Ch.20 The Lymphoid System and Immunity Part 1

pathogens

Responsible for many diseases in humans.

lymphoid system

Includes the cells, tissues, and organs responsible for defending the body against both environmental hazards,such as pathogens and internal threats, such s cancer cells.

Lymphocytes

The primary cells of the lymphoid system, that act to eliminate threats or render them harmless through a combination of physical or chemical attacks; account for 20-30 percent of the circulating leukocyte population.

immune response

Also know as a specific defense in where lymphocytes organize a defense a particular type of bacterium.

non-specific defense

Mechanisms that either prevent or slow the entry of infectious organisms or attack them if they do succeed in entry but do not distinguish one potential threat from another.

immune system

A physiological system that includes not only the lymphoid system, but also components of integumentary, cardiovascular, respiratory, digestive, and other system.

lymph

A fluid that resembles plasma but contains a much lower concentration of suspended proteins.

lymphatic vessels

Often called lymphatics; is a network which begin in peripheral tissues and end at connection of veins.

lymphoid tissues and lymphoid organs

Where most of the body's lymphocytes are produced and stored.

lymphoid tissues

Tonsils are an example of these.

lymphoid organs

Spleen and thymus are an example of these.

lymphatic capillaries

smallest lymphatic vessels, also known as terminal lymphatics branch through peripheral tissues.

4 Differences between lymphatic capillaries and blood capillaries.

1. Originate as pockets rather than forming continuous tubes.
2. Have larger diameters
3. Have thinner walls
4. Typically have a flattened or irregular outline in sectional view.

Superficial Lymphatics

Located in the subcutaneous layer deep to the skin; in the areolar tissues of the mucous membranes lining the digestive, respiratory,urinary, and reproductive tracks; and in the areolar tissues of the serious membranes lining the pleural, pericardial, and

Deep lymphatics

Larger lymphatic vessels that accompany deep arteries and veins supplying skeletal muscles and other organs of the neck, limbs, and trunk, and the walls of the visceral organs.

thoracic duct

begins inferior to the diaphragm at the level of vertebra L2.

cisterna chyli

The base of the thoracic duct is an expanded, saclike chamber called:

right lymphatic duct

formed by the merging of the right jugular, right subclavian and right bronchomediastinal trunks in the area near the clavicle.

lymphdema

Blockage of the lymphatic drainage from a limb produces; a condition in which interstitial fluids accumulate and the lymph gradually becomes swollen and grossly distended.

Three classes of lymphocytes that circulate the blood

T cells (Thymus dependent)
B cells (Bone-marrow derived)
NK cells (Natural killer)

Primary types of T cells

Cytotoxic T cells, Helper T cells, Suppressor T cells.

Cytotoxic T cells

Attack foreign cells or body cells infected by viruses. Their attack commonly involves direct contact; primary cells involved in the production of cell-mediated immunity, or cellular immunity.

Helper T cells

Stimulate the activation and function of both T and B cells

Suppressor T cells

Inhibit the activation and function of both T cells and B cells

Plasma cells

Responsible for the production and secretion of antibodies.

Antibodies

soluble proteins also known as immoluglobbins

Antigens

Specific chemical targets

lymphopoiesis

lymphocyte production; involves the bone marrow, thymus and peripheral lymphoid tissues.

stromal (stroma, bed) cells

B cells development involves intimate contact with_______ in the bone marrow?

blood-thymus barrier

Does not allow free exchange between the interstitial fluid and the circulation, protecting the T-cells from being prematurely activated.