Topic 3- Capillaries and tissue fluid

Question 1

What is the structure of capillaries?

Answer 1

-have a very small diameter (lumen)
-Capillaries branch between cells
-Substances can diffuse between the blood and cells quickly as there is a short diffusion distance
- wall of the capillary is made solely from a single layer of endothelial cells
-The wall is only one cell thick – this reduces the diffusion distance for oxygen and carbon dioxide between the blood and the tissues of the body
-The cells of the wall have gaps called pores which allow blood plasma to leak out and form tissue fluid

Question 2

Why does plasma contain a lot of water?

Answer 2

Because it is a good solvent

Question 3

What is the difference between plasma and tissue fluid?

Answer 3

Tissue fluid contains fewer proteins

Question 4

What does tissue fluid coat?

Answer 4

almost all the cells of the body outside of the circulatory system

Question 5

Exchange of substances between cells and the blood occurs via what?

Answer 5

Tissue fluid

Question 6

What is the 1st step in the formation of tissue fluid?

Answer 6

When blood is at the arteriole end of a capillary, the hydrostatic pressure is great enough to push molecules out of the capillary

Question 7

What is the 2nd step in the formation of tissue fluid?

Answer 7

proteins remain in the blood; the increased protein content creates a water potential between the capillary and the tissue fluid

Question 8

What is the 3rd step of the formation of tissue fluid?

Answer 8

At the venule end of the capillary, less fluid is pushed out of the capillary as pressure within the capillary is reduced

Question 9

What is the 4th step in the formation of tissue fluid?

Answer 9

The water potential gradient between the capillary and the tissue fluid remains the same as at the arteriole end, so water begins to flow back into the capillary from the tissue fluid

Question 10

What is the 5 th step in the formation of tissue fluid?

Answer 10

Overall, more fluid leaves the capillary than returns, leaving tissue fluid behind to bathe cells

Question 11

What is oedema?

Answer 11

-blood pressure is high (hypertension) then the pressure at the arteriole end is even greater
-This pushes more fluid out of the capillary and fluid begins to accumulate around the tissues

Question 12

Are the lymph capillaries separate from the circulatory system?

Answer 12

Yes

Question 13

Where do larger molecules that cannot pass through the capillary wall go?

Answer 13

enter the lymphatic system as lymph

Question 14

-The liquid moves along the larger vessels of this system by compression caused by body movement. Any backflow is prevented by 1._______
This is why people who have been sedentary on planes can experience swollen lower limbs
-The lymph eventually reenters the bloodstream through 2.veins located close to the heart
-Any 3._____ proteins that have escaped from the blood are returned to the blood via the lymph capillaries
-If plasma proteins were not removed from tissue fluid they could lower the water potential (of the tissue fluid) and prevent the reabsorption of water into the blood in the capillaries
-After digestion lipids are transported from the intestines to the bloodstream by the lymph system

Answer 14

1.valves
2.veins
3.plasma