Tissue fluid and lymph fluid

https://www.youtube.com/watch?v=FjY15FXbITM

What does blood consist of

Blood cells, such as RBC transporting oxygen, and WBC playing a role in immune system, contains platelets as well which are involved in blood clotting

Blood cells are suspended in water solution called blood plasma, contains a range of dissolved molecules such as glucose, amino acids, mineral ions, plasma proteins

Whats tissue fluid.

The blood passes through capillaries. In the capillaries, fluid passes out of the blood and bathes the tissue cells, this is called tissue fluid.

Tissue fluid leaves the blood at the parts of the capillary which are near the artery.

Tissue fluid transfers molecules such as oxygen and glucose to the tissue cells.

Waste molecules from the tissue cells such as co2 pass into tissue fluid.

Tissue fluid then returns back to bloodstream at parts of capillary which are near the vein

What happens at the arterial end of a capillary / hydrostatic pressure.

The blood has just passed through an artery and arteriole, because of this the blood at arterial end is under relatively high pressure, this is called hydrostatic pressure

Hydrostatic pressure tends to force fluid out of the blood and into the tissue.

What is oncotic pressure at arterial end

Plasma contains plasma proteins, they are hydrophilic so they lower the water potential of blood plasma.

Because of plasma protein , theres a tendency for water to move back into the blood by osmosis, this is oncotic pressure.

Whats ultrafiltration

At arterial end , hydrostatic pressure is greater than oncotic pressure, so tissue fluid is forced out of the capillary through the gaps between the endothelial cells.

This is called ultrafiltration.

Blood cells and plasma proteins are too large to leave, so they stay in blood plasma.

Why is hydrostatic pressure lower at venous end

A large amount of water has left the blood, oncotic pressure is still high due to the plasma proteins in the blood plasma.

So hydrostatic pressure is less at venous end, causing water to move back into the blood by osmosis.

90% of tissue fluid is reabsorbed back into the blood.

What happens to the 10% of tissue fluid that isnt reabsorbed into blood at venous end of a capillary

Drains into a series of blind ended vessels called lymph capillaries

Lymph capillaries connect into larger lymph vessels, forming the lymphatic system.

How does lymph fluid move along

Moves along when lymph vessels are squeezed by nearby skeletal muscles, valves in the lymph vessels help to keep lymph fluid moving forward

Eventually the lymph fluid returns to the bloodstream via blood vessels under the collar bone.