Disorders of Circulatory System – Class 11 | Chapter – 18 | Biology Short Notes Series PDF

Disorders of Circulatory System: The circulatory system may be defined as the system which is involved in the circulation of lymph and blood throughout the body. The circulatory system consists of many parts like heart, blood vessels, blood cells, lymph, lymphatic vessels, and glands. This disorder may be affected by the following factors:

  1. An emotional response to distressing events like an accident.
  2. Blockage of a blood vessel.
  3. Formation of tumours in blood vessels.
  4. Reduction in the artery diameter

Types of Disorders of Circulatory System


Hypertension is the condition characterised by persistent high blood pressure. In hypertension, the systolic pressure has a reading of 140 (140 mm of Hg) and the diastolic pressure has a reading of 90 (90 mm of Hg), i.e., (140/90) or higher. 

Usually cholesterol build up causes narrowing of the lumen of arteries, as a result of which blood pressure increases. This increases the workload of the heart to pump blood. 

Higher the pressure, more is the stress on the heart. The heart muscle thickens, tends to enlarge, and gets weaker over time. 

Due to high blood pressure, several heart diseases occur. This affects other vital organs as well such as the brain, kidneys, eyes etc.

Causes of Hypertension

The causes of hypertension are enlisted below:

  • Increased cholesterol levels
  • Stress
  • Smoking
  • Kidney disorders

Coronary Artery Disease

Coronary artery disease, often described as atherosclerosis, occurs due to plaque formation in the blood vessels supplying blood to the heart. 

The plaque is composed of cholesterol, calciumfat and fibrous tissue. Atherosclerotic plaque formation causes deformity in the arterial wall. With the gradual growth of these plaques, the lumen of arteries become progressively narrower which hampers proper blood supply. Build up of such a plaque in the coronary artery (artery that supplies blood to the heart muscles) hinders blood supply to the heart. This may result in a heart attack.


Arteriosclerosis is the condition of hardening and loss of elasticity of arteries due to calcification of plaques. This makes the walls stiff and rigid. Formation of plaque occurs when calcium salts precipitate with cholesterol. The walls of arteries may rupture due to loss of elasticity. Blood comes out of the ruptured wall which after forming a clot blocks the path of blood flow. This may lead to heart attack.

Atherosclerosis vs Arteriosclerosis

Atherosclerosis  Arteriosclerosis
Atherosclerosis is the condition caused by the formation of plaques in the lumen of arteries due to deposition of fatty substances such as cholesterol and triglycerides.  Arteriosclerosis is the condition caused by the calcification of plaque deposited in the arterial wall.
Atherosclerosis leads to narrowing of arterial lumen. Arteriosclerosis leads to rigidity, thickening and stiffness of the arterial wall.


Angina is also known as angina pectoris. The term is derived from the Latin words ‘angere’ (to strangle) and ‘pectus’ (chest). It is also described as ‘a strangling feeling in the chest’. It occurs due to deficiency of oxygen reaching to the heart muscles due to narrowing of arteries. The blood flow is affected. The symptom of angina is acute chest pain. Men and women of any age may suffer from angina. It is more common among the middle-aged and elderly.

Myocardial infarction

Myocardial infarction is also known as heart attack. The plaque deposited in the arteries when rupture and block the coronary artery, hinder blood flow to cardiac muscles. The blockage results in the damage or death of the cardiac muscle tissue. As a result, the functions of the heart get affected. This can have fatal consequences.

Heart Failure

Heart failure is a state in which the heart doesn’t pump blood effectively to meet the requirements of the body. It is also known as congestive heart failure because one of the main symptoms is the congestion of lungs.

Cardiac Arrest

Cardiac arrest is the condition when the heart stops beating. As a result, the blood stops flowing to the brain and other vital organs.

Congenital Heart Disease

Congenital heart disease refers to any defect in the heart since birth. It occurs due to defects in normal development of the heart during embryonic stages. 

The defect in the child can be caused due to infections in mothers during pregnancy like infection with Rubella virus. Administration of harmful drugs during the first trimester of pregnancy is another reason. Chromosomal abnormalities occur in congenital heart defects.


The condition characterised by irregular beating of the heart is called arrhythmia. It is the result of improper coordination of myocardial signals.

It is of two major types:

  • Bradycardia: Slow beating of the heart
  • Tachycardia: Fast beating of the heart


Leucocytosis is the condition characterised by increased WBCs in the blood. It is usually the response to underlying infections. However, in certain cases, the increased level of white blood cells doesn’t return to normal even after the elimination of the infection. Such situations require immediate medical intervention.

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By Team Learning Mantras