Topic2.2 - The Circulatory System

Question 1

Functions of the circulatory system

Answer 1

Transport of substances
Protection against diseases
Regulation of body temperature

Question 2

The circulatory system is composed of 3 basic components

Answer 2

A network of tubes (blood vessels)
A fluid (blood)
A pump (heart)

Question 3

Structure of red blood cells

Answer 3

Biconcave shape to increase SA.

Doesn’t contain nucleus, mitochondria or ribosomes - leaves more room for many haemoglobin molecules.

Question 4

Function of red blood cells

Answer 4

Transport oxygen to body cells and deliver CO2 to lungs.

Question 5

Function of white blood cells

Answer 5

Important in defence against disease.

Lymphocytes produce antibodies and phagocytes engulf and digest microorganisms in a process called phagocytosis.

Question 6

Function of platelets

Answer 6

Important in blood clotting and formation of scabs.

Convert the protein fibrinogen to fibrin.

Question 7

Function of plasma

Answer 7

Responsible for the transport of:

• blood cells
• absorbed food molecules (eg glucose, amino acids)
• CO2
• hormones
• urea

Question 8

Substances transported by the blood

Answer 8

Oxygen (for respiration)

CO2 (from respiration)

Products of digestion - molecules such as glucose, amino acids, vitamins and minerals.

Urea (waste product found in urine)

Hormones (eg adrenaline and insulin)

Question 9

Structure of arteries

Answer 9

Thick outer wall
Thick layer of muscle and elastic fibres
Smooth lining
Small lumen

Question 10

Why are arteries structured in the way that they are?

Answer 10

The thick outer wall and sub-layer allow the arteries to expand as blood flows through them in a pulsatile way.

Maintenance of pressure is also helped due to reduced diameter of vessels’ lumen.

Question 11

Structure of veins

Answer 11

Fairly thin outer wall
Thin layer of muscle and elastic fibres
Smooth lining
Large lumen

Question 12

Why are veins structured in the way that they are?

Answer 12

Wide lumen to accommodate low pressure.

Risk of back flow - valves to prevent this as they are only able to open in one direction (forced closed of blood flows backwards). The

Question 13

Structure of capillaries

Answer 13

Walls made of a single layer of cells

Very small lumen

Question 14

Why are capillaries structured in the way that they are?

Answer 14

Responsible for exchange of gases in lungs and entry of nutrients into blood.

Diffusion distances are minimised due to walls being only 1 cell thick and there being gaps between.

Question 15

How do valves work?

Answer 15

Blood flowing upwards pushes valve open.

Blood trying to flow downwards pushes valve shut.

Question 16

Apart from valves, what helps blood back to the heart?

Answer 16

Contractions of skeletal muscles as you move around - the muscles in your legs help blood back to heart against force of gravity.

Question 17

Order of vessels blood flows through

Answer 17

Aorta
Arteries
Arterioles 
Capillaries
Veins
Vena cava

Question 18

Function of arterioles

Answer 18

Constrict and dilate to regulate blood flow and blood pressure

Question 19

Learn circulatory system diagram

Answer 19

Learn circulatory system diagram

Question 20

What is the heart made of?

Answer 20

Specialised muscle tissue called cardiac muscle

Question 21

Which sides pump the different types of blood?

Answer 21

Left hand side pumps oxygenated blood

Right hand side pumps deoxygenated blood

In a healthy individual, these 2 types should never mix.

Question 22

How is the direction of blood flow controlled?

Answer 22

Valves: held in place by tendons (heart strings)

Question 23

When your atria and ventricles relax…

Answer 23

They fill with blood

Question 24

Learn heart diagram

Answer 24

Learn heart diagram

Question 25

What is the difference between the atrium walls and the ventricle walls?

Answer 25

The ventricles have much thicker walls -> this will generate much greater pressure when it contracts - allows blood to travel further.

Question 26

What is the difference between the left ventricle wall and the right ventricle wall?

Answer 26

The left ventricle has a thicker wall:

• > the right ventricle pumps blood to the lungs and therefore less pressure required
• > the left ventricle pumps blood to every other organ in the body - requires much greater pressure

Question 27

Explain double circulation

Answer 27

The right side is responsible for pumping deoxygenated blood to the lungs to pick up oxygen; the left is responsible for pumping oxygenated blood to the organs of the body to allow respiration.
This means that to complete one ‘lap’ of the body, the blood travels through the heart twice.

Question 28

Factors affecting heart rate

Answer 28

Diet
Body size
Stress
Heart size 
Gender
Injury
Fitness
Exercise

Question 29

Your pulse corresponds to

Answer 29

The contraction of the left ventricle - a reflection of the pulsatile flow of blood through the arterial system.

Question 30

What is heart rate measured in?

Answer 30

Bpm

Question 31

Top athletes’ resting heart rate

Answer 31

Top athletes have a low resting heart rate (35bpm) as they have a larger heart - this means it doesn’t need to contract as often as it holds a greater volume of blood.

Question 32

What happens to the heart rate during exercise?

Answer 32

Heart and breathing rate increase - the demand for oxygen and fuel for your muscle tissue increases. Therefore blood has to be pumped to these cells more often.

Question 33

Supply and demand of blood

Answer 33

If cells need energy for movement then they need oxygen and glucose (the basic ingredients to allow respiration).

Question 34

Adrenaline

Answer 34

(The fight or flight hormone) released during stress - increases heart rate in preparation for an event that requires more energy.

Question 35

How is tissue fluid formed?

Answer 35

Plasma is forced out of the capillaries into the spaces between the cells making up the tissues due to…

• blood still being under high pressure on arrival to capillary network
• the leaky nature of the capillary walls

Question 36

Function of tissue fluid

Answer 36

Bathes all body cells - allows every cell to be supplied with dissolved nutrients and absorbs any waste materials produced by the cells.

Question 37

The lymphatic system

Answer 37

Another network of vessels.

The ‘used’ tissue fluid drains into the lymph vessels (the fluid in these vessels is called lymph) and actually returned to the main circulation (at the subclavian veins).

Question 38

Learn plasma, tissue fluid and lymph diagram

Answer 38

Learn plasma, tissue fluid and lymph diagram

Question 39

What is atherosclerosis?

Answer 39

Furring up of arteries by fatty substances

Question 40

Causes of atherosclerosis

Answer 40

• a diet high in cholesterol (which is deposited in areas called plaques)
• smoking: cigarette smoke contains many toxins, some of which make the lining of the vessels more susceptible to fat being laid down
• a sedentary lifestyle (lack of physical activity)

Question 41

How to avoid/minimise risk of atherosclerosis

Answer 41

• avoid fatty foods (esp animal fats)

- eat more foods rich in antioxidants (eg fresh f+v) which can reverse the process to some extent

Question 42

What is one way of preventing growth/minimising effects of plaque in the arteries?

Answer 42

Insert a tube carrying a deflated balloon into the vessel.

The balloon is inflated, compressing the deposit and keeping lumen open.

Question 43

What is another way of preventing growth/minimising effects of plaque in the arteries?

Answer 43

Insert a more rigid sheath that’ll hold the vessel open.

Or a tube can be inserted with a small cutting device to completely remove the plaque.

These types of procedures are known as catheterisation.

Question 44

What other effect does plaque have on the blood vessels?

Answer 44

Can make the vessels more rigid. If this happens in the arteries, they won’t be able to accommodate the pulsing flow of blood. This means the vessel walls could burst - can lead to internal bleeding and in severe cases, death.