Heart Anatomy and Physiology: Structure and Function

Heart: Function

The heart is responsible for carrying oxygen in the blood and nutrients to all body cells for proper functioning. It is also in charge of collecting and transporting waste material for disposal.

Heart: Structure

The heart is a hollow organ the size of a fist, located in the center of the left chest between the lungs. It consists of a heart wall and four cavities.

Heart Wall

The heart wall has three parts:

• The endocardium is the innermost layer and is in contact with blood.
• The myocardium is the middle layer, composed of cardiac muscle tissue, and it is thick.
• The pericardium is the outer layer containing liquid, and it also absorbs the friction of the heart.

Cardiac Cavities

The heart is divided into two halves, which in turn are divided into two parts: upper atria and lower ventricles. The atria and ventricles are interconnected by valves that allow blood flow in one direction by preventing its decline.

Major Blood Vessels

Two arteries come from the heart: the aorta and pulmonary artery. The vena cava and pulmonary veins reach the heart.

Aorta

The aorta arises from the left ventricle and leads blood to all tissues except the lungs. It consists of several segments:

• Ascending aorta: a short segment located at the edge of the heart.
• Aortic arch: a curved section of the aorta.
• Descending aorta: a long stretch that starts from the arch and goes down into the abdominal cavity through the diaphragm.

Coronary Arteries

Two coronary arteries emerge from the ascending aorta and supply blood to the myocardium.

Carotid Arteries

The carotid arteries are born in the aortic arch and ascend to the neck and head. They branch into two:

• Facial artery: carries blood to the face.
• Temporal artery: passes through the pinna to the head.

Subclavian Arteries

The subclavian arteries are born in the arch and go to the upper extremities. They include:

• Brachial artery: located on the side of the arm, which in turn is divided into the ulnar and radial arteries.
• Ulnar artery: located on the anterior and medial side of the forearm and wrist.
• Radial artery: located on the front and lateral side of the forearm and wrist.

Mesenteric Arteries

The mesenteric arteries are born in the descending aorta and supply the abdominal cavity.

Renal Artery

The renal artery is born in the descending aorta and supplies blood to the kidneys.

Iliac Artery

The descending aorta is divided at the end of the section into:

• Femoral artery: located in the groin and thigh.
• Popliteal artery: located in the back of the knee.
• Posterior tibial artery: a branch of the popliteal artery that runs through the leg and internal malleolus.
• Pedal artery: located in the medial part of the tarsus.

Pulmonary Artery

The pulmonary artery arises in the right ventricle of the heart and carries blood to the lungs for gas exchange. The blood that flows through it is venous and branches into two: the right and left lung.

Vena Cava

The vena cava carries blood from all body tissues to the heart, except the lungs, and empties into the right atrium. It is formed by:

• Superior vena cava: carries blood from the head, neck, and upper limbs. It is formed by two veins: the jugular (from the head and neck) and the subclavian (from the upper limbs).
• Inferior vena cava: formed in the abdominal cavity, it passes through the diaphragm carrying blood to the pelvic cavity, abdomen, chest, and lower extremities.