The Circulatory System

Question 1

What is the function of the circulatory system?

Answer 1

This is a specialised transport system to carry raw materials from specialised exchange organs to their body cells- this is the circulatory system.

Question 2

Whether or not there is a transport medium is determined by what two features?

Answer 2

• The activity level of the organisms.

- The surface area to volume ratio.

Question 3

Pulmonary artery

Answer 3

Carries blood from… heart

Carries blood to… lungs

Question 4

Pulmonary vein

Answer 4

Carries blood from… lungs

Carries blood to… heart

Question 5

Aorta

Answer 5

Carries blood from… heart

Carries blood to… body

Question 6

Vena Cava

Answer 6

Carries blood from… body

Carries blood to… heart

Question 7

Hepatic artery

Answer 7

Carries blood from… body

Carries blood to… liver

Question 8

Hepatic vein

Answer 8

Carries blood from… liver

Carries blood to… vena cava

Question 9

Hepatic portal vein

Answer 9

Carries blood from… gut

Carries blood to… liver

Question 10

Renal artery

Answer 10

Carries blood from… body

Carries blood to… kidneys

Question 11

Renal vein

Answer 11

Carries blood from… kidneys

Carries blood to… vena cava

Question 12

What are the characteristics of arteries?

Answer 12

Carry blood from heart to rest of the body.
Thick, muscular walls have elastic tissue- cope with the higher pressure from heartbeat.
Endothelium is folded to stretch and cope with high pressure.
All arteries carry oxygenated blood except for the pulmonary arteries, which take deoxygenated blood to the lungs.

Question 13

What are the characteristics of arterioles?

Answer 13

Arteries divide into smaller vessels called arterioles.
These form a network throughout the body.
Blood is directed to different areas of demand in the body by muscles inside the arterioles, which contract to restrict the blood flow or relax to allow full body flow.

Question 14

What are the characteristics of veins?

Answer 14

Take blood back to the heart under low pressure.
Wider lumen than arteries, with very little elastic or muscle tissue.
Veins contain valves to stop the blood flowing backwards.
Blood flow through the veins is helped by the contraction of the body muscles surrounding them.
All veins carry deoxygenated blood (used by body cells), except for the pulmonary veins, which carry oxygenated blood to the heart from the lungs.

Question 15

What are capillaries?

Answer 15

Arterioles branch into capillaries which are the smallest of the blood vessels.
Substances like glucose and oxygen are exchanged between cells and capillaries, so they’re adapted for efficient diffusion.
Capillaries are always found very near cells in exchange tissues, so there’s a short diffusion pathway.
There are a large number to increase surface area for exchange.

Question 16

What are networks of capillaries in tissue called?

Answer 16

Capillary beds.

Question 17

What is tissue fluid?

Answer 17

The fluid that surrounds cells in tissues.
It’s made from substances that leave the blood, e.g oxygen, water and nutrients (e.g glucose and amino acids).
Cells taken in oxygen and nutrients from the tissue fluid, and release metabolic waste into it.

Question 18

How does pressure filtration work in tissue fluid?

Answer 18

At the start of the capillary bed, nearest the arterioles, the hydrostatic pressure inside the capillaries is greater than the hydrostatic pressure in the tissue fluid.
This difference in hydrostatic pressure forces fluid out of the capillaries and into spaces around the cells, forming tissue fluid.
As fluid leaves, the hydrostatic pressure reduces in the capillaries- lower at the end of capillary bed nearest to veins.
Due to fluid loss, water potential at the end of the capillaries is lower than in the tissue fluid- some water re-enters the capillaries from the tissue fluid at the vein end by osmosis.

Question 19

Where is any excess tissue fluid drained?

Answer 19

Into the lymphatic system, which transports the excess fluid from the tissues and dumps it back into the circulatory system.

Question 20

Why do mammals need a mass transport system?

Answer 20

Mammals have a low surface area: volume ratio so they can’t rely on diffusion to exchange substances with their environment- the distance is too large.

Question 21

Name two blood vessels that carry blood into the heart.

Answer 21

Pulmonary vein, vena cava

Question 22

Which blood vessel carries deoxygenated blood to the lungs?

Answer 22

Pulmonary artery

Question 23

What is the function of the hepatic portal vein?

Answer 23

To carry blood from the gut to the liver

Question 24

Which blood vessel carries blood to the kidneys?

Answer 24

Renal artery

Question 25

Which vessels supply the heart tissue with blood.

Answer 25

The (left and right) coronary arteries.

Question 26

Name the blood vessels which have valves in them.

Answer 26

Veins

Question 27

Give ways in which capillaries are adapted for efficient diffusion.

Answer 27

The walls are only one cell thick.
They’re always near the cells in exchange tissues.
There’s a large number of them in exchange tissues.

Question 28

What is the basic layered structure in arteries, arterioles and veins?

Answer 28

Tough outer layer- that resists pressure changes from both within and outside.
Muscle layer- that can contract and so control flow of blood.
Elastic layer- that helps maintain blood pressure by stretching and springing back.
Thin inner lining (endothelium)- that is smooth to prevent friction and thin to allow diffusion.
Lumen- central cavity blood flows through.

Question 29

Artery structure related to function.

Answer 29

Muscle layer thick compared to veins- smaller arteries can be constricted and dilated in order to control volume of blood.
Elastic layer is relatively thick compared to veins- important blood pressure is kept high if blood is to reach extremities of body.
Thickness of wall is large- resists vessel bursting under pressure.
There are no valves- because blood is under constant high pressure and therefore does not tend to flow backwards.

Question 30

Arteriole structure related to function?

Answer 30

The muscle layer is relatively thicker than in arteries- contraction of this muscle allows constriction of lumen and control movement of blood into capillaries.
Elastic layer is relatively thinner than in arteries because blood pressure is lower.

Question 31

Vein structure related to function?

Answer 31

Muscle layer is relatively thin compared to arteries because veins carry blood away from tissues and therefore their constriction and dilation cannot control the flow of blood to the tissues.
Elastic layer and overall thickness of wall is relatively thin because low pressure of blood within veins will not cause burst.
Valves are throughout to prevent blood flow.

Question 32

What is more domineering hydrostatic pressure or osmosis?

Answer 32

Hydrostatic pressure

Question 33

How does blood plasma differ from tissue fluid?

Answer 33

Tissue fluid does not contain proteins because the molecules are too large to pass through the capillary wall.
Tissue fluid is going to contain less glucose because it is being diffused into the surrounding cells for respiration.

Question 34

What is hydrostatic pressure?

Answer 34

Pressure that results from the force of a liquid on a surface.