Heart Anatomy, Physiology and Functions: An Overview

Photo by OpenStax College, CC BY 3.0, via Wikimedia Commons

Heart anatomy! The human heart is divided into four chambers, two on the left side and two on the right side. The upper two chambers are the atria and the lower two are the ventricles: the right atrium, right ventricle, left atrium and left ventricle.

Blood returning from the body enters the right atrium, which passes it to the right ventricle. The right ventricle pumps this oxygen-poor blood to the lungs. Oxygen-rich blood then returns to the left atrium and moves into the left ventricle, which pumps it out to the body.

Your heart sits between the lungs, behind the breastbone (sternum), slightly to the left of center in the chest. A double-layered sac called the pericardium surrounds and protects it. The heart is about the size of your fist and is protected by the rib cage.

Right Side of Heart Anatomy

The right side of the heart receives oxygen-poor blood from the body through the superior and inferior vena cava into the right atrium. Blood then flows into the right ventricle, which pumps it to the lungs.

The tricuspid valve controls flow from the right atrium to the right ventricle. It has three flaps (cusps) that prevent backflow. The pulmonary valve, a semilunar valve, sits between the right ventricle and the pulmonary artery.

Left Side Heart Anatomy

Same as the right side of the heart, the left side of the heart has left atrium and left ventricle. Oxygenated blood from the lungs is poured into the left atrium by pulmonary veins. The left atrium contracts and moves this oxygen-rich blood into the left ventricle through the mitral valve. The mitral valve has two cusps and prevents backflow. When the left ventricle contracts, blood is pumped through the aortic valve into the aorta and on to the whole body.

Superior Vena Cava / Inferior Vena Cava

The deoxygenated blood from the whole body is poured into the right atrium by two large veins. The superior vena cava collects blood from the head, neck, arms and upper chest, while the inferior vena cava collects blood from the legs, pelvis and abdomen.

Pulmonary Arteries & Pulmonary Veins

Pulmonary arteries carry oxygen-poor blood from the right ventricle to the lungs. Pulmonary veins carry oxygen-rich blood from the lungs to the left atrium. Elsewhere in the body, arteries carry oxygen-rich blood and veins carry oxygen-poor blood; the pulmonary vessels are the exception.

Aorta

The aorta is the body's largest artery. It carries oxygen-rich blood from the left ventricle to the rest of the body. Its main sections and branches include:

Aortic arch branches

Three large arteries leave the arch: the brachiocephalic trunk, the left common carotid artery and the left subclavian artery. Together they supply the head, neck and arms.

Descending thoracic aorta

It runs down through the chest and supplies the chest wall and organs.

Abdominal aorta

It supplies the abdominal organs and then divides to supply the pelvis and legs.

Coronary Artery

The heart is a muscle that pumps blood around the whole body. Like other muscles, it needs its own oxygen supply. The right and left coronary arteries branch off the aorta just above the aortic valve and carry oxygen-rich blood to the heart muscle.

If the coronary arteries narrow from fatty plaque or are blocked by a clot, blood flow to the heart muscle drops. This lack of oxygen causes ischemic Heart Diseases, including angina and heart attack.

Heart Physiology

The heart is a vital organ that pumps blood to nourish every cell in the body. Through the blood it pumps, the heart helps:

Deliver oxygen to all the body's cells.
Keep the brain supplied with blood, which it needs constantly.
Maintain blood pressure so blood reaches every organ.
Deliver nutrients from your food to the body.
Carry carbon dioxide and other wastes away from cells to the lungs, kidneys and liver.
Transport hormones, immune cells and proteins to where they are needed.

Heart Conduction System

The heart wall has three layers: the endocardium (inner lining), the myocardium (muscle) and the epicardium (outer layer). Each heartbeat is a muscle contraction controlled by electrical signals.

These signals start in the sinoatrial (SA) node in the upper right atrium, known as the heart's natural pacemaker.

The signal travels through the atria, which contract and push blood into the ventricles. It then reaches the atrioventricular (AV) node, which briefly slows it so the ventricles can fill.

From there, the signal travels down the bundle of His and Purkinje fibers in the ventricle walls, making the ventricles contract. Problems anywhere in this system can cause an irregular rhythm of the heart, called an arrhythmia.

HP Thoughts: Some people think their hearts are made of steel and could withstand diseases or drugs without realizing that they are making their hearts sick, instead. Take the case of a popular personality who believed that taking a particular drug might avert contracting a deadly virus: Donald Trump.