Thorax Part 3 Flashcards
Name the structure.
Heart
Where is the heart placed?
Middle Mediastinum
Where is the heart contained?
Pericardium / Pericardial cavity
What is the pericardium?
Fibroserous sac surrounding heart and its great vessels
Describe the structure of the pericardium.
- Consists of 2 layers
- Fibrous
-
Serous (has 2 parts)
- Parietal – lines fibrous
- Visceral – adheres to heart
What are the steps of the cardiac cycle (7)?
- Atrial systole
- Isovolumetric contraction
- Ventricular ejection phase
- Reduced ejection
- Isovolumetric relaxation
- Rapid ventricular filling
- Reduced passive filling
What happens during atrial systole of the cardiac cycle?
- Prior to atrial systole, the blood will passively flow through the atrioventricular orifice into the ventricles through open atrioventricular valves (Mitral & tricuspid valves)
What happens during isovolumetric contraction of the cardiac cycle?
- Atrioventricular and semi-lunar valves are closed, as pressure is accumulating through isometric contraction
What happens during ventricular ejection phase of the cardiac cycle?
- 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
What happens during reduced ejection phase of the cardiac cycle?
- 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
What happens during isovolumetric relaxation phase of the cardiac cycle?
- Early phase of ventricular diastole: Ventricular muscle relaxes, pressure on remaining blood within the ventricle begins to decrease
What happens during rapid ventricular filling phase of the cardiac cycle?
- 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
What happens during reduced passive filling phase of the cardiac cycle?
- Slow filling of the ventricles (Diastasis)
Name the branches of the aortic arch.
-
Brachiocephalic branch
- Right subclavian artery
- Right common carotid artery
- Left common carotid artery
- Left subclavian artery
Name the branches of the brachiocephalic vein.
- Right brachiocephalic vein
- Right subclavian vein
- Right internal jugular vein
- Left brachiocephalic vein
- Left internal jugular vein
- Left subclavian vein
Name the four cardiac valves.
- Right atrioventricular / tricuspid valve
- Left atrioventricular / bicuspid / mitral valve
- Pulmonary valve
- Aortic valve
How does the aortic valve differ from the pulmonary valve?
There is an opening for the right coronary artery.
Which artery supplies the cardiac muscles?
Coronary arteries
Describe the branching of the coronary arteries.
- Aorta
- Right coronary artery
-
Left coronary artery
- Anterior interventricular branch of the left coronary artery
- Circumflex branch of the left coronary artery
Which veins drain the cardiac muscles?
Coronary vein
Describe the branching of the coronary veins.
Cardiac veins drain into coronary sinus
Describe the SA node.
- Primary pacemaker cells located in wall of right atrium
- Rate: 60-100bpm
- Usually determines normal heart rhythm
What are the 3 latent pacemaker cells?
- AV node
- Bundle of His
- Purkinje fibers
Describe the AV node.
- Located at base of right atrium, near septum
- Rate: 40-60bpm
Describe the Bundle of His.
- Divides into right and left bundle branches, travels through septum between ventricles
- Rate: 20-40bpm
Describe the Purkinje fibers.
- Spread throughout ventricles
- Rate: 20-40bpm
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
-
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
- Phases 1, 2 absent in pacemaker cells
The heart and pericardium sit within which part of the mediastinum?
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.
Deoxygenated blood leaves the heart via which vessel?
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.
What is the innermost layer of pericardium?
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.
What is the second branch of the aortic arch?
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.
What is the second branch of the aortic arch?
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.
Which valve prevents blood entering the left atrium during ventricular contraction?
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).
