8.3 - Blood,tissue Fluid Amd Lymph Flashcards
What does blood consist of ?
55% plasma
40% water
5% RBC
What does the plasma do in the blood ?
Carries a wide variety of red blood cells , white blood cells and other components such as dissolved glucose,amino acids, mineral ions , hormones and large plasma proteins
What does blood transport ?
- O2 in and CO2 from the respiring cells
- digested food from the small intestine
- nitrogenous waste products from the cells to the excretory organs
- chemical messages ( hormones )
- food molecules from storage compounds to the cells that need them
- platelets to damaged areas
- cells and antibodies involved in the immune response
What other things does the blood contribute too
- maintenance of a steady body temperature
- acts as a buffer minimising pH changes
What does having a positive pressure mean ?
Moving out of the blood
What does having a negative pressure mean ?
Moving into the blood
Name a plasma protein
Albumin
Define hydrostatic pressure
The pressure exerted by a fluid eg. Blood
Define oncotic pressure
- This is the osmotic pressure exerted by plasma proteins within a blood vessel it usually pulls water into the circulatory system
- tendency of water to move into the blood by osmosis
What does how much liquid leaves the plasma to form tissue fluid depend on ?
- hydrostatic pressure
- oncotic pressure
How is tissue formed ?
- blood flows into the capillary at high hydrostatic pressure in the arteriole end
- high pressure forces fluid through the gaps in the cells of the capillary where nutrients and oxygen dissolve into it
- this fluid with the dissolved oxygen and nutrients seep in between the cells of the tissue = tissue fluid
How does fluid return to the blood ?
- the hydrostatic pressure of the blood is pushed back my the hydrostatic pressure of the fluid which pushes the fluid back into the capillaries
- the water potential of the tissue fluid is higher than the blood
- therefore water moves back into the blood from the fluid by osmosis
Where do substances that are dissolved in plasma pass through ?
Fenestrations In the capillary walls except large plasma proteins
What is the osmotic effect ?
Gives the blood in the capillaries a relatively high solute potential and relatively low water potential compared with the surrounding fluid
How many KPa is oncotic pressure ?
-3.3 KPa
Explain what happens as blood flows through arterioles
- Blood flows through the arterioles into the capillaries
- still under pressure from the surge of blood that occurs every time the heart contracts = hydrostatic pressure
What occurs at the arterial end of the capillary ?
- hydrostatic pressure forces the fluid out of the capillaries is relatively high
- higher than the oncotic pressure attracting water in by osmosis = fluid is squeezed out of the capillaries
- this fluid fills the spaces between the cells and is called tissue fluid
What does tissue fluid have the same composition of ?
Plasma but without RBC and plasma proteins
What happens when the blood travels towards the venous end ?
- balance of forces change
- hydrostatic pressure falls to around 2.3KPa in the vessels as fluid has moved out and the pulse is completely lost
- oncotic pressure is still -3.3KPa —> no stronger than the hydrostatic pressure
- water moves back into the capillaries by osmosis as it reaches the venous end
How much of the tissue fluid is reabsorbed back into the blood ?
90%
What is the hydrostatic pressure in KPa ?
4.6 KPa
What is filtration pressure ?
Filtration pressure = hydrostatic pressure - oncotic pressure
How is lymph formed ?
- formed when intercostal fluid comes into contact with the blood
- most fluid leaves the blood vessels and goes into the tissue fluid
- but some goes into the blood vessels whilst the rest enters the lymphatic system
- where it is transported to the veins to mix with the blood and become lymph
How is the fluid transported through the lymph capillaries ?
By squeezing of the body muscles
