Heart Flashcards
What is the structure of the pericardium?
There are 2 layers to the pericardium:
- Fibrous pericardium
- Serous pericardium
What are the properties of the fibrous pericardium?
- The fibrous pericardium defines the borders of the middle mediastinum.
- It is conical in shape.
- It is inelastic and does not allow for expansion.
- It is innervated by the phrenic nerve.
- Its blood supply is from the pericardiophrenic vessels of the internal thoracic arteries.
What are the attachments of the fibrous pericardium?
- Inferiorly: Diaphragm
- Superiorly: Continuous with the tunica adventitia of the great vessels
What is the structure of the serous pericardium?
- Consists of 2 layers:
1. Parietal layer - Lines inside of fibrous pericardium.
2. Visceral layer - Lines outside of heart. - Between the 2 layers is the pericardial cavity containing small amounts of serous fluid. This reduces friction between the 2 layers during contraction.
- The 2 layers are continuous with each other at 2 separate borders around the arteries and veins connecting to the heart.
- The parietal pericardium is innervated by the phrenic nerve.
- The visceral pericardium is innervated by visceral afferents running with sympathetic fibres.
What are the pericardial sinuses?
- The transverse sinus is a space formed between the arterial reflection (anterior) and the venous reflection (posterior). It allows for slings to be passed around the great vessels in order to tie them off during surgery.
- The oblique sinus is a space formed between the venous reflections. It is directly posterior to the left atrium and so facilitates its distension.
What are the functions of the pericardium?
- Reduces friction during contractions.
- Protects heart from infections of surrounding tissues.
- Fibrous pericardium anchors heart to diaphragm, preventing excess movement (and therefore torsion of great vessels).
- Prevents overdistension of the heart during diastole.
What are the surfaces and margins of the heart?
- Anterior surface: 2/3 right ventricle, 1/3 left ventricle.
- Diaphragmatic surface: 1/3 right ventricle, 2/3 left ventricle.
- Right pulmonary surface: Right atrium.
- Left pulmonary surface: Mostly left ventricle, small amount of left atrium.
- Base: Origins of the great vessels.
- Apex: Left ventricle.
- Inferior margin: Mostly right ventricle and some left ventricle.
- Obtuse margin: Mostly left ventricle and some left auricle.
What is the structure of the heart?
- The heart is divided into 4 chambers: The right/left atria and the right/left ventricles.
- The atria are divided from the ventricles by the coronary sulcus.
- Left side divided from right side by atrioventricular septum.
- The right atrium/ventricle effectively lie anterior to the left atrium/ventricle.
What is the path of the right coronary artery (RCA)?
- The RCA originates from the right aortic sinus (just above aortic valves) and passes between right auricle and pulmonary trunk.
- It enters the coronary sulcus and gives off the atrial branch which gives rise to the SA-nodal branch supplying the SAN (in 60% of people).
- It travels inferiorly and to the right in the right coronary sulcus.
- It gives off the right marginal branch just before it winds posteriorly onto the diaphragmatic surface.
- Along the diaphragmatic surface, it gives rise to the posterior interventricular artery (in 90% of people) which descends along the diaphragmatic surface in the interventricular sulcus. It also gives off the AV-nodal branch.
What is the path of the left coronary artery (LCA)?
- The LCA originates from the left aortic sinus and passes anteriorly between the left auricle and pulmonary trunk.
- It enters the coronary sulcus and bifurcates into the anterior interventricular (left anterior descending) artery and the circumflex artery.
- The anterior interventricular artery descends on the anterior surface in the anterior interventricular groove.
- The circumflex artery travels in the coronary sulcus before winding onto the left pulmonary surface, where it gives off the left marginal branch along the oblique margin.
- It continues onto the diaphragmatic surface, where it terminates.
What are the anatomical variations in blood supply of the heart?
- Right dominance (90%): Posterior interventricular artery (and AV-nodal artery) given off by the RCA.
- Left dominance (10%): Posterior interventricular artery (and AV-nodal artery) given off by the circumflex artery.
- Dominance is decided by which artery supplies the AVN, not which one supplies the largest area (since LCA always supplies larger area).
- In 40% of people, SA-nodal branch given off by the LCA.
Which parts of the myocardium does the RCA supply?
- Right ventricle
- Right atrium
- Part of left ventricle
- Posterior IV septum
Which parts of the myocardium does the anterior IV supply?
- Left ventricle
- Anterior IV septum
Which parts of the myocardium does the circumflex artery supply?
- Left atrium
- Left ventricle
What type of blood supply does the heart have?
- The coronary arteries are functional end arteries as the areas of the myocardium supplied by them are supplied by no other arteries.
- They have poor anastomoses.