The Structure of Heart

The human heart is a muscular organ that is roughly the size of a closed fist and is located in the chest, slightly left of centre.
It consists of four chambers – two atria (upper chambers) and two ventricles (lower chambers).
The right side of the heart has the right atrium and right ventricle, responsible for receiving deoxygenated blood from the body and pumping it to the lungs.
The left side, consisting of the left atrium and left ventricle, receives oxygenated blood from the lungs and pumps it to the rest of the body.
The walls of the heart are primarily made up of a type of muscle known as myocardium, which is responsible for the heart’s rhythmic contractions.
The septum, a wall of muscle, separates the left and right sides of the heart to prevent oxygen-rich and oxygen-poor blood from mixing.
The atria and ventricles are separated by valves: the tricuspid valve lies between the right atrium and the right ventricle; the pulmonary valve connects the right ventricle and the pulmonary artery; the mitral valve is present between the left atrium and left ventricle; and the aortic valve is found between the left ventricle and the aorta.
These valves ensure that blood flows in only one direction.
The heart’s electrical system, consisting of the sinoatrial node (SA node) and the atrioventricular node (AV node), regulates the heart beat. The SA node initiates the electrical signals and is therefore often referred to as the heart’s natural pacemaker.
Coronary arteries provide the heart muscle with oxygen and nutrient-rich blood. They branch off from the aorta and spread across the surface of the heart.
The rhythmic pumping activity of the heart includes a cycle of relaxation and contraction, known as diastole and systole respectively.
Blood supply to the heart muscle can decrease or stop due to a blockage in the coronary arteries which could potentially lead to a heart attack.
The structure and workings of the heart demonstrate principles of evolved biological systems, including specialisation for particular functions and coordination of responses.