Blood Vessels and Tissue Fluid

Question 1

Why do organisms need mass flow?

Answer 1

Their SA:Vol ratio is too small, meaning that the diffusion distance may be too long.

Question 2

Describe the human circulatory system.

Answer 2

Closed unit, double circulatory system

Question 3

Describe the structure of arteries.

Answer 3

Thick muscular layer which allows the artery to stretch and recoil under high pressure.
Small lumen to maintain high pressure.

Question 4

Describe the structure of veins.

Answer 4

Thin muscle and elastic layer as blood is at a lower pressure, therefore has a large lumen as a result.
Contains veins to prevent backflow of blood.

Question 5

Why do mammals have a double circulatory system?

Answer 5

Blood needs to be pumped to the lungs to pick up oxygen before it can be pumped around the body.

Question 6

What are arterioles?

Answer 6

Smaller branches off the main artery.

Question 7

What are capillaries?

Answer 7

Very small blood vessels that branch off arterioles and venule and are only one cell thick.

Question 8

What are venules?

Answer 8

Smaller branches off veins

Question 9

What is tissue fluid?
Name 4 things that it contains.

Answer 9

A fluid that surrounds all cells in the body, containing dissolved ions, gases, biomolecules, water etc

Question 10

What is the purpose of tissue fluid?

Answer 10

To provide cells with vital substances such as water, ions, dissolved gases etc

Question 11

What is tissue fluid formed from?

Answer 11

Blood plasma

Question 12

What surrounds capillaries to prevent them from leaking?

Answer 12

Collagen

Question 13

What is hydrostatic pressure?

Answer 13

Pressure exerted by a fluid on walls

Question 14

1. Formation of tissue fluid
   Where is hydrostatic pressure created in a capillary and how?

Answer 14

Hydrostatic pressure created at the arterial end by the heart pumping.

Question 15

2. Formation of tissue fluid
   A build of hydrostatic pressure at the arterial end causes tissue fluid to move from/to?
   What is the name of this process?

Answer 15

Tissue fluid moves out of blood plasma in the capillery.
This is called ultrafiltration.

Question 16

How is tissue fluid different to plasma and why?

Answer 16

Contains fewer proteins. This is because proteins are too large to leak through gaps in the capillary wall.

Question 17

3. Formation of tissue fluid
   How is a water potential gradient created between protein and tissue fluid?
   Where does water move from/to despite this?

Answer 17

As plasma contains more proteins, the water potential is more negative than the tissue fluid.
But still, water moves from capillaries to tissue fluid.

Question 18

4. Formation of tissue fluid
   At the venule end of the capillary, why is less fluid pushed out of the capillary?

Answer 18

There is a lower pressure in the capillary here.

Question 19

5. Formation of tissue fluid
   How does the water potential gradient at the venule end compare to the water potential gradient at the arteriole end?
   Where does water start to move from/to?

Answer 19

Water potential is the same, so water begins to flow back into the capillary from the tissue fluid.

Question 20

How can hypertension (high blood pressure) affect pressure at the arteriole end?
How does this affect the volume of tissue fluid that leaves the capillary?

Answer 20

Increases pressure, leading to more fluid leaving the capillary and accumulating around tissue.

Question 21

What is lymph?
What system does it travel to?

Answer 21

Fluid containing large molecules that cannot pass through the capillary wall. Passes through the lymphatic system.

Question 22

Describe the difference between lymph capillaries and normal blood capillaries.

Answer 22

They have closed ends and large pores that allow large molecules to pass through.

Question 23

How is lymph fluid pushed through the body?

Answer 23

By movement and compression

Question 24

How is backflow of lymph prevented?

Answer 24

Due to the presence of valves.

Question 25

Where does lymph re enter the blood?

Answer 25

Through veins close to the heart.

Question 26

How are plasma protiens that have escaped from the blood returned?

Answer 26

Via lymph capilleries.

Question 27

What would happen to water potential of tissue fluid if plasma proteins were not returned to to the blood? How does this effect blood?

Answer 27

Lowers water potential of tissue fluid which could prevent reabsorption of water into the blood in capillaries.