An overview to help learn things by heart for the 1st year anatomy exam at Cambridge medical school.

1. Notes on lymphatics 1
C. Riedinger 2011
LYMPHATIC SYSTEM
Consists of:
lymph - lymphocytes - lymphatic vessels - lymph nodes - lymphatic organs
Function:
- maintains fluid balance (prevent oedema)
- absorbs facts from small intestine
- proliferation, development and storage of immune cells
- defends against microorganisms and foreign substances
- =part of circulatory and immune system!
Lymph:
- formed from interstitial fluid (derived from blood)
- consistency similar to blood plasma (cellular components of blood cannot
leave the capillaries)
- taken up by passive diffusion and transient negative pressures in their lumina,
generated by contractile activity of smooth muscles in largest lymphatic vessel
walls (or by movement of other tissues)
- clear and colourless, but from small intestine: dense and milky due to
chylomicrons
- lymph in lacteals (because lymph here is white!) of small intestine is called
chyle
Lymphatic vessels:
- parallel circulatory system
- originates in peripheral tissues as blind-ended endothelial tubes (simple
squamous with valves)
- not present in cornea, cartilage, thymus, CNS, PNS, bone marrow, epidermis
and very few in endomysium of skeletal muscles
- collect excess fluid form the interstitial spaces (10%)
- smallest = lymph capillaries
o resemble capillaries but endothelial lining permeable to larger
molecules, such as colloidal proteins and particulate material (cell
debris, microorganisms)
o have funnel-shaped valves
o area between two valves: lymphangion
o intercellular junctions lack tight junctions
o no intrinsic contractility
o extrinsic forces for propulsion: respiratory movement, muscle
contraction, pulse pressure of adjacent arteries
- terminal lymphatic vessels in mucosa of small intestine: lacteals
- lymphatic capillaries join into larger vessels which pass to local lymph nodes
- lymph passes through series of nodes until it reaches a major collecting duct
(few drain directly, such as thyroid, oesophagus, coronary and triangular
ligaments of liver to thoracic duct)
- largest lymphatic vessels (200um) like small veins, but with more valves
(semilunar)
- lymph drains into large veins in the root of the neck
- almost all reach either thoracic or right lymphatic duct

2. Notes on lymphatics 2
C. Riedinger 2011
Right lymphatic duct:
- Drains right half of head and neck, right arm and right hemithorax
Thoracic duct:
- Similar to medium-sized vein, but more prominent smooth muscle in tunica
media.
- Drains rest of body
- Ascends in the posterior mediastinum between the descending thoracic aorta
and the azygos vein
- Length 38-45cm
- From L2 to root of the neck
capillaries  afferent vessels  lymph node  efferent vessels  lymph trunk 
terminal vessels (TD, right lymphatic duct)  great veins
Lymph nodes:
- filter lymph
- have convex cortex into which afferent vessels open
- also have medulla and hilum (concave surface), through which efferent vessel
exits
- are encapsulated centres of antigen presentation and lymphocyte activation,
differentiation and proliferation
- generate antigen-primed B and T cells
- filter particles (i.e. microbes) from the lymph by phagocytic macrophages
- ~450 in total
o 60-70 head and neck
o 100 thorax
o 250 abdomen and pelvis
- mainly close to viscera, in mesenteries
- lymph flows through channels in lymph nodes after entering from afferent
vessels
- reticulin to support sinus macrophages
- superficial lymph nodes: inguinal region, axilla, neck
o receive lymph from skin, mucous membranes, serous linings
o superficial system drains to the deep system
- deep lymphatic vessels: preaortic, para-aortic, bronchomediastinal
o drain organs
o accompany arteries or veins
Lymphatic organs:
- clusters of lymphocytes and other cells (macrophages) in framework of short
branching connective tissue fibres
- lymphocytes from bone marrow, but proliferate within lymphatic organs
- tonsils, spleen, thymus gland
Spread of disease:
- easy for tumour to enter, slow flow does little damage to foreign cells
- presence of metastases in lymph nodes indicates metastases to distant organs
- lymphadenitis: inflammation, lymphangitis: infection of vessels (red line
under skin) lymphoma: cancer of lymphocytes