Cardiovascular system

Question 1

Where is the heart located

Answer 1

In the mediastinum behind the body of the sternum between 2nd and 6th ribs

Question 2

What are the internal and external pericardium (heart covering) made up of? What is the function?

Answer 2

External:
Fibrous pericardium; tough, loose fitting and inelastic sac

Internal:
Parietal layer: mining inside the fibrous pericardium
Visceral layer: adheres to outside of heart

Prevents friction
Allows the heart to move within the sac

Question 3

What are the layers of the heart wall?

Answer 3

Epicardium - serous pericardium attached to heart
Myocardium - cardiac cells which from a suncytium via intercalated discs and gap junctions
Endocardium - delicate membrane lining the internal wall of myocardium and blood vessels

Question 4

What are the difference between the valves on the right and left side of the heart?

Answer 4

Left = bicuspid
Right = tricuspid

Both sides have semilunar valves where the pulmonary valve and aorta arise from left and right ventricles

Question 5

Describe the process of blood flow

Answer 5

• Blood enters the right atrium via superior and inferior venae cava
• Passes through right atrioventricular valve into right ventricle
• Passed through pulmonary valve formed by 3 semilunar cusps into pulmonary artery
• Pulmonary artery splits into two and carries blood to lungs
• Blood enters the left atrium via pulmonary vein
• Blood passed through left atrioventricular valve into left ventricle
• Blood is pumped around the body via aorta

Question 6

How is the heart itself supplied with blood?

Answer 6

Right and left coronary arteries branch off from aortic supply and form smaller branches which form anastomoses.
Small coronary veins drain the deoxygenated blood into the right atrium.

Question 7

What are the 4 structures of the conduction system?

Answer 7

Sinoatrial node - initiates the action potential in the right atrial wall
Atrioventricular node - small mass of special cardiac fibres in the right atrium at the interatrial septum
Atrioventricular bundle - bundle of HIS extending from AV node in two branches on the sides of the interventricular wall
Purkinje fibres - continues with AV bundle and attaches to apex of heart

Question 8

What are the steps of the cardiac cycle?

Answer 8

1. Atrial systole: contraction and emptying of atria, relaxation and filling of ventricles
2. Isovolumetric ventricular contraction: Initial contraction of ventricle and opening of semilunar valve, blood volume remains the same
3. Ejection: ventricle pressure higher than artery pressure so blood passes through semilunar valve
4. Isovolumetric ventricular relaxation: semilunar valves close and AV valve opens
5. Passive ventricular filling: Increased atrial pressure due to influx of venous blood causes passive ventricular filling

Question 9

How is blood pressure measured?

Answer 9

Highest ventricular systole (120mmHG) and lowest ventricular diastole (80mmHG)

120/80

Question 10

What factors affect heart rate?

Answer 10

10th cranial nerve

Carotid reflexes (pressure reflexes in neck communicate with brain)(high BP causes inhibition via 10th cranial nerve)

Aortic reflex (on aortic arch, detects BP rise and communicates with brain)

Hormones