Module 12: The Lymphatic System Flashcards
What are the three basic functions of the lymphatic system?
Fluid balance, fat absorption, and immunological defense.
Lymphatic tissue
Groups of lymphocytes and macrophages that provide immune protection.
Lymph nodes
Encapsulated masses of lymphatic tissue found along lymph vessels.
Lympth
Watery liquid formed from interstitial fluid and found in lymph vessels.
When does interstitial fluid become lymph?
Interstitial fluid becomes lymph when it enters a lymph vessel.
Where is lymph returned to the circulatory system?
It enters the system either through the right lymphatic trunks or the thoracic duct, which dump the lymph into the subclavian veins.
Lymph capillaries
Porous, blind beginnings of lymphatic vessels. They are made of epithelial cells.
How does lymph flow through the lymphatic system?
Skeletal muscles squeeze the lymph vessels, “pumping” them. One-way valves prevent the lymph from flowing backwards. Also, in the larger lymph vessels, contraction of smooth muscle moves the lymph. When you breathe, pressure changes in the thoracic region, pulling lymph into the thoracic duct and speeding its return to the subclavian vein.
Edema
A buildup of excess interstitial fluid in the tissues, which lead to swelling.
How does interstitial fluid leave the capillary?
Blood is flowing through the capillary under pressure, so it pushes out the fluid through pores. Blood cells and proteins are too large to be pushed out, however, leaving the interstitial fluid behind.
How does interstitial fluid reenter the capillary?
After bathing the cells in oxygen and nutrients and picking up waste products and carbon dioxide, the fluid is drawn back into the capillary by osmosis.
If the 10% of interstitial fluid left behind by the capillaries were not removed, what would happen to the body?
Too much interstitial fluid creates too wide a space between the cells and the all-important capillary blood supply, and diffusion of oxygen and nutrients to the cell is slowed. This can cause cells to die if the situation becomes severe enough.
Where does the 10% of interstitial fluid go since it cannot reenter the blood capillary?
The lymph capillaries pick up the fluid (now called lymph). It is sent into the larger lymphatic vessels, where it goes through one or more lymph nodes to be filtered. Then, the lymphatic system deposits its lymph into one of the two subclavian veins in the shoulders.
How does the lymphatic system maintain fluid balance?
It picks up the excess interstitial fluid in the tissues and returns it to the circulatory system.
Lacteals
Specialized lymph capillaries in the lining of the small intestine that collect fats absorbed by the small intestine during the digestive process.
Chyle
Lymph of the lacteals that has absorbed fat and taken on a milky-white color.
How do fats get into the circulatory system?
Lacteals collect fat and turn lymph into chyle. The chyle is then returned to the bloodstream at the left subclavian vein.
Immunological defense
The process by which the body protects itself from pathogenic invaders such as bacteria, fungi, parasites, and foreign substances.
Mucosa-associated lymphoid tissue (MALT)
Concentrations of lymphatic tissue without a connective tissue capsule.
Where is MALT located and why is that important?
MALT is located deep to the mucous membranes of the respiratory, digestive, urinary, and reproductive systems. These membranes line passages that open to the outside of the body and are therefore prone to infection by foreign invaders. MALT is strategically located to intercept such invaders.
Diffuse lymphatic tissue
Scattered lymphocytes, macrophages, and other cells found deep to mucous membranes. The least-organized form of MALT.
Where is diffuse lymphatic tissue usually found?
Besides its location deep to mucous membranes, is is found around lymph nodules and in the spleen.
Lymph nodules
Lymphatic tissue arranged into compact, somewhat spherical structures, but without a capsule.
Name the lymphoid nodules that form a protective ring around the throat.
The palatine tonsils (located on each side of the throat), the lingual tonsils (located at the base of the tongue), and the adenoids (located in the nasopharynx).
Peyer’s patches
Similar to tonsils, they are groups of lymphocytes in lymph nodules that are in the last third of the small intestine and in the vermiform appendix. They prevent the friendly bacteria that inhabit the large intestine from stirring up trouble in the small intestine.
Germinal centers of the lymph node
Centers formed by lymph nodules in a lymph node where rapid mitosis of lymphocytes can take place in response to a foreign invader found in the lymph.
What are the three main functions of lymph nodes?
- They test and monitor the blood through samples of blood plasma.
- If the sample is rife with foreign invaders, the nodes activate macrophages and lymphocytes to destroy them.
- They filter the lymph they have so clean lymph is returned to the blood.
What is the white pulp of the spleen composed of?
The white pulp is composed of diffuse lymphatic tissue and lymph nodules that surround the arteries that enter the spleen.
What is the red pulp of the spleen composed of?
The red pulp is made up of specialized veins with reticular fibers. They receive blood that was in the capillaries of the spleen.
How does the spleen filter the blood?
As the blood passes through the white pulp of the spleen, foreign invaders stimulate a response from the diffuse lymphatic tissue or the lymph nodules.
How does the spleen clear the blood of worn-out erythrocytes?
As the blood leaves the spleen through the veins, it passes through the red pulp. Old red blood cells are stiff, and their membranes break as they go through the reticular fibers of the red pulp. Macrophages in the red pulp engage in phagocytosis to remove the old blood cells.
How does the spleen act as a reservoir for oxygen-rich blood?
The spleen holds more blood than it needs. If the body detects blood loss due to hemorrhage, the sympathetic division of the ANS stimulates the smooth muscle in the spleen’s capsule to contract and push the backup supply of blood into the bloodstream to compensate for the blood loss.
What are the three primary functions of the spleen?
- It filters the blood.
- It clears the blood of old erythrocytes.
- It acts as a reservoir for oxygen-rich blood in the case of blood loss.
How does the thymus gland change as a person matures?
When a person is young, the gland grows and is mostly made of lymphatic tissue. After puberty, it gradually decreases in size, becoming mostly fibrous and fatty tissue in old age.
Thymic education
Pre-T lymphocytes leave the red bone marrow (where they were made) and and travel to the thymus. Thymic education is the maturation process that turns beneficial pre-T lymphocytes into T lymphocytes and eliminates detrimental pre-T lymphocytes.
Pathogenic bacteria
Harmless bacteria that do no damage and may even benefit the body, but also give you sinus infections, infected cuts, etc.
