The Heart: Superficial and Internal

What are the internal structures of the right atrium and their functions?

*Crista Terminalis*- A ridge/boundary where the pectinate muscles attach to the smooth muscle portion of the atrium. *Sulcus Terminalis Cordis* *Fossa Ovalis*- Remnant of the forament ovale during heart development. *Limbus Fossa Ovalis*- The lip of the fossa ovalis formed from the septum secundum fusing. *Interatrial Septum* *Pectinate Muscles*- Helps push the 20% of blood in the atrium that is not pushed by the pressure differential *Triscuspid Valve*

What are the three layers of the heart and their functions?

*Epicardium*- (visceral pericardium)- outermost layer, has adipose, vasculature, nerve fibers, and lined with mesothelium. *Myocardium*- the middle layer, has cardiac muscles, cardiac conductive fibers (perkinje), and blood vessels *Endocardium*- the internal layer, has inner epithelium like an endothelium and a subtending CT layer.

What are the two layers of the pericardium?

*Fibrous pericardium*: outer layer, next to the pleural cavity. *Serous pericardium*: Has two layers: *Parietal Layer*: lines the surface of the fibrous pericardium. *Visceral Layer*: directly adheres to the heart. Note: The serous pericardium has reflections (like a plastic bag folding over an object) that make it continuous and allows for the fluid filled pericardial cavity for ease of movement of the heart.

What are some key features to orient the heart?

*If you are facing the anterior portion of the heart*: Can see the aortic arch and the apex points down and to the left (anatomically). Can see both coronary and interventricular sulci. *If you are facing the posterior*: Can see the pulmonary veins and the apex is down and to the right (anatomically). Can only see coronary sulci (divides ventricles and atria). *Inferior view*:the opening to the IFC can be seen and both coronary and interventricular sulci can be seen.

What are the Right and Left coronary arteries and their main branches?

*Right*: SA node and Conus branch as well as right marginal artery, and posterior interventricular artery. *Left*: Circumflex artery, left marginal artery, lateral diagonal branch, anterior interventricular (or left anterior descending artery (LAD)). Note: there can be significant variation in coronary artery vasculature.

What is the opening and closing of valves in systole and diastole?

*Systole (Ventricular Contraction)*- The AV valves close due to relatively high ventricular pressure. The semilunar valves open due to this same higher pressure. *Diastole (Ventricular Relaxation)*- AV valves open passively as atrial pressure exceeds ventricular pressure. Semiluar valves remain closed due to increased arterial pressure forcing their cusps down.

What is the most common heart defect? and what is the most life threatening?

Atrial septal defect is the most common. Occurs when the foramen ovale doesn't close completely Transposition of the great arteries is the most life threatening and must be surgically fixed at time of birth.

Picture of heart location and surface for sounds

Best place to listen isn't at the valve because the sternum blocks sound waves. Best locations are shown in the following diagram.

What are the posterior coronary arteries?

Circumflex artery, right coronary artery, posterior interventricular artery, left ventricular branch, right posterolateral branch, and posterior artery of the left ventricle.

What is the Cardiac Skeleton and what is it's function?

Connective tissue that is dense and forms four rings in a plane that separates atria and ventricles. It maintains integrity of openings and shape of the heart (cardiac muscles) It is also an electric isolation of atria and ventricles. The trigone lies between three valve rings and is where the AV node is located.

What does CABG stand for?

Coronary Artery Bypass Graft

What is the mesocardium?

It is a membrane that connects the heart to the posterior body wall. *Dorsal Mesocardium*- connects all veins *Visceral Mesocardium*-connects the two major arteries leaving the heart (aorta and pulmonary)

Where does the Pacemaker Attach?

Near Apex of the heart and perkinje fibers.

Labeled Heart

Note the pulmonary trunk into the pulmonary arteries.

What are the major structures in the right ventricle and what are their functions?

Note: Chordae tendinae are only in the AV valves. Papillary Muscles- Tighten Chordae tendinae Trabeculae carneae- ventricular contraction septomarginal trabecula conus arteriosus pulmonary valve Chordae tendinae- tether the valve to the ventricle so that it doesn't blow away or move all over.

What are the posterior veins of the heart?

Oblique vein of left atrium, Great cardiac vein, coronary sinus, posterior vein of left ventricle, middle cardiac vein, and small cardiac vein. *(they run along side their arterial counterparts)*

What is referred pain and what is its significance in heart attacks?

Pain fibers run with the autonomic nerves and the CNS has a difficult time telling where the signal is coming from exactly. (related to proprioreception)

Trace a drop of blood through the entire circulatory system starting in the right atrium.

Right Atrium, Right Ventricle, Pulmonary Valve, Pulmonary Trunk, Lung, Pulmonary veins, right atrium, mitral valve, right ventricle, aortic valve, ascending aorta, aortic arch, descending aorta, body, systemic venous return into the right atrium.

What are the variations of coronary artery vasculature and their relative occurrence?

Right sided coronary supplies more (70% of people) Left supplies more (15% of people) Right sided+ (15% of people)

What enters the Right atrium?

SVC and IVC lead into the right atrium. Coronary sinus comes into the right atrium. This is where the blood supplying the heart drains into the heart. Ostia?

What are the nodes of the heart and their relative location?

Sino-atrial (SA)- impulse starts here, it is the cardiac pacemaker, at end of crista terminalis at the junction of the SVC and right atrium. Atrioventricular Node (AV)- After atrium is excited by SA it stimulates the AV node, near the coronary sinus. it is the beginning of the conducting tissue system known as the AV bundle. AV bundle- Continuation of the AV node and carry signal into their respective ventricles. Subendocardial Plexus of conduction cells (perkinje fibers)- the terminal branches of bundles.

What are the anterior veins of the heart?

Small cardiac vein, Anterior Cardiac veins, Greater cardiac vein. *(they run along side their arterial counterparts)*

What are the limits of the heart?

Superior limit: pericardium (2nd intercostal space) and up to 3rd, makes a space that includes SVC, ascending Aorta, and pulmonary trunks. Right limit: next to sternum Inferior limit: at the level of the xiphisternal junction

What are the pericardial sinuses and where are they located?

They are created via the reflection of the serous pericardium: *Oblique pericardial sinus*- Found between the pulmonary veins and created only by the dorsal mesocardium. *Transverse pericardial sinus*-Posterior to the ascending aorta and pulmonary trunk. It is created between the two mesocardia. Note: Transverse pericardial sinus is a land mark to pinch off blood flow for surgery. The Oblique pericardial sinus has very little fluid flow so bacteria can accumulate in that space.

What are the major structures in the left ventricle?

Thick myocardium- needs to push the blood throughout the body. Papillary muscles- attach to chordae tendinae Chordae tendinae- keep valve in position Mitral Valve Aortic Valve

What are the types of aortic aneurysms?

Type A or proximal- Includes Type I and Type II, the dissection is closer to the heart and likely in the aortic arch. Type B or distal- Includes Type III- occurs in the descending aorta.

What is the nerve supply to the superficial heart?

Vagus nerve and Phrenic nerve

What are the major structures in the left atrium?

Valve of Fossa Ovale Interatrial septum Mitral valve