Heart Anatomy: Complete Guide with Parts, Names, Functions & Diagram

Overview of Human Heart Anatomy

The heart is a vital muscular organ in most animals that powers the circulation of blood through the body. In heart anatomy, blood vessels help form the circulatory system, which delivers oxygen and nutrients to tissues and removes waste like carbon dioxide. This waste is carried to the lungs for expulsion. In human anatomy, the heart is roughly the size of a closed fist and lies between the lungs in the chest’s central area. This area is known as the mediastinum. It has four chambers: two upper atria (right and left) and two lower ventricles (right and left). The right side (right atrium and ventricle) and the left side (left atrium and ventricle) function together to ensure that blood flows in the proper direction.

Heart Function

The heart’s primary job is to pump blood, deliver oxygen and essential nutrients to cells, and carry away waste products for other organs to process. Beyond pumping, the heart also:

• Regulates heart rate and rhythm.
• Maintains blood pressure.

This organ works closely with other systems to support these functions:

• Nervous System: The nervous system controls heart rate by signaling it to slow down during rest or speed up under stress.
• Endocrine System: Hormones released by the endocrine system influence blood pressure by signaling blood vessels to constrict or relax. The thyroid gland, for example, releases hormones that can alter the heart’s speed.

In this article, we will see the detailed anatomy of the heart with its different parts & systems that make every living thing breathe.

Heart Anatomy Diagram

Anatomy of the Heart

External Structure of Heart Anatomy

Apex

The apex of the heart is located at the tip of the left and right ventricles, opposite the base of the heart. It is facing toward the left side of the chest and angled slightly forward.

The apex plays a key role in blood circulation. With each heartbeat, it twists and makes contact with the front of the chest, creating the apex beat. You can feel the apex beat by placing a hand just below the left nipple line.

The apex helps the ventricles efficiently pump blood: The left ventricular apex pushes oxygen-rich blood to the body, while the right ventricular apex channels blood to the lungs for oxygenation.

This movement aids in wringing out the ventricles and helps them push blood upward and out of the heart, ensuring a steady flow through the body and lungs.

Base

The base of the heart is positioned upwards, slightly backward, and to the right, aligning with the fifth to eighth thoracic vertebrae. It sits close to the esophagus, aorta, and thoracic duct.

It is primarily formed by the left atrium, with a small portion contributed by the right atrium, and the base has a quadrilateral shape.

The base lies beneath the point where the pulmonary artery splits and is bordered at the bottom by the coronary sulcus. The coronary sulcus is a groove that houses the coronary sinus.

• On the right, the base is defined by the sulcus terminalis of the right atrium.
• On the left, it is marked by the ligament of the left vena cava and the oblique vein of the left atrium.

The left atrium receives four pulmonary veins, with two on each side, and the right atrium takes in blood from the superior vena cava at the top and the inferior vena cava below.

Coronary Sulcus

The coronary sulcus is a shallow groove on the heart’s surface that separates the upper chambers (atria) from the lower chambers (ventricles).

It is located near the base of the right auricle and contains key blood vessels that supply the heart with oxygen. In the front, this groove is interrupted by the pulmonary trunk, the large vessel carrying blood to the lungs.

On the back side of the heart, the coronary sulcus houses the coronary sinus—a large vein that collects blood returning from the heart’s muscle tissue. This sinus extends from the area near the third left rib to the middle of the right sixth rib.

There are two coronary sulci in the heart anatomy.

• The left portion of the coronary sulcus starts behind the pulmonary trunk and runs down between the left atrium and left ventricle. The circumflex branch of the left coronary artery and the coronary sinus follow this path.
• On the right side, the coronary sulcus is visible from the front. It marks the path of the right coronary artery and the small cardiac vein. This part of the sulcus separates the right atrium from the right ventricle and continues down to wrap around the heart’s underside.

Anterior Interventricular Sulcus

The anterior interventricular sulcus is a groove on the front side of the heart that helps separate the two lower chambers, called ventricles. It works alongside another groove at the back of the heart, known as the posterior interventricular sulcus.

Sometimes, these grooves are called the paraconal and subsinosal interventricular grooves, respectively. The anterior interventricular sulcus runs from the coronary sulcus (a groove encircling the heart) down to the tip of the heart, known as the apex.

When it reaches the underside of the heart, it ends at a small indentation called the cardiac apex notch. This groove holds the anterior interventricular artery (a branch of the left coronary artery) and the great cardiac vein.

Posterior Interventricular Sulcus

The posterior interventricular sulcus is a distinct groove on the back of the heart and marks the boundary between the two lower chambers or ventricles.

It is paired with the anterior interventricular sulcus on the heart’s front and provides a pathway for critical blood vessels. It is the subsinosal interventricular groove and extends from the heart’s base near the right side to the apex.

This sulcus protects the posterior interventricular artery and the middle cardiac vein, which are essential in delivering oxygenated blood to the heart tissue and carrying deoxygenated blood away.

Pericardium

The pericardium is a protective sac made of tough, flexible tissue that surrounds the heart. It has two layers: the outer fibrous pericardium, which is strong and helps keep the heart in place, and the inner serous pericardium, which is smooth and slippery to reduce friction as the heart beats.

This design protects the heart, anchors it in the chest, and allows it to move easily while pumping blood. The pericardium doesn’t cover the heart entirely—it leaves openings where the large blood vessels connect and where it rests on the diaphragm.

1. Fibrous Pericardium

The fibrous pericardium is a tough, non-flexible layer of connective tissue directly connected to the central tendon of the diaphragm. Its rigid nature limits the heart’s ability to overfill quickly, providing structural support.

However, this inflexibility can lead to life-threatening complications, such as cardiac tamponade, when fluid builds up and compresses the heart.

2. Serous Pericardium

It is housed within the fibrous pericardium and the serous pericardium has two distinct layers. The outer parietal layer adheres to the inside of the fibrous pericardium, while the inner visceral layer, also called the epicardium, lies directly on the heart’s surface.

Both layers consist of a single layer of specialized epithelial cells called mesothelium, which help reduce friction during heart movement.

Layers of the Heart Wall

In the heart anatomy, the heart wall has three main layers: the epicardium, myocardium, and endocardium. These layers are similar to the three layers found in blood vessels, which are called the tunica adventitia, tunica media, and tunica intima.

In both structures, each layer serves a comparable purpose: the outer layer protects, the middle layer is muscular and controls movement, and the inner layer provides a smooth lining for blood flow.

Epicardium

The epicardium is the outer protective layer of the heart. It is made up of mesothelial cells, connective tissue, and fat. It covers the heart and the beginnings of major blood vessels like the aorta, superior vena cava, and inferior vena cava.

As part of the pericardium—the heart’s enclosing membrane—the epicardium shields the heart from external harm and friction. Beyond protection, it has several key roles in heart health and development.

During embryonic growth, it sends important signals that guide the formation and maturation of the heart.
Additionally, it secretes factors crucial for the growth and survival of cardiomyocytes, the muscle cells of the heart.

Epicardial cells can also act as progenitor cells, with the potential to develop into various cell types needed by the heart.

Myocardium

The myocardium, located in the middle, is the thickest layer. It sits between the thin, inner endocardium layer and the outer epicardium, part of the pericardium that protects the heart.

The myocardium is made up of special muscle cells called cardiomyocytes, which are designed for the heart’s pumping action. These cells have unique structures called intercalated discs that contain gap junctions.

These junctions allow quick communication between cells, helping the heart muscle contract well-coordinatedly.

The myocardium’s primary job is to help the heart contract and relax, allowing it to pump blood effectively through the body.

Additionally, the myocardium supports the heart’s structure and helps transmit electrical signals needed for a steady heartbeat.

Endocardium

The endocardium is the heart’s innermost tissue layer, lining its chambers and protecting the valves. Structurally, it resembles the endothelial cells that line blood vessels, reflecting shared biological origins.

It is positioned beneath the thicker myocardium—the heart’s muscular layer responsible for pumping. The endocardium is a smooth interface, promoting efficient blood flow through the heart.

The epicardium is the heart’s outermost layer and has a small volume of lubricating fluid within the pericardium, a protective fibrous sac. This layered structure enables the heart’s smooth and powerful contractions.

Heart Chambers Anatomy

Right Atrium

The right atrium receives deoxygenated blood from three main sources:

1. Superior vena cava
2. Inferior vena cava
3. Coronary veins.

This blood is then funneled through the tricuspid valve, which controls the flow into the right ventricle.

The right atrium is located on the right side of the heart and is connected to a small, expandable pouch called the right auricle, or right atrial appendage.

This pouch helps increase the atrium’s blood-holding capacity. Inside the right atrium, there are two main areas separated by a ridge called the crista terminalis. Each area has a specific role and developmental origin:

1. Sinus Venarum: This smooth-walled part, located behind the crista terminalis, receives blood from the superior and inferior vena cavae. It originates from a fetal structure known as the sinus venosus.
2. Atrium Proper: Found in front of the crista terminalis, this area includes the right auricle and has rough, muscular walls due to pectinate muscles.

Each part of the right atrium is specialized to support blood movement through the heart.

Left Atrium

The left atrium is a chamber in the heart that receives oxygenated blood from the lungs through four pulmonary veins.

It pumps this blood into the left ventricle via the left atrioventricular orifice. This orifice is an opening regulated by the mitral valve to ensure one-way blood flow.

It is positioned at the back of the heart in anatomical terms; the left atrium forms the heart’s base. The left auricle is attached to its upper part, which is a small, ear-shaped pouch that partially covers the base of the pulmonary trunk. The main artery carries blood from the heart to the lungs.

The inner surface of the left atrium has two distinct regions with different origins:

• Inflow area: This smooth-surfaced section receives blood from the pulmonary veins, forming directly from them during development.
• Outflow area: Located toward the front and containing the left auricle, this region has muscle ridges known as pectinate muscles, developed from the embryonic atrium.

Each part of the left atrium plays a role in efficiently moving oxygen-rich blood through the heart and into the body’s circulation.

Right Ventricle

The right ventricle receives deoxygenated blood from the right atrium and pumps it into the pulmonary artery via the pulmonary valve. It is triangular in shape & forms most of the heart’s front border.

It has two main sections: the inflow section, where blood enters, and the outflow section, where blood exits to the lungs. These sections are divided by a muscular ridge called the supraventricular crest.

• Inflow Section: The inner surface of the inflow section is lined with muscular ridges called trabeculae carneae, which give it a sponge-like appearance. These trabeculae carneae have three main structures:
  • Ridges – muscles attached along their entire length, forming raised lines along the ventricle walls.
  • Bridges – muscles connected at both ends but free in the middle. Among these is the moderator band, which contains parts of the heart’s right bundle branch, helping to transmit electrical signals efficiently.
  • Papillary Muscles – These muscles anchor to the ventricle walls and connect to thin, fibrous strings called chordae tendineae. The chordae tendineae attach to the flaps of the tricuspid valve. It prevents them from flipping backward during contraction by tightening when the papillary muscles contract.
• Outflow Section (Conus Arteriosus): The outflow section, located at the top of the right ventricle, leads to the pulmonary artery. This part is known as the conus arteriosus and originates from the fetal heart structure called the bulbus cordis. It has smooth walls free of trabeculae carneae, which gives it a distinctly different appearance from the rest of the right ventricle.

Left Ventricle

The left ventricle receives oxygen-rich blood from the left atrium and pumps it through the aortic valve into the aorta. It is positioned at the apex of the heart in anatomical terms. It also contributes to the heart’s left and diaphragmatic borders.

Like the right ventricle, it has two main sections:

• Inflow Portion: The inner walls of the inflow portion are lined with muscular ridges called trabeculae carneae, similar to those in the right ventricle. Attached to the mitral valve, two papillary muscles play a critical role in stabilizing the valve, preventing blood from flowing backward.
• Outflow Portion: The outflow portion, called the aortic vestibule, is a smooth-walled region, free of trabeculae carneae. This part originates from the embryonic bulbus cordis and is specially structured to ensure efficient blood flow into the aorta.

Valves of the Heart Anatomy

The heart is a powerful muscle that pumps blood through the entire body, supplying each organ with oxygen and nutrients. Inside the heart, there are valves act like gates, opening and closing with each heartbeat to control blood flow between its chambers and maintain a steady rhythm.

These valves ensure blood moves in the right direction and at the right moment, preventing any backward flow. As they open and shut, they produce two distinct sounds—the familiar “lub-dub” of a heartbeat.

Atrioventricular (AV) Valves

The atrioventricular valves, positioned between the atria and ventricles, play a crucial role in heart function. At the onset of ventricular contraction (systole), these valves close tightly to prevent blood from flowing backward, creating the distinct first heart sound.

1. Tricuspid Valve

The tricuspid valve is positioned between the right atrium and right ventricle, regulating blood flow through the right atrioventricular opening.

It features three distinct cusps—anterior, septal, and posterior—each securely attached at its base to a fibrous ring encircling the orifice. This structure ensures efficient, one-way blood movement within the heart.

2. Mitral (Bicuspid) Valve

The mitral valve is found between the left atrium and the left ventricle. It helps to control blood flow through the left atrioventricular opening.

Often called the bicuspid valve, it has two flaps or cusps—one at the front (anterior) and one at the back (posterior). Each cusp is anchored to a strong fibrous ring that encircles the opening, ensuring it stays securely in place.

Semilunar Valves

The semilunar valves sit between the heart’s ventricles and the major blood vessels that carry blood out of the heart. They close at the start of the heart’s relaxation phase, known as diastole, and create the second “dub” sound in the heartbeat. There are two of these valves.

1. Pulmonary Valve

The pulmonary valve sits at the junction of the right ventricle and the pulmonary trunk. It comprises three cusps—left, right, and anterior. These are named for their original orientation during fetal heart development before rotation occurs.

2. Aortic Valve

The aortic valve is positioned between the left ventricle and the ascending aorta. It also consists of three cusps: right, left, and posterior.

The left and right aortic sinuses are small pockets in the aortic wall that give rise to the left and right coronary arteries. During diastole, as the heart relaxes, blood briefly flows backward, filling these sinuses.

It ensures blood enters the coronary arteries to supply oxygen and nutrients to the heart muscle, supporting its function.

Blood Vessels Connected to the Heart

The great vessels of the heart are important blood vessels that connect directly to the heart. These include arteries and veins that carry blood between the heart and the lungs, as well as to the rest of the body.

Pulmonary Circuit

The pulmonary circuit connects the heart and lungs, ensuring blood is refreshed with oxygen.

• Main Pulmonary Artery – The main pulmonary artery carries oxygen-poor blood from the right ventricle. This artery splits into two branches, one for each lung. In the lungs, the blood releases carbon dioxide and absorbs oxygen.
• Pulmonary Veins – Once oxygenated, the blood travels back to the heart through the pulmonary veins. Typically, there are four pulmonary veins—two from each lung—which deliver the oxygen-rich blood into the left atrium. This continuous cycle keeps the body supplied with oxygen for its essential functions.

Systemic Circuit

• The ascending aorta, the initial section of your aorta, transports oxygen-rich blood from the left ventricle of your heart. This blood then moves through various aorta branches, supplying oxygen and nutrients to the entire body.
• The superior vena cava is a large vein responsible for carrying oxygen-depleted blood from the upper part of your body to the right atrium of your heart.
• Similarly, the inferior vena cava, another major vein, brings oxygen-depleted blood from the lower parts of your body into the right atrium.

Supporting Structures of Heart Anatomy

The chordae tendineae and papillary muscles are important parts of the heart that help the valves work correctly. They work together to keep the valves in place and ensure blood flows in the right direction.

Chordae Tendineae

The chordae tendineae are thin, string-like structures inside the heart’s ventricles. They connect the small muscles on the inner walls of the heart, called papillary muscles, to the flaps of the heart valves. Some of these strings branch into multiple strands, while others stay as single cords.

In the right ventricle, they attach to the three flaps of the tricuspid valve, and in the left ventricle, they connect to the two flaps of the mitral valve.

Their main job is to hold the valve flaps in place during heartbeats, stopping them from flipping backward into the atria and making sure blood flows in the right direction.

Papillary Muscles

Papillary muscles are small but vital parts inside the heart’s ventricles. They play a key role in helping the heart’s valves work correctly by connecting to them with thin, string-like fibers called chordae tendineae. These muscles ensure that blood flows in the right direction.

In the heart anatomy, there are a total of five papillary muscles.

• In the right ventricle, there are three—named anterior, posterior, and septal papillary muscles—that support the tricuspid valve.
• In the left ventricle, there are two—anterolateral and posteromedial papillary muscles—that assist the mitral valve.

When the heart beats and pumps blood (a phase called ventricular systole), the papillary muscles contract. This action pulls on the chordae tendineae, keeping the valves tightly shut so blood doesn’t leak backward into the atria. This coordinated effort is essential for proper blood circulation and helps prevent issues like valve leakage.

Coronary Circulation – Parts of the Heart

Coronary circulation refers to the flow of blood through a network of arteries and veins that deliver oxygen and nutrients to the heart muscle (myocardium) while removing waste products. This system ensures the heart functions efficiently by meeting its constant energy demands.

Coronary Arteries

• Left Main Coronary Artery (LMCA): This plays a crucial role in heart function by delivering oxygen-rich blood to the left atrium and left ventricle. These chambers receive oxygenated blood from the lungs and pump it throughout the body. Additionally, the LMCA branches supply most of the interventricular septum, supporting the heart’s ability to efficiently circulate blood.
• Right Coronary Artery (RCA): This artery supplies blood to the right atrium and right ventricle, which are essential for pumping deoxygenated blood to the lungs. It also supplies the sinoatrial (SA) and atrioventricular (AV) nodes, which control the heart’s electrical signals and ensure coordinated muscle contractions. Additionally, branches of the RCA nourish about one-third of the interventricular septum, the wall separating the heart’s lower chambers and supporting its structural and functional integrity.

Cardiac Veins

The heart’s veins play an essential role in carrying deoxygenated blood back to the heart chambers.

• Anterior Cardiac Veins: Usually numbering 2 to 5, these veins carry blood from the front of the right ventricle directly into the right atrium.
• Great Cardiac Vein: This vein starts at the heart’s apex (the tip) and moves upward along the front groove between the ventricles. It joins with a small vein from the left atrium to form the coronary sinus, which is located on the back of the heart.
• Middle Cardiac Vein: Beginning at the apex, this vein travels along the lower groove between the ventricles and empties into the coronary sinus near its end.
• Small Cardiac Vein: Also called the right coronary vein, it collects blood from parts of the right atrium and right ventricle.
• Thebesian Veins: These are very small, valve-free veins found in the walls of all four chambers of the heart. They directly drain blood from the heart muscle (myocardium) into the corresponding chamber.

Coronary Sinus

The coronary sinus is the heart’s largest vein, carrying most of the heart muscle’s deoxygenated blood back to the right atrium.

It begins at the back of the heart, where the great cardiac and the oblique vein of the left atrium meet. It is positioned in the groove between the left atrium and left ventricle and gathers blood from several smaller veins.

Finally, it delivers blood to the right atrium through an opening, often guarded by a tiny flap called the valve of the coronary sinus.

Conduction System of the Heart Anatomy

The heart’s conduction system is an internal electrical network that ensures a steady heartbeat by coordinating the contraction and relaxation of heart muscles.

It generates and transmits electrical impulses along precise pathways and synchronizes the movements of the heart’s chambers. This system ensures blood is pumped efficiently and delivers oxygen and nutrients to the body.

Sinoatrial (SA) Node

The sinoatrial (SA) node is a cluster of specialized pacemaker cells located in the upper wall of the right atrium, near the entry point of the superior vena cava. These cells have the unique ability to spontaneously produce electrical signals to initiate the heart’s rhythmic contractions.

The electrical impulses generated by the SA node propagate through gap junctions across both atria and trigger their contraction (atrial systole). This action pumps blood from the atria into the ventricles to ensure continuous blood flow.

The autonomic nervous system modulates the activity of the SA node to regulate heart rate:

• The sympathetic nervous system accelerates the SA node’s firing, increasing heart rate.
• The parasympathetic nervous system slows its activity, decreasing heart rate.

This dynamic regulation ensures that the heart adapts to the body’s changing needs.

Atrioventricular (AV) Node

Once electrical signals pass through the atria, they reach the atrioventricular (AV) node. It is located in the wall separating the atria near the coronary sinus.

The AV node briefly slows these signals, delaying them for about 120 milliseconds. This pause allows the atria enough time to fully transfer blood into the ventricles before the ventricles contract.

After this delay, the signals move into the atrioventricular bundle, continuing the electrical pathway that drives the heart’s coordinated contractions.

Atrioventricular Bundle

Purkinje Fibers

Purkinje fibers called the sub-endocardial conduction network, are special heart cells that play a key role in keeping the heart working smoothly. These fibers are packed with glycogen and are tightly connected by gap junctions, which allow quick and efficient communication between cells.

Purkinje fibers are found just beneath the inner surface of the ventricles and carry electrical signals from the atrioventricular (AV) bundle to the heart’s ventricular walls. This fast signal ensures that the ventricles contract together during a heartbeat (ventricular systole).

As a result, the heart pumps blood efficiently—sending oxygen-poor blood to the lungs through the pulmonary artery and oxygen-rich blood to the rest of the body through the aorta.

Read More-

Lower Limb

• Hip Bone Anatomy – Complete Guide with Parts, Names, Functions & Diagram
• Complete Guide on Leg Anatomy with Parts, Functions & Diagram
• Complete Guide to Thigh Muscle Anatomy: Learn Parts, Names & Diagram
• Knee Anatomy: Complete Guide to Parts, Names, Functions & Diagram
• Femur Anatomy: Complete Guide with Parts, Names, Functions & Diagram
• Hip Muscle Anatomy – Complete Guide with Parts, Names, Functions & Diagram

Upper Limb

• Complete Guide to Finger Anatomy with Parts, Names, Functions & Diagram
• Complete Guide to Forearm Anatomy: Parts, Names, Functions & Diagram
• Comprehensive Guide to Arm Anatomy: Parts, Names & Diagram
• Comprehensive Guide to Hand Anatomy: Parts, Functions & Diagram
• Ultimate Guide to Bicep Anatomy: Parts, Names, Functions & Diagram
• Shoulder Anatomy: Ultimate Guide to Parts, Names, Functions & Diagram
• Wrist Anatomy: Ultimate Guide to Parts, Names, Functions & Diagram
• Complete Guide to Nail Anatomy with all Parts, Names & Diagrams

Human Head

• Skull Anatomy: Complete Guide with Parts, Names, Functions & Diagram
• Ultimate Guide to Eye Anatomy: Parts, Structure, Functions & Diagram
• Tongue Anatomy: Complete Guide with Parts, Names, Functions & Diagram
• Mouth Anatomy: Complete Guide with Parts, Names, Functions & Diagram
• Complete Guide to Tooth Anatomy: Learn Parts, Names & Diagram
• Ultimate Guide to Ear Anatomy: Parts, Structure, Functions & Diagram

Organs

• Kidney Anatomy: Complete Guide with Parts, Names, Functions & Diagram
• Liver Anatomy: Complete Guide with Parts, Names, Functions & Diagram

External Sources-

• Wikipedia
• KenHub
• Optometrists
• Cleveland Clinic
• American Academy of Ophthalmology