Week 2 Ch 16: The lymphatic system and lymphoid tissue

lymph nodes

filter lymph as they travel along the lymphatic system; filter and trap bacteria, viruses, cancer cells and other unwanted substances

lymph

fluid formed in the tissue spaces - interstitial fluid; transported by way of lymphatic vessels to reenter the circulatory system; clear and colourless; opaque and milky from small intestine

lymphatic capillaries

tiny blind-ended tubes distributed in tissue spaces; sheets consisting of one cell layer of simple squamous epithelium; poor fit btwn adjacent cells results in porous walls; called lacteals in the intestinal wall

fluid balance, protection from infection, absorption of fats

what are 3 main functions of lymphatic system?

supports the immune system

major defense against foreign organisms and impurities; protection from infections and cancers; lymphoid tissue filters pathogens, foreign matter, tumor cells and waste from body fluids

absorption of fats

fats are too big to enter blood capillaries; lymphatic capillaries absorb digested fats from the villi of the small intestine; carried in lymphatic vessel until lymph is added to blood

lymphatic circulation

one way system - have valves to ensure a one way flow through; beings in tissues, ends in bloodstream

superficial

immediately below the skin; often beside superficial veins

deep

deep vessels are usually larger and accompany the deep veins

right lymphatic duct, thoracic duct

what are 2 terminal vessels?

right lymphatic duct

short vessel that receives only the lymph from the upper right quadrant of the body; empties into the right subclavian vein; opening into this vein is guarded by two pocket like semi-lunar valves

thoracic duct

drains the rest of the body - all parts of body except those superior to diaphragm on right side, empties into left subclavian vein; largest lymphatic vessel

chyle

combination of fat globules & lymph; milky fluid that drains from the lacteals in the small intestine

valves in lymphatic vessels, skeletal muscle contraction, breathing

how does lymph move toward the heart?

lymph nodes

distributed throughout the body and filter lymph; located in clusters along the pathway of lymphatic vessels; cannot regenerate if destroyed

lymphoid tissue

makes up the specialized organs of the lymphatic system - spleen, thymus, tonsils; provides immune function, development of immune cells

defense, wbc formation

what are the lymph nodes and lymphoid organs functions?

afferent lymphatic vessels

carry unfiltered lymph into the node

hilum

indented area which serves as the exit for efferent lymphatic vessels

efferent lymphatic vessels

carry the filtered lymph out of the node so that it can continue its return to the circulatory system

metastasis

cancer cells can easily move through lymphatic vessels to other parts of the body through this process

outer cortex, inner medulla

what are the two regions lymph nodes are divided into?

cervical nodes

located in the neck in deep and superficial groups; drain parts of the head and neck; enlarge from upper respiratory infections

axillary nodes

located in armpits; enlarged after infections of the upper extremities and the breasts

mesenteric nodes

found between the two layers of peritoneum that form the mesentery

tracheobronchial nodes

found near the trachea and bronchial tubes; filled with airborne contaminates in people who smoke, are exposed to smoke or live in highly polluted areas

inguinal nodes

located in the groin area; drain from the lower extremities and from the external reproductive organs; buboes term used when enlarged

spleen

soft, purplish organ, approx 6 in long and 3 in wide - largest lymphoid organ; contains lymphoid tissue designed to filter blood; located in the upper left quadrant of abdomen, under diaphragm; has large blood supply

functions of spleen

cleanses the blood filtration and phagocytosis; destroys old, worn out rbc; produces rbc before birth; serves as a reservoir for the blood

splenectomy

surgical removal of the spleen; other lymphoid tissue can take over its functions; studies show this significantly increases mortality from cardiovascular disease

thymus gland

located in the upper thorax behind sternum; plays key role in early immune system development before birth and into the first few months of life - until puberty; shrinks after puberty - replaced by connective tissue and fat; produces thymosin

mucosal-associated lymphoid tissue (malt)

important barrier against infection; found in portions of the digestive, respiratory and urogenital mucosal linings; helps to destroy foreign contaminants

tonsils

masses of lymphoid tissue that removes contaminants and traps pathogens; surgery recommended if recurrent infection or enlarged tonsils make swallowing/breathing difficult

palatine tonsils

visible on each side of palate

pharyngeal tonsil

adenoid; behind nose - commonly enlarged in children

lingual tonsils

at posterior of tongue

lymphadenopathy

disease of the lymph nodes; enlarged lymph nodes due to cancer and infectious diseases; early sign of HIV

lymphadenitis

inflammation of the lymph nodes

infectious mononucleosis

acute viral infection; caused by herpes virus - epstein barr virus; results in cervical lymphadenitis; spread by saliva

lymphangitis

inflammation of the lymphatic vessels; usually begins in area of infected and neglected injury; characterized by red streaks - due to inflamed vessels radiating from source of infection; can result in septicemia

lymphedema

edema due to obstruction of lymph flow - caused by infection, malignant growth, loss of vessels; more prone to infection bc cannot filter lymph

elephantiasis

form of lymphedema; enlargement of the lower extremities resulting from blockage of the lymphatic vessels by parasite infestation

splenomegaly

enlargement of the spleen due to certain acute infectious diseases - scarlet fever, typhoid fever, syphilis, blood fluke

lymphoma

any tumor, benign or malignant that occurs in lymphoid tissue

hodgkin’s lymphoma

chronic malignant tumor of lymph nodes; unknown cause; common in young men; nodes are enlarged, esp in neck and also in armpit, thorax and groin

non-hodgkin’s lymphoma

more common; early sign - enlargement of lymph nodes especially in cervical region; affects older adults and individuals with deficient immune systems (aids)