Heart Flashcards
Describe the three layers of the heart.
Epicardium - thin outer layer of connective tissue
Myocardium - thick middle layer of cardiac muscle tissue
Endocardium - thin inner layer of endothelial tissue
What are the four heart chambers?
Left and right atrium - “superior” chambers that receive blood
Left and right ventricle - “inferior” chambers that eject blood
What are the four valves that help separate the heart chambers?
2 atrioventricular valves - separate the atria from the ventricles
(Flaps open inferiorly and allow blood to enter the ventricles)
2 semilunar valves - separate the ventricles from the arteries that emerge from the heart
(Flaps open superiorly and allow blood to exit the ventricles)
What are the external surface of the heart - 2 sulci (groves) that hold the coronary blood vessels + mark the external boundary between chambers?
Coronary sulcus - encircles the heart and roughly marks the external boundary between the atria and ventricles
Interventricular sulci - grooves on the anterior/posterior surface that roughly mark the external boundary between the ventricles
What is systemic circulation?
System of blood vessels that carry oxygenated blood from the heart to the majority of the body and return deoxygenated blood to the heart - therefore, the blood loses oxygen in this circuit
What is pulmonary circulation?
System of blood vessels that carry deoxygenated blood from the heart to the lungs and returns oxygenated blood to the heart - therefore, the blood gains oxygen in this circuit
What path does blood take to enter systemic circulation?
- The right atrium receives blood from the superior vena cava and inferior vena cava
- Blood passes through the tricuspid valve and into the right ventricle
- Blood passes through the pulmonary valve into the pulmonary trunk
- Blood passes through pulmonary arteries and enters the pulmonary circulation (Deoxygenated blood to lungs)
- Left atrium receives blood from pulmonary veins
- Blood passes through the bicuspid valve into left ventricle
- Blood passes through the aortic valve into the aorta
8.Blood enters the systemic circulation (Oxygenated blood to the body)
What is the name of the only artery that carries deoxygenated blood?
The pulmonary arteries
What is the name of the only vein that carries oxygenated blood?
The pulmonary veins
Describe the cardiac conduction system (5 steps).
- Cells in the sinoatrial (SA) node located in the wall of right atrium spontaneously depolarize, loading to the generation of an action potential
- The action potential spreads through the right and left atria via gap junctions, causing contraction of the atria
- The action potential reaches cells in the atrioventricular (AV) node are located in the interatrial system
- The action potential travels down the AV bundles (“bundle of his”) and conducting fibers in the inter-ventricular septum to the apex of the heart
- The action potential spreads through the left + right ventricles via purkinje fibers in the ventricular walls, causing contraction of the ventricles
What is the “pacemaker” of the heart?
The SA node
What is the job of the AV node?
If there is a problem with the SA node, the cells in the AV node will “kick-in” and act as a pacemaker for the heart
Describe the cardiac cycle.
- The SA node generates an action potential that spreads through the atria, causing them to contract. This contraction increases the pressure within the atria, which pushes blood through the AV valves into the ventricles. As this happens, the action potential is making its way through the conduction system to the ventricles.
- The action potentials spread through the ventricles via the purkinje fibers, causing them to contract. This contraction increases the pressure within the ventricles. When the pressure in the ventricles is greater than the pressure in the atria, the AV valves are pushed closed = “LUB” - first heart sound
- When the pressure in the ventricles is greater than the pressure in the atria + pulmonary trunk, the semilunar valves are pushed open and blood exits the heart
- As the atria and ventricles are relaxing the pressure within them drops. When the pressure in the atria becomes less than the pressure in the veins that drain into them, blood enters the atria. When pressure in the ventricles becomes less than the pressure in the aorta and pulmonary trunk, the semilunar valves are pushed close = “DUB” - second heart sound
- The pressure in the atria increases as blood enters from the veins. When the pressure in the atria is greater than the pressure in the ventricles, the AV valves are pushed open + blood enters the ventricles.
- The SA node generates an action potential… (see #1)
