7.4 - The structure of the heart

Question 1

Break down the structure of the heart in terms of pumps

Answer 1

it’s like 2 pumps lying side by side:
- the 1 on the left = deals with oxygenated blood from the lungs
- the 1 on the right = deals with deoxygenated blood from the body
- each pump has 2 chambers (the atrium and the ventricle)

Question 2

What is the atrium

Answer 2

• receives blood
• thin-walled and elastic —> so it stretches when it collects blood

Question 3

What is the ventricle

Answer 3

• pumps blood
• therefore has a much thicker muscular wall (because it has to be striking enough to pump blood some distance — to lung or the rest of the body)

Question 4

Why are there 2 pumps that make up the heart (left and right)

Answer 4

• when blood returns from the lungs to the heart, its pressure can be increased again before it’s distributed around the rest of the body = so the blood to the rest of the body is quick and efficient
• it is also essential that oxygenated blood (in the left pump) is kept separated from the deoxygenated blood (right pump)

Question 5

Where does the right ventricle pump blood, how is it adapted for this?

Answer 5

• The lungs
• has a thinner muscular wall than the left ventricle

Question 6

Where does the left ventricle pump blood, how is it adapted for this

Answer 6

• pumps blood to the rest of the body
• has a thick muscular wall, enabling it to contract to create enough pressure to pump blood to the rest of the body

Question 7

Do the 2 pumps of the heart, pump in time with each other

Answer 7

Yes
- both atria contract together
- and then both ventricles contract together
- pumping the same volume of blood

Question 8

What stops backflow of blood into the atria when the ventricles contract

Answer 8

The 2 atrioventricular valves:
- the left AV (bicuspid) valve
- the right AV (tricuspid) valve

Question 9

What is connected to the 4 chambers of the heart that carries blood away/towards the heart

Answer 9

• large blood vessels
  —> ventricles pump blood away from the heart into arteries (A for away)
  —> atria receive blood from the veins
  —> the vessels connecting the heart to the lung are called the pulmonary vessels

Question 10

What are all the vessels connected to the 4 chambers called

Answer 10

• aorta
• vena cava
• pulmonary artery
• pulmonary vein

Question 11

Where is the aorta located and what is its job

Answer 11

• connected to the left ventricle
• carries oxygenated blood to all parts of the body (except lungs)

Question 12

Where is the vena cava located and what is its job

Answer 12

• connected to the right atrium
• brings deoxygenated blood back from the tissues of the body

Question 13

Where is the pulmonary artery and what is its job

Answer 13

• connected to the right ventricle
• carries deoxygenated blood to the lungs, where its oxygen is replenished and its carbon dioxide is removed

Question 14

Where is the pulmonary vein located and what is its job

Answer 14

• connected to the left atrium
• brings oxygenated blood back from the lungs

Question 15

What holds the atrioventricular valves in place

Answer 15

• valve tendons which are attached to papillary muscles
• the papillary muscles contract at the same time as the ventricles —> holds the valves closed

Question 16

What separates the left and right halves of the heart

Answer 16

The septum

Question 17

What type of muscle is the heart made out of? Describe its composition

Answer 17

• cardiac muscle
• composed of cells called myocytes
• when myocytes receive an electrical impulse they contract, causing a heartbeat

Question 18

Because the heart is beating constantly what does this mean for the myocytes

Answer 18

• the myocytes are constantly active —> require great amounts of oxygen
• so are fed by numerous capillaries from 2 coronary arteries
• these arise from the aorta as it leaves the heart

Question 19

How does blood that was taken away via the coronary arteries, get returned back to the heart.

Answer 19

• blood returns via the coronary sinus, which draws directly into the right atrium

Question 20

What might happen if the coronary arteries are blocked (e.g. by. Blood clot)

Answer 20

• leads to myocardial infraction, or heart attack
• because an area of the heart muscle is deprived of blood —> it is deprived of oxygen
• the muscle cells in this region are unable to respire (aerobically) and so die

Question 21

Answer 21

Question 22

What are some of the risk factors associated with cardiovascular disease

Answer 22

• smoking
• high blood pressure
• blood cholesterol
• diet

Question 23

Why is smoking a risk factor of cardiovascular disease

Answer 23

Due to 2 main constituents of tobacco
1) Carbon monoxide
2) Nicotine

Question 24

How does carbon dioxide being in tobacco lead to an increased risk of cardiovascular disease

Answer 24

• combines easily and irreversibly with haemoglobin in red blood (forms carboxyhaemoglobin)
• thereby reducing the oxygen-carrying capacity of the blood
• in order to make up for this, the heart works harder —> leads to higher blood pressure —> increased risk of coronary heart disease and strokes
• insufficient oxygen-carrying capacity of the blood also means insufficient supply to heart during exercise, leading to chest pain (angina) and sometimes a myocardial infarction (heart attack)

Question 25

How does Nicotine being in tobacco lead to an increased risk of cardiovascular disease

Answer 25

• stimulates production of adrenaline, increasing heart rate and raises blood pressure
• resulting in a higher risk of stroke or coronary heart disease
• nicotine also makes blood “sticky”, leading to a higher rick of thrombosis and hence strokes or myocardial infarction

Question 26

Why is high blood pressure a risk factor of cardiovascular disease

Answer 26

• lifestyle factors (such as: excessive prolonged stress, certain diets and lack of exercise) and genetics can cause an increased risk of high blood pressure, which increases the risk of heart disease for the following reasons
  1) heart has to work harder (due to higher pressure in arteries) to pump blood into them, and is therefore prone to failure
  2) the higher pressure in arteries causes an increased risk of developing aneurysms (weakening of the wall) and burst, causing haemorrhage
  3) in order to resist the higher pressure within them, the walls of arteries will thicken and may harden, restricting the flow of blood

Question 27

Why is blood cholesterol a risk factor of cardiovascular disease

Answer 27

• it’s an essential component of CSM, as such it needs to be transported in the blood plasma (carried by lipoproteins) in order to construct CSMs
• there’s 2 main types of lipoproteins that transport it:
  1) High-density lipoproteins (HDLs)
  2) Low-density lipoproteins (LDLs)

Question 28

What do HDLs do

Answer 28

• these remove cholesterol from tissues and transport it to the liver for excretion.
• they help protect the arteries against heart disease

Question 29

What do LDLs do

Answer 29

• these transport cholesterol from the liver to the tissues, including artery walls, which they infiltrate
• leading to the development of atheroma, which may cause heart disease

Question 30

Why is diet a risk factor of cardiovascular disease

Answer 30

• diets with high levels of salt = raise blood pressure
• diets with high levels of unsaturated fat = increase LDL levels and hence blood cholesterol concentration
  —CONTRASTINGLY—> some foods (e.g. vitamin C and dietary fibre) act as antioxidants and reduce the risk of heart disease