Q#1: Describe the structure of the human heart.
Ans.
Introduction to the Human Heart
The human heart is one of the most important organs responsible for sustaining life. It is a muscular organ with four chambers. The size of the heart is about the size of a clenched fist.
The human heart functions throughout a person’s lifespan and is one of the most robust and hardest-working muscles in the human body.
Besides humans, most other animals also possess a heart that pumps blood throughout their bodies. Even invertebrates such as grasshoppers possess a heart-like pumping organ, though they do not function the same way a human heart does.
Position of the heart in the human body
The human heart is located between the lungs in the thoracic cavity, slightly to the left of the sternum (breastbone). It is derived from the embryonic mesodermal germ layer.
Internal Structure of the Human Heart
The internal structure of the heart is rather intricate, with several chambers and valves that control the flow of blood.
- The human heart is about the size of a human fist and is divided into four chambers, namely two ventricles and two atria.
- The ventricles are the chambers that pump blood, and the atrium is the chamber that receives blood.
- Among these, both the right atrium and ventricle make up the "right heart," and the left atrium and ventricle make up the "left heart."
- The structure of the heart also houses the biggest artery in the body, the aorta.
- The right and left regions of the heart are separated by a wall of muscle called the septum.
- The right ventricle pumps the blood to the lungs for re-oxygenation through the pulmonary arteries.
- The right semilunar valves close and prevent the blood from flowing back into the heart. Then, the oxygenated blood is received by the left atrium from the lungs via the pulmonary veins.
Chambers of the Heart
Humans have four chambers, namely:
- Left atrium
- Right atrium
- Left ventricle
- Right ventricle
Atria are thin, have fewer muscular walls, and are smaller than ventricles. These are the blood-receiving chambers that are fed by the large veins.
Ventricles are larger and more muscular chambers responsible for pumping and pushing blood out into circulation. These are connected to larger arteries that deliver blood for circulation.
The right ventricle and right atrium are comparatively smaller than the left chambers. The walls consist of fewer muscles compared to the left portion, and the size difference is based on their functions. The blood originating from the right side flows through the pulmonary circulation, while the blood arising from the left chambers is pumped throughout the body.
External Structure of the Heart
The heart is a muscular structure that is situated in the front of the chest. It pumps blood all through the body in a process called circulation. Apart from the heart, the blood vessels and blood as a unit constitute the cardiovascular system.
- The human heart is a hollow, muscular organ.
- The size of an adult heart is 12 cm in length, 8–9 cm in breadth, and about 6 cm in thickness.
- The average weight of a human heart is about 300 g in adult males and about 250 g in adult females.
- The heart is a double pump.
- It is divided into two halves, the right and left.
- Each half consists of two chambers: the upper, smaller auricle, or atrium, and the lower, larger ventricle. In this way, the heart has four chambers.
- The auricles form the upper part of the heart.
- They are separated externally from the ventricle by a groove called the coronary sulcus.
- The ventricles form a large part of the heart.
- The two ventricles are separated externally by a groove called the interventricular sulcus.
One of the very first structures that can be observed when the external structure of the heart is viewed is the pericardium.
Pericardium
The human heart is situated to the left of the chest and is enclosed within a fluid-filled cavity described as the pericardial cavity. The walls and lining of the pericardial cavity are made up of a membrane known as the pericardium.
The pericardium is a fibrous membrane found as an external covering around the heart. It protects the heart by producing serous fluid, which serves to lubricate the heart and prevent friction between the surrounding organs. Apart from the lubrication, the pericardium also helps by holding the heart in its position and by maintaining a hollow space for the heart to expand itself when it is full. The pericardium has two exclusive layers:
- Visceral Layer: It directly covers the outside of the heart.
- Parietal Layer: It forms a sac around the outer region of the heart that contains the fluid in the pericardial cavity.
Structure of the Heart Wall
The heart wall is made up of three layers, namely:
- Epicardium: The epicardium is the outermost layer of the heart. It is composed of a thin-layered membrane that serves to lubricate and protect the outer section.
- Myocardium: This is a layer of muscle tissue, and it constitutes the middle layer of the wall of the heart. It contributes to the thickness and is responsible for the pumping action.
- Endocardium: It is the innermost layer that lines the inner heart chambers and covers the heart valves. Furthermore, it prevents the blood from sticking to the inner walls, thereby preventing potentially fatal blood clots.
No comments:
Post a Comment