Science, Tech, Math › Science The Anatomy of the Heart, Its Structures, and Functions Share Flipboard Email Print StockSnap / Pixabay Science Biology Anatomy Basics Cell Biology Genetics Organisms Physiology Botany Ecology Chemistry Physics Geology Astronomy Weather & Climate By Regina Bailey Biology Expert B.A., Biology, Emory University A.S., Nursing, Chattahoochee Technical College Regina Bailey is a board-certified registered nurse, science writer and educator. Her work has been featured in "Kaplan AP Biology" and "The Internet for Cellular and Molecular Biologists." our editorial process Regina Bailey Updated April 05, 2020 The heart is the organ that helps supply blood and oxygen to all parts of the body. It is divided by a partition (or septum) into two halves. The halves are, in turn, divided into four chambers. The heart is situated within the chest cavity and surrounded by a fluid-filled sac called the pericardium. This amazing muscle produces electrical impulses that cause the heart to contract, pumping blood throughout the body. The heart and the circulatory system together form the cardiovascular system. Heart Anatomy The heart is made up of four chambers: Atria: Upper two chambers of the heart.Ventricles: Lower two chambers of the heart. Heart Wall The heart wall consists of three layers: Epicardium: The outer layer of the wall of the heart.Myocardium: The muscular middle layer of the wall of the heart.Endocardium: The inner layer of the heart. Cardiac Conduction Cardiac conduction is the rate at which the heart conducts electrical impulses. Heart nodes and nerve fibers play an important role in causing the heart to contract. Atrioventricular Bundle: A bundle of fibers that carry cardiac impulses.Atrioventricular Node: A section of nodal tissue that delays and relays cardiac impulses.Purkinje Fibers: Fiber branches that extend from the atrioventricular bundle.Sinoatrial Node: A section of nodal tissue that sets the rate of contraction for the heart. Cardiac Cycle The Cardiac cycle is the sequence of events that occurs when the heart beats. Below are the two phases of the cardiac cycle: Diastole phase: The heart ventricles are relaxed and the heart fills with blood.Systole phase: The ventricles contract and pump blood to the arteries. Valves Heart valves are flap-like structures that allow blood to flow in one direction. Below are the four valves of the heart: Aortic valve: Prevents the backflow of blood as it is pumped from the left ventricle to the aorta.Mitral valve: Prevents the backflow of blood as it is pumped from the left atrium to the left ventricle.Pulmonary valve: Prevents the backflow of blood as it is pumped from the right ventricle to the pulmonary artery.Tricuspid valve: Prevents the backflow of blood as it is pumped from the right atrium to the right ventricle. Blood Vessels Blood vessels are intricate networks of hollow tubes that transport blood throughout the entire body. The following are some of the blood vessels associated with the heart: Arteries Aorta: The largest artery in the body, of which most major arteries branch off from.Brachiocephalic artery: Carries oxygenated blood from the aorta to the head, neck, and arm regions of the body.Carotid arteries: Supply oxygenated blood to the head and neck regions of the body.Common iliac arteries: Carry oxygenated blood from the abdominal aorta to the legs and feet.Coronary arteries: Carry oxygenated and nutrient-filled blood to the heart muscle.Pulmonary artery: Carries deoxygenated blood from the right ventricle to the lungs.Subclavian arteries: Supply oxygenated blood to the arms. Veins Brachiocephalic veins: Two large veins that join to form the superior vena cava.Common iliac veins: Veins that join to form the inferior vena cava.Pulmonary veins: Transport oxygenated blood from the lungs to the heart.Venae cavae: Transport de-oxygenated blood from various regions of the body to the heart.