ANATOMY AND PHYSIOLOGY

The Immune System A second line of defense is housed

within the body: a finely tuned immune

system that recognizes and destroys

foreign substances and organisms that

enter the body. The immune system can

distinguish between the body's own

tissues and outside substances called

antigens. This allows cells of the

immune army to identify and destroy

only those enemy antigens. The ability

to identify an antigen also permits the

immune system to "remember" antigens

the body has been exposed to in the

past; so that the body can mount a

better and faster immune response the

next time any of these antigens appear.

The immune system also includes other

proteins and chemicals that assist

antibodies and T cells in their work.

Among them are chemicals that alert

phagocytes to the site of the infection.

The complement system, a group of

proteins that normally float freely in the blood, move toward infections, where they

combine to help destroy microorganisms and foreign particles. They do this by

changing the surface of bacteria or other microorganisms, causing them to die.

* enzyme (EN-zime) is a protein that helps speed up a chemical reaction In the body. * antigens (AN-tih-jens) are substances that are recognized as a threat by the body's

immune system, which triggers the formation of specific antibodies against the

substance. * bone marrow is the soft tissue inside bones where blood cells are made. * lymphatic (lim-FAH-tik) system is a system that contains lymph nodes and a network

of channels that carry fluid and cells of the immune system through the body. * immunity (ih-MYOON-uh-tee) is the condition of being protected against an infectious

disease. Immunity often develops after a germ is introduced to the body. One type of

immunity occurs when the body makes special protein molecules called antibodies to

fight the disease-causing germ. The next time that germ enters the body, the antibodies

quickly attack it, usually preventing the germ from causing disease.

Primarily, the immune system classifies a substance as:

a. Self-non-foreign – they are normally ignored and tolerance and is exhibited

towards these substances. They are not deemed harmful.

b. Non-self – termed as an “antigen”; a specific response is developed to a specific

antigen. The response is then stored in the immune system’s memory cells for

future reference.

Components of the Immune System:

1. Lymphoid Structures Spleen

- Composed of red and white pulp, acts somewhat like a filter.

- The red pulp is the site where old and injured red blood cells are

destroyed.

- The white pulp contains concentrations of lymphocytes.

Lymph Nodes- Are distributed throughout the body

- Are connected by lymph channels and capillaries, which remove

foreign material from the lymph before it enters the bloodstream.

2. Immune Cells – Lymphocytes

a. B lymphocytes (or B cells) - produce immunoglobulins.

b. T lymphocytes (or T cells) - help control the immune response and destroy

foreign antigens directly.

c. Plasma Cells - are white blood cells that produce large volumes of

antibodies.

3. Tissues – The remaining lymphoid tissues, such as the tonsils and adenoids and

other.

Mucoid Lymphatic Tissue – contain immune cells that defend the body’s

mucosal surfaces against microorganisms.

Types of Immune Defense:a. Innate or Nonspecific Immunity

- Also termed as the person’s natural resistance, and are the most basic and

primary of all defenses in the body. (skin, mucus membranes, phagocytic

activity)

4. Immune Cells – Lymphocytes

d. B lymphocytes (or B cells) - produce immunoglobulins.

e. T lymphocytes (or T cells) - help control the immune response and destroy

foreign antigens directly.

f. Plasma Cells - are white blood cells that produce large volumes of

antibodies.

5. Tissues – The remaining lymphoid tissues, such as the tonsils and adenoids and

other.

Mucoid Lymphatic Tissue – contain immune cells that defend the body’s

mucosal surfaces against microorganisms.

2 Types of Immunity Active – acquired through previous exposure of the disease or through

immunization wherein the body “actively” participates in formation of antibodies

for future reference.

Passive – refers to whole, “ready made” immunity acquired from another, the

body is just “passive” in the process of developing antibodies, as it is already

made and given readily.

4 Types of Active Immunitya. Humoral Immunity

b. Mucosal Immunity

c. Cell-mediated Immunity

d. Delayed HypersensitivityReaction

Antibodies or Immunoglobulins – developed from B-cells through the stimulation

of cytokines produced by helper T-cells in the presence of an antigen. They attach to

specific determinant sites on antigens, and carries out phagocytosis and initiating

inflammation.

IgG 75% Crosses placental barrier; present in circulation and tissue

spaces; antiviral, antitoxic and anti-bacterial properties;

activates complement

IgA 15% Found in body secretions and breast milk; protects mucous

membranes from microorganisms

IgM 10% Forms natural ABO antibodies; present in early immune

responses; activates complement

IgE .2% Hypersensitivity reaction mediator; Involved in parasitic

infectious

IgD .004% Necessary for maturation of B lymphocytes

Hematologic SystemTwo types of blood vessels carry blood throughout our bodies:

1. Arteries carry oxygenated blood (blood that has received oxygen from the lungs)

from the heart to the rest of the body.

2. Blood then travels through veins back to the heart and lungs, where it receives

more oxygen.

The blood that flows through this network of veins and arteries is whole blood,

which contains three types of blood cells:

1. Red blood cells (RBCs) - (also called erythrocytes) are shaped like slightly

indented, flattened disks. RBCs contain the iron-rich

protein hemoglobin. Blood gets its bright red color when

hemoglobin picks up oxygen in the lungs. As the blood

travels through the body, the hemoglobin releases

oxygen to the tissues.

- The body contains more RBCs than any other type of cell, and each has a life

span of about 4 months. Each day, the body produces new RBCs to replace

those that die or are lost from the body.

2. White blood cells (WBCs) - (also called leukocytes) are a key part of the body's

system for defending itself against infection. They can

move in and out of the bloodstream to reach affected

tissues. Blood contains far fewer WBCs than red blood

cells, although the body can increase WBC production

to fight infection. There are several types of WBCs, and their life spans vary from

a few days to months. New cells are constantly being formed in the bone

marrow.

- Certain types of WBCs produce antibodies, special proteins that recognize

foreign materials and help the body destroy or neutralize them. The white cell

count (the number of cells in a given amount of blood) in someone with an

infection often is higher than usual because more WBCs are being produced or

are entering the bloodstream to battle the infection.

3. Platelets- (also called thrombocytes) are tiny oval-shaped cells

made in the bone marrow. They help in the

clotting process. When a blood vessel breaks,

platelets gather in the area and help seal off the leak.

Platelets survive only about 9 days in the

bloodstream and are constantly being replaced by

new cells.

- Platelets and clotting factors work together to form solid lumps to seal leaks,

wounds, cuts, and scratches and to prevent bleeding inside and on the surfaces

of our bodies. The process of clotting is like a puzzle with interlocking parts.

When the last part is in place, the clot happens — but if even one piece is

missing, the final pieces can't come together.

Cardiovascular System

The heart is a muscular organ found in all vertebrates that is responsible for

pumping blood throughout the blood vessels by repeated, rhythmic contractions. The

term cardiac (as in cardiology) means "related to the heart" and comes from the Greek

καρδιά, kardia, for "heart."

The vertebrate heart is composed of cardiac muscle, which is an involuntary

striated muscle tissue found only within this organ. The average human heart, beating

at 72 beats per minute, will beat approximately 2.5 billion times during an average 66

year lifespan. It weighs on average 250 g to 300 g in females and 300 g to 350 g in

males.

The external structures of the heart include the ventricles, atria, arteries and

veins. Arteries carry blood away from the heart while veins carry blood into the

heart.The vessels colored blue indicate the transport of blood with relatively low content

of oxygen and high content of carbon dioxide. The vessels colored red indicate the

transport of blood with relatively high content of oxygen and low content of carbon

dioxide.

Layers of the Hearta. Endocardium (innermost layer)

b. Myocardium (middle layer)

c. Epicardium (visceral pericardium or outermost layer)

Heart Chambers Atria

a. Right atrium – receives de-oxygenated blood from the superior and inferior

vena cava.

b. Left atrium – receives oxygenated blood from the left and right pulmonary

veins.

Ventricles

a. Right ventricle – pumps blood into the pulmonary circulation for the lungs.

b. Left ventricle – pumps blood into the systemic circulation for the rest of the

body.

Heart Valves Atrioventricular (AV) Valves – are one way valves that ensure that blood flows

from the atria to the ventricles

a. Right AV valve b. Left AV valve

Semilunar (SL) Valves – prevent blood from flowing back into the ventricles

a. Pulmonary semilunar valve b. Aortic semilunar valve

The Heart’s Electrical Conduction System SA Node

AV Node

AV Bundle

Purkinje Fibers

The Cardiac Cycle Systole – contracting part of the heart

Diastole – period of time when the heart relaxes after contraction in preparation

for refilling with circulating blood.