What are the differences between arterial and venous interstitial pressures?
- The main difference is that in arterials the capillary hydrostatic pressure is higher than in veins
- The other values are the same
- This difference creates a tendency of the fluid to leave the arterial components, while venous components have a tendency for fluid to enter them
Why is interstitial fluid pressure negative?
- Negative, bc the balance of forces at the capillary membrane require a negative interstitial force to maintain a fluid equilibrium
- The negativity is maintained by the continuous pumping of proteins into the lymphatic system from the interstitial spaces
- Without this negative pressure there would be a net inflow of interstitial fluid back into the capillary
What is oedema?
- Where there is excess interstitial fluid in the tissues a swelling or oedema of the tissues may occur
What is the excess interstitial fluid in oedema due to?
An increased interstitial fluid pressure from its normal negative value (-6.3 mmHg) to a positive value due to a number of possible disease conditions:
1. Increased capillary pressure - due to local venous obstruction by blood clots; frequently right cardiac failure, venous pressure;
- Decreased plasma proteins - severe burns lead to loss of albumin; in nephritis lots of plasma proteins are lost, decreased P.C.O.P.;
- Lymphatic obstruction - protein accumulation in interstitial fluid, increased I.F.C.O.P. usually due to filariasis.
- Increased capillary permeability - loss of fluid and protein into the interstitial spaces as a result of burns or allergic reactions.
All of this will harm the correct drainage of fluid to the lymphatic system
What are the three main functions of the lymphatic system?
- To collect and return interstitial fluid to the blood vascular system
- To protect against disease
- To absorb lipids from the gastrointestinal tract (GIT)
Where is there a large accumulation of white blood cells?
The lymph nodes contain lymphocytes (type of white blood cell), which has to do with the immune system
Lymphatic vessels?
- Are like blood capillaries but end blindly in terminal lymphatic capillaries
- Have a thin and permeable endothelium with loose overlapping cells which are free to flap inward forming small non-return valves
- Interstitial fluid, proteins, particles, bacteria enter but cannot leave
Lymphatic pump?
The larger lymphatic vessels with non-return valves function as a lymphatic pump helped by contraction of the body muscles
When does lymphatic flow increase and decrease?
Increases during exercise and decreases during rest
Lymphatic capillaries?
Drains excess interstitial fluid from the capillary beds
Small lymph vessels?
A thin and permeable endothelium wall with overlapping cells that flap inwards to form non-return valves. End blindly in terminal lymphatic capillaries
Large lymph vessels?
A thin and permeable endothelium wall with overlapping cells that flap inwards to form non-return valves. Function as a lymphatic pump helped by contraction of the muscles
Lymph?
- Fluid in lymphatic vessels
- Created when there is a breakdown in the osmotic pressure, and there is some interstitial fluid left behind. The lymphatic system picks this fluid up and it comes lymph
Lymph nodes?
Found at the junctions of lymph vessels, and acts as filters in the body, sending out lymphocytes and macrophages (white blood cells) to stop bacteria and foreign invaders
Lymphocytes?
Produces antibodies, kills cancer cells and directs an immune response
Macrophages?
Detects and kills bacteria through phagocytosis
What are the three main functions of the lymphatic system?
- Collects and returns interstitial fluid to the blood system
- Protects against disease
- Absorbs lipids from the GIT
How does cancer travel through the lymphatic system?
Once the cancer metastasizes (breaks apart), it travels through the lymphatic system, spreading. You can determine how bad the cancer is from how far it spreads in the lymphatic system
Lymphatic system flow (left)?
blood capillaries - interstitial space - terminal lymph capillaries - lymphatic vessels - thoracic duct (or lower limbs) - enters venous system at subclavian and left jugular vein
Lymphatic system flow (right)?
blood capillaries - interstitial space - terminal lymph capillaries - lymphatic vessels right lymphatic duct - enters venous system at right subclavian vein/right jugular vein
