The lymphatic system Flashcards
What is lymph and what is it composed of?
A fluid similar to blood plasma, containing lymphocytes, water, electrolytes, waste from the cells and some proteins, although far fewer plasma proteins than blood plasma
What is lymph formed from?
It is formed from the blood plasma and tissue fluid
Does lymph return as venous or arterial flow?
Venous
What speed relative to blood flow does lymph circulate?
Much slower
What actions generate lymphatic flow?
Indirect:
Pressure gradients
Muscleskeletal pump
Respiratory pump
Direct:
Contraction of smooth muscle and valves in vessel walls
What structural differences are there between veins and lymphatic vessels?
Lymphatic vessels are thinner and have more valves inside of them
What are the two main lymphatic ducts?
Right lymphatic duct, thoracic duct
Where does lymph enter back into the bloodstream?
Right and left subclavian veins
What is the structure of lymph nodes?
Small bean shaped organs (0.5-2.5cm long) with a convex face receiving 4-5 afferent lymph vessels and a concave face where an artery enters and a vein and efferent lymph vessel leave. Inside, large clusters of lymphocytes and macrophages called lymph modules are separated and encased by a fibrous capsule and reticular tissue.
What is the function of lymph nodes?
Detoxification and filtration of lymph
How many efferent vessels does each lymph node have?
One
What is the largest lymphatic organ?
The spleen
What is the internal structure of the spleen?
Venous sinuses called red pulp, and white pulp
What is red pulp?
Storage areas of red blood cells in the spleen
What is white pulp?
Storage areas of white blood cells in the spleen
What are the main functions of the spleen?
Controlling the levels of white blood cells, red blood cells and platelets
Screening the blood removing old or damaged red blood cells
Storing iron for future use
Storage of blood (≈350mL)
Erythropiesis
How does the spleen help screen the blood?
By extracting microbes and destroying them with phagocytosis
How does the spleen aid in haematopoiesis?
By enabling leukocytes to complete maturation
How much excess fluid is filtered out from blood capillaries each day?
3-4 L
What are the lymphatic organs?
Red bone marrow, spleen, thymus, tonsil
Where are lymphocytes located?
Some are fixed in lymphoid organs and other circulate through the blood and lymph allowing them to ‘patrol’ all areas of the body
Why do lymphatic vessels have more valves than blood vessels?
They have a slower and weaker flow of fluid so need more valves to prevent backflow
What routes do lymphatic vessels of the viscera follow?
They follow the arteries, forming plexuses around them
What routes do lymphatic vessels generally follow in the skin?
The same as veins through subcut tissue
Where do the lumbar lymph trunks drain lymph from?
Lower limbs, pelvic region, kidneys and adrenal glands
Where does the intestinal lymph trunk receive fluid from?
The stomach, intestines, pancreas, spleen and liver
What fluid does the intestinal lymph truck receive?
Chyle, lymph mixed with ingested fats
Where do the bronchomediastinal lymph trunks drain lymph from?
The lungs, mediastinal organs, mammary glands and thoracic wall
Where do the subclavian lymph trunks receive lymph from?
Upper limbs and axilla
Where do the jugular lymph trunks drain lymph from?
The head and neck
Where is the cisterna chyli located?
Anterior to L2
What are the primary lymphatic organs?
Sites where lymphocytes are activated. Red bone marrow and thymus
What are the secondary lymphatic organs?
Sites where most immune responses occur. Lymph nodes, spleen and tonsils.
What are the specific regions of the body associated with clusters or particular abundance of lymph nodes?
Pericranial ring
Cervical nodes
Tracheal nodes
Axillary nodes
Deep nodes
Inguinal nodes
Femoral nodes
Where is the thymus located?
Directly behind the sternum, extending from the top of the sternum to the 4th costal cartilage
What lymphocytes develop in the thymus?
T lymphocytes
Where is the spleen located?
In the left hypochondrium of the abdomen, lying between the diaphram, stomach and kidneys
What is the purpose of the lymphatic system?
To drain and filter the excess interstitial fluid that is not reabsorbed into the capillary bed and return it to venous flow
Transport dietary lipids and lipid soluble vitamins absorbed via the GI tract
Immune response
Where in the body does lymph return to the venous circulation?
The left and right subclavian veins
What immune cells do lymph nodes contain?
Lymphocytes and macrophages
Why are fats absorbed by the lymphatic system?
They are too large to be absorbed straight into the blood stream, they would clog the intestinal capillaries
