Biology 🧬 Unit 8 - blood plasma, tissue fluid and lymph

What is blood plasma; what does it contain

pale yellow liquid

Mostly water with a variety of substances dissolved in it eg. Nutrients such as glucose, and waste products such as urea; amino acids; CO2; oxygen

Plus protein molecules (plasma proteins) which remain in the blood all the time

What is tissue fluid

The fluid which fills the spaces between the cells within body tissues

What is tissue fluid formed from

blood plasma which has leaked out through the spaces in capillary walls

(Contains dissolved nutrients eg glucose and oxygen)

What are the differences between blood plasma and tissue fluid

Tissue fluid has:

No red blood cells

Few/no plasma proteins

A few white blood cells (less than blood plasma)

No platelets

Always low pressure

Some fates

Not in vessels

how does exchange occur between tissue fluid and cells

By diffusion and facilitated diffusion

How does tissue fluid form

Due to hydrostatic pressure → where the pressure of the blood inside a capillary is sufficient to push fluid out into the space between the tissues; this is due to the contraction of the heart (left ventricle) it is therefore particularly high at the arteriole end of a capillary bed

As tissue fluid lacks the high concentration of plasma proteins, present in blood plasma, a water potential gradient is created and water moves by osmosis down the gradient from tissue fluid → capillaries (carrying any dissolved waste such as CO2)

Thus fluid flows out at arteriole end and fluid flows in at venous end of capillary bed; overall there is a net loss of fluid to tissues

Where in the capillary bed is hydrostatic pressure higher

Arteriole end

90% of fluid that leaks from capillaries seeps back into them; where does the remaining 10% go

Returns to the blood via the lymph vessels (lymphatics)

Tissue fluid can flow into lymphatics but not out, why?

due to tiny valves

Can large protein fit through the valves in the lymph vessels (lymphatics), and why is this important

Yes, the valves are big enough for large protein molecules to pass through; this is very important because they are too big to get into a capillary and if they are not removed from the tissue space between your cells you could die within 24 hours

What is oedema

Where tissue fluid builds up due to poor drainage through the lymphatics

What is it called when tissue fluid builds up due to poor drainage through the lymphatics 

oedema

What is the fluid inside lymphatics called

Lymph → and is virtually identical to tissue fluid

Tissue fluid and Lymph in the liver have high concentrations of…..

protein

Where are high concentrations of lipid found

In the lymph in the walls of the small intestine, where lipids are absorbed from digested foods

Lymphatics join to form Larger lymph vessels which transport…..

lymph back up to the subclavian veins (large veins which run just beneath the collarbone)

lymph moves through the lymphatics in the same way as….

Blood in the veins - with valves to prevent back flow, and the contraction of surrounding muscles provides pressure

The flow through the lymph vessels is ……….. than blood flow

Slower

The flow is ver slow \~100 cm3 per hour through the thoracic duct ( the largest lymph vessel) in a resting human, compare blood flow at \~80 cm3 per ……

Second

What is diapedesis

The passage of blood cells through the intact walls of the capillaries, typically accompanying inflammation