Heart Structure

Question 1

Why do animals need a transport system?

Answer 1

• Animals have a small surface area to volume ratio and a large diffusion distance
• Diffusion is too slow to supply respiring cells with oxygen and remove waste carbon dioxide.
• Transport system is needed to prevent carbon dioxide build-up and maintain a high metabolic rate and temperature.

Question 2

What is the structure of the heart?

Answer 2

• Has 4 chambers.
• Heart contains 2 Atria and 2 Ventricles.
• Atria are located on top (with ‘A’ pointing upwards), while the Ventricles are lower (with ‘V’ pointing downwards).

Question 3

What is the role of the Atria in the heart?

Answer 3

• Atria receive blood from veins bringing blood back into the heart.
• RHS atrium always receives deoxygenated blood from the body.
• LHS atrium always receives oxygenated blood from the lungs.
• Two atria never mix their blood due to the wall that separates them.

Question 4

What is the role of Ventricles in the heart?

Answer 4

• Ventricles are the lower two chambers of the heart.
• Separated from the atria by valves that open when blood needs to travel between the chambers.
• RHS ventricle receives deoxygenated blood from the RHS atrium.
• LHS ventricle receives oxygenated blood from the LHS atrium.
• Septum ensures that the blood in the ventricles never mixes - ensures maximum oxygenated blood is pumped to all cells for maximum respiration.

Question 5

What is a double circulatory systems in animals?

Answer 5

• Mammals have a double circulatory system where blood moves through the heart twice.
• Pulmonary circulation- blood moves from the heart to the lungs and back.
• Systemic circulation- blood moves from the heart to the rest of the body and back.

Question 6

Explain the cardiac cycle in detail

Answer 6

1. Pulmonary vein transfers oxygenated blood from the lungs to the left atrium
2. Left atrium fills with blood and the muscular walls of the atrium contract - squeezes blood into the left ventricle
3. Left ventricle fills with oxygenated blood and its wall contracts - squeezes the blood out to the aorta
4. Aorta carries the blood to cells - oxygen is used for aerobic respiration and carbon dioxide is produced
5. Vena cava carries deoxygenated blood back to the right atrium - fills and contracts- squeezes the blood into the right ventricle
6. Right ventricle fills with blood and contracts- pushes deoxygenated blood into the pulmonary artery - carries it to the lungs to pick up oxygen and remove carbon dioxide

Question 7

Why does the left side of the heart have more muscle in its walls?

Answer 7

• Left side has more muscle in its walls to contract more strongly- pushes blood out at high pressure so it can travel large distances throughout the body
• Right side only pumps blood to the lungs - a shorter distance

Question 8

Why does the right ventricle generate less pressure than the left ventricle?

Answer 8

• Right ventricle- less pressure because the blood is only pumped to the lungs- short distance
• Left ventricle- more pressure as it pumps blood around the entire body- has thicker cardiac muscle in the walls

Question 9

What are the AV valves

Answer 9

• AV valves are located between the atria and ventricles
• Right side has the tricuspid valve
• Left side has the bicuspid valve.

Question 10

How do AV valves work?

Answer 10

• Blood enters the atria- pressure in the atria is high- pressure in the ventricles is low- AV valves open
• Blood moves into the ventricles- pressure in the ventricles is high- pressure in the atria is low- AV valves close

Question 11

What is the role of AV valves

Answer 11

• Prevent the backflow of blood
• If the valves fail- more blood flows backward- reduces amount of oxygenated blood pumped out of the heart- leads to fatigue

Question 12

What are the semi-lunar valves and how do they work?

Answer 12

• Semi-lunar valves are located between the ventricles and arteries
• Open when the pressure in the ventricles rises above the pressure in the arteries
• Blood moves into the arteries- pressure in the ventricles drops- higher pressure in the arteries- valves closed- prevent backflow

Question 13

What is the role of the hepatic portal vein, hepatic vein, and hepatic artery?

Answer 13

• Hepatic portal vein: carries blood containing digested food from the intestines to the liver
• Hepatic vein: carries blood from the liver to the vena cava
• Hepatic artery: carries blood from the aorta to the liver.