Circulatory system & the heart

Question 1

Name 2 common features of transport systems of many mammals

Answer 1

• Suitable medium in which to carry materials e.g blood. Is normally a liquid based on water as water readily dissolves substances + can be moved around easily
• Form of mass transport in which transport medium is moved around in bulk over large distances - more rapid than diffusion
• Closed system of tubular vessels + contain transport medium + forms branching network to distribute it to all parts of organism
• Mechanism for moving transport medium within vessels - requires a pressure difference betw. 1 part of the system + another

Question 2

How can materials be transported in animals & plants?

Answer 2

• Animals use muscular contraction of body muscles/specialised pumping organ e.g heart
• Plants rely of natural passive processes e.g evaporation of water

Question 3

How can materials be transported in mammals?

Answer 3

• Through a mechanism to maintain mass flow movement in 1 direction (e.g valves)
• By a means of controlling flow of transport medium to suit the changing needs of diff. parts of organism
• Through a mechanism for mass flow of water/gases (e.g intercostal muscles + diaphragm during breathing )

Question 4

How would you describe the circulatory system of mammals? Explain why it is described this way

Answer 4

Mammals have a closed, double circulatory system.

Blood is confined to vessels + passes twice through the heart for each complete circuit of the body - when blood is passed through the lungs its pressure is reduced + when blood is returned to the heart it boost its pressure before being circulated to rest of tissues

Question 5

Why is it necessary for substances to be delivered to the rest of the body quickly in mammals?

Answer 5

As mammals have a high body temp. + hence a high rate of metabolism

Question 6

What process is the final part of the journey to cells after the transport system?

Answer 6

Diffusion

Question 7

Why is the final exchange from blood vessels to cells rapid?

Answer 7

It takes place over a large SA, across short distances + there is a steep diffusion gradient

Question 8

What is the heart and where is it found?

Answer 8

A muscular organ found in the thoracic cavity behind the sternum (breastbone) - it operates continuously + tirelessly throughout the life of an organism

Question 9

Give a very brief description of the structure of the heart (left + right + blood)

Answer 9

• Made up of two separate pumps
• Left deals with oxygenated blood from lungs
• Right deals with deoxygenated blood from the body

Question 10

Name the two chambers that make up each pump

Answer 10

Atrium & ventricle

Question 11

What is the problem with having only one pump?

Answer 11

• Lungs have to collect O2 then go to rest of body before returning to heart
• Blood has to pass through tiny capillaries in lungs to present large SA for gas exchange
• Therefore there is a v large drop in pressure + blood flow to rest of body would be v slow (this is why in mammals blood is returned to heart to increase pressure before distributed to rest of body)
• Essential to separate deoxygenated and oxygenated blood

Question 12

Describe the right ventricle and its function

Answer 12

Pumps blood only to the lungs + has thinner muscular walls than left ventricle

Question 13

Describe the left ventricle and its function

Answer 13

Thicker muscular wall + therefore it can contract to create enough pressure to pump blood to the rest of the body

Question 14

Describe how both (pumps) sides of the heart work together

Answer 14

• Pump in time with each other but blood doesn’t mix

- Both atria contract together + both ventricles contract together + pump same vol. of blood

Question 15

What do valves do and where are they found in the heart?

Answer 15

Valves prevent the backflow of blood into the atria when ventricles contract. They are found in atria and ventricles.

Question 16

What are the two valves found that prevent backflow of blood into atria when ventricles contract?

Answer 16

• Left atrioventricular (bicuspid) valve

- Right atrioventricular (tricuspid) valve

Question 17

What is connected to each of the 4 chambers of the heart?

Answer 17

Each of the 4 chambers of the heart connected to large blood vessels that carry blood towards/away from the heart

Question 18

What are pulmonary vessels?

Answer 18

Vessels connecting heart to lungs

Question 19

Name the vessels connected to the 4 chambers of the heart

Answer 19

• Aorta
• Vena cava
• Pulmonary artery
• Pulmonary vein

Question 20

Describe the function of the aorta and name the chamber it is connected to

Answer 20

Aorta is connected to left ventricle + carries oxygenated blood to all parts of body (except lungs)

Question 21

Describe the function of the vena cava and name the chamber it is connected to

Answer 21

Vena cava is connected to right atrium

It brings deoxygenated blood back from tissues of the body (except lungs)

Question 22

Describe the function of the pulmonary artery and name the chamber it is connected to

Answer 22

Pulmonary artery is connected to right ventricle
It carries deoxygenated blood to lungs where O2 is replenished + CO2 is removed (unusual for artery to carry deoxy. blood)

Question 23

Describe the function of the pulmonary vein and name the chamber it is connected to

Answer 23

Pulmonary vein is connected to left atrium

It brings oxygenated blood back from lungs (unusual for vein to carry oxy. blood)

Question 24

How is oxygen supplied to the heart muscle?

Answer 24

• Heart muscle is supplied with oxygen by its own vessels called the coronary arteries
• Although oxy. blood passed through left side of heart, the heart doesn’t use this O2 to meet its own great respiratory needs

Question 25

Where are the coronary arteries found?

Answer 25

Coronary arteries branch off aorta shortly after it leaves the heart

Question 26

What causes the coronary arteries to be blocked? Explain the effect of this blockage

Answer 26

Blood clot can lead to myocardial infarction (heart attack)
because an area of the heart is deprived of blood + therefore oxygen - muscle cells in this region unable to respire (aerobically) + so die

Question 27

What are the 4 types of blood vessel?

Answer 27

Arteries
Arterioles
Capillaries
Veins

Question 28

What types if blood vessel are the aorta and the vena cava?

Answer 28

• Aorta is an artery

- Vena cava are veins

Question 29

Name the basic layered structure of arteries, arterioles + veins (from outwards to inwards)

Answer 29

• Tough fibrous outer layer
• Muscle layer
• Elastic layer
• Thin inner lining (endothelium)
• Lumen (not actually a layer but central cavity of a blood vessel)

Question 30

Describe the function of the tough fibrous outer layer

Answer 30

It resists pressure changes from both within + outside

Question 31

Describe the function of the muscle layer

Answer 31

It can contract + so control flow of blood

Question 32

Describe the function of the elastic layer

Answer 32

It helps maintain blood pressure by stretching + springing back (recoiling)

Question 33

Describe the function of the thin inner lining (endothelium)

Answer 33

It is smooth to reduce friction + thin to allow diffusion

Question 34

Describe the function of the lumen

Answer 34

It is the central cavity of a blood vessel through which blood flows

Question 35

Explain the structural difference between veins + arteries

Answer 35

Same structures (layers) but veins are more wide + arteries are more narrow

Question 36

What are capillaries made up of?

Answer 36

Only thin lining layer and lumen

Question 37

Describe the function of arteries

Answer 37

Arteries transport blood rapidly under high pressure from heart to tissue

Question 38

How is the muscle layer (structure) adapted to the function of the arteries?

Answer 38

Muscle layer is thick compared to veins - means that smaller arteries can be constricted + dilated to control vol. of blood passing through them

Question 39

How is the elastic layer (structure) adapted to the function of the arteries?

Answer 39

• Elastic layer is relatively thick compared to veins - it is important that blood pressure in arteries is kept high so blood can reach all parts of body
• Elastic wall is stretched at each beat of heart (systole) + springs back when heart relaxes (diastole)
• Stretching + recoiling action helps to maintain high blood P + smooth P surges created by beating of heart

Question 40

How is the overall wall adapted to the function of the arteries?

Answer 40

Overall thickness of wall is great - this resists vessel from bursting under pressure

Question 41

Why don’t the arteries have valves (except in arteries leaving the heart)?

Answer 41

The blood is under constant high pressure due to heart pumping blood into arteries - therefore tends not to flow backwards

Question 42

Describe the function of the arterioles

Answer 42

The arterioles carry blood under lower pressure than arteries, from arteries to capillaries + control flow of blood between the two

Question 43

How is the muscle layer adapted to the function of the arterioles?

Answer 43

Muscle layer is relatively thicker than in arteries - contraction of this layer allows constriction of lumen of arteriole. This restricts flow of blood + so controls its movement into capillaries that supply tissues with blood

Question 44

How is the elastic layer adapted to the function of the arterioles?

Answer 44

Elastic layer is relatively thinner than in arteries as blood pressure is lower

Question 45

Describe the function of veins

Answer 45

Veins transport blood slowly, under low pressure from capillaries in tissues to heart

Question 46

How is the muscle layer adapted to the function of the veins?

Answer 46

Muscle layer is relatively thin compared to arteries -

as veins carry blood away from tissues + therefore their constriction + dilation cannot control flow of blood to tissues

Question 47

How is the elastic layer adapted to the function of the veins?

Answer 47

Elastic layer is relatively thin compared to arteries -

as low pressure (P) of blood within veins will not cause them to burst + P is too low to create recoil action

Question 48

How is the overall wall adapted to the function of the veins?

Answer 48

Overall thickness of wall is small -
]as there is no need for thick wall as pressure within veins is too low to create any risk of bursting.
Allows them to be flattened easily, aiding flow of blood

Question 49

How are the valves adapted to the function of the veins?

Answer 49

• Valves at intervals throughout veins -
  to ensure blood doesn’t flow backwards, which it might otherwise do as pressure (P) is too low.
• When muscles contract, veins are compressed, pressurizing blood within them
• Valves ensure this P directs blood in one direction only (towards heart)

Question 50

Describe the function of the capillaries

Answer 50

• Exchange of metabolic materials e.g O2, CO2 + glucose between blood + cells of body
• Flow of blood in capillaries i much slower which allows more time for exchange in materials

Question 51

How are the walls adapted to the function of the capillaries?

Answer 51

Capillary walls consist mostly of lining layer - makes them extremely thin (1 cell thick), so there is short distance over which diffusion happens.
Allows for rapid diffusion of materials between blood + cells

Question 52

What feature of the capillaries provides large SA for exchange?

Answer 52

Numerous + highly branched

Question 53

How is the diameter of the capillaries adapted to its function?

Answer 53

Capillaries have narrow diameter - so they can permeate (spread out) tissues which means that no cell is far from a capillary + there is a short diffusion pathway

Question 54

How is the lumen adapted to the function of the capillaries?

Answer 54

Lumen is so narrow that red blood cells are squeezed flat against side of capillary + this brings them even closer to cells to which they supply O2 which again reduces diffusion distance

Question 55

How do the spaces between lining (endothelium) cells help capillaries with their function?

Answer 55

The spaces between lining cells allow white blood cells to escape in order to deal with infections within tissues

Question 56

What is tissue fluid?

Answer 56

Tissue fluid is the liquid solution that bathes the tissues

Question 57

Where are the final journey of metabolic tissues made?

Answer 57

The final journey of metabolic materials is made in the tissue fluid