The Circulatory System

Question 1

What is the circulatory system made up of?

Answer 1

The heart and blood vessels

Question 2

What are the two circuits of the circulatory system?

Answer 2

One takes blood from the heart to the lungs, then back to the heart. the other takes blood around the rest of the body

Question 3

What supplies the heart with blood?

Answer 3

The left and right coronary arteries

Question 4

What is the structure of an artery?

Answer 4

Thick, muscular walls which have elastic tissue that stretches and recoils as the heart beats - helps maintain high pressure. The endothelium is folded, allowing the artery to stretch - maintaining high pressure

Question 5

What are arterioles?

Answer 5

They form a network throughout the body. Blood is directed to different areas of demand in the body by muscles inside the arterioles, which contract and relax to control blood flow

Question 6

What is the structure of a vein?

Answer 6

They have a wide lumen with very little elastic or muscle tissue. They contain valves to stop the back flow of blood. Blood flow through veins is helped by the contraction of body muscles surrounding them

Question 7

How are capillaries adapted for efficient diffusion?

Answer 7

1. They’re always found near cells in exchange tissues - short diffusion pathway
2. Their walls are one cell thick - short diffusion pathway
3. Large number to increase SA

Question 8

What are network of capillaries called?

Answer 8

Capillary beds

Question 9

What is tissue fluid?

Answer 9

Fluid that surrounds cells in tissues

Question 10

What is tissue fluid made from?

Answer 10

Small molecules that leave blood plasma

Question 11

How do substances move out of capillary beds into the tissue fluid?

Answer 11

Pressure filtration

Question 12

Explain pressure filtration

Answer 12

1. At the start of the capillary bed, near the arteries, the hydrostatic pressure inside the capillaries is greater than the hydrostatic pressure in the tissue fluid
2. The difference in hydrostatic pressure forces fluid out the capillaries and into the spaces around the cells forming tissue fluid
3. This reduces the hydrostatic pressure in the capillaries - so they hydrostatic pressure is much lower at the venue end of the capillary bed
4. Due to the fluid loss, and an increasing conc of plasma proteins, the water potential at the venue end of the capillary bed is lower than the water potential of the tissue fluid
5. This means water re-enters the capillaries from the tissue fluid at the venue end by osmosis

Question 13

Where is excess tissue fluid drained?

Answer 13

Into the lymphatic system which transports this excess fluid from the tissues back into the circulatory system