Overview of the Human Heart

In humans, the heart is located beneath the breastbone, in between two lungs and somewhat to the left of the centre. It is supported by the diaphragm, the muscular barrier that separates the chest and abdominal cavities. The human heart is a fist-sized hollow muscular organ made up of specialized cell types that is responsible for pumping blood through the circulatory system. It's the human circulatory system's principal organ. The heart of animals with lungs like amphibians, reptiles, birds, and mammals has evolved from a single pump to a double pump that circulates blood. The heart is made up of four main chambers that are driven by electrical impulses and are formed of muscle. Your heart's function is controlled by your brain and nerve system.

The article discusses the anatomy and the physiology of the human heart, it also describes aspects like the structure of the heart and the function of the heart. Questions like where is the heart located in the human body is also answered in the article.

Where is the Heart Located in the Human Body?

The human heart is positioned in the thoracic cavity, inside the mediastinum, which is the region between both lungs. The pericardium, or pericardial sac, separates the cardiac from the other mediastinal organs inside the mediastinum, and it resides in its own compartment termed the pericardial cavity. The heart's dorsal surface is close to the vertebral bodies, while its anterior surface is close to the sternum and costal cartilages. The major veins, the inferior and superior vena cava, and the major arteries, the aorta and pulmonary trunk, are all connected to the base of the heart. The heart’s apex, or inferior tip, is located directly to the left of the sternum, near the articulation of the fourth and fifth ribs with the costal cartilages. The anatomical positioning of the heart would be understood greatly by the following diagram.

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Structure of the Heart

Since we have seen about the location of the heart let us look into the structure of the heart or the anatomy, the layers and walls would be discussed in detail in this section. The myocardial layer surrounds the heart, and is made up of numerous layers. The heart cavity is split along the centre into two chambers, each of which is dissected into a right and left heart. The atrium is the upper chamber, while the ventricle is the lower chamber. The two atria serve as blood receiving chambers, while the more muscular ventricles pump blood out of the heart. To understand the structure of the human heart let us look into each aspect of the anatomy individually, walls, chambers, valves and blood vessels are discussed in the anatomy.

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Walls of the Heart

The septum is a membrane of muscle tissue that separates the left and right sides of the heart. Pericardium, endocardium, myocardium, and epicardium are the four layers of the heart. 

  • The pericardium or pericardial sac is the layer that covers the heart and creates the pericardial region. The outer fibrous pericardium and the inner serous pericardium are two different sublayers of the pericardium. 

  • Epicardium is an interior visceral pericardium that is connected to the heart and constitutes the heart wall. The epicardium is made up of a simple squamous epithelium known as the mesothelium, which is supported by loose, irregular, or areolar connective tissue that connects to the pericardium. 

  • Between the epicardium and the pericardium is the pericardial cavity, which is filled with lubricating serous fluid. The lubricating serous fluid that fills the pericardial space and decreases friction while the heart contracts are secreted by this mesothelium.

  • The myocardium, which is mostly made up of cardiomyocytes, is the main and broadest portion. It has a collagenous fibre structure, as well as blood arteries that replenish the myocardium and nerve fibres that assist control the heart. Blood is pumped by the heart and then into the main arteries by contracting the myocardium.

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Valves of Heart

The valves guarantee that blood flows through the heart in just one way. The heart valves act as portals between both chambers of the heart. To enable blood to pass through, the valves open and close. The atrioventricular (AV) valves connect the upper and lower chambers of your heart. Tricuspid and Mitral valves are two of the AV valves. The Tricuspid valve allows blood to flow from the right atrium to the right ventricle, whereas the Mitral valve allows blood to flow from the left atrium to the left ventricle.

When blood rushes out of your ventricles, semilunar (SL) valves open. Aortic and pulmonary valves are two of them. When blood travels from the left ventricle to the aorta, the aortic valve opens (an artery that carries oxygen-rich blood to your body). When blood travels from your right ventricle to your pulmonary arteries, the pulmonary valve opens (the only arteries that carry oxygen-poor blood to your lungs).

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Chamber of Heart

It is the most important part of the structure of the heart, the contraction and relaxation of the chamber of the heart regulate the function of the heart. The heart is separated into four compartments: two atrium regions on top and two ventricles compartments on the bottom. The right atrium is supplied with oxygen-depleted blood by 2 major veins. The superior vena cava is a vein in the upper body that transports blood. The inferior vena cava is a vein that transports blood from the bottom body back to the heart. The blood is then pumped to the right ventricle by the right atrium. 

The right lower chamber of the heart (ventricle) pumps oxygen-poor blood to the lungs through the pulmonary artery. The lungs replenish oxygen in the blood. The pulmonary veins bring blood to the left atrium after the lungs have filled it with oxygen. The blood is pumped to the left ventricle. The left ventricle is somewhat bigger than the right ventricle. It circulates oxygen-rich blood throughout your body.

Blood Vessels in the Structure of the Heart

The heart is supplied with three types of blood vessels, the artery, the veins and the capillaries. The arteries carry the oxygenated blood the only exception is the pulmonary artery. The veins carry deoxygenated blood with the exception of the pulmonary vein. The capillaries are the finer vessels where the gaseous exchange occurs. 

The Function of the Heart: Circulatory System 

The human heart is divided into four compartments: one atrium and one ventricle on each side. The right and left atriums of each of the top chambers serves as a receiving chamber, contracting to force fluid into the lower chambers, the right and left ventricles, respectively. The heart's ventricles are the main pumping compartments, delivering blood to the lungs or the rest of the body. The pulmonary and systemic circuits are two separate but interconnected pathways in the cardiovascular system. Even though both channels transmit blood one may look at them from the perspective of gases at first. The pulmonary circuit distributes blood to and from the lungs, where it takes in oxygen and exhales carbon dioxide.

The systemic circuit delivers oxygenated blood to almost all of the body's tissues while returning substantially deoxygenated blood and carbon dioxide to the heart for recirculation towards the pulmonary circulation. Deoxygenated blood is pumped from the right ventricle into the pulmonary circulation, which goes to the lungs and divides into the left and right pulmonary arteries. These veins branch several times before reaching the pulmonary capillaries, allowing carbon dioxide to escape the circulation and oxygen to enter. The only arteries in the body that convey significantly deoxygenated blood are the pulmonary trunk arteries and their branches. The pulmonary veins are the only veins in the human that transport substantially oxygenated blood. 

Blood flows from the pulmonary veins into the left atrium, which forces everything into the left ventricle, which then pumps oxygenated blood into the aorta and out to the various branches of the systemic circuit. These veins will eventually lead to the systemic capillaries, which are where the body's tissue fluid and cells are exchanged. In this instance, oxygenated blood leaves the systemic capillaries to be utilised by the cells in their metabolic activities, while CO2 and toxic byproducts enter the bloodstream.

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In conclusion of the article, we have an alert about the structure of the heart, the function of the heart. We have also seen the anatomical positioning of the human heart. 

FAQs (Frequently Asked Questions)

1. Name two commonly found heart diseases.

Ans: Coronary artery disease, heart attack also known as myocardial infarction, atrial fibrillation and arrhythmia are among some of the commonly found heart diseases. Coronary artery disease is a condition where the coronary artery develops a plaque deposition, leading to hindered movement of blood. Myocardial infarction is the condition in which oxygen supply to the heart is stopped due to artery blockage. Atrial fibrillation is a condition in which the atrium receives irregular electrical impulses.

2. What is the heart wall made up of?

Ans: There are several layers in the heart wall namely, pericardium, epicardium. Myocardium and endocardium. The myocardium is the most important layer, it is composed of myocytes, it is responsible for the transmission of the electrical impulse generated by the nodes. The contraction and relaxation of the heart chambers is the result of myocardium functioning.