Lesson 5 - The human heart

Question 1

meaning septum

Answer 1

the thick muscular dividing wall through the centre of the heart that prevents oxygenated and deoxygenated blood from mixing

Question 2

meaning cardiac muscle

Answer 2

the special muscle tissue that makes up the bulk of the heart, which has an intrinsic rhythmicity and does not get tired

Question 3

meaning right atrium

Answer 3

the upper right-hand chamber of the heart that receives deoxygenated blood from the body

Question 4

meaning right ventricle

Answer 4

the chamber that receives deoxygenated blood from the right atrium and pumps it into the lungs via the pulmonary arteries

Question 5

meaning tricuspid valve

Answer 5

the valve between the right atrium and the right ventricle that prevents backflow of blood from the ventricle to the atrium when the ventricle contracts

Question 6

meaning tendinous cord

Answer 6

tough and non-elastic cords that prevent the atrioventricular valves from turning inside out due to the high pressure when the ventricles contract

Question 7

meaning pulmonary artery

Answer 7

blood vessel that carries deoxygenated blood from the right ventricle to the lungs

Question 8

meaning pulmonary vein

Answer 8

blood vessel that carries oxygenated blood from the lungs to the left atrium

Question 9

meaning left atrium

Answer 9

the upper left-hand chamber of the heart that receives oxygenated blood from the lungs

Question 10

meaning left ventricle

Answer 10

the chamber that receives oxygenated blood from the left atrium and pumps it around the body via the aorta

Question 11

meaning bicuspid valve

Answer 11

the valve between the left atrium and the left ventricle that prevents backflow of blood into the atrium when the ventricle contracts

Question 12

meaning aorta

Answer 12

it carries oxygenated blood from the left ventricle to the body under high pressure

Question 13

meaning systole

Answer 13

the contraction of the heart

Question 14

meaning atrial systole

Answer 14

when the atria of the heart contract

Question 15

meaning ventricular systole

Answer 15

when the ventricles of the heart contract

Question 16

meaning diastole

Answer 16

when the heart relaxes and fills with blood

Question 17

meaning cardiac cycle

Answer 17

the cycle of contraction and relaxation in the heart

Question 18

meaning coronary arteries

Answer 18

carry oxygenated tissue to the cardiac tissue of the heart. It also stores lots of myoglobin, which stores oxygen for the respiration needed to keep the heart contracting regularly

Question 19

describe how the blood enters the right atrium

Answer 19

the inferior vena cava collects deoxygenated blood from the lower part of the body, while the superior vena cava collects deoxygenated blood from the upper part of the body. This blood is delivered to the right atrium

Question 20

describe how the blood enters the right ventricle

Answer 20

as the right atrium fills with blood, pressure increases and the tricuspid valve opens. So, blood enters the right ventricle too. When the atrium is full, it contracts to force blood into the ventricle. The tricuspid valve and tendinous cords prevent the backflow of blood back into the atrium

Question 21

how does the structure of atria differ from ventricles

Answer 21

the walls of the atria are thinner and have less muscle. This is because it receives blood at a lower pressure, and has weaker muscle contractions as it only needs to pump blood into the ventricle

Question 22

how does the tricuspid valve and the tendinous cords work together to prevent the backflow of blood

Answer 22

the tricuspid valve allows blood to enter the right ventricle from the right atrium, but only in one direction. The tough tendinous cords prevent the valves from turning inside out, by the pressure exerted when the ventricles contract

Question 23

describe how the blood enters the pulmonary artery from the right ventricle

Answer 23

the right ventricle is filled with blood under some pressure when the right atrium contracts. Its muscular walls produces more pressure to push the blood into the pulmonary artery. As the ventricle starts to contract, the tricuspid valve closes to prevent the backflow of blood into the atrium. The semilunar valves prevent the backflow of blood back into the ventricle from the artery

Question 24

describe how the blood travel to the left ventricle from the lungs

Answer 24

the oxygenated blood from the lungs is returned to the heart via the pulmonary vein. The blood enters the left atrium under a relatively low pressure. The right atrium contracts and forces blood into the left ventricle. The bicuspid valves prevent the backflow of blood back into the left atrium

Question 25

describe how the blood travels to the body from the left ventricle

Answer 25

the left ventricle contracts, pushing blood into the aorta, under high pressure. The semilunar valves prevent the backflow of blood back into the ventricle

Question 26

why is the right side of the heart less muscular than the left

Answer 26

the right side pumps blood to the lungs, which is relatively close to the heart. The capillaries need blood delivered at a relatively low pressure to maximise gas exchange via diffusion, and to prevent the capillaries from bursting

Question 27

why is the left side of the heart more muscular than the right

Answer 27

as the left side of the heart pumps blood to the whole body, so needs to produce sufficient force to move the blood under high pressure to reach all of the body cells, and to overcome the elastic recoil of the arteries.

Question 28

what is the function of the septum

Answer 28

to prevent oxygenated blood mixing with deoxygenated blood

Question 29

describe how the patent foramen ovale or the 'hole in the heart' condition occurs

Answer 29

when the foramen ovale, does not close over during birth

Question 30

what is the foramen ovale

Answer 30

a gap in the septum that allows deoxygenated and oxygenated blood of a fetus to mix as the lungs do not function yet

Question 31

how are the 'lub-dub' sounds of the heart produced

Answer 31

by the opening and closing of the heart valves

Question 32

what are the 3 stages of the cardiac cycle

Answer 32

atrial systole, ventricular systole, diastole

Question 33

Description of diastole

Answer 33

- the ventricles relaxes - blood enters the atria from the veins - the semilunar valves close

Question 34

Description of atrial systole

Answer 34

- the atria contracts - the atrioventricular valves are pushed open - blood is pushed into the ventricles

Question 35

Description of ventricular systole

Answer 35

- the ventricles contract - the atrioventricular valves close - the semilunar valves are pushed open - blood flows into the arteries

Question 36

describe the structure of the heart's walls

Answer 36

consists of 3 layers: - outer epicardium: layer of flattened epithelial cells and supporting connective tissue - myocardium: very thick muscular layer of cardiac muscle - inner endocardium: flattened epithelial cells supported by a delicate layer of connective tissue

Question 37

meaning cardiac output

Answer 37

the amount of blood pumped around the body

Question 38

what are 3 functions/ adaptations of the heart's walls

Answer 38

- secretes fluid which reduces friction between the heart and the surrounding tissue - non-elastic to prevent the heart from being overfilled and overstretched - attached to the diaphragm to keep the heart in position

Question 39

how to calculate cardiac output

Answer 39

stroke volume * heart rate

Question 40

meaning stroke volume

Answer 40

the volume of blood pumped by the left ventricle in each heart beat - for adults at rest, the value is typically 75 cm^3

Question 41

meaning heart rate

Answer 41

the number of beats per minute - for adults at rest, the value is typically 70 bpm

Question 42

what are the 4 types of valves

Answer 42

- atrioventricular valves (tricuspid valve & bicuspid valve) - semilunar valves - pulmonary semilunar valves - aortic semilunar valves

Question 43

what is the function of the valves

Answer 43

they increase the ventricular pressure, causing the blood to begin to flow backwards, forcing the valves shut and preventing any further backflow

Question 44

meaning papillary muscle

Answer 44

small projections of the inner walls of the ventricles, attached to the valves by the tendinous cords. The papillary muscle increases the tension of the cords so they can resist the strong back pressure of the blood, so the valve flaps close tightly against each other. They contract the same time as the ventricles

Question 45

describe the structure of cardiac muscle

Answer 45

- made of myocytes - muscle fibres are short, fat, branched and interconnected - contains lots of myocytes to store oxygen for heamoglobin - joined together by intercalated discs, which allows almost simultaneous contraction

Question 46

describe the cardiac cycle

Answer 46

1. Atrial Diastole: Both atria are relaxed, and blood flows passively into them from the vena cava and pulmonary veins. The AV valves are open, while semilunar valves are closed. 2. Ventricular Diastole: As the atria fill with blood, the pressure inside increases. The AV valves remain open, allowing blood to flow into the ventricles, which are still relaxed. 3. Atrial Systole: The atria contract, pushing the remaining blood into the ventricles. This ensures the ventricles are full. The AV valves are still open, and semilunar valves remain closed. 4. Ventricular Systole: The ventricles contract, increasing the pressure sharply. This causes the AV valves to close, producing the first heart sound ("lub"). The semilunar valves are still closed at this moment, so the volume of blood in the ventricles doesn’t change. 5. Ventricular Systole: As ventricular pressure exceeds that in the aorta and pulmonary artery, the semilunar valves open. Blood is ejected into these arteries. The atria begin to relax and refill during this time Ventricular Diastole: After contraction, the ventricles relax, causing pressure to drop. The semilunar valves close, creating the second heart sound ("dub"), preventing backflow. All valves are now closed, so volume remains constant briefly. Cycle Reset: As ventricular pressure falls below atrial pressure, the AV valves reopen, and blood flows passively from the atria to the ventricles. The cycle restarts.