Human Heart-Gross structure and Anatomy




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.

Structure:

heart is composed of three layer of tissue.

  1. Pericardium
  2. Myocardium
  3. Endocardium

Pericardium

  • 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

  • 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

  • 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.

Chambers of heart:

  • Heart consists of 4 chambers
  • At first heart is divided into right and left side by the septum
  • Each side is further divided into 2 chamber each by artioventricular valve
  • The upper two chambers are called atrium and lower two are called ventricles.

Atrium

  • 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

Ventricle

  • 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.

Valves

1. Atrioventricular valve

  • 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.

2. Semilunar valve

  • 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.

Human Heart-Gross structure and Anatomy