Nov 4 - Anatomy of the Heart and Great Vessels Flashcards
What is the heart?
Muscular, 4-chamber pump that propels blood throughout the systemic and pulmonary circulation
Where is the heart?
It is found within a pericardial sac in the middle mediastinum
What controls the heart?
It has it’s own pacemaker. Autonomic innervations (sympathetic and parasympathetic) modulate the heart’s actions
Describe how the heart is connected to the lungs?
In the hilum of each lung, one pulmonary artery enters the lung and two pulmonary veins leave the lung and enter the heart
Describe the position of the heart?
The apex of the heart, formed by the left ventricle, is shifted anteriorly left. All the valves, found at the base of the heart, are shifted obliquely (making it hard to listen)
Where is the base of the heart found?
Behind the sternum
Why does the heart move up and down?
The pericardium, or pericardial sac, is attached to the central tendon of the diaphragm
Name the layers of the pericardium from superficial to deep
The fibrous pericardium, the parietal layer of the serous pericardium, the pericardial cavity, the epicardium (visceral layer of the serous pericardium), the myocardium and the endocardium
Describe the fibrous pericardium
The outer layer of the pericardium. It is very tough and non elastic. It attaches to the diaphragm inferiorly
Describe the serous pericardium
Two layers: the parietal layer is attached to the fibrous pericardium and the visceral layer or epicardium lines the surface of the heart. The pericardial cavity contains fluid
What is the role of the pericardium?
It gives the heart room to move independently and reduces friction
Name the two recesses/sinuses
The oblique sinus, behind the heart and the transverse pericardial sinus
Describe the location of the transverse pericardial sinus
Posterior to the pulmonary trunk and the the ascending aorta. It separates the outgoing and incoming vessels of the heart (surgeon’s landmark)
What structure is posterior to the heart
The esophagus is found posterior to the heart
What attaches the aortic arch and the left pulmonary trunk?
The ligamentum arteriosum
What creates the brachiocephalic vein?
The junction of the right subclavian and the right internal jugular
Describe the positions of the main bronchi in the left and right hilum of the lung in relation to the pulmonary artery
The left main bronchus is inferior to the pulmonary artery and the right main bronchus is posterior to the pulmonary artery
How does the heart sit in the mediastinum
More on its posterior inferior surface against the diaphragm (often referred to as the diaphragmatic surface). The apex is to the left (the heart doesn’t stand on its apex)
Why can’t you see the right ventricle in a chest X-ray
Because it’s not border forming (anteriorly)
What separates the left and right ventricles?
The interventricular septum (IVS)
Which ventricle has a thicker myocardium? Why?
The left ventricle because it’s pumping blood into the systemic circulation (whereas the right ventricle pumps blood into the pulmonary circulation)
How is the myocardium arranged?
In a spiral way starting from the apex and then pushing the whole volume of blood upward
Name the contents of the ventricles
Trabeculae carneae, the papillary muscles, chordae tendinae, atrioventricular valves (AV valves), semilunar valves
What is trabeculae carneae?
It’s the rugged surface of the ventricles
What are papillary muscles? How many are in each ventricle?
They join with the chordae tendineae to anchor the tips/leaflets of the mitral and tricuspid valves (AV valves) to the ventricular wall. There are two in the left ventricle and three in the right
How do papillary muscles function?
During atrial contraction of the heart, they are relaxed and the valve is open. During ventricular contraction, the papillary muscles pull the valves closed (active closure to ensure the blood doesn’t escape into the atrium
What is found in the right ventricle that is not found in the left? What does it do?
The septomarginal trabecula aka moderator band. It carries part of the right AV bundle
Describe the flow of blood out from and in to systemic circulation
Deoxygenated blood flows into the inferior and superior vena cava, then into the right atrium. The blood flows through the right atrioventricular valve into the right ventricle, which pumps it through the right semilunar valve into the pulmonary trunk. The blood flows through the pulmonary circulation to become oxygenated. Oxygenated blood flows back through the pulmonary veins into the left atrium. The blood flow through the left AV valve into the left ventricle. The left ventricle pumps the blood through the left semilunar valve into the ascending aorta and into the systemic circulation
Name the four great vessels
The aorta (ascending, arch and descending)
The pulmonary trunk (left and right)
The pulmonary veins (2 left and 2 right)
The superior and inferior vena cava
Describe the atria
The atria are the receiving chambers of the heart. Each atrium has a protruding auricle. Pectinate muscles are present in the auricles and the rest of the atrial wall is smooth similar to veins
Describe the ventricles
The ventricles are the discharging chambers of the heart. Papillary muscles and trabeculae carneae muscles mark the walls of the ventricular walls
What separates the ventricular volume from the atrial volume?
The atrioventricular valves (mitral (left) and tricuspid (right) valves)
What separates the ventricular volume from the great vessels of the outflow tract?
The semilunar valves (the aortic and pulmonary valves)
What is ventricular diastole?
Relaxation of the heart. It’s when the heart refills with blood
What is ventricular systole?
Contraction of the heart forcing the blood out
Describe how the mitral valve opens and closes
It opens passively during diastole and closes actively by the contraction of papillary muscles
Describe how the aortic valve opens and closes
It opens passively during systole and closes passively during diastole
What is the role of the holes in the aortic valve?
They are the openings of the coronary blood vessels (coronary arteries)
What is the role of coronary arteries?
They supply the heart muscle with blood so that the heart can get the nutrients during diastole, when the myocardium is relaxed
What valves are involved in the high pressure system?
The aortic and the mitral valves
What valves are involved in the low pressure system?
The pulmonary and the tricuspid valves
What does auscultation mean?
Listening to the internal sounds of the body, using stethoscope
Where do you place the stethoscope to listen to the aortic valve?
The right second intercostal space
Where do you place the stethoscope to listen to the pulmonary valve?
The left second intercostal space
Where do you place the stethoscope to listen to the mitral valve?
The left fifth intercostal space
Where do you place the stethoscope to listen to the tricuspid valve?
The right fifth intercostal space
Name all the arteries that supply the heart with blood (5)
The right and left coronary arteries (RCA and LCA)
The marginal artery (MA)
The circumflex artery (CA)
The anterior interventricular artery (AIA) aka left anterior descending artery (LAD)
The posterior interventricular artery (PIA)
Name all the veins that supply the heart with blood (3)
The small cardiac vein (SCV) The anterior cardiac vein (ACV) The great cardiac vein (GCV) The posterior cardiac vein (PCV) The coronary sinus (CS) The middle cardiac vein (MCV)
During what action is the heart perfused? Systole or diastole?
Diastole
Describe the flow of venous blood in the coronary veins
All the coronary veins fuse with the coronary sinus, which empties into the right atrium
What does the LCA typically supply?
The left atrium, most of the left ventricle, part of the right ventricle, the anterior 2/3 of IVS, AV bundle, and SA node (in 40% of cases)
What does the RCA typically supply?
The right atrium, most of the right ventricle, diaphragmatic surface of the left ventricle, posterior 1/3 of the IVS, AV bundle, SA node (60% of cases), AV node (80% of cases)
Describe the pacemakers of the heart
They are under the endocardium. Very small specialized cardiac muscle cells/cardiomyocytes.
What is the SA node?
The sinoatrial node. Found in the right atrium. It is the node that usually initiates the electrical impulses that trigger cardiac contraction. It naturally discharges at about 60 beats/min
What is the AV node
The atrioventricular node. Found between the atrium and the ventricle of the heart. Electrical impulse form the SA node activates the AV node. The AV node delays the impulse about 0.12 of a second to ensure the atria have emptied their load before the ventricle contract. The AV node discharges at about 40 beats/min
What happens if the SA node fails?
The AV node picks up the work
What is the His bundle?
Same thing as the AV bundle. They conduct electrical impulses from the AV node. They discharge at about 20 beats/min
What are purkinje fibres?
Specialized cardiomyocytes. They are found in the inner ventricular walls of the heart, just beneath the endocardium. They conduct cardiac action potentials to contract synchronously the walls of the ventricles. They are important for maintaining heart rhythm
Describe the autonomic regulation of the heart
Parasympathetics from the brain stem travel with the vagus nerve to enter the cardiac plexus. Sympathetics from T2-T4 synapse in the cervical sympathetic ganglia and reach the heart via the cardiac plexus
How does sympathetic regulation affect the heart?
Sympathetic stimulation acts on the SA and AV nodes, and on the ventricular myocardium. It increases the heart rate (chronotropic), electrical conduction (dromotropic), excitability (bathmotropic) and contractility of the ventricular myocardium (inotropic)
How does parasympathetic regulation affect the heart?
Parasympathetic stimulation acts on the SA and AV nodes (not on the ventricles). It decreases electrical condcution (dromotropic), heart rate (chronotropic) and excitability (bathmotropic)
How are sympathetics stimulated?
Via neuronal control and via hormonal control through epinephrin and norepinephrin (beta-1-receptors)
