module 15 cardiovascular system blood, lymphatic...

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Objective 1. Characterize the properties of the blood that make it a connective tissue, and

describe the general functions of the blood.

Blood is one component of the

cardiovascular system, the others being the

heart and blood vessels. As the body’s

transport medium, the blood provides a

means to transport oxygen, carbon dioxide,

hormones, and nutrients. The blood also

contains most of the cells, proteins, and

chemicals required to initiate and support

resistance to diseases. Body temperature

and pH are also regulated by the blood.

Because the blood has access to the entire

body, disorders and diseases associated with

the blood are not localized disorders.

All connective tissues share similar properties; they have cells and an extracellular matrix.

Blood fits these parameters. The blood contains various types of cells and cell fragments,

suspended in an extracellular matrix called the plasma.

The blood has three basic functions: transportation, regulation, and protection. Each of the

individual components of the blood has a specific function. Together, they provide a very

efficient means of delivering nutrients and removing wastes to and from all areas of body.

Every cell in the body requires a continuous supply of oxygen and nutrients. Restricting

the blood supply to a tissue, even for a short period of time, will result in some amount of

cellular death. This is exactly what happens in the majority of heart attacks and strokes; the

blood supplies to the heart and brain become blocked and the cells are injured or die.

Assignment: Tortora, p. 690 or Wiley Plus – 19.1 Functions and Properties of Blood

Module 15

Cardiovascular System

Blood, Lymphatic System & Immunity

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Objective 2. Describe the physical characteristics of the blood.

The blood has a number of physical characteristics that give it its functional properties.

Assignment: Tortora, p. 690 or Wiley Plus – 19.1 Functions and Properties of Blood

Property Characteristic

Viscosity Thicker than water due to solutes, colloids, and suspended formed

elements

Temperature 38o C (100.4o F)

pH Slightly alkaline, 7.35-7.45

Color Variable shades of red depending on the amount of oxygen present

Volume 4-6 liters depending on gender and body mass

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Objective 3. Identify and describe the components of whole blood.

Blood has two main components, the formed

elements (mostly cells) and plasma. The

term formed elements sounds like a weird

term for the cellular components of the

blood, but it is accurate. The formed

elements consist of the red blood cells

(RBCs), the white blood cells (WBCs) and

the platelets (thrombocytes). The reason

they are called formed elements is because

of the platelets; they aren’t cells; they are

fragments of cells.

When a tube of whole blood is spun in a

centrifuge, the denser cells will sink to the

bottom of the tube, and it leaves the less

dense plasma on top. The formed elements

account for about 45% of the total volume,

plasma 55%. It is very rare for a patient to

receive a whole-blood transfusion. They

always get one or more of the components,

whether it is RBCs, plasma, or platelets,

depending on their need.

When a person donates

blood, the laboratory will

spin the bag in a specially

designed centrifuge to

separate the blood

components.

Blood plasma is a clear,

yellow liquid. It is 92%

water and 8% solutes. The

majority of the solutes (7%

of the 8%) are plasma

proteins.

Assignment: Tortora, pp. 691-693 or Wiley Plus – 19.1 Functions and Properties of Blood

590

Objective 3 (continued). Identify and describe the components of whole blood.

There are many types of plasma proteins, and they have individual functions, frequently as

carrier molecules, but collectively, they contribute to the osmotic balance of the blood. The

hepatocytes of the liver produce the majority of the plasma proteins. They include the

albumins (54%), the globulins (38%) and fibrinogen (7%), a clotting protein. The remaining

1% of plasma is made up of miscellaneous solutes: electrolytes, nutrients, gases, hormones,

and waste products.

One of the important types of globulins are the gamma globulins. These are also known as

immunoglobulins or antibodies. These plasma proteins are produced in response to organic

molecules that the body recognizes as foreign. They serve as flags for the immune system,

so it knows what needs to be destroyed.

As previously mentioned, the formed elements consist of the red blood cells, white blood

cells, and platelets. Each of these along with the immune system will be addressed in detail

later in this module.

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Objective 4. Define and describe hematopoiesis (hemopoiesis).

Hematopoiesis (hemato - blood; -poieisis - making) is the formation of the formed elements

of the blood. All blood cells begin as pluripotent stem cells in the red bone marrow. These

stem cells can be influenced by the body to

become any of the mature blood cells.

In infants, all of the bones contain red bone

marrow and are actively making formed

elements. As an individual matures, the red

bone marrow in the long bones is replaced

with yellow bone marrow, which is mostly

adipose tissue.

Assignment: Tortora, pp. 693-695 or Wiley Plus – 19.2 Formation of Blood Cells

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Objective 4 (continued). Define and describe hematopoiesis (hemopoiesis).

Proliferation and maturation of blood cells depends on specific cytokines, chemical signals

from one group of cells to stimulate another. Under the influence of these cytokines

(growth factors, colony-stimulating factors, and interleukins) cells differentiate into the

various cell types. The stem cells differentiate into either the myeloid group of the

lymphoid group. The names indicate where the cells are formed and mature. The

immature myeloid (bone marrow) cells differentiate and become red blood cells, platelets,

and many types of white blood cells. The lymphoid cells mature in the lymphatic system

and give rise to a specific group of white blood cells called lymphocytes.

Cytokines Effect

Erythropoietin (EPO) Increases number of early red blood cells in the

bone marrow

Thrombopoietin (TPO) Increases the formation of platelets

Colony-stimulating factors (CSFs)

and interleukins

Increases the production and differentiation of

white blood cells.

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Objective 5. Describe the structure and function of the red blood cells (RBCs).

Red blood cells have characteristics that make them perfect transporters of oxygen: they are

biconcave discs, they demonstrate reversible-deformity, they don’t consume the oxygen

they carry, and they lack a nucleus. Each of these properties is important to the appropriate

function of the RBC.

Their biconcave shape gives them a high surface-to-volume ratio, thus allowing them to

carry a great deal of oxygen in relation to their size. Think of this shape as a donut, but the

hole in the middle doesn’t go all the way through.

Red cells lack mitochondria, so they don’t

produce ATP by oxidative metabolism; they

utilize glycolysis to stay alive. So, they use

glucose for energy, but they transport all of

the oxygen they pick up. This is like a

person carrying around a candy bar and not

eating it. Most people couldn’t do it.

RBCs are required to squeeze through really small spaces, specifically blood capillaries. As

they pass through these small spaces, they become almost torpedo-like, but when they

come out the other side, they revert back to their biconcave shape.

Because a RBC lacks a nucleus, it allows all of the cytoplasmic space to carry oxygen.

Before the nucleus is lost, it provides the instructions to produce hemoglobin, the oxygen-

carrying molecule of the red cell.

Red cells live for approximately 120 days. This isn’t too bad due to the fact that they are

constantly damaged from squeezing through small spaces, and they don’t have a nucleus or

any organelles to repair any damage that takes place. If red cells are damaged, they are

removed from the circulation by phagocytic white blood cells, the spleen, and the liver.

Assignment: Tortora, pp. 695-696 or Wiley Plus – 19.3 Red Blood Cells

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Objective 6. Identify the components of the hemoglobin molecule and describe its

function.

As previously mentioned, hemoglobin is the

oxygen-carrying molecule of the red blood

cell. There are approximately 280 million

hemoglobin molecules in each red cell. One

hemoglobin molecule consists of two main

components, heme and globin. Globin is a

protein that is made up of four-polypeptide

chains, two alpha chains and two beta

chains. Each polypeptide chain has a heme

molecule bound to it. Heme is a ringed

molecule with one iron (Fe2+) atom at the

center. The iron atom is the binding site for

oxygen; each Fe2+ can pick up one oxygen molecule (O2) at the lungs. So, if there are 280

million hemoglobin molecules in a red cell and each hemoglobin molecule has four hemes,

and each heme can pick up one oxygen molecule, one red cell can carry 1.1 billion oxygen

atoms. The total amount of hemoglobin in the blood ranges from 14-16 g/dl.

At the lungs, hemoglobin

has a high affinity for

oxygen; it wants to pick it up

and hold on to it. At the

tissue level, hemoglobin has

a lower affinity for oxygen.

Hemoglobin wants to let go

of oxygen, thereby allowing

it to diffuse into the cells. It

doesn’t do any good to pick

up oxygen and just hold on

to in the blood. Hemoglobin

also picks up a little bit of

CO2 from the tissues to

transport back to the lungs

and be exhaled.

Assignment: Tortora, pp. 696-697 or Wiley Plus – 19.3 Red Blood Cells

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Objective 7. Describe the process of erythropoiesis.

Erythropoiesis is part of

hematopoiesis, specifically

relating to the production

and maturation of red blood

cells.

Red cells are produced

continuously (approximately

2 million per second) to keep

up with red cell destruction.

The average person has 4.00-

6.00 x 106 RBCs/mm3 of

blood. If the number of red

cells lost exceeds the

number made, hypoxemia

(too little oxygen in the

blood) will result. In this case,

the lack of oxygen is not due

to problems with breathing;

there just aren’t enough red

cells to transport the

available oxygen around the

body. The decreased

amount of oxygen is

detected in the kidneys and

the kidneys secrete

erythropoietin (EPO), a

hormone to increase the rate

of erythropoiesis. EPO

increases the development of

red cells in the bone

marrow.

Assignment: Tortora, p. 698 or Wiley Plus – 19.3 Red Blood Cells

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Objective 7 (continued). Describe the process of erythropoiesis.

Early red cells are large, they have a nucleus, very little cytoplasm, and they lack

hemoglobin. As a red cell matures, it becomes smaller, increases its hemoglobin content,

and loses its nucleus. The loss of the nucleus results in the red cell gaining its biconcave

shape, but it isn’t mature yet; it still contains some mitochondria, ribosomes, and

endoplasmic reticulum. This almost-mature red cell is called a reticulocyte. These

reticulocytes are released into the blood stream and will mature over the next 1-2 days.

Normally, 0.5-1.5% of circulating red blood cells are reticulocytes. If this percentage

increases, a person has a high rate of erythropoiesis. If it goes down, they have a low rate.

Physicians will try to determine why the person is making more or less than normal.

The relative amount of red cells in the blood can be measured by determining a patient’s

hematocrit (Hct). The Hct is the % of a patient’s whole blood that is occupied by red blood

cells. This averages about 45%, a little higher in men and a little lower in women.

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Objective 8. Define terms associated with increased or decreased numbers of red cells, and

describe examples of these changes.

Polycythemia is the presence of too many red blood cells. Polycythemia can manifest as a

primary or secondary disease. Primary polycythemia is also known as polycythemia vera

(PV). It is an abnormality of the bone marrow causing an overproduction of red blood cells,

and it may also result in an increase of white cells and platelets. The biggest problem with

PV is that it increases the viscosity of the blood which can make the heart work harder and

increase the likelihood of clotting.

Secondary polycythemia is an increase in red cell numbers due to another condition. Any

stimulus that causes hypoxemia can cause the bone marrow to increase the production of

red cells. Examples include smoking, sleep apnea, prolonged exposure to low atmospheric

oxygen, or heart disease.

Assignment: Tortora, pp. 693, 711 or Wiley Plus – 19.2 Formation of Blood Cells & 19.8 Blood Groups and Blood Types (Disorders: Homeostatic Imbalances)

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Objective 8 (continued). Define terms associated with increased or decreased numbers of

red cells, and describe examples of these changes.

Anemia is a decrease in the

normal number of red blood

cells. The various forms of

anemia are classified based

on the size of the red cells

(microcytic, normocytic, and

macrocytic), the amount of

hemoglobin in the red blood

cell (hypochromic and

normochromic) and the

cause of the low red cell

numbers.

Anemia Examples

Type Size Amt. of

Hemoglobin Cause

Hemorrhagic anemia Normocytic Normochromic Bleeding

Iron deficiency anemia Microcytic Hypochromic Lack of iron

Pernicious anemia Macrocytic Normochromic Vitamin B12 deficiency

Hemolytic anemia Normocytic Normochromic Destruction of RBCs

Aplastic anemia Normocytic Normochromic Bone marrow failure

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Objective 9. Define leukocyte, and identify the various types of white blood cells normally

present in the blood.

Leukocyte is another term for a white blood cell. White blood cells (WBCs) are very

different from red cells: they have nuclei, they are larger, they don’t have hemoglobin, and

there are different types with unique functions. There are fewer white cells circulating in

the blood stream than red cells. A normal white blood cell count is 5.0-10.0 x 103 WBCs/

mm3.

WBCs can be separated into

two groups based on the

presence of cytoplasmic

granules. They are the

granulocytes (granular

leukocytes) and the

agranulocytes (agranular

leukocytes). These granules

are visible under a

microscope when the cells

are stained.

The granulocytic group

includes three specific

WBCs: neutrophils,

eosinophils, and basophils.

The names of these cells

come from their staining

characteristics. The granules

of an eosinophil stain red

with an eosin stain. The

granules of a basophil stain

dark purple, and the

granules of a neutrophils

stain somewhere in the

middle.

The agranulocytes do

contain some cytoplasmic

granules but they are much

less prominent and they don’t stain as well and their granulocytic counterparts.

Lymphocytes and monocytes are included in this group.

Assignment: Tortora, pp. 699-701 or Wiley Plus – 19.4 White Blood Cells

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Objective 10. Define and describe conditions related to leukocytosis and leukopenia.

Leukocytosis is an increase in the number of white blood cells. Leukocytosis is a normal

physiologic response, up to a certain point. An individual wants their white cell numbers to

increase as a response to diseases or conditions. Any disruption of homeostasis can cause an

increase in white cell numbers. Common causes would be bacterial infections, viruses,

parasites, stress, temperature extremes, etc.

An increase in white blood cell numbers above 40,000 WBCs/mm3 is never a normal

response. An individual can have a severe bacterial pneumonia and their white count will

not increase to that degree. Levels above 40,000 would indicate an abnormal proliferation

of white cells. Frequently this is one of the various types of leukemia. Leukemia is a cancer

of the blood-forming cells, most often the white cells. Can an individual have leukemia of

early, precursor, red cells or platelets? Yes, but these are rare. In some leukemia cases,

white cell numbers can increase above 300,000 WBCs/mm3.

Leukopenia is a decrease in white cell numbers, and it is never a normal response. There

isn’t a normal physiological reason for a person’s white count to go down. Causes can

include: AIDS, chemotherapy, or bone marrow failure (aplastic anemia).


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Objective 11. Describe the basic functions of the individual white blood cells.

White blood cells provide a powerful

protection against microorganisms and other

injurious agents. Each, based on its

structure, has unique functional

possibilities.

When a patient has an increased white blood cell count, a physician will frequently order a

white blood cell differential analysis. With a differential, the physician wants to know the

percentage of each type of white cell in the blood. This provides information relating to the

patient’s condition. If an individual has an increased number of white blood cells and the

overall percentage of neutrophils is increased, it is likely that they have a bacterial infection

taking place.


Leukocyte % of total WBCs

in blood stream Function

Neutrophil 60-70% Powerful phagocyte, increased in bacterial

infections and inflammation

Lymphocyte 20-25% Increased in viral infections

Monocyte 3-8% Differentiate into macrophages (phagocyte),

present in chronic inflammation

Eosinophil 2-4% Allergic reactions, parasitic infections

Basophil 0.5-1% Function poorly understood, chronic inflammation

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Objective 11 (continued). Describe the basic functions of the individual white blood cells.

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Objective 12. Describe the production and function of platelets.

Platelets, also called thrombocytes, are cytoplasmic fragments of large cells in the bone

marrow called megakaryocytes. These cells are 10-15 times larger than a red cell, and due

to their size, they don’t escape the bone marrow and show up in the blood stream. An

individual megakaryocyte can release 2000-5000 platelets. The normal range for platelets in

the blood is 150-400 x 103/mm3.

Platelets have a very short

lifespan, approximately 5-9

days. Platelets help limit

blood loss by forming a

platelet plug and releasing

chemicals to encourage

vasoconstriction and activate

the clotting process.

Assignment: Tortora, pp. 701-702 or Wiley Plus – 19.5 Platelets

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Objective 13. Define hemostasis and describe the three mechanisms that contribute to

hemostasis.

The term hemostasis, not to be confused

with homeostasis, has a Greek origin,

meaning blood stagnation. It is very

complex process which when activated

causing a cessation of bleeding. There are

three mechanisms involved: vascular spasm,

platelet plug formation, and coagulation.

Vascular spasm is the constriction of

damaged blood vessels. This limits the

amount of blood lost. The vascular

constriction is due to chemicals released from platelets, damage to the smooth muscle of the

vessels, and pain receptor reflexes.

Platelets are very active in the hemostatic process. Think of them as little bags of

procoagulant chemicals. Platelets form a plug through a three-step process. First, the

platelets adhere to the wall of the blood vessel. Second, the platelets release their chemical

contents. This encourages further vasoconstriction and recruitment of other platelets.

Lastly, due to chemical

release, the activated and

newly-recruited platelets

become sticky. The

clumping of platelets is

called platelet aggregation.

With the activation of

enough platelets, a loose

platelet plug is formed.

Assignment: Tortora, pp. 703-705 or Wiley Plus – 19.7 Hemostasis

605

Objective 13 (continued). Define hemostasis and describe the three mechanisms that

contribute to hemostasis.

Everyone witnesses this

event sometime in their life,

some more than others.

When someone cuts

themselves shaving, it is

common practice to place a

piece of toilet paper over the

cut. This keeps blood off

their clothing and it makes

an attempt at stopping the

bleeding. Because the

individual is usually in a

hurry, (that is why they cut

themselves in the first place)

they remove the toilet paper prior to going out into public. They are disappointed to find

out that they begin bleeding again. What happened to the platelets? They are on the toilet

paper, so there isn’t an intact platelet plug. Now, that is embarrassing.

The last mechanism in hemostasis is coagulation. An easy way to think of coagulation is

taking that which is liquid (plasma) and make it a solid (clot) or at least a semi-solid.

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Coagulation is a complex series of enzymatic

reactions that occur in a stepwise or

cascading fashion. Think of the steps as

dominos standing next to each other, ready

to fall, and when injury occurs, it tips over

the first domino. Just like tipping over the

dominos, all of the dominos have to be in

place to get to the end. If one is removed, it

stops. The dominos in this game are called

clotting or coagulation factors. Once one is

activated, the new active form stimulates

the next factor, which activates the next,

and so on. Most of these factors are

synthesized by the liver and they are

enumerated with Roman numerals (factors

I, III, IV, X, VIII, etc.).

There are two separate pathways to activate

coagulation, and they merge to form a common pathway. A person may ask, why are there

so many? The presence of two pathways attempts to guarantee that bleeding stops. Each of

the pathways is activated in a slightly

different fashion, and the name gives a hint

to their activator.

The extrinsic pathway is activated by

damage outside of the vessel, specifically

tissue. A tissue protein called tissue factor

(TF) or tissue thromboplastin is released

from the damaged tissue into the blood

vessels. The extrinsic pathway has fewer

steps and occurs rapidly.

The intrinsic pathway is activated by

substances within or associated with the vessel. Exposed vascular collagen, damaged

endothelium, or activated platelets are all potent coagulation activators.

Objective 14. Describe the process of coagulation: stimuli, pathways, and products.


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Objective 14 (continued). Describe the process of coagulation: stimuli, pathways, and

products.

Regardless of the pathway, the goal is to

merge at a common pathway by activating an enzyme called prothrombinase.

Prothrombinase acts on prothrombin (factor II) to become thrombin. The newly formed

thrombin will activate fibrinogen (factor I) to become fibrin. Fibrin proteins are the

threads that form the clot and strengthen the platelet plug.

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There are a number of cofactors that must be present for clotting factor synthesis and for

coagulation to occur. Vitamin K is a cofactor in the synthesis of clotting factors II, VII, IX,

and X. The mineral calcium is required as a cofactor for almost every step of the

coagulation process. So, a person with vitamin K deficiency or a reduced amount of blood

calcium would have difficulty clotting.

Understanding coagulation helps one

understand the difference between plasma

and serum. Plasma is the liquid portion of

unclotted blood. Serum is the liquid portion

of clotted blood. If a sample of blood hasn’t

been allowed to clot, it still has available,

yet-to-be-activated, clotting factors;

therefore it is plasma. If the sample has

clotted, the clotting factors have been

utilized, so it is serum. This is why a patient

is given plasma, not serum. They don’t

want to limit their ability to clot.

If the clot is stationary, it is

called a thrombus. If it is a

clot that is moving in the

blood stream, it is an

embolus. To complicate

things a little, if it was a

thrombus that detached and

is now moving, it is often

called a thromboembolus.

Objective 14 (continued). Describe the process of coagulation: stimuli, pathways, and

products.

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Objective 15. Compare the fibrinolytic system with the process of coagulation.

Coagulation is not an infrequent event. People, with minor trauma to tissue and blood

vessels, clot multiple times per day, every day. If these clots were allowed to persist and

accumulate, it would cause problems with blood flow. The body has a mechanism to

dissolve these clots. It is called the fibrinolytic system and results in fibrinolysis (clot

dissolution).

As coagulation occurs, substances from both the tissue and the blood activate an enzyme

called plasminogen to become plasmin. Plasmin is a very potent proteolytic enzyme. It

dissolves the clot by digesting fibrin and interferes with new clot formation but inactivating

fibrinogen, prothrombin, and other clotting factors.


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Objective 16. Relate the use of anticoagulants and thrombolytics to the coagulation process.

If someone has, or is prone to forming, clots they are often given anticoagulants. These are

commonly referred to as blood-thinners. They do not change the viscosity of the blood,

and they don’t decrease a person’s hematocrit, so they are not blood-thinners. They do

however inhibit coagulation, so the correct term is anticoagulant.

There are a number of anticoagulants. Some are used for therapeutic reasons and some for

specimen collection. The common goal is to inhibit the coagulation process.

Warfarin is not just used in people. It is used as a pesticide, specifically a rodenticide to

control mouse and rat populations. D-Con® is a common brand people use. It is not a

mouse poison, it is a mouse anticoagulant. The mouse consumes enough over time until

they have a lethal dose. Without the ability to clot, they will simply bleed to death.

It is important to inhibit clotting in high-risk individuals, but what if the person has already

formed clots? What can be done for them? Thrombolytics are medications used to dissolve

clots that are already present.

Assignment: Tortora, p. 707 or Wiley Plus – 19.7 Hemostasis

Anticoagulant Examples

Anticoagulant Use

Heparin Administered intravenously to a stroke or heart attack victim,

also used in surgery and dialysis

Coumadin® (warfarin) Oral medication used to inhibit clotting in high-risk patients

EDTA Present in blood-draw tubes used for blood counts

Sodium Citrate Present in blood collection bags for blood donations

Aspirin Inhibits platelet aggregation

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Objective 17. Describe the development and identification of the ABO and Rh blood

groups.

Red blood cells, like all other cells contain

genetically-determined cellular markers.

These markers provide a cell’s signature.

Through this signature, cells can be

identified. A person inherits genes from

their parents that dictate which markers will

appear on their on their cells, in this case

specifically red cells. Two of the major

blood groups appear from this process, the

ABO and Rh systems. Many other blood

groups exist, but they will not be addressed

in this course.

When a person is blood typed, their cells are

evaluated for the presence or absence of

specific markers. These markers, because

they can react with products of the immune

system, are called antigens. The immune

system can make specific antibodies to these

antigens.

The ABO blood group is the most important

blood group system to consider. A person’s

ABO blood type simply identifies the

presence or absence of A and B antigens on

their red cells, due to the inheritance of

certain genes. Both a father and mother will

pass an ABO blood-type gene to their

offspring. The choices are A, B, or O. If a

person inherits the A gene from at least one

parent, they will have A antigens on their

cells. If they inherit the B gene from at least

one parent, they will have B antigens on

their cells. If they inherit both genes, one

from each parent, they will have both A and

B antigens on their cells.

Assignment: Tortora, pp. 708-709 or Wiley Plus – 19.8 Blood Groups and Blood Types

612

Objective 17 (continued). Describe the development and identification of the ABO and Rh

blood groups.

Lastly, if they don’t inherit

either the A or B gene, they

will be identified as having

the O blood type. The

reason for this expression is

because the A and B genes

are dominant genes. That

means a person will

demonstrate the antigens on

their cells if they inherit the

genes. So, the possible blood

types within the ABO group

are: A, B, AB, and O.

To make things a little more

confusing, a person will

have antibodies in their plasma to the A or B antigens they lack. So, if a person lacks the A

antigen on their cells, they will have A antibodies in their plasma. A lack of B antigens will

result in the presence of B antibodies in their plasma. A person with the O blood type lacks

both antigens, so they will have both A and B antibodies in their plasma. This is why a

person’s blood type must be considered when a patient needs a blood transfusion. If type-A

blood is given to a type-B person, the A antibodies will flag the red cells for destruction by

the immune system.

A person isn’t born with A

and B antibodies, but they

are formed shortly after

birth (within six months).

Research doesn’t know what

causes this, but the current

theory is that the immune

system reacts with

something in the

environment that appears, to

the immune system, like A

and/or B antigen.

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Objective 17 (continued). Describe the development and identification of the ABO and Rh

blood groups.

The cause must be something along this line because, as a rule, the immune system will

only react to something it sees and recognizes as foreign. So, it has to see A antigen or at

least something that looks like it to form A antibodies.

The Rh blood type is a little easier to understand. It is determined simply by the presence

or absence of the Rh antigen on red cells. If a person inherits the Rh gene from either

parent, they will have the antigen, so they are Rh-positive. If they don’t inherit it, they will

be Rh-negative.

Another important aspect of this system is that individuals don’t make antibodies to the Rh

antigen unless the immune system sees it. So, unless an Rh-negative person sees Rh-

positive blood, they will not have any Rh antibody.

Inherited Gene(s) Antigens on RBCs Antibodies in the Plasma

A gene A antigens B antibodies

B gene B antigens A antibodies

A and B genes A and B antigens no A or B antibodies

Neither A or B genes Neither A or B A and B antibodies

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Objective 18. Describe the considerations of the ABO and Rh blood groups with blood

transfusions.

When a person needs a blood transfusion, the

blood groups must be considered. In the

medical laboratory, there are many blood groups

they have to be considered, but this discussion

will be restricted to the ABO and Rh systems.

The most important thing to remember is that

the immune system will only react to that which

it sees. If there is nothing to see, the immune

system won’t care. This is like a child hiding

candy in their room. If mom and dad can’t see it,

there isn’t a problem. If they find it, there are

likely consequences.

If a person has a low red count and hematocrit, and they are struggling to oxygenate, a physician

will order a blood transfusion. To understand blood-compatibility, it is important to understand

99% of the blood transfusions are just red blood cells. It is very rare for a person to receive whole

blood.

In a blood transfusion, RBCs from a generous donor are

given to a needy recipient. With this in mind, two things

have to be considered. One, what antigens are on the

donor’s cells, and two, what antibodies are in the recipient’s

plasma. When receiving blood, the patient doesn’t want to

see any antigens they haven’t seen before or any antigen to

which they already have antibodies, or the newly transfused red cells will be flagged for destruction

by the immune system. This cellular destruction is called a transfusion reaction. To avoid this

problem, the medical laboratory will put donor red cells and recipient plasma in a tube to check for

compatibility before the patient is given the red cells. If it doesn’t work in a tube, it won’t work in

the patient.

The O blood type is commonly referred to as the

universal donor. This is because there isn’t any

A or B antigen on the red blood cells; therefore,

there isn’t anything for the immune system to

see. The AB blood type is called the universal

recipient because they don’t have any A or B

antibodies in their plasma. Their system already

knows what A and B antigens look like, so they

aren’t foreign to them. As an example, an A

patient can receive type-A or type-O blood. A

patient who is type B, can have B or O.

Assignment: Tortora, pp. 709-710 or Wiley Plus – 19.8 Blood Groups and Blood Types

Blood Type Compatible Blood

A A or O

B B or O

AB A, B, AB, or O

O Only O

615

Objective 19. Describe the interactions of the blood groups that cause hemolytic disease of

the newborn (HDN).

Hemolytic disease of the newborn is caused by a blood incompatibility between a fetus and

an expectant mother. Hemolytic of course means that red blood cells are being destroyed.

In this situation, the mother is producing an antibody against antigens on her child’s red

cells.

Normally, the mother and baby’s blood

don’t come into contact with one another.

But, if some of baby’s blood gets into mom’s

circulation, the mother can make antibodies

to any foreign antigens her immune system

sees. The most common opportunity for

this to take place is during delivery. As the

placenta separates, a sample of baby’s blood

can enter the mother’s circulation. Now,

any antigens present on the newborn’s cells

can encourage an immune response. This

does not cause a problem for this particular child because the mother and baby are no

longer attached by the umbilical cord. But, it may be a problem for later children.

Here is an important concept to help understand this disorder. To provide immune

protection for a developing fetus, a mother will produce and transport antibodies to her

child. This can protect baby from various diseases during pregnancy. The good thing is

that baby gets antibodies from its mother; the bad thing is that a baby gets antibodies from

its mother. If an antibody is designed to protect the child, that is a good thing. If it is an

antibody that targets any of the baby’s cells,

that isn’t good. The problem is that the

placenta can’t tell the difference.

There are different classes of antibodies.

One of these types is called immunoglobulin

G or IgG antibodies. This class is the one

that is actively transported across the

placenta. These classes will be discussed in

more detail later in the unit.

Assignment: Tortora, p. 710 or Wiley Plus – 19.8 Blood Groups and Blood Types

616

Objective 19 continued). Describe the interactions of the blood groups that cause

hemolytic disease of the newborn (HDN).

Here is an example of the scenario. If a

mother is Rh-negative, and the baby is Rh-

positive, her child has an antigen on its cells

that she doesn’t. How did the baby get it? It

was dad’s fault. The father gave the child

the gene to be Rh-positive. If the mother is

exposed to the child’s red cells, she will

likely make an Rh-antibody. Now, if she

gets pregnant again and the next child is Rh-

positive, she has a pre-formed antibody

against the fetus’ red cells. Her antibody can

cross the placenta and target the fetus’ red cells.

Can medical science keep the mother from

forming an Rh antibody? Well, it does. An

Rh-negative mother, who delivers an Rh-

positive child, is given a shot of Rhogam®.

Rhogam® is a dose of Rh-antibody. Wait,

the physician didn’t want her to get an Rh-

antibody. The key is that the antibody from

the injection wasn’t developed by her

immune system. If they can give her an Rh-

antibody that helps get rid of the Rh-

positive cells without her immune system

seeing them, the cells are gone, and she

never develops Rh-antibody of her own.

What if the Rh types from the previous example are reversed? What if the mother is Rh-

positive and the baby is Rh-negative. This isn’t a problem, but why? The baby is Rh-

negative; therefore there isn’t an Rh antigen to see, and if there was, who cares. Mom is Rh

-positive. She already has the Rh antigen. The immune system doesn’t make antibody to

antigen it doesn’t recognize as foreign, and the Rh antigen isn’t foreign to her.

OK, here is another question. How can a mother who is blood-type A have a baby with

type- B blood? An A person has B antibodies, and they’ve had them for the majority of

their life. The answer is in the antibodies. The A and B antibodies a person produces are

not IgGs, they are IgMs (different class). Therefore they are not transported across the

placenta and therefore not usually an issue.

617

Objective 20. Describe the structure and primary functions of the lymphatic system.

The lymphatic system is a system throughout the body made up of lymphatic vessels and

supporting organs that drain excess interstitial fluid, transport dietary lipids, and facilitate

immune responses.

The lymphatic system includes: lymphatic

fluid, lymphatic capillaries, vessels, trunks,

ducts, lymph nodes and nodules, red bone

marrow, the thymus gland, and the spleen.

Lymphatic vessels are a little different from

blood vessels. Blood vessels contain blood

that circulates to and from the heart. The

lymphatic vessels carry lymphatic fluid

(lymph) one way, from the tissue, back into

the blood stream.

Lymph vessels begin as small lymphatic capillaries that are located throughout the body in

the interstitial spaces. Lymphatic capillaries have overlapping endothelium that allows

interstitial fluid in, but not out. If pressure in the interstitial space is high, fluid flows in; if

it is low, the flaps close and fluid doesn’t enter. The lymphatic capillaries are held in place

by anchoring filaments. These are specialized fibers arising from the capillaries that extend

into the tissue.

As lymphatic capillaries converge, they form larger lymphatic vessels. Lymphatic vessels

have thin walls and valves to encourage one-way fluid movements.

Lymph nodes are present at intervals along

the lymphatic vessels. The lymph nodes

provide an opportunity for the lymphatic

fluid to come into contact with the immune

system. It is like a specialized sampling

process. The immune system gets a

continuous flow of information about what

is taking place in the body.

Assignment: Tortora, p. 832 or Wiley Plus – 22.1 Lymphatic System Structure and Function

618

Objective 21. Compare plasma, interstitial fluid, and lymphatic fluid (lymph).

Plasma is filtered by the capillary walls to form interstitial fluid. Most of the interstitial

fluid is reabsorbed back into the blood stream. Any excess fluid is drained from the tissue

through the lymphatic capillaries. On an average day, 20 liters of fluid passes from the

blood into the interstitial space; 17 liters are

reabsorbed back into the capillaries. The

lymphatic vessels drain the remaining three

liters.

Because proteins are too large to easily pass

through the capillary walls, the plasma

contains a much higher amount of protein

than interstitial fluid and lymph. Lymphatic

fluid is essentially just drainage from the

tissue, so it is identical to interstitial fluid.

Assignment: Tortora, p. 834 or Wiley Plus – 22.1 Lymphatic System Structure and Function

619

Objective 22. Describe the formation and flow of lymphatic fluid.

Two mechanisms assist with lymph flow. Skeletal muscle contraction “milks” the

lymphatic vessels and encourages lymph movement. Respiratory movements encourage

lymph flow by increasing and decreasing thoracic and abdominal pressures. In both

scenarios, the valves present in the lymphatic vessels restrict back-flow of lymph.

Assignment: Tortora, pp. 834-836 or Wiley Plus – 22.1 Lymphatic System Structure and Function

620

Flow of Fluids

1. Plasma in the blood

vessels

2. Interstitial fluid

3. Lymphatic capillaries

4. Lymphatic vessels

5. Lymphatic ducts

6. Back into the blood

stream

Objective 22 (continued). Describe the formation and flow of lymphatic fluid.

621

The secondary lymphatic organs and tissues

are sites where the majority of immune

responses take place. Lymph nodes and the

spleen are secondary lymphatic organs;

lymphatic nodules are secondary lymphatic

tissue. The difference is the presence or

absence of a capsule. Lymph nodes have a

connective tissue capsule, nodules do not.

Examples of lymphatic nodules include the

Peyer’s patches in the intestinal tract,

portions of the appendix, and the tonsils

(pharyngeal, adenoid and palatine).

Objective 23. Differentiate primary from secondary lymphatic organs/structures.

The primary lymphatic organs are the

locations where stem cells divide to produce

cells for immune functions. As these cells

mature, they become immunocompetent,

which means they can facilitate an immune

response. The primary lymphatic organs are

the bone marrow and the thymus gland.

Stem cells in the bone marrow divide to

produce both B lymphocytes and T

lymphocytes. B lymphocytes will remain in

the bone marrow to mature. T lymphocytes

will leave as pre-T lymphocytes and migrate

to the thymus gland to become

immunocompetent.

The thymus gland is located in the

mediastinum between the sternum and the

aorta. In infants, the thymus gland is

approximately 70 g. It will remain

approximately this size until after puberty

when connective and adipose tissue will

replace the thymic cells. By the time an

individual reaches old age, the thymus will

only weigh about 3 g, but it will continue to

release some mature T cells.


622

Objective 24. Describe the locations, structure, and function of lymph nodes.

Lymph nodes are bean-shaped lymphatic organs and are anywhere from 1 to 25 mm in

length. There are approximately 600 lymph nodes in the body, and they occur at intervals

along the lymphatic vessels. There are regions in the body where the lymph nodes are

group together more prominently: cervical, submandibular, axillary, and inguinal.

A lymph node is surrounded by a connective

tissue capsule. Extensions of the capsule

(trabeculae) divide the node into

compartments. There are two regions of a

lymph node, the cortex and the medulla.

Both regions contain large numbers of white

blood cells and macrophages. The types of

cells present in each region differ slightly.

The lymph node is the location where the

immune system gets a sample of the

interstitial fluid. It would be cumbersome

and costly to test every drop of water that passed through a water-purification facility, but

samples are checked on a regular basis. The lymph nodes in the body act as a sampling

system.

Lymph flows into a node through afferent lymphatic vessels. The lymph flows through the

cortex, where it comes into

contact with large

populations of B

lymphocytes, dendritic cells,

and macrophages. The lymph

continues to flow through

the node into the medulla.

There it is exposed to more B

lymphocytes, plasma cells

(activated B cells), and more

macrophages. The lymph

will then exit the lymph

node through efferent

vessels.


623

Objective 25. Contrast innate and adaptive immunity.

Innate immunity consists of a number of different cellular and chemical barriers which

non-specifically protect the body and respond to pathogenic organisms. In addition to

being non-specific, innate immunity is non-adaptive, meaning that the response doesn’t

change from exposure to exposure. Components of innate immunity include: the skin and

mucous membranes, cilia, antimicrobial chemicals, phagocytes, inflammation, and fever.

In contrast with innate immunity the adaptive immune response is specific, adaptive, and

generates memory. Components of adaptive immunity include: T lymphocytes, B

lymphocytes, plasma cells, and antibodies. The ability to respond against specific invaders

is the main function of adaptive immunity.

Assignment: Tortora, pp. 842 & 846 or Wiley Plus – 22.3 Innate Immunity

624

Objective 26. Compare the lines of defense associated with innate immunity.

There are two lines of defense associated with innate immunity. If the first barrier is

compromised, the second takes over, and to guarantee a response, the adaptive immunity

takes over.

The chemical and physical barriers of the

first line of defense include: mucus, mucus-

coated hairs, cilia, the lacrimal apparatus,

salivary glands, the flow of urine, vaginal

secretions, defecation, vomiting, sebaceous

secretions, perspiration, and gastric fluids.

Each of these barriers protects the various

external openings of the body.

The second line of defense includes a large

number of internal defenses. As part of this

line, the body produces natural antimicrobial

substances like interferons, complement, and

iron-binding proteins to decrease microbial

growth.

Non-specific phagocytes and natural killer

cells are part of this line. Natural killer (NK)

cells are actually a type of lymphocyte. They

make up 5-10% of our circulating

lymphocytes. There role is to release

chemicals from their granules to either

induce apoptosis or cause lysis of a targeted cell.

Assignment: Tortora, pp. 842-846 or Wiley Plus – 22.3 Innate Immunity

625

Objective 26 (continued). Compare the lines of defense associated with innate immunity.

There are two groups of phagocytes in the second line of defense, neutrophils and

macrophages. Neutrophils are released in large numbers, very quickly, but their lifespan is

relatively short. The bone marrow releases monocytes that enlarge and develop in to

macrophages as they migrate to the site of infection or injury. These are called wandering

macrophages. Other macrophages, called fixed macrophages, may occupy specific tissues.

Don’t be confused by their names. To identify these individual groups, they may have

unique names: Kupffer cells (liver), alveolar macrophages (lung), microglial cells (CNS), etc.

They are just names; there functions are the essential the same.

Fever is part of our non-specific internal

defenses. Fever is often thought of as a bad

thing, and from a patient-comfort point of

view, that probably is correct. But, to fight

off disease, fever is a good thing. An

increase in body temperature, speeds up

chemical reactions, increases antimicrobial

activity, and sequesters nutrients essential

for bacterial growth.

Inflammation is a big part of our non-

specific internal defenses. The process of inflammation has three stages, vasodilation and

increased vascular permeability, emigration of phagocytes from the blood to the tissue, and

tissue repair.

626

Objective 27. List and describe the local signs of inflammation.

As a reminder, inflammation is a

non-specific, non-adaptive, innate response.

The stimulus for inflammation could be a

burn, chemical exposure, heat, cold, trauma,

etc., but the inflammatory response is the

same. The local signs of inflammation are

easy to recognize; redness, pain, heat,

swelling, and possibly loss of function.

These signs relate to the stages of

inflammation. The redness and heat are due

to the increased blood flow. The swelling is

because of the increased vascular

permeability. The cytokines and pro-

inflammatory chemicals, released as part of

inflammation, target free nerve endings that

result in the perception of pain.

The loss of tissue function

depends on the degree of

damage and the extent of the

inflammation. Too much of

a good thing may be bad.

Assignment: Tortora, pp. 844-845 or Wiley Plus – 22.3 Innate Immunity

627

Objective 28. Define the term antigen and relate its characteristics to the adaptive immune

system.

A substance that is recognized as foreign and reacts with product of the immune system is

an antigen. An adaptive response to an antigen demonstrates specificity and memory. Both

of these characteristics will be described in

detail.

There are four main characteristics that

determine the antigenicity of substance:

recognition as foreign, structural

complexity, size, organic in nature.

Recognition as foreign is the most important

of the three. A potential antigen could fit

all of the others, but if the body deems it as

part of itself, it will leave it alone.

If a molecule fits all of the criteria, except

for size (<10,000 mw), it is referred to as a hapten. A hapten doesn’t trigger an immune

response, unless it binds to another molecule, now it is big enough.

If a pathogen is large enough, it may have multiple sites that can react with the immune

system. These sites are called antigenic determinants or epitopes.

Assignment: Tortora, pp. 846-849 or Wiley Plus – 22.4 Adaptive Immunity

628

Objective 29. List and describe the subtypes of T and B lymphocytes.

As described earlier, lymphocytes are classified by the location where they matured. T

lymphocytes originate from stem cells in the bone marrow, leave as pre-T cells and mature

in the thymus gland. B lymphocytes originate and mature in the bone marrow.

There are subtypes of these lymphocytes

that have unique functions within the

immune system. Memory cells of each of

the T-helper and T-cytotoxic cells are

produced for the purpose of facilitating a

rapid response in the event of future

exposures to the same antigen.

Similar to identifying antigens on a red

blood cell, markers on white cells can

indicate a specific cell type. Initially,

researchers thought that these markers

occurred in groups or clusters, so the name “clusters of differentiation” was used, or CD for

short. It is now known that these markers are individual proteins on the surface of cells,

but they do help to identify particular cell types.

Assignment: Tortora, pp. 848-849, 856 or Wiley Plus – 22.4 Adaptive Immunity & 22.5 Cell-Mediated Immunity

Lymphocyte Function

T-helper cells The middle-man or main “helper” of the immune response. The

T-helper cells will receive information from non-specific

phagocytic cells and pass that information on to generate a

specific response to a particular antigen. These are also called

CD4 T-cells, due to the presence of the CD4 marker.

T-cytotoxic cells These T-cells destroy abnormal cells. Virally-infected cells and

cancerous cells are their main targets. These are also called CD8

T-cells.

T-regulator cells T-regulator cells keep the immune system from getting out of

control. They decrease the reactivity of the other types of T-

cells. This is essential for maintaining self-tolerance.

Memory T-cytotoxic

and

Memory T-helper

cells

Produced with an initial exposure to an antigen to provide

memory of the event and a rapid-response if re-exposed to the

antigen. Memory cells do not participate the first time around.

629

Each of these cells responds

to a specific antigen because

they have antigen receptors

for it. T-cells and B-cells

can respond to all antigens

presented to the immune

system, and because these

cells are spread throughout

the body, they are

constantly ready for any

exposure to specific

antigens. It sounds

impossible that the body can

respond to all potential

antigens, but the shuffling

genes (genetic

recombination) during

lymphocyte production give

the cell its specificity. Then

if one cell, specific to a

particular antigen, is active,

many copies of that cell can

be produced.

Objective 30. Compare cell-mediated and antibody-mediated immunity.

Cell-mediated and antibody-mediated

immunity are the two types of adaptive

immunity. Both mechanisms are triggered

by exposure to specific antigens.

In cell mediated immunity, T-cytotoxic cells

are activated directly against abnormal cells,

such as cancer cells or even tissue

transplants. In antibody-mediated

immunity, B-lymphocytes are activated to

become plasma cells, which produce and

secrete specific antibodies. Because T-

helper cells are the middle-men of adaptive

immunity, they are a part of both cell-

mediated and antibody-mediated immunity.

Assignment: Tortora, pp. 848, 856 or Wiley Plus – 22.4 Adaptive Immunity & 22.5 Cell-Mediated Immunity

630

Objective 31. Describe the major histocompatibility complex (MHC).

The major histocompatibility complex

(MHC) is a group of genes that codes for a

group of transmembrane proteins on the

surface of cells, sometimes called MHC

molecules or human leukocyte antigens

(HLA). Originally, they were thought to

exist only on leukocytes, so the name HLA

fit. Now it is known that they are present

on all nucleated cells.

These molecules are very important in the processing and presentation of antigen. They

allow a cell to respond to an antigen directly or to present the antigen to the rest of the

immune system.

There are two major types of MHC

molecules, class-I and class-II. MHC class-I

molecules are present on all body cells,

except red blood cells. MHC class-II

molecules are demonstrated on the surface

of antigen-presenting cells (APC).


631

Objective 32. List and describe the general steps of antigen processing and presentation.

Phagocytes are a very important part of the innate immune response, but if every antigen

were simply disposed of by phagocytes, components of the adaptive immune response would

very seldom get information about what took place. Therefore, there wouldn’t be a cell-

mediated or antibody response or memory. This requires cells that initially detect the

antigen to present it to the rest of the immune system. These cells are called antigen-

presenting cells (APCs).

APCs are commonly phagocytes, but B cells can present antigen. Antigen processing and

presentation differs slightly depending on whether or not the antigen was present outside of

the body cells (exogenous) or inside (endogenous). Examples of endogenous antigens include

viral proteins within virally-infected cells, toxins from intracellular bacteria, and abnormal

proteins in cancer cells.


632

Objective 32 (continued). List and describe the general steps of antigen processing and

presentation.

Once an antigen is presented on the surface

of an APC, it can now be recognized by the

adaptive immune response. This is where

the T-cell middle-man comes in. An

inactive T-helper cell, specific for the

antigen, will bind with its T-cell receptor to

the presented antigen on the APC. This will

activate the T-cell. The activated T-cell will

proliferate (increase its numbers) and

differentiate (mature). This process is called

clonal selection. Through this process the

active T-helper cells and T-memory cells are

produced.

An inactive T-cytotoxic cell will bind to

MHC class-I presented antigen infected

body cells. With the assistance

(costimulation) of the T-helper cells, the

cytotoxic cell becomes active. Through

clonal selection, a population of active T-

cytotoxic cells and memory T-cytotoxic cells

are produced.

633

Objective 32 (continued). List and describe the general steps of antigen processing and

presentation.

Lastly is the activation of B-cells; they can

be activated by two different mechanisms,

direct antigen attachment to B-cell

receptors or stimulation by activated T-

helper cells. Some new B-cell clones will

become B-memory cells, others will mature

into plasma cells and secrete antibodies

specific to the particular antigen.

Steps in Antigen Processing and Presentation

Exogenous Antigens Endogenous Antigens

Ingestion of the antigen Digestion of the antigen into fragments

Digestion of the antigen into fragments Synthesis of MHC class-I molecules

Synthesis of MHC class-II molecules Binding of fragments to class-I molecules

Vesicular packaging of class-II molecules Vesicular packaging of class-I molecules

Fusion of fragment and class-II vesicles

Insertion of the antigen-MHC class-I

complexes in the plasma membrane for

recognition

Binding of fragments to class-II molecules

Insertion of the antigen-MHC class-II

complexes in the plasma membrane for

recognition

634

Objective 33. Describe the role of cytokines in the immune response.

Cytokines are chemical signals from one cell

that influences another. These chemicals act

as small protein hormones to control cellular

growth and maturation. Each type of

cytokine has a cellular origin and specific

function. For example, erythropoietin is a

cytokine from the kidneys increases the

number and activity of red cell precursors in

the bone marrow. With modern research

techniques, the list of known cytokines is

becoming very large.

Assignment: Tortora, p. 852 or Wiley Plus – 22.4 Adaptive Immunity

Common Groups of Cytokines

Interleukins Cytokines between white blood cells

Interferon Anti-viral properties and stimulators of the immune

system

Tumor-necrosis factor (TNF) Produced by macrophages to encourage inflammation.

635

Objective 34. Describe the basic structure of antibodies and their actions in the immune

response.

Antibodies are commonly called gamma globulins, as well as immunoglobulins (Ig). They

have a specific structure that provides for their specificity. A general antibody consists of 4

polypeptide chains, two long (heavy chains) and two short (light chains). Disulfide bonds

link the chains together. This simple arrangement gives the antibody a characteristic Y-

shape. Most antibodies are one Y-shaped unit (monomer), but some can contain multiple

units (dimer and pentamer).

There are two main regions of an antibody,

the constant region and the variable region.

The variable region consists of the distal

segments of the heavy and light chains and

forms the antigen-binding site. This region

gives the antibody its specificity. The

constant region differs slightly for the

different classes of antibodies.

Assignment: Tortora, pp. 857-858 or Wiley Plus – 22.6 Antibody-mediated Immunity

636

Objective 34 (continued). Describe the basic structure of antibodies and their actions in the

immune response.

Antibodies don’t destroy anything directly, but they act as a great flagging system for the

immune system. Maybe a better statement is that they signal antigen for destruction, and

they disable antigen.

Antibody Action Result

Neutralizing antigen Neutralizes toxins and binds to viruses to restrict their binding

to host cells

Immobilizing bacteria Restricts the spread of motile bacteria by binding to cilia or

flagella

Agglutinating and

precipitating antigen

Multiple antigen-binding sites can result in one antibody

binding to 2 or more antigen, causing agglutination, binding

may cause soluble antigen to become insoluble

Activating complement Antigen/antibody complexes initiate the classical complement

pathway

Enhance phagocytosis Opsonize (flag) for phagocytosis

637

Objective 35. Identify and describe the five classes of antibodies.

Assignment: Tortora, p. 859 or Wiley Plus – 22.6 Antibody-mediated Immunity

Antibody Class General Structure, Location, and Function

IgG

Monomer, two antigen-binding sites, found in blood, lymph and

intestines, 80% of the antibody in the blood, only class to cross the

placenta, provide long-term immunity

IgM Pentamer, 10 antigen-binding sites, first to be secreted by plasma cells,

great complement activator, short-lived

IgA Dimer, four antigen-binding sites, found in sweat, tears, saliva, mucus,

breast milk, and gastrointestinal secretions, levels decrease during stress

IgE Monomer, two antigen-binding sites, less than 0.1% of antibody in the

blood, located on mast cells in tissue

IgD Monomer, two antigen-binding sites, 0.2% of antibody in the blood,

found as receptors for antigen on B-cells

638

Objective 36. List and describe ways to acquire adaptive immunity.

Adaptive immunity can be acquired in a

number of different ways: actively or

passively, and naturally or artificially.

Active acquisition of immunity means that

someone’s immune system was stimulated,

and they generated a cell and antibody-

mediated response as well as memory.

Passive immunity simply means the

products of immunity were given to them,

without any effort of their own. Active

immunity provides long-term immunity.

Passive is a short-lived response, the

acquired cells die or the antibodies are

eventually lost.

Active immunity is like baking a pie. An

individual pulls out the recipe book, makes

the crust and filling, and bakes the pie.

Using the same illustration, passive

immunity is simply buying a pie. The end

result is the same, there is a pie, but with

active immunity, memory is gained, and

immune products can be made over and

over again.


Acquiring Adaptive Immunity

Method Result

Naturally-acquired active immunity Immune products acquired following

exposure to antigen

Naturally-acquired passive immunity

Transfer of antibody from non-medical

source; IgG through the placenta, IgA

through breast milk

Artificially-acquired active immunity

Immune products acquired through

vaccination; antigens given that are

immunogenic but not pathogenic

Artificially-acquired passive immunity Prepared injection of antibody

639

Objective 37. Describe the components of the complement system and its role in

immunity.

The complement system is a very powerful

group of proteins that “complement” the

action of the immune system. This system

can be compared with the coagulation

system in that there are multiple pathways

to activate the system and the fact that it

functions in a stepwise or cascading fashion.

Each step results in the fragmentation of one

protein that then becomes the activator of

the next step

The system consists of nine

main proteins, identified as

C1-C9. The complement

system functions to flag a

microbe for phagocyte

ingestion (opsonization),

encourage inflammation,

and if the system is activated

completely, cytolysis.

Cellular destruction is

accomplished by the

formation of a membrane-

attack complex. This is a

group of complement

proteins that are inserted

into the plasma membrane

to form a pore in the

membrane of the microbe.

This causes extracellular

fluid to flow into the cells

and the lysis of the microbe.

Assignment: Tortora, pp. 859-860 or Wiley Plus – 22.6 Antibody-mediated Immunity

640

Objective 38. Contrast the primary and secondary immune responses.

The differences between the primary and secondary immune responses illustrate the ability

of the immune system to demonstrate memory. The primary immune response is the

sequence of events and outcomes of the immune response with an initial exposure to an

antigen. The secondary response relates to second or subsequent exposures.

The indicator for an

antibody-mediated response

is an antibody titer. A titer

is a test that detects the

relative amount of antibody.

To understand an antibody

titer, it might be easy to

relate it to making

lemonade. When someone

makes lemonade, they add a

particular amount of

lemonade power to water.

If they add more water, it

decreases the concentration.

If they keep adding water,

they will eventually not be

able to even taste a hint of lemon. If the lemonade was initially very concentrated, they

would add a great deal of water before they couldn’t taste any lemon.

This is how antibody titers work. A clinical laboratorian will take a patient’s plasma and

determine whether or not there is any of a particular type of antibody. If there is, they will

dilute it and determine if they can still detect any antibody. If they can, they dilute it

again, and so on.

If a patient has an antibody titer of 256, their plasma was diluted 256 times before there

wasn’t any detectable antibody. The higher the number, the greater the concentration of

antibody there was originally in the plasma.


641

Objective 38 (continued). Contrast the primary and secondary immune responses.

There are two main differences between the primary and secondary immune responses:

time and antibody titer.

The first time the immune system recognizes an antigen, it takes a short period of time for

antigen processing, presentation, and antibody production. This period lasts approximately

5-7 days. Initially, the plasma cells will produce a population of IgM antibodies, followed

by a population of IgG. The goal of the primary response is to provide an initial antibody-

mediated response and produce a population of memory cells.

Because the primary response generates memory cells, the secondary response is immediate.

The antigen can be taken care of before a person even becomes symptomatic. Time to

process and present antigen is not necessary. There is an immediate increase in IgM

antibodies, followed quickly by a large, long-lasting increase in the amount of IgG

antibodies. This is one of the main reasons to provide booster shots for various

vaccinations.

642

Objective 39. Define self-recognition and self-tolerance and relate the terms to

autoimmune disease.

To keep from destroying oneself, the immune system must have two characteristics, self-

recognition and self-tolerance. Self-recognition is the ability to recognize one’s own

cellular markers. If a person’s immune system didn’t know what they look like, the

immune system would not able to recognize anything foreign.

Self-tolerance means to leave oneself alone. If any T or B cells have self-reactive antigen

receptors, they are either inactivated or deleted from the population.

A failure of self-recognition or self-tolerance would result in the development of

autoimmune diseases. Either scenario would result in the immune system’s perceiving that

various autoantigens were foreign and should be destroyed.

Assignment: Tortora, pp. 862, 867-868 or Wiley Plus – 22.7 Self-Recognition and Self-Tolerence & 22.9 Aging and the Immune System (Disorders: Homeostatic Imbalances)

643

Objective 40. Describe the effects of aging on the immune system.

It’s not a secret that individuals are more susceptible to infections and the development of

cancers as they age. This is due to a decreased function of the immune system. The thymus

atrophies as a person ages; this leads to lower T-cell numbers and a slower response. Due to

the lack of T-cells available to coordinate activities, the B-cell response is also slower. With

a slower immunological response, it is important that the elderly are properly vaccinated

against various infections.

The elderly have a similar quantity of antibodies as a middle-aged population, but a much

larger percentage of the antibodies are autoimmune antibodies. This is due to a lifetime of

slow and subtle cellular changes which can result in a decrease of self-tolerance.

Assignment: Tortora, p. 864 or Wiley Plus – 22.9 Aging and the Immune System

module 15 cardiovascular system blood, lymphatic...

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