Short Notes On Biology: Human Heart

Short Notes On Biology: Human Heart

Here we are providing the short notes on Biology which will be help to crack science part in may examinations like SSC, Railway and other competitive exams.


The heart circulates blood through two pathways: 

  1. The pulmonary circuit
  2. The systemic circuit

In the pulmonary circuit, deoxygenated blood leaves the right ventricle of the heart via the pulmonary artery and travels to the lungs, then returns as oxygenated blood to the left atrium of the heart via the pulmonary vein.

In the systemic circuit, oxygenated blood leaves the body via the left ventricle to the aorta, and from there enters the arteries and capillaries where it supplies the body’s tissues with oxygen. Deoxygenated blood returns via veins to the vena cava, re-entering the heart’s right atrium.

The cardiovascular system circulates blood from the heart to the lungs and around the body via blood vessels.

Blockage of any artery can cause a heart attack, or damage to the muscle of the heart. A heart attack is distinct from cardiac arrest, which is a sudden loss of heart function that usually occurs as a result of electrical disturbances of the heart rhythm.

The heart contains electrical “pacemaker” cells, which cause it to contract — producing a heartbeat.

The aorta is the main artery leaving the heart.

The pulmonary artery is the only artery that carries oxygen-poor blood.

The pulmonary artery carries deoxygenated blood to the lungs.

The veins have valves that prevent backflow of blood Blood pressure.

Important Points:


The largest artery in the body. It carries oxygen-rich blood away from the heart to vessels that reach the rest of the body.


The chambers of the heart, to which the blood returns from the circulation.


The smallest of the body’s blood vessels. Oxygen and glucose pass through capillary walls and enter the cells. Waste products such as carbon dioxide pass back from the cells into the blood through capillaries.

Cardiac Valves (Heart Valves)

Any of the four heart valves that regulate the flow of blood through the chambers of the heart.

Oxygenated Blood -> Oxygen-rich blood.

Deoxygenated Blood -> Oxygen-poor blood.

Heart Ventricles

The lower right and left chambers of the heart.

Interventricular Septum

Interventricular septum is the stout wall separating the lower chambers (the ventricles) of the heart from one another.


One of a pair of organs in the chest that supplies the body with oxygen, and removes carbon dioxide from the body.


The muscular substance of the heart; the middle of the three layers forming the outer wall of the human heart.

Pulmonary Artery

The pulmonary artery and its branches deliver blood rich in carbon dioxide (and lacking in oxygen) to the capillaries that surround the air sacs.

Pulmonary Circulation

The circulation of the blood through the lungs.

Pulmonary Veins

The veins that return the oxygenated blood from the lungs to the left atrium of the heart.

Superior Vena Cava

The large vein that carries blood from the head, neck, arms, and chest to the heart.

Vena Cava

A large vein which returns blood from the head, neck and extremities to the heart.

➧Endothelium is the innermost layer of blood vessels that consists of just a single layer of cells.

➧Veins are blood vessels that carry blood to the heart in an even flow. They have thin walls large lumens and valves.

➧ A pulse is the alternate contraction and relaxation of an artery as blood passes through it.

➧Blood pressure is the force blood exerts on the walls of blood vessels.

➧A sphygmomanometer is used for measuring blood pressure(normally 120/80 mmHg)

➧Atherosclerosis is the hardening of artery walls due to a build-up of fatty deposits.

➧Smoking causes heart rate and blood pressure to increase. Diet high in saturated fats increase blood pressure and atherosclerosis. Exercise helps lower blood pressure.

Blood Groupings

  • Father of Blood Grouping : Karl Landsteiner
  • He discovered A, B and O blood groups
  • Decastello and Sturle discovered AB blood groups

RH factor

  • It is a blood antigen found in RBC
  • A person can be Rh+ or Rh- depending upon the presence of Rh factor in RBC
  • Rh+ can receive blood from both Rh+ and Rh- but Rh- can receive blood only from Rh- only

Blood transfusion techniques was developed by Dr. James Blundell.



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