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.
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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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.
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 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.
1. What is the human heart, and what is its primary function in the body?
The human heart is a muscular organ, about the size of a fist, located in the chest cavity. Its primary function is to act as a pump for the circulatory system. It continuously pumps blood throughout the body, delivering oxygen-rich blood and nutrients to all tissues and organs while carrying away waste products like carbon dioxide.
2. What are the four main chambers of the human heart and their roles?
The human heart is divided into four chambers that work together to circulate blood. These are:
Right Atrium: Receives deoxygenated blood from the body.
Right Ventricle: Pumps the deoxygenated blood to the lungs.
Left Atrium: Receives oxygenated blood from the lungs.
Left Ventricle: Pumps the oxygenated blood to the rest of the body. This chamber has the thickest muscular wall as it needs to pump blood over the greatest distance.
3. What is meant by “double circulation,” and why is this system important?
Double circulation is a key feature of the human circulatory system where blood passes through the heart twice for each complete circuit of the body. The two circuits are:
1. Pulmonary Circulation: Moves deoxygenated blood from the right ventricle to the lungs for oxygenation, and then returns oxygen-rich blood to the left atrium.
2. Systemic Circulation: Moves oxygen-rich blood from the left ventricle to all other parts of the body and returns deoxygenated blood to the right atrium.
This system is crucial because it ensures the strict separation of oxygenated and deoxygenated blood, allowing for highly efficient oxygen delivery to body tissues.
4. What are the different layers that make up the wall of the human heart?
The heart wall is composed of three distinct layers, all enclosed within a protective sac called the pericardium. The layers are:
Epicardium: The outermost layer of the heart wall.
Myocardium: The thick middle layer composed of cardiac muscle tissue. It is responsible for the heart's powerful contractions.
Endocardium: The thin, smooth inner layer that lines the heart chambers and valves, allowing blood to flow without friction.
5. Why are valves so important in the heart, and what happens if they malfunction?
Heart valves are crucial because they act like one-way gates, ensuring that blood flows in only one direction through the heart's chambers. They open to allow blood to pass through and then close tightly to prevent any backflow. If a valve malfunctions (e.g., it doesn't open fully or close properly), it can disrupt normal blood flow, forcing the heart to work much harder. This can lead to conditions like heart murmurs, fatigue, and eventually, heart failure.
6. What causes the characteristic “lub-dub” sound of a heartbeat?
The “lub-dub” sound is not from the muscle contracting but from the heart valves closing.
The first sound, “lub” (S1), is produced by the closure of the atrioventricular valves (the tricuspid and mitral valves) when the ventricles begin to contract.
The second sound, “dub” (S2), is produced by the closure of the semilunar valves (the aortic and pulmonary valves) after the ventricles have ejected blood.
7. How does the heart muscle itself receive the oxygen and nutrients it needs to function?
This is a common point of confusion. The blood flowing inside the heart's chambers does not directly nourish the heart muscle. Instead, the heart has its own dedicated blood supply system through the coronary arteries. These arteries branch off from the aorta and wrap around the outside of the heart, delivering oxygen-rich blood directly to the myocardium (heart muscle). A blockage in these specific arteries is what leads to a myocardial infarction, or heart attack.
8. What is the difference between an artery and a vein in the circulatory system?
The primary difference between arteries and veins lies in their function and structure, not necessarily the type of blood they carry.
Arteries are blood vessels that carry blood away from the heart. They have thick, muscular, and elastic walls to withstand high pressure. The main artery is the aorta.
Veins are blood vessels that carry blood towards the heart. They have thinner walls and often contain valves to prevent the backflow of blood, as the pressure within them is much lower.