BIO202 - Lecture Exam #3 - Lymphatic System & Immunity Ch 20-21

Lymphatic System Organs

lymph nodes, lymphatic vessels, thymus, spleen, tonsils

Thymus gland location

behind the sternum in the mediastinum; partially overlies the heart

Thymus gland function & characteristics

•Regulates T cell development (prevent autoimmunity)

•Increases in size and most active during childhood

•Stops growing during adolescence, then gradually atrophies

•Still produces immunocompetent cells, though slowly

Lymph Nodes & primary locations

• Principle lymphoid organs of the body

• Embedded in connective tissue, in clusters along lymphatic vessels

• Near body surface in inguinal (groin), axillary (armpit), and cervical (neck) regions of body

Lymph Node functions

1.Filter lymph—macrophages destroy microorganisms and debris

2.Immune system activation—lymphocytes activated and mount attack against antigens

Bubo

inflamed, swollen, tender lymph nodes •that result when nodes are overwhelmed by what they are trying to destroy (example: bacteria, viruses, etc.)

Types of Tonsils & Locations

1. Palatine tonsils: pair at posterior margin of oral cavity; most often infected

2. Lingual tonsils: pair at root of tongue

3. Pharyngeal tonsil (adenoids): single tonsil on wall of nasopharynx

4. Tubal tonsils: surrounding openings of auditory tubes into pharynx

Function of Tonsils

• gather and remove pathogens in food or air

• trap and destroy bacteria and particulate matter

MALT (mucosa-associated lymphatic tissue)

•Lymphoid tissues in mucous membranes throughout body

•Protects from pathogens trying to enter body

•Largest collections of MALT in tonsils, Peyer's patches, appendix

•Also in mucosa of respiratory and genitourinary organs; rest of digestive tract

Peyer's Patches

collections of lymphatic tissue found in the submucosa of the small intestine

Spleen function

• Stores breakdown products of RBCs (e.g., iron) for later reuse

• Stores blood platelets and monocytes

• May be site of fetal erythrocyte production (normally ceases before birth, can function again if bone marrow is unable)

• Contains lymphocytes, macrophages, and huge numbers of erythrocytes

Spleen

Largest lymphatic organ

a large dark-red oval organ on the left side of the body between the stomach and the diaphragm

splenectomy

Surgical removal of ruptured spleen

Once standard treatment to prevent hemorrhage and shock, but has been discovered spleen can often repair itself

Lymphatic capillaries (vs blood capillaries)

Similar to blood capillaries, except

• More/very permeable (take up proteins, cell debris, pathogens, and cancer cells)

• the gaps between endothelial cells in the lymphatic capillaries are larger then those of the blood capillaries

Lymph vessels

• Returns interstitial fluid (lymphocytes, dietary fats, excess tissue fluid) and leaked plasma proteins (lymph) back to blood

• One-way system; lymph flows toward heart

lymph

the fluid that the lymphatic system collects and returns to the bloodstream

Lymphocytes

A type of white blood cell that make antibodies to fight off infections

main warriors of the immune system; arise in red bone marrow

mature into one of two main varieties: T cells & B cells

Neutrophils

Most abundant white blood cell. Phagocytic and tend to self-destruct as they destroy foreign invaders, limiting their life span to a few days.

Large numbers indicate bacterial infection

B Cells

Differentiate into memory B cells & plasma cells

Mature in bone marrow

T Cells

Mature in the thymus

Provide defense against intracellular antigens

Two main types based on glycoprotein surface receptors displayed: Helper T cells & Cytotoxic T cells

Plasma cells

Made by B-cells

secrete antibodies for 4-5 days and die

Macrophages

phagocytize cellular debris and foreign particles

help activate T-cells

Helper T cells

Activated T cell

Activates B cells, other T cells, macrophages, & direct adaptive immune response.

Without Helper T cells there is NO immune response

HIV (human immunodeficiency virus) destroys helper T cells which depresses cellular immunity leading to AIDS

Cytotoxic T Cells

Activated T cell

Directly attack and kill other cells

Circulate in blood and lymph and lymphoid organs in search of body cells displaying antigen they recognize (virus infected cells, cells with intracellular bacteria or parasites, cancer cells, foreign cells (transfusions or transplants))

Release perforins & granzymes (stimulate apoptosis)

Lymphadenopathy

Chronic or excessive swelling of lymph nodes "swollen glands" (buboes) may indicate infections, endocrine disorders, or cancer

Diapedesis

Passage of white blood cells through intact vessel walls into tissue

Pathogen

disease causing organism

Antigens

chemical markers on foreign substances that trigger the attack of antibodies in the immune response.

Antibodies

• Secreted by Lymphocytes

• a blood protein produced in response to and counteracting a specific antigen. Antibodies combine chemically with substances that the body recognizes as alien, such as bacteria, viruses, and foreign substances in the blood.

Innate Immunity

Non-specific immune defense mechanisms that we are born with.

Constitutes first and second lines of defense:

*First line of defense: external body membranes (skin and mucosae)

*Second line of defense: antimicrobial proteins, phagocytes, and other cells (inhibit spread of invaders; inflammation most important mechanism)

Immune System First Line of Defense

external body membranes: skin and mucous membranes

Cell-mediated Immunity

Type of adaptive immune defense when immune cells (T lymphocytes) respond to antigens that are presented on a body cell.

Nonspecific Immunity

Another name for the body's Innate defense system (from birth)

The body's defense system against pathogens and infections in general. Examples are healthy skin, fever, and white blood cells.

Acquired Immunity

Immunity that the body develops after it overcomes a disease, or through inoculation (such as vaccination) and is highly specific

Perforin

One of the proteins released by cytotoxic T cells on contact with their target cells. It creates pores in the target cell membrane that contribute to cell killing.

Isograft

transplant from identical twin

Autograft

organ/tissue transplant from one body site to another in the same person (self)

Allograft

transplant between individuals of same species who are not identical twins

most common type of transplant

Xenografts

grafts taken from another animal species

Symptoms of (acute) inflammation

redness, heat, swelling, pain, disturbance of function

Major Histocompatibility Complex (MHC)

•glycoproteins that are individualized to you (millions of combinations possible) & part of what your cells recognize as "self" and don't react against (unless your immune system isn't properly "programmed");

determines compatibility and rejection of transplants

Antibody classification groups

IgA, IgD, IgE, IgG, IgM

Mnemonic to help remember types: GAMED

IgG

most abundant, crosses placenta (Greatest concentration/ Mom (G) -> baby (g))

IgA

secreted into mucus, teArs, sAlivA, breAst milk; helps prevent entry of pathogens

IgM

first antibody produced/Made: largest/Mega (think: biggest is sent out first)

IgE

allergic reactions (think: aller-gEE); causes mast cells and basophils to release histamine (mediator of inflammation)

IgD

Acts as a B cell receptor; least understood

Acquired Immune Deficiency Syndrome (AIDS)

•Cripples immune system by interfering with activity of helper T cells

•Characterized by severe weight loss, night sweats, and swollen lymph nodes (symptoms begin when immune system collapses)

Opportunistic infections occur, including pneumocystis pneumonia

•Caused by human immunodeficiency virus (HIV) transmitted via body fluids—blood, semen, and vaginal secretions

•HIV enters the body via blood transfusions; blood-contaminated needles; sexual intercourse and oral sex; mother to fetus

HIV - Destroys TH cells which depresses cellular immunity