Thorax Part 3

Question 1

Name the structure.

Answer 1

Heart

Question 2

Where is the heart placed?

Answer 2

Middle Mediastinum

Question 3

Where is the heart contained?

Answer 3

Pericardium / Pericardial cavity

Question 4

What is the pericardium?

Answer 4

Fibroserous sac surrounding heart and its great vessels

Question 5

Describe the structure of the pericardium.

Answer 5

• Consists of 2 layers
  
  • Fibrous
  • Serous (has 2 parts)
    
    • Parietal – lines fibrous
    • Visceral – adheres to heart

Question 6

What are the steps of the cardiac cycle (7)?

Answer 6

1. Atrial systole
2. Isovolumetric contraction
3. Ventricular ejection phase
4. Reduced ejection
5. Isovolumetric relaxation
6. Rapid ventricular filling
7. Reduced passive filling

Question 7

What happens during atrial systole of the cardiac cycle?

Answer 7

• Prior to atrial systole, the blood will passively flow through the atrioventricular orifice into the ventricles through open atrioventricular valves (Mitral & tricuspid valves)

Question 8

What happens during isovolumetric contraction of the cardiac cycle?

Answer 8

• Atrioventricular and semi-lunar valves are closed, as pressure is accumulating through isometric contraction

Question 9

What happens during ventricular ejection phase of the cardiac cycle?

Answer 9

• Period at which the ventricular pressure exceeds aortic and pulmonary pressure (afterload), the semi-lunar (pulmonary & aortic) valves open, demarcating the initiation of this phase

Question 10

What happens during reduced ejection phase of the cardiac cycle?

Answer 10

• Blood is ejected from the ventricles at a reducing rate, and ventricular pressure subsequently decreases simultaneously with volume reduction; aortic and pulmonary pressure eventually exceeds ventricular pressure, stimulating the closure of the semi-lunar valves

Question 11

What happens during isovolumetric relaxation phase of the cardiac cycle?

Answer 11

• Early phase of ventricular diastole: Ventricular muscle relaxes, pressure on remaining blood within the ventricle begins to decrease

Question 12

What happens during rapid ventricular filling phase of the cardiac cycle?

Answer 12

• Atrial pressure increases (ventricular pressure decreases via relaxation) to the extent that the atrioventricular valves open, enabling blood flow along the pressure gradient through the atrioventricular orifice into the ventricles

Question 13

What happens during reduced passive filling phase of the cardiac cycle?

Answer 13

• Slow filling of the ventricles (Diastasis)

Question 14

Name the branches of the aortic arch.

Answer 14

• Brachiocephalic branch
  
  • Right subclavian artery
  • Right common carotid artery
• Left common carotid artery
• Left subclavian artery

Question 15

Name the branches of the brachiocephalic vein.

Answer 15

• Right brachiocephalic vein
  
  • Right subclavian vein
  • Right internal jugular vein
• Left brachiocephalic vein
  
  • Left internal jugular vein
  • Left subclavian vein

Question 16

Name the four cardiac valves.

Answer 16

• Right atrioventricular / tricuspid valve
• Left atrioventricular / bicuspid / mitral valve
• Pulmonary valve
• Aortic valve

Question 17

How does the aortic valve differ from the pulmonary valve?

Answer 17

There is an opening for the right coronary artery.

Question 18

Which artery supplies the cardiac muscles?

Answer 18

Coronary arteries

Question 19

Describe the branching of the coronary arteries.

Answer 19

• Aorta
  
  • Right coronary artery
  • Left coronary artery
    
    • Anterior interventricular branch of the left coronary artery
    • Circumflex branch of the left coronary artery

Question 20

Which veins drain the cardiac muscles?

Answer 20

Coronary vein

Question 21

Describe the branching of the coronary veins.

Answer 21

Cardiac veins drain into coronary sinus

Question 22

Describe the SA node.

Answer 22

• Primary pacemaker cells located in wall of right atrium
• Rate: 60-100bpm
  
  • Usually determines normal heart rhythm

Question 23

What are the 3 latent pacemaker cells?

Answer 23

• AV node
• Bundle of His
• Purkinje fibers

Question 24

Describe the AV node.

Answer 24

• Located at base of right atrium, near septum
• Rate: 40-60bpm

Question 25

Describe the Bundle of His.

Answer 25

• Divides into right and left bundle branches, travels through septum between ventricles
• Rate: 20-40bpm

Question 26

Describe the Purkinje fibers.

Answer 26

• Spread throughout ventricles
• Rate: 20-40bpm

Question 27

Describe the action potential phases of the pacemaker cells of the heart.

Action potentials in pacemaker cells
* Rapid electrical changes across membrane of pacemaker cells
* Conducted to rest of heart

Answer 27

• Phase 4: sodium moves into cell through funny channels (open in response to hyperpolarization); slowly depolarizes cell until threshold potential met
  
  • Responsible for instability of resting membrane potential
• Phase O: strong inward calcium current; responsible for rapid depolarization
• Phase 3: strong potassium current moves out of cell; responsible for repolarization
  
  • Phases 1, 2 absent in pacemaker cells
    
    • No plateau

Question 28

The heart and pericardium sit within which part of the mediastinum?

Answer 28

Middle

The mediastinum is divided into superior and inferior parts. The inferior part is further subdivided into anterior, middle and posterior. The heart sits in the middle part.

Question 29

Deoxygenated blood leaves the heart via which vessel?

Answer 29

Pulmonary trunk

Oxygenated blood leaves the heart via the ascending aorta. The 3 branches of the next part of the aorta, the arch, are the brachiocephalic trunk, the left common carotid artery and the left subclavian artery. Deoxygenated blood leaves the heart via the pulmonary trunk and following oxygenation in the lungs, is returned to the heart via the pulmonary veins.

Question 30

What is the innermost layer of pericardium?

Answer 30

Visceral serous

The pericardium is a fibroserous sac surrounding the heart and its great vessels. It consists of 2 layers, fibrous and serous. The serous layer has 2 parts: parietal, which lines the fibrous layer, and the visceral layer, which is closely adherent to the heart.

Question 31

What is the second branch of the aortic arch?

Answer 31

Left common carotid artery

The 3 branches of the aortic arch are the brachiocephalic trunk, the left common carotid artery and the left subclavian artery. The brachiocephalic trunk divides into the right common carotid and right subclavian arteries.

Question 32

What is the second branch of the aortic arch?

Answer 32

Left common carotid artery

The 3 branches of the aortic arch are the brachiocephalic trunk, the left common carotid artery and the left subclavian artery. The brachiocephalic trunk divides into the right common carotid and right subclavian arteries.

Question 33

Which valve prevents blood entering the left atrium during ventricular contraction?

Answer 33

Mitral valve

The heart has 2 atrioventricular (between the atrium and the ventricle) valves which prevent blood returning to the atria from the ventricles during ventricular contraction. These are the tricuspid valve (right side) and the mitral valve (left side). Semilunar valve is the name given to the 2 valves which prevent blood returning to the ventricles following ventricular contraction. One is between the right ventricle and the pulmonary trunk (pulmonary valve) and one is between the left ventricle and the aorta (aortic valve).