Human Heart-Gross structure and Anatomy

Heart

Heart is a myogenic muscular organ that pumps blood throughout the blood vessel by repeated rhythemic contraction.

Figure: Anatomy of Human Heart

Shape and size: it is roughly cone shaped hollow organ which is about 10 cm long. It is approximately the size of owner’s closed fist and weight about 250-300 gm in female and 300-350gm in male.
Location: heart lies in the thoracic cavity in the space between the lungs (mediastinum) anterior to the vertebral column and posterior to sternum. It lies obliquely a little more to left than right.

heart is composed of three layer of tissue.

It is double walled layer which encloses heart; the space between the two layer is filled with pericardial fluids.
Outer layer is called fibrous pericardium
Inner layer is called serous pericardium. It secrete serous fluid.
During heart beat, pericardial fluid prevent heart from shock and mechanical injury

Myocardium is the middle layer which is composed of specialized cardiac muscle (only found in heat)
Myocardium is striated muscle but not under voluntary movement.
When impulse is generated, it spread from cell to cell via branches and intercalated disc over the whole sheet of cardiac muscle causing contraction of muscle fiber.
The sheet arrangement of cardiac muscle enables the atrium and ventricle to contract in coordinated and efficient manner.
Myocardium is the thickest at the apex than the base. Similarly thicker at left ventricle than right ventricle. This reflects the amount of workload.
Cardiac skeleton: The myocardium is supported by the network of fine fiber, called as fibrous skeleton of heart

Endocardium is the inner layer of heart which lines the chamber and valves of the heart
It is thin, smooth membrane that permits smooth flow of blood
It consists of flattened epithelial cells and is continuous with endothelium layer of blood vessels.

Atrium are thin walled chamber separated by interauricular septum
Right atrium receive impure blood from body through the opening via superior and inferior venacava
The opening is guided by Eustachian valve and coronary valve.
In right atrium, there is a oval depression adjoining the inter-auricular septum called fossa ovalis which communicate two auricle during fetal life
Left atrium receive pure (oxygenated) blood from lungs through the four opening of pulmonary vein
Each atrium has flap like appendages called auricle of unknown function

Ventricles are thick walled chamber separated by thick inter-ventricular septum
Left ventricle is thicker and longer than right ventricle
The wall of ventricle has muscular ridges or projection called columnae cornea (Trabeculae cornae)
Columnae cornea divides the cavity of ventricles into smaller spaces called fissures
Right ventricle receive impure blood from right atrium and pumps via pulmonary arteries to lungs
Left ventricle receive oxygenated blood from left atrium and pumps the blood to aorta.

These are two in number
The right artioventricular valve has three cusps or flaps, called tricuspid valve
Left artioventricular valve has only two cusps, called as bicuspid valve
These valves open only in ventricles and hence prevent back flow of blood
These valves are attached to the wall of ventricles by means of tendon called chordae tendinae
The function of chordae tendinae is to hold the valve and prevent enter of valve to auricle during forceful ventricular contraction.

Right ventricle pumps blood through pulmonary aorta to lungs and left ventricle pumps blood through aorta. These opening is guided by three cusps semi lunar valve
Left semilunar valve is called aortic valve and right semilunar valve is called pulmonary valve.