Anatomy of the Heart

Study Notes

The heart is a triangular-shaped organ, broad at the superior surface and tapering to the apex.
It is made up of four chambers: two upper chambers (left atrium and right atrium) and two lower chambers (left and right ventricles).
The heart has four valves: the tricuspid, pulmonary, mitral, and aortic valves.

The heart wall is divided into three layers: epicardium, myocardium, and endocardium.
These layers are embryologically equivalent to the three layers of blood vessels: tunica adventitia, tunica media, and tunica intima.

Coronary arteries are the arterial blood vessels of the coronary circulation.
They are named as such because they encircle the heart, like a crown.
The two main coronary arteries are the left coronary artery (LCA) and the right coronary artery (RCA).
The left coronary artery supplies blood to the left heart muscle (left ventricle and left atrium).
The right coronary artery supplies blood to the right side, S.A. node, A.V. node, and bundle of heart between ventricle.

The left coronary artery branches to yield the left anterior descending (LAD) artery, also called the anterior interventricular artery.
The LCA also gives off the left marginal artery (LMA) and the left circumflex artery (Cx).
In 20-25% of individuals, the left circumflex artery contributes to the posterior interventricular artery (PIv).
The right coronary artery branches to form the right marginal artery (RMA) anteriorly.
In 80-85% of individuals, it also branches into the posterior interventricular artery (PIv) posteriorly.

The heart length, width, and thickness are 12 cm, 8.5 cm, and 6 cm, respectively.
The mean weight of the heart is 280-340 g in males and 230-280 g in females.

The heart pumps blood throughout the body by heart muscle contraction.
It controls heart rate and maintains blood pressure by signal electrical production via autogenerating in the right atrium SA node.
The SA node, also known as the sinus node, initiates the electrical impulses to stimulate contraction.
The heart rate depends on the rate at which the sinoatrial node produces action potentials.
At rest, the heart rate is between 60 and 100 beats per minute.

There are five types of blood vessels: arteries, arterioles, capillaries, venules, and veins.
Arteries carry blood away from the heart.
Capillaries are where the exchange of water and chemicals between the blood and tissues occurs.
Veins carry blood from the capillaries back towards the heart.

The circulatory system is divided into two separate loops: the pulmonary circuit and the systemic circuit.
The pulmonary circuit exchanges blood between the heart and the lungs for oxygenation.
The systemic circuit distributes blood throughout all other systems and tissues of the body.
Both circuits begin and end in the heart.