Describe the sections of the mediastinum. What separates the two vertical components?
Superior mediastinum Inferior mediastinum: divided into anterior, middle and posterior mediastinum They superior and inferior mediastinum are separated by an imaginary horizontal drawn from the manubriosterno junction to the middle of T4 and T5.
Define what borders the heart and what levels it sits on
The heart sits in the pericardial sac which adheres to the central tendon The heart sits in the middle mediastinum behind the body of the sternum and spans vertically from T5 to T8.
What are the layers of the pericardium?
An outer fibrous layer that is very substantial Inner serous envelope: visceral layer lining the outer surface of the heart and a parietal layer connecting to the inner fibrous pericardium The visceral and parietal layers are continuous with one another (have potential space between them for friction fee movement)
What aspects of the heart as seen anteriorly and what posteriorly?
Anteriorly: Right atrium makes up the majority of the view with some right ventricle lining the bottom of the heart and a small portion of the left ventricle forming the left border (forming the apex) Posteriorly: Majority is the left ventricle and the left atrium
What forms the right and left borders of the heart (viewed anteriorly)?
Right atrium on the right and left ventricle on the left
What forms the apex and where does it lie?
The apex is formed by the left ventricle and the apex is at about the level of the 5th intercostal space down the mid-clavicular line on the left side of the body
Describe the inner surface of the right atrium
It is grooved by muscular ridges called musculi pectinati except for the posterior wall which is smooth (called the sinus venarum)
What delineates the chambers of the heart? And what structures run through them?
Sucli (grooves) and coronary vessels run through them: Interventricular: anterior and posterior Atrioventricular: coronary sulcus
What is the crista terminalis?
The definitive line at which the musculi pectinati becomes the sinus venarum
What are the two main veins draining into the right atrium?
IVC draining all blood from below the diaphragm and SVC draining all the blood from above the diaphragm
What is the significance of the oval imprint on the posterior wall of the RA?
The fossa ovalis is a remnant of the foramen ovalis which was a shunt in utero that bypassed the pulmonary circuit
Where do the IVC and SVC enter the right atrium and what do they drain?
IVC enters inferiorly and directly into the right atrium at the level of T8 The SVC enters behind the 3rd rib
Describe the inner surface of the right ventricle
The walls of the ventricles are much thicker than that of the atria (have to pump) All surfaces (except small area) of the ventricle are lined by large muscular ridges called TRABECULAE CARNAE
What are the three atypical ridges known as and what do they connect to?
They are the papillary muscles that extend from the wall into the centre giving off chordae tendinae which attach to the cusps/leaflets of the atrioventricular valves.
What is the outflow valve of the right ventricle and where does it lead to?
Right ventricle pumps blood out through the pulmonary valve which leads to the pulmonary trunk which branches into the pulmonary arteries into the lungs for oxygenation
What is the major difference between the left and right ventricles?
The left ventricle is much thicker than the right The left ventricle contains a mitral valve (bicuspid)
Describe the inner surface of the left atrium. What are the structures coming off the left atrium?
The inner surface of the left atrium is smooth, thin walled. It only has the four inserting pulmonary veins going into it.
What is the outflow valve of the left ventricle? What about it affects the papillary muscles of the left ventricle?
Blood is pumped through the aortic valve. The papillary muscles of the left ventricle do not connect to the aortic valve
What are the supportive ring structures around the valves made up of? What is the major function of the structures forming the valves? (2)
Fibrous skeleton They serve to: 1. Electrically separate the chambers of the heart 2. Provide mechanical support to the valves
What are the rings called? What are they all joined together by?
Two RINGS around the AV valves Two CORONETS around the pulmonary/aortic valves They are all joined together by 2 TRIGONES
What is the difference between the atrial and ventricular surfaces of the atrioventricular valves?
The cusps are smooth on the atrial surface and roughened on the ventricular surface by the chordae tendinae
What is special about the chordae tendinae off papillary muscles?
Adjacent chordae tendinae of one papillary muscle will attach to the different cusps such that contraction of the one papillary muscle pulls on all the cusps tightly closing the valve
Do the valves and the associated muscles open and close actively or passively?
The closure of the valves is done passively: pressure driven The only active part of the process is during systole when the heart is in contraction (this contraction extends to the papillary muscles) whose contraction ensures the AV valves are shut)
What are the Semilunar Valves?
The aortic and pulmonary valves: three leaflet valves each cusp looks like a half moon shape
What is the place where the apices of the valves meet called?
They meet at the middle of the valve: nodules
Describe the conduction pathway. Where does the SA node lie?
The conduction pathway starts at the Sinoatrial (SA) node which sits in the right atrium at the top of the cristae terminalis. From there fibres span down the atrial wall to the AV node (in the right AV septa) Then the fibres span down the coronary sinus and bridges across the fibrous skeleton of the IV septa (Bundle of His) and splits into right or left sides of the IV septum (left and right bundle branches) where they move back up the outside walls of the heart (Pukinje Fibres)
What nervous structure is at the base of the heart and what are its divisions?
The Cardiac plexus at the base of the heart (around the great vessels) Divided into superficial and deep
What branches supply this nervous structure? The Cardiac plexus (2)
The vagus nerve and the sympathetic trunks
Draw and describe the arterial supply of the heart
Draw and describe the venous drainage of the heart