W11 Intro to lymphatic system Flashcards
What is the Lymphatic System?
the lymphatic system acts as a countercurrent system draining from the tissues all waste materials and recycling surplus fluid, salts, proteins, fat and immune cells back to body
the Lymphatic System is the cleansing system
The lymphatic system (Drainage)
a network of drainage tubes connected to lymph glands which act as drainage channels for the body’s tissues
one way drainage system
Starting with small blind ending tubes like sea anemones they drain into small streams and then ever bigger channels drain to lymph glands and beyond before eventually draining back into the blood circulation in the great vveins of the neck
Lymphatic system appearen
Dermal lymphatic vascular network
Lymphatic capillaries (initial lymphatics):
Blind ended
No smooth muscle
Incontinuous basement membrane
Collecting vessels:
Smooth muscle coverage
Luminal valves
Basement membrane
Initial lymphatics absorb …
Initial lymphatics absorb fluid, salts, proteins and cells from the tissues to make lymph.
Lymp is transported to?
transported down bigger lymphatic vessels which actually contract so pumping lymph onwards
Valves ensure?
Valves ensure lymph flow is in one direction (downstream) to the lymph glands (nodes) and beyond
Once absorbed into initial lymphatics lymph …
Once absorbed into initial lymphatics lymph is pumped up the leg because larger lymphatic vessel contract in a similar way to our main heart
Lymph nodes filter…
filter the lymph where there is also interaction with the immune system
Discharging lymph
After passing through a series of lymph nodes large lymphatic vessels eventually discharge lymph into great veins of the neck
What is Lymph?
Lymph is interstitial (tissue) fluid containing salts, proteins and cells,
originally formed from a plasma ultrafiltrate
What are Lymph Nodes (Glands)?
Lymph glands are filter stations positioned at intervals along the lymph drainage route
Lymph nodes function
To clean up the lymph before it re-enters the blood stream, by sieving out, trapping and destroying (inorganic) foreign materials
Monitoring the lymph for tell tale signs of (organic) predators e.g.infection, so playing a vital role in our immune system responses
The first function of the Lymphatic System
The first function of the Lymphatic System is fluid balance(homeostasis)
‘Clears away the mess the CVS leaves behind!’
Lymp facts
Upwards of 8 litres a day of plasma is filtered into the tissues and then reabsorbed almost entirely by the lymph drainage
Steady state
all vascular filtrate/interstitial fluid drains via the lymphatic with only periods of transient reabsorption directly back into the blood circulation.
So any build up of fluid in the tissues for any length of time i.e. oedema, represents a failure of the lymph system to do its job properly i.e. act as an overflow pipe
CHRONIC OEDEMA
= LYMPHATIC FAILURE
Either lymph drainage is insufficient or lymph load (vascular fluid filtration) exceeds lymph drainage capacity
A swollen ankle
e.g. in the heat or after a long haul flight, is not normal and always means lymph drainage is not keeping up with fluid filtration (lymph load) from the blood vessels
Lymphatic failure with increased capillary filtration
(high lymph load overwhelming lymph drainage capacity) = relative lymphatic failure
Lymphatic failure with no increase in capillary filtration
(normal lymph load) = absolute lymphatic failure (lymphoedema)
Lymphatic failure resulting from sustained increased capillary filtration
exhausting lymph drainage capacity = absolute lymphatic failure (lymphoedema)
Chronic venous disease and oedema
higher volume of fluid leaving the blood vessels (small veins and capillaries) and entering the tissues of the feet, ankles and legs
has to be drained from the tissues by the lymph
If lymph drainage overwhelmed = venous oedema
but rate limiting step = lymph drainage
Chronic venous disease and no oedema
If the lymph drainage is robust no oedema occurs despite the high volumes of fluid entering
Breast cancer related lymphoedema
commonest disease (of lymph)
chronic swelling due to lymph drainage failure
If oedema persists after treatment of the veins….
then the lymph drainage is permanently damaged and a state of lymphoedema now exists
Lymphoedema following treated heart failure
Eventual and permanent failure of lymph drainage from high sustained lymph load (equivalent to hypertensive heart failure
The second function of the Lymphatic
tissue immunity
The Lymphatic System houses the immune system and is responsible for tissue immunosurveillance
A common complication of impaired lymph drainage is disturbed immune cell trafficking and infections
Cellulitis (erysipelas)
Cellulitis frequently reflects a problem with lymph drainage. Recurrent cellulitis always means a problem with lymph drainage
The dermal lymphatic holds ?
The dermal lymphatic holds centre stage immunologically in any tissue
The third function of the Lymphatic System
is fat homeostasis
The Lymphatic System is responsible for gut fat absorption and peripheral fat resorption
The intestinal lymphatic system is responsible for ?
for absorption of dietary fat. Disturbances in lacteal function lead to malabsorption.
Impaired lymph drainage in peripheral tissues
results in a build up of subcutaneous fat as seen in Breast Cancer Related Lymphoedema.
Lymphoedema which arises from a failure of lymph drainage is not just a fluid problem
Close relationship between fat and lymphatics
The lymph system appears important for fat homeostasis. Obesity impairs lymphatic function.
Lymphoedema occurs when
when the lymphatic system fails
Lymphoedema results
in swelling such as a leg with build up of fluid, cells and fat, as well as a predisposition to infections
podoconiosis
Here lymph vessels become poisoned from silicates in the soil entering the skin and lymph system when children walk barefoot.
Chronic oedema caused by
by a developmental abnormality of the lymphatic system
Damage to lymph drainage is known as
secondary lymphoedema
Primary lymphoedema
when lymphoedema occurs for reasons of of an intrinsic fault in drainage and may be much more common than generally realised
What is the management of lymphoedema/chronic oedema?
not one drug or one operation known to improve lymph drainage
treatment = physically based, to stimulate lymph drainage and reduce blood vascular filtration (lymph load)
The structural basis of the active lymph transport system:
Intraluminal valves
- unidirectional flow
Lymphatic smooth muscle
- pumping
Respiratory disease:
Asthma, Chronic airways disease
CVS :
Hypertension, Plasma volume homeostasis, Atherosclerosis
CNS
Glaucoma, Dementia
Infection and Immunity
HIV, Organ rejection, Autoimmunity, Cellulitis, Sepsis, wound healing, tissue repair
GI
Crohn’s disease
Other Diseases of Lymphatic Dysfunction
Cancer Metastases
Obesity and Hypercholesterolaemia
