Topic 1 - Circulatory system

Question 1

Explain the jorney of the red blood cell

Answer 1

Blood flows through the heart in a specific sequence. Deoxygenated blood enters the right atrium, where it is then pumped into the right ventricle. From the right ventricle, it is pumped into the lungs, where it is oxygenated. Oxygenated blood then returns to the heart and enters the left atrium, where it is pumped into the left ventricle. The left ventricle then pumps oxygenated blood to the rest of the body through the aorta.

Question 2

When are the sound “LUB” and “DUB” produced respectively during heart beat?

Answer 2

The first sound LUB is produced when the atrioventricular valves i.e. tricuspid and bicuspid valves close at the start of ventricular systole. The second sound DUB is produced at the beginning of ventricular diastole when the pulmonary and aortic semilunar valves close.

Question 3

Why do we need a circulatory system

Answer 3

• As SA icreases , SA:Vol decreases
• As we are multicellular organisms, SA:Vol decreases
• diffusion is no longger sufficient to give us what we need as theres too many cells and distance gets greater

Question 4

Define mass flow

Answer 4

Movement of substances efficiently over a long distance due to pressure differences (translocation + transpiration)

Question 5

Why are there difference created in the heart

Answer 5

Cardiac muscles of the left ventricle have thicker walls compared to the atria. This is because they have to pump blood a further distance than the atria (out of the heart and to the rest of the body) and withstand higher pressures.

Question 6

Define AV (atrioventricular) valves

Answer 6

The atrioventricular (AV) valves are valves which connect the atria to the ventricles. They stop blood flowing back into the atria when the ventricles contract and are also known as the tricuspid and bicuspid valves.

Question 7

Describe what tendinous chords are and their function

Answer 7

Tendinous chords, also known as valve tendons, prevent atrioventricular valves turning inside out. This can happen due to the pressure inside.

Question 8

Describe what the septum is and its function

Answer 8

The septum consists of muscle and connective tissue. It prevents oxygenated and deoxygenated blood from mixing.

Question 9

What are the advantages of the double circulatory system

Answer 9

• Maintained concentration gradient – this is due to oxygenated and deoxygenated blood not mixing.
• Blood pressure to lungs is slower – to avoid damaging delicate tissues and increase time for gas exchange.
• Blood pressure to body tissues is higher.

Question 10

Explain the process of the cardiac cycle

Answer 10

1. Cardiac diastole – both the atria and ventricles are relaxed (0.4 seconds). Whilst the heart is in the relaxation phase, blood enters the atria. As this happens, the pressure behind the AV valves increases, pushing them open. Blood then enters the ventricles from the atria and the SL valves remain closed.
2. Atrial systole – atria contract and ventricles remain relaxed (0.1 second). The atria contract to push any remaining blood into the ventricles. The SL valves remain closed.
3. Ventricular systole – the atria relax and the ventricles contract (0.3 seconds). The ventricles contract after a certain amount of blood is filled, increasing the pressure, closing the atrioventricular valves. In response to the pressure, the semilunar valves open where blood flows out of the heart. As the pressure decreases, the semilunar valves then close.

Question 11

What are the functions of erythocytes

Answer 11

red blood cells which are able to transport oxygen via haemoglobin and some carbon dioxide. Their biconcave shape and lack of nucleus are adaptations in order to fit through capillaries.

Question 12

What are the functions of thrombocytes

Answer 12

is the process of forming a blood clot, known as a thrombus, within a blood vessel. It acts to prevent blood loss when a blood vessel is damaged, as well as preventing the entry of disease from microorganisms. It also works to provide a framework to begin repairing.

Question 13

What is plasma

Answer 13

solvent for dissolved substances and help create a suspension within the cells

Question 14

Describe the structure of the arteries

Answer 14

• Thick walls to handle pressure w/o tearing.
• Higher elastic tissue allows recoil (maintain BP) and stretch (withstand BP)
• Narrow lumen to maintain pressure
• Smooth endothelium - low friction to flow

Question 15

Describe the structure of the veins

Answer 15

• Thin collagen walls due to lower pressure. Require valves to ensure blood doesnt flow backwards.
• Has less smooth muscule and elastic tissues as they dont have to control blood flow.
• Wide lumen - low volume of blood acts as a blood reservoir

Question 16

Describe the structure of cappilaries

Answer 16

• Walls are only one cell thick; short diffusion distance pathway
• very narrow, so can penetrate tissues and red blood cells can lie flat against the wall, effectively delivering oxygen to tissues
• numerous and highly branched, providing large surface area

Question 17

Suggest how skeletal muscle aid the role of veins

Answer 17

Skeletal muscles contract causing veins to be compressed which increases the blood pressure due to the valves in the veins so the increase of pressure drives blood to the heart