The Lymphatic System

Vocabulary flashcards covering the functions, circulation, ducts, and organs (lymph nodes, spleen, tonsils, and thymus gland) of the lymphatic system.

Lymphatic system functions

1. Drain excess fluids from tissues and return them to the venous system to maintain fluid balance among plasma, interstitial fluid, and lymph;

2. Maintain the proper balance of molecules in the interstitial fluid;

3. Help fight disease.

Lymphatic circulation

A one-way delivery system that does not circulate; it begins at closed-ended lymph capillaries and carries lymph forward to empty into the venous system.

Lymph capillaries

Microscopic vessels that branch throughout most soft tissues with closed outer ends, possessing a structure otherwise similar to blood capillaries.

Lymph

A colourless to pale yellow fluid formed when interstitial fluid diffuses into lymph capillaries.

Lymph veins

Vessels formed by the merging of lymph capillaries; structurally similar to blood veins, but containing more valves.

Right lymphatic duct

A large lymphatic vessel that collects lymph from the upper right quadrant of the body and empties it into the right subclavian vein.

Thoracic lymphatic duct

A large lymphatic vessel that collects lymph from the rest of the body (excluding the upper right quadrant) and dumps it into the left subclavian vein.

Lymph nodes

Bean-shaped structures occurring in clusters (found in the throat, groin, abdomen, armpits, and behind the knees where larger lymphatic veins meet) that filter lymph, produce lymphocytes, and trap circulating bacteria.

Macrophages (in lymph nodes)

Specialized cells within lymph nodes that trap and destroy bacteria circulating through the body.

Swollen glands

Enlarged lymph nodes that occur when an infection triggers an increase in white blood cell (WBC) count.

Spleen: quality control

The splenic function of filtering blood to remove old, malformed, or damaged RBCs, utilizing WBCs to break down rejected RBCs, and storing recovered iron to return it to the bone marrow.

Spleen: blood reservoir

The spleen's capacity to adjust vessel diameter to store an extra $250\,\text{ml}$ of blood, which can be released into circulation in the event of trauma.

Spleen: immune function

The filtering of lymph to recognize bacteria and respond by producing lymphocytes; its absence leaves individuals more vulnerable to infections.

Spleen: embryonic stage function

The production of red blood cells (RBCs) during embryonic development.

Spleen non-essentiality

The characteristic of the spleen being non-essential for life because all of its functions can also be performed by the liver, lymph nodes, and/or bone marrow.

Tonsils

Lymphoid structures that produce lymphocytes and act as protective barriers preventing bacteria from entering the lower body by filtering lymph and releasing lymphocytes.

Palatine tonsils

The pair of tonsils located at the back of the mouth.

Lingual tonsils

The set of tonsils situated at the base of the tongue.

Adenoids

Tonsillar tissue located in the upper pharynx that is sometimes surgically removed.

Thymus gland

A lymphatic organ where T cells are trained to attack only foreign cells; it grows throughout childhood and gradually shrinks following the onset of puberty.