Rheumatic fever is an autoimmune disease which occurs 2-4 weeks after throat infection usually a streptococcal infection. The antibodies developed to combat the infection cause damage to the heart. Effects include fibrous nodules on the mitral valve, fibrosis of the connective tissue and accumulation of fluid in the pericardial cavity.

Blood vessels that supply blood to the cardiac muscles with all nutrients and removes wastes are the coronary arteries and veins. Heart muscle is supplied by two arteries namely right and left coronary arteries. These arteries are the first branch of the aorta. Arteries usually surround the heart in the manner of a crown, hence called coronary artery.

Rh factor is a protein (D antigen) present on the surface of the red blood cells in majority (80%) of humans. This protein is similar to the protein present in Rhesus monkey, hence the term Rh, Individuals who carry the antigen D on the surface of the red blood cells are Rh⁺ (Rh positive) and the individuals who do not carry antigen D, are Rh ^- (Rh negative).

(i) Eosinophils increase during certain types of parasitic infections and allergic reactions.
(ii) Eosinophils have distinctly bilobed nucleus and the lobes are joined by thin strands. They are non - phagocytic and constitute about 2 - 3% of the total WBCs.

The average life span of RBC is about 120 days after which they are destroyed in the spleen which is called the graveyard of RBC