The Lymphatic system Flashcards
What is the lymphatic system? Give its functions and what it consists of
Absorbs dietary fat from the intestine, protects from foreign invaders, maintains ECF volume by returning excess tissue fluid to the blood.
It consists of lymph, lymphocytes, lymphatic plexuses and vessels, lymph nodes and other lymphoid organs.
Describe the journey of lymph through the lymphatic system
The lymphatic capillaries carry the lymph first through lymphatic plexuses→lymphatic vessels→lymphatic trunks → drains into the venous system through the thoracic and right lymphatic duct.
What does this image show?
Valves are the denser green sections. The lymphatic capillaries communicate w the deep collecting vessels
What is lymph and what does it contain?
Lymph is formed from interstitial (tissue) fluid
ISF originates as a plasma filtrate
Lymph contains salts, proteins, fat, lymphocytes, dendritic cells and macrophages
What are lymph nodes/glands?
Lymph travels from lymphatic capillaries to collecting vessels, into lymph nodes
Lymph nodes filter the lymph and check for foreign invaders
Label this lymph gland
Why is the lymphatic system so important in immunity?
Lymph vessels absorb microbes and transport them to lymph glands for acquired immunity.
Secondary Lymphoid Organs capture foreign invaders, and lymphocytes are activated. SLOs inc:
- Lymph nodes
- Mucosa-associated lymphoid tissue (MALT) e.g. tonsils, Peyer’s patches
- Spleen
What is tissue fluid homeostasis?
Tissue fluid is formed from plasma escaping through the blood vessel wall
Tissue (interstitial) fluid drains predominantly as lymph and not by venous reabsorption
Using starling’s principle of fluid exchange, explain why pulmonary oedema occurs in left sided heart failure
The lung generates lymph
Pulmonary capillaries undergo filtration bc pulmonary interstitial protein conc is high. So, osmotic pa gradient
Left sided HF increases pulmonary capillary pa, increasing filtration. If lymph drainage doesn’t increase→oedema in lung parenchyma.
ISF can overflow into alveoli and impair O2 exchange
What type of lymph biopsy is taken in suspected cancer?
Sentinel lymph node biopsy (taking an axila lymph node to look for cancer cells)=staging investigation for breast cancer.
What is pitting oedema?
Indicates an excess of interstitial fluid. Results from:
- too much fluid filtration from blood vessels, overwhelming lymph drainage
- or too little lymph drainage
What is venous oedema?
Varicose veins or venous engorgement e.g. heart failure, creates high venous pa. This increases microvascular fluid filtration into tissues.
If lymph drainage is adequate then oedema can be avoided
What is lymphoedema?
Occurs in failure of lymph drainage w no increase in capillary filtration, eg:
breast cancer lymphoedema due to removed lymph gland or radiation damage to lymph drainage pathway
Elephantiasis-worm infection transmitted by mosquitoes, blocks lymph vessels
Primary lymphoedema: due to an inborn, genetic lymph drainage fault - eg Milroy Disease due to mutations in the VEGFR3 gene
What is cellulitis?
Cellulitis is a common, recurrent complication of impaired lymph drainage
Impaired immune cell trafficking→failure to eradicate the infection→serious inflammation.
How is the lymphatic system involved in fat transport?
The mucosa of the small intestine is covered w villi.
Lymph capillaries called lacteals in villus center absorb the fat from the intestine.
Lymph capillaries merge to form the lymph nodes which filter the lymph. Lymph empties into subclavian veins.
So fat level never rises sharply in blood and it helps in maintaining the health of arterial walls.
