Introduction to the Lymphatic System Flashcards
what is the Lymphatic System?
→ countercurrent system draining from the tissues all waste materials and recycling surplus fluid, salts, proteins, fat and immune cells back to body
→ Lymphatic System is the cleansing system
The lymphatic system (Drainage)
→network of drainage tubes connected to lymph glands
→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 veins of the neck.
Lymphatic system appearance
→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
what do Initial lymphatics absorb?
→ fluid
→ salts
→proteins and cells from the tissues to make lymph.
where is lymph transported to?
→transported down bigger lymphatic vessels which actually contract so pumping lymph onwards
what do valves ensure?
→Valves ensure lymph flow is in one direction (downstream) to the lymph glands (nodes) and beyond
what happens once the lymph is absorbed into initial lymphatics?
→Once absorbed into initial lymphatics
→lymph is pumped up the leg
→because larger lymphatic vessel contract in a similar way to our main heart
what do 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
what is the function of lymph nodes?
→ 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
→ plays a vital role in our immune system responses
what is the first function of the lymphatic system?
fluid balance(homeostasis)
How many litres of plasma is filtered a day?
8 litres
What is the process do filtration dependent on?
dependent on Starlin forces. The balance of foces eg the hydrostatic pressure of the water an osmotic pressure
What is the nature of venous filtration?
is only transient and does not occur in the steady state. We now know there is a steady state of filtration along the blood vessels.
What is interstitial fluid at any time dependent on?
on how much is filtered from the blood vessel and how much is drained by the lymphatic system.
What are the three mechanisms of chronic oedema?
- Lymphatic failure with increased capillary filtration (high lymph load overwhelming lymph drainage capacity) = relative lymphatic failure e.g. heart failure, venous oedema
- 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)
How does venous oedema arise?
• Vecarious veins result in higher venous pressure and hydrostatic pressure within the veins that forced more fluid in to the tissue
What happens if one’s drainage is robust?
• If the lymph drainage is robust no oedema occurs despite the high volumes of fluid entering.
What is lymphoedema?
Lymphoedema is a chronic swelling due to lymph drainage failure.
results in swelling such as a leg with build up of fluid, cells and fat, as well as a predisposition to infections
What happens in varicose veins in venous disease?
there is a higher volume of fluid leaving the blood vessels (small veins and capillaries) and entering the tissues of the feet, ankles and legs
Second function of the lymphatic system
tissue immunity
What is the lymphatic system responsible in terms of immunity?
houses the immune system and is responsible for tissue immunosurveillance
What is cellulitis?
Recurrent cellulitis always means a problem with lymph drainage.
Up to 50% lymphoedema patients suffer at least one attack of cellulitis.
the lymphatic system is damaged or overloaded and does not function adequately to fight infection
What is he dermal lymphatic?
holds centre stage immunologically in any tissue.
to promote the movement of interstitial fluid and protein molecules back to the circulation.
What is the role of the lymphatic system in terms of fat homeostasis?
responsible for gut fat absorption and peripheral fat resorption:
for absorption of dietary fat.
Lacteal lymphatic capillary that absorbs dietary fats in the villi of the small intestine
Disturbances in lacteal function lead to malabsorption
What is the role of the sentinel lymph biopsy?
designed to detect lymphatic spread of cancer and guide treatment.
What is podoconiosis?
lymph vessels become poisoned from silicates in the soil entering the skin and lymph system when children walk barefoot
Primary Lymphoedema, ad give causes
intrinsic failure of the lymphatic system
• Chronic oedema caused by a developmental abnormality of the lymphatic system
• Phenotypes vary in age of onset, site, inheritance patterns, associated features, genetic causes
AT least 4 genes involved
Give examples of lymphoedema treatment
- Intraluminal valves- unidirectional flow
* Lymphatic smooth muscle- pumping
Recall some diseases associated with lymphatic dysfunction(7)
- Respiratory disease: Asthma, Chronic airways disease, Bronchiectasis, Plural effusion
- CVS : Hypertension, Body fluid balance, Atherosclerosis, recovery from Myocardial Infarction
- CNS: Glaucoma, Dementia
- Infection and Immunity: HIV, Organ rejection, Autoimmunity, Cellulitis, Sepsis, wound healing, tissue repair
- GI: Crohn’s disease causing disturbed phagocytosis
- Cancer Metastases
- Obesity and Hypercholesterolaemia
Describe pulmonary oedema
Pulmonary oedema in heart failure is due to raised pulmonary venous pressure causing increased amounts of interstitial fluid which is not sufficiently cleared by lymph so congesting the lung. This interstitial oedema spills out into the alveoli and interferes with O2 exchange
What failure of a side of the heart increases pulmonary capillary?
Left sided heart failure increases pulmonary capillary pressure, increasing filtration. Unless lymph drainage increases accordingly, oedema occurs in lung parenchyma
The lung generates lymph even though…
pulmonary capillary pressure (10mm Hg is much lower than plasma COP (25 mm Hg).
Pulmonary capillaries are in a filtration state because pulmonary interstitial protein concentration is high (70% of plasma). The COP gradient is therefore lower than the Hydraulic pressure gradient.
What is the role of the sub glycocalyx?
The subglycocalyx acts as a regulator or stabilizer for filtration so the default position is no reabsorption
