Structural Organisation Of Animals And Plants

Erythrocytes (red blood corpuscles) of mammals (man) are found, biconcave and non-nucleated. Life span of mammalian RBC is about days ( months) whereas life span of frogs RBC is about days.

Circulatory system of cockroach is open or lacunar type. Tubular heart of cockroach is situated in pericardial sinus over the dorsal diaphragm. It is longitudinally beaded with chambers perforated by ostia having valves.

The process of formation of blood corpuscles is called haemopoiesis or hematopoiesis. During embryonic and foetal life, blood cells are formed in yolk sac, liver, spleen, thymus gland, lymph nodes and bone marrow. In adults, red bone marrow is responsible for producing red blood cells, granular leucocytes and platelets.

Cloacal aperture of frog is a small, median chamber that is used to pass faecal matter, urine and sperms to the exterior.

Clitellum segment of earthworm constitutes to segments.

The tentorium (pi. tentoria) is a term used to refer the framework of internal supports within an arthropod head. It is formed by in growths of the exoskeleton called apophyses which fuse in various ways to provide rigid support to the muscles of head.