells become a HIV factory
Some possible triggers for HIV activation are:
1)
2)
Other co-infections
Contain a special activation gene



Decrease in helper T cells weakens the immune system
The body loses its ability to fight disease
Becomes more susceptible to opportunistic infections and malignancies
Spread of HIV
1)
2)
3)
Sexual contact
Blood-to-blood contact
Mother to fetus during pregnancy or at time of birth. In rare cases through breast milk
Prevention of HIV and AIDS
1)
2)
3)
Abstinence from sexual activity
Use of a latex condom plus spermicide
Avoid sharing of needles during intravenous drug use
17