1.
Describe the structure of the heart of man with the help of neat labelled diagram.
Answers
Answer:
The human heart is a hollow muscular, cone-shaped, and pulsating organ situated between the lungs. It is about the size of a closed fist. The heart is covered by the double-walled pericardium, which consists of the outer fibrous pericardium and inner serous pericardium.
The serous pericardium is double layered, outer parietal layer and inner visceral layer. These two layers are separated by pericardial spaces, which is filled with pericardial fluid. This fluid reduces friction between the two membranes and allows free movement of the heart.
The human heart has four chambers with two smaller upper chambers called atria and two larger lower chambers called ventricles.
Atria
These are thin-walled receiving chambers.
The right one is larger than the left.
The two atria are separated by a thin inter-atrial septum.
The right atrium receives deoxygenated blood from different parts of the body through three caval veins like two precaval veins and one post caval vein.
The right atrium also receives blood from the wall of the heart through the coronary sinus, whose opening into the right atrium is guarded by the valve of Thebesius.
The opening of the post caval vein is guarded by Eustachian valve. It is functional in the fetal stage and directs the blood from post caval vein into the left atrium through foramen ovale. But it is non-functional in the adult.
The openings of the precaval veins into the right atrium have no valves.
The left atrium receives oxygenated blood from the lungs through a pair of pulmonary veins, which open into the left atrium through a common pore.
Atrioventricular septum separates atria and ventricles. It has right and left atrioventricular apertures.
Tricuspid valve guards the right atrioventricular aperture.
Bicuspid valve guards the left atrioventricular aperture.
Ventricles
These are the thick-walled blood pumping chambers, separated by an interventricular septum.
The wall of the left ventricle is thicker than that of the right ventricle as the left ventricle must force the blood to all the parts of the body.
The inner surface of the ventricles is raised into a muscular ridge called columnae carneae.
Some of them are large and conical and known as papillary muscles.
Collagenous cords are known as chordae tendinae are present between atrioventricular valves and papillary muscles.
They prevent the cusps of valves from bulging too far atria during ventricular systole.
Nodal tissue
A specialised cardiac musculature called the nodal tissue is also distributed in the heart.
Sinoatrial node(SAN) – present in the right upper content of right atrium.
Atrioventricular node (AVN) – present in the lower left corner of the right atrium.
Aortic arches
The human heart has two aortic arches.
1)Pulmonary arch
Arises from the left anterior angle of the right ventricle. It carries deoxygenated blood to the lungs. It’s opening from right ventricle is guarded by the pulmonary valve made with 3 semilunar valves.
2)Left systemic arch
Arises from the left ventricle to distribute oxygenated blood to various parts of in the body. Its opening is also guarded by aortic valve made with a set of 3 semilunar valves. A fibrous strand, known as ligamentum arteriosum is present at the point of contact of the systemic and pulmonary arches. It is the remnant of the ductus arteriosus, which connects the systemic and pulmonary arches in the embryonic stage
Short answer
The heart is divided into four chambers consisting of two atria and two ventricles; the atria receive blood, while the ventricles pump blood. The right atrium receives blood from the superior and inferior vena cavas and the coronary sinus; blood then moves to the right ventricle where it is pumped to the lungs.
