The Heart Structure

Question 1

Simple diffusion was enough to supply the early prokaryotes with enough oxygen to meet metabolic demand, however, as organisms grew larger this was no longer adequate.
Explain why

Answer 1

• Smaller organisms have larger SA:V therefore higher rate of diffusion.
• Larger organisms have a smaller SA:V ratio, a greater diffusion distance and a higher metabolic rate.
• Therefore, a new system was needed.

Question 2

How does an open circulatory system work

Answer 2

• The open circulatory system is a type of circulatory system in which there are no blood vessels.
• The organs and tissues in the bodies of the organisms are directly fed with the transport medium (haemolymph)

Question 3

Describe the limitations of the open circulatory system

Answer 3

1. Blood distribution cannot be altered
2. The organism must be small
3. The organism must have a low metabolic rate

Question 4

Describe the features of a closed circulatory system

Answer 4

• Transport medium (e.g. blood)
• Mass transport system (e.g. heart to pump)
• Closed system of vessels

Question 5

Describe the significance of a transport medium in a closed circulatory system

Answer 5

Transport medium allows for transport over larger distances, and allows a concentration gradient to be maintained

Question 6

Describe the significance of mass flow in a closed circulatory system

Answer 6

Mass flow will be faster than diffusion as distance is large

Question 7

Describe the significance of a closed system vessel in a closed circulatory system

Answer 7

Closed system allows flow to be controlled to different organs in the body

Question 8

Explain the importance of mass transport systems to large organisms (5)

Answer 8

• Transport over long distances = diffusion only efficient over very short distances
• larger organism has smaller SA:V
• Needs transport system to maintain concentration gradient for diffusion
• large animals are more active / higher demand for energy
• Oxygen needs to be supplied / CO2 removed at high rate

Question 9

Describe the role of the coronary arteries

Answer 9

The coronary arteries supply the cardiac muscle with oxygenated blood

Question 10

What do arteries do with the blood

Answer 10

AWAY from heart

Question 11

What do veins do with blood

Answer 11

Take it back to the heart

Question 12

Describe the passage of blood through the heart

Answer 12

• Blood fills the right atrium from the vena cava, a vein, and the left atrium from the pulmonary vein.
  (The vena cava brings blood from the body the pulmonary vein from the lungs)
• Once blood has filled the atria. The blood then passes through a valve into the two ventricles (click). These valves are called the atrioventricular valves
• Once the ventricles have filled, the blood moves upwards and out of the heart.
  -They pass through more valves first - these are called semi-lunar valves.
  -The blood leaves the heart through the two main arteries:
  The aorta to the rest of the body, and the pulmonary artery to the lungs.

Question 13

Describe the route taken by deoxygenated blood from the body to the lungs

Answer 13

• Blood from the body returns to the heart via the vena cava
• The blood from the vena cava enters the right atrium
• The blood flows through the right atrioventricular valve into the ventricles
• The blood flows through the right semi-lunar valves into the pulmonary artery

Question 14

Describe the route taken by oxygenated blood from the lungs to the body

Answer 14

• Blood from the lungs returns to the heart via the pulmonary vein
• The blood from the pulmonary vein enters the left atrium
• The blood flows through the left atrioventricular valve into the ventricles
• The blood flows through the left semi-lunar valves into the aorta

Question 15

Vena cava

Answer 15

• Joins to the right atrium
• Brings deoxygenated blood from the body back to the heart

Question 16

Pulmonary artery

Answer 16

• Joins to the right ventricle
• Takes deoxygenated blood from the heart to the lungs

Question 17

Pulmonary vein

Answer 17

• Joins to the left atrium
• Brings oxygenated blood from the lungs to the heart

Question 18

Aorta

Answer 18

• Joins to the left ventricle
• Takes oxygenated blood from the heart to the rest of the body

Question 19

Septum

Answer 19

• In the middle of the heart between the left and right sides
• Stops deoxygenated and oxygenated blood from mixing

Question 20

Atrioventricular valves

Answer 20

• Separates the atria and the ventricles
• Stops backflow of blood between ventricles and the atria

Question 21

Semi-lunar valves

Answer 21

• Separates the ventricles and the arteries
• Stops backflow of blood from the arteries to the ventricles.

Question 22

Describe the role of the cardiac muscle in the walls of the heart

Answer 22

Contracts to create pressure in the heart, which is needed to move the blood

Question 23

Why is the cardiac muscle wall thicker on the left side of the heart

Answer 23

The left side of the heart needs to contract more forcefully to produce the higher pressures needed to pump blood around the whole body. The right side only pumps blood to the lungs so does not need to generate as much pressure