Lymphatic system pathology Flashcards
What is the lymphatic system?
cleansing system for body
countercurrent system draining from the tissues, plus waste molecules
How is the lymphatic system organised?
network of drainage tubes connected to lymph glands which act as drainage channels for the body’s tissues.
What is the nature of lymphatic capillaries?
= initial lymphatics
- bling ended
- no smooth muscle
- non-continuous basement membrane
essentially endothelium with some incomplete basement membrane
act as a sponge to drain fluid from the peripheral tissues
What is the nature of collecting vessels in the lymph system?
- smooth muscle coverage
- luminal valves
- basement membrane
How is lymph fluid formed at the tissues?
Initial lymphatics absorb fluid, salts, proteins and cells from the tissues to make lymph.
Lymph is transported down bigger lymphatic vessels which actually contract so pumping lymph onwards.
Valves ensure lymph flow is in one direction (downstream) to the lymph glands (nodes) and beyond
What is the function the LNs in lymph fluid drainage?
to filter the lymph and allows interaction with the immune system
then lymph drains into the greater vessels of the neck
What is lymph?
interstitial fluid containing salts, proteins and cells originally formed from a plasma ultrafiltrate
What are lymph nodes?
filter stations positioned at intervals along the drainage route.
2 main functions:
- clean the lymph before it re-enters systemic circulation
- monitor lymph for signs of organic predators (e.g. infection)
What are the 3 main functions of the lymphatic system?
- fluid balance
- immune function
- fat balance
What happens when plasma ultrafiltration exceeds lymph drainage over a period of time?
plasma ultrafiltration = lymph load
OEDEMA develops
What is chronic oedema a sign of?
LYMPHATIC FAILURE
either lymph drainage is insufficient
or
lymph load exceeds lymph drainage capacity
What are the mechanisms for chronic oedema?
RELATIVE LYMPHATIC FAILURE
increased capillary filtration e.g. heart failure, venous oedema
ABSOLUTE LYMPHATIC FAILURE no increase in capillary filtration (normal lymph load) or exhaustive lymph drainage capacity e.g. lymphoedema
What is the cause of venous oedema?
high lymph load from venous hypertension which overwhelms the lymph drainage
When may a state of lymphoedema exist?
if lymph drainage system is permanently damaged
What is cellulitis?
infection/inflammation of skin
usually caused by strep or staph A
can be present in lymphoedema patients
caused by inefficient immune cell trafficking, unable to therefore reach infection site
What is an alternative name for cellulitis?
erysipelas
What is the function of lymph system in fat balance?
The Lymphatic System is responsible for gut fat absorption and peripheral fat resorption
What may disturbances in lacteal function cause?
malabsorption (of fat)
What is non-pitting oedema?
lymphoedema with high fat content
What is the relationship between lymphatic system and fat homeostasis?
2 way relationship
lymph system is important for fat absorption
BUT obesity can impair lymphatic function
What are 2 tropical cause of lymphoedema?
filariasis (elephantiasis)
Podoconiosis (silicate poisoning in feet)
What is primary lymphoedema?
= intrinsic failure of the lymphatic system
- usually caused by developmental abnormality
- phenotypes vary in onset, site, inheritance and associated features etc
What is secondary lymphoedema?
= damage to lymph system
What is a lymphatic malformation?
lymphatic birthmark
affects tissue-specific defects only
usually caused by post-zygotic de novo mutation or mosaicism
What is the management of chronic oedema?
“physically based”
intended to stimulate lymph drainage and reduce vascular plasma filtration
e.g. compression stockings
Which diseases are associated with lymphatic dysfunction?
- respiratory disease (asthma, bronchiectasis)
- CVS (hypertension, MI)
- CNS (glaucoma, dementia)
- infection and immunity (HIV, organ rejection)
- GI (Crohn’s disease)
- Cancer mets
- obesity and hypercholesteraemia
What is the structural basis of the active lymph transport system?
INTRALUMINAL VALVES
- unidirectional flow
LYMPHATIC SMOOTH MUSCLE
- pumping
