principles of lymphatic system Flashcards
What is the lymphatic system?
part of circulatory system (sometimes said to be part of immune system too)
What is the lymphatic system comprised of?
- lymph
- lymphatic vessels
- immune cells
- lymphoid organs
What does the lymphatic system do?
- fluid balance (returns interstitial fluid back to circulation)
- protection (scanning/processing of pathogens)
- fat absorption from GI tract
What is lymph?
fluid similar to plasma but containing substances too large to pass through blood capillary walls
How is lymph formed?
fluid gets pushed out of capillaries by high arterial (hydrostatic) pressure
Where does lymph go?
it is brought back into venous circulation via a network of lymphatic vessels
Where do networks of lymphatic vessels start?
blind-ended capillaries found in intercellular spaces
What is a key feature of lymphatic capillary lumen?
they are bigger than blood capillaries
What are the key features of lymphatic capillary walls?
- one layer of endothelial cells
- lack tight junctions
- discontinuous basal lamina
- anchoring filaments made of collagen
What are key features of lymphatic vessel walls?
- increasing amounts of smooth muscle and connective tissue
- still relatively thin
- valves are present (beaded appearance)
What is an afferent lymphatic vessel?
takes lymph into lymph node
What is an efferent lymphatic vessel?
takes lymph away from lymph node
Describe superficial lymphatic vessels
- subcutaneous layer of skin (follow veinous drainage)
- drain superficial structures
- drain into deep lymphatic vessels
Describe deep lymphatic vessels
- accompany arteries
- drain viscera (internal organs)
- larger and drain into lymphatic trunks
What are the key features of lymphatic trunks?
- receive lymph from lymph vessels
- unite to form lymphatic ducts
How are lymphatic trunks named?
they are named according to the region of the body they drain
What are the 4 pairs of lymphatic trunks?
- lumbar (abdomen)
- bronchomediastinal (thorax)
- subclavian (around clavicles)
- jugular (neck)
What are the key features of lymphatic ducts?
- similar to small veins
- underdeveloped tunica adventitia
- vasa vasorum
What are the two main lymphatic ducts?
- right lymphatic duct
- thoracic duct
What does the right lymphatic duct drain and into what?
drains the right upper quadrant of the body into the right venous angle
What does the thoracic duct drain and into what?
drains remainder of body into left subclavian vein
What is the cisterna chyli?
dilated collecting sac formed by merging of lymphatic trunks draining the lower half of the body
Where does the thoracic duct originate from?
cisterna chyli
Which lymphatic duct is the largest in the body?
thoracic duct
What does the thoracic duct ascend through?
aortic hiatus in diaphragm (hole in diaphragm for passage of aorta)
What do the primary lymphoid organs do?
production and maturation of lymphocytes
What are the primary lymphoid organs?
- bone marrow
- thymus
What happens in the bone marrow (in terms of immunity)?
- T cell and B cell differentiation
- B cell maturation
What happens in the thymus (in terms of immunity)?
T cell maturation
What are secondary lymphoid organs for?
activation of lymphocytes and immune response initiation
What are some examples of secondary lymphoid organs?
- lymph nodes
- aggregations of lymphatic tissues in mucosal tissues
- spleen
What are the functions of the spleen?
- filters blood
- immunity to blood borne pathogens
- removes senescent and defective erythrocytes (RBCs)
- recycles iron from degraded haemoglobin
What is the largest lymphatic organ and where is it located?
- spleen
- abdominal cavity
What are the two main regions of the spleen?
- white pulp
- red pulp
Describe the white pulp region of the spleen
consists of lymphatic tissue
Describe the red pulp region of the spleen
large numbers of erythrocytes, macrophages, other immune cells
Describe the structure of lymph nodes?
- oval
- slight depression on side called hilum
- fibrous capsule and gland substance
- below capsule is sub capsular substance
What is the gland substance divided into?
- cortex: outer portion
- medulla: inner portion
What are the functions of lymph nodes?
- filtration of lymph
- immunity (plasma cells here produce antibodies)
- produce lymphocytes (in germinal centre of lymphatic nodules)
- provide portal of entry to lymphocytes into lymphatic vessels
What are primary nodes?
the first node/group within a chain
What are terminal nodes?
last node/group within a chain
How is lymph drainage of the breast distributed?
- 75% axillary
- 25% parasternal nodes
What are the 3 important mucosa associated lymphoid tissues?
- GI tract (GALT)
- respiratory system (BALT)
- genitourinary tract (MALT)
