Heparin is a hormone secreted by the liver. This is anticoagulant in its property. It prevents cloting of blood inside the heart and blood vessels. Heart attack is the result of a block in the blood vessels supplying blood to the walls of the heart.

The hormone adrenaline also called epinephrine is known as a stress harmone. In emotional upset (like fear, anger etc.) this harmone is poured into the blood and it accelerates heart beat. The hormone acetylcholine decelerates heartbeat rate.

The red blood corpuscles  or erythrocytes usually carry antigens and there are two types of antigens. The A group persons have antigen A in their red corpuscles and the B group have antigen B in their red corpuscles. The AB group person have both antigen A and antigen B in their erythrocytes. The 'O' group persons have no antigens in their red corpuscles.

The clotting of blood is a chain reaction initiated by the enzyme thrombokinase produced by the platelets. This causes prothrombin to be converted into thrombin in the presence of Ca++ion.

Thrombin combines with fibrinogen  to produce fibrin threads which entangles the corpuscles to form the clot.

The blood of some invertebrate animals like the earthworm is red due to haemoglobin pigment, but the pigment is dissolved in the plasma. In vertebrates the same pigment is found in the red corpuscles and not in the plasma.

Autotroph: This term means organisms that synthesise their own food. Troph means feeding. Auto means self. The green plants which synthesise their own food are called autotrophs. All others which depend upon the plants directly or indirectly are called heterotrophs.

The word coprodaeum refers to the last part of the elimentary canal.The excreta (undigested, matter) comes out of that part. So, the organisms that take in such materials are called coprophagous.

The feeding mechanism is of several types. If it is entirely plant-like (photosynthesis),it is called holophytic. It is entirely (holo) animal-like (zoic), that is devouring already existing food, it is called holozoic.