The heart and circulation

Question 1

What is the position of the heart

Answer 1

It is centrally positioned, flanked and partially obscured by the lungs. It’s in the middle mediastinum

Question 2

What is the heart surrounded by

Answer 2

A pericardial sac - the pericardium

Question 3

What is the pericardium

Answer 3

The sac that surrounds the heart. It is fibrous - tough, dense connective tissue

Question 4

What is the function of the pericardium

Answer 4

To protect, anchor to surrounding structures, prevent overfilling

Question 5

Describe heart function

Answer 5

It is a muscular pump. It lies within a lubricated, potential space allowing expansion and contraction. It has synchronous contraction

Question 6

What do valves do

Answer 6

They encourage the unidirectional blood flow

Question 7

What is the arterial system

Answer 7

It is the conductance vessels that carry the blood around the body

Question 8

What is microcirculation

Answer 8

It is where transfer of nutrients, waste and water occurs

Question 9

What is the venous system

Answer 9

It is the capacity vessels, that store and return blood to the heart

Question 10

Describe the flow of blood through the heart

Answer 10

• The deoxygenated blood flows through the superior vena cava and the inferior vena cava into the right atrium
• The right atrium contracts pushing the blood through the tricuspid valve into the right ventricle
• The right ventricle contracts pushing the blood through the pulmonary valve into the pulmonary artery
• The pulmonary artery carries the blood to the lungs, oxygenating the blood
• The oxygenated blood returns back to the heart via the pulmonary vein to the left atrium
• The left atrium contracts and the blood is pumped through the mitral valve into the left ventricle
• The left ventricle contracts and pumps the blood through the aortic valve and out a major artery know as the aorta
• The aorta carries oxygenated blood around the body

Question 11

What is systole

Answer 11

When the heart contracts

Question 12

What is diastole

Answer 12

When the heart relaxes

Question 13

What are semi-lunar cusps

Answer 13

The pulmonary and aortic valves have them. During systole blood passes through the valve, forcing the cusps against the vessel wall. During diastole elastic recoil in the pulmonary trunk and aorta forces blood between the cusps and the vessel wall

Question 14

How do left and right coronary arteries arise

Answer 14

They arise from the aortic sinuses, just above the valve cusps. Vessels lie in the epicardium and branch inwards

Question 15

Describe the convergence of coronary veins

Answer 15

Apart from the anterior cardiac veins that drain directly into the right atrium, the veins of the heart converge on the coronary sinus, which enters the right atrium

Question 16

Describe coordinated contraction

Answer 16

Both the left side and the right side of the heart contract at the same time and in a balanced symmetry. The coordination of these events is determined by the electrical activity which originates in the right atrium and moves throughout the heart

Question 17

Describe the electrical conduction pathways of the heart

Answer 17

• From the SA node, depolarisation spreads through the atria
• Depolarisation spreads to the AV node
• Contraction of the atria take place immediately following
• The impulse is carried down the septum via the bundle of His, L/R Bundle branches to the Purkinje fibres in the ventricle walls
• Ventricle then contracts