7.4 - The structure of the heart Flashcards
Break down the structure of the heart in terms of pumps
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)
What is the atrium
- receives blood
- thin-walled and elastic —> so it stretches when it collects blood
What is the ventricle
- 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)
Why are there 2 pumps that make up the heart (left and right)
- 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)
Where does the right ventricle pump blood, how is it adapted for this?
- The lungs
- has a thinner muscular wall than the left ventricle
Where does the left ventricle pump blood, how is it adapted for this
- 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
Do the 2 pumps of the heart, pump in time with each other
Yes
- both atria contract together
- and then both ventricles contract together
- pumping the same volume of blood
What stops backflow of blood into the atria when the ventricles contract
The 2 atrioventricular valves:
- the left AV (bicuspid) valve
- the right AV (tricuspid) valve
What is connected to the 4 chambers of the heart that carries blood away/towards the heart
- 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
What are all the vessels connected to the 4 chambers called
- aorta
- vena cava
- pulmonary artery
- pulmonary vein
Where is the aorta located and what is its job
- connected to the left ventricle
- carries oxygenated blood to all parts of the body (except lungs)
Where is the vena cava located and what is its job
- connected to the right atrium
- brings deoxygenated blood back from the tissues of the body
Where is the pulmonary artery and what is its job
- connected to the right ventricle
- carries deoxygenated blood to the lungs, where its oxygen is replenished and its carbon dioxide is removed
Where is the pulmonary vein located and what is its job
- connected to the left atrium
- brings oxygenated blood back from the lungs
What holds the atrioventricular valves in place
- valve tendons which are attached to papillary muscles
- the papillary muscles contract at the same time as the ventricles —> holds the valves closed
What separates the left and right halves of the heart
The septum
What type of muscle is the heart made out of? Describe its composition
- cardiac muscle
- composed of cells called myocytes
- when myocytes receive an electrical impulse they contract, causing a heartbeat
Because the heart is beating constantly what does this mean for the myocytes
- 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
How does blood that was taken away via the coronary arteries, get returned back to the heart.
- blood returns via the coronary sinus, which draws directly into the right atrium
What might happen if the coronary arteries are blocked (e.g. by. Blood clot)
- 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
What are some of the risk factors associated with cardiovascular disease
- smoking
- high blood pressure
- blood cholesterol
- diet
Why is smoking a risk factor of cardiovascular disease
Due to 2 main constituents of tobacco
1) Carbon monoxide
2) Nicotine
How does carbon dioxide being in tobacco lead to an increased risk of cardiovascular disease
- 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)
How does Nicotine being in tobacco lead to an increased risk of cardiovascular disease
- 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
Why is high blood pressure a risk factor of cardiovascular disease
- 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
Why is blood cholesterol a risk factor of cardiovascular disease
- 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)
What do HDLs do
- these remove cholesterol from tissues and transport it to the liver for excretion.
- they help protect the arteries against heart disease
What do LDLs do
- these transport cholesterol from the liver to the tissues, including artery walls, which they infiltrate and can build up
- leading to the development of atheroma, which may cause heart disease due to blockage of blood flow
Why is diet a risk factor of cardiovascular disease
- 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
