a. The two testes lie in the respective scrotal sacs. The scrotum acts as a thermoregulator organ and provides an optimum temperature for the formation of sperms. The sperms develop at a temperature of 1-3°C lower than the normal body temperature. Hence scrotum remains outside the body of human males.
b. The wall of the stomach is protected by mucus. Hence the wall of the stomach is not digested by its own enzymes. Further the gastric enzyme pepsinogen is present only in inactive form and converted into active pepsin only when food enters the stomach

Functions of ovaries :
(i) The ovaries are the female gonads which produce ova or the female gametes.
(ii) They also secrete the female sex hormones namely oestrogen and progesterone.
Functions of uterus :
(i) Uterus is a pear-shaped muscular, hollow structure present in the pelvic cavity.
(ii) Development of foetus occurs inside the uterus

Each kidney consists of more than one million nephrons. Nephrons or uriniferous tubules are structural and functional units of the kidneys. Each nephron consists of Renal corpuscle or Malphigian corpuscle and renal tubule. The renal corpuscle consists of a cup-shaped structure called Bowman's capsule containing a bunch of capillaries called glomerulus. Blood enters the glomerular capillaries through afferent arterioles and leaves out through efferent arterioles. The Bowman's capsule continues as the renal tubule which consists of three regions proximal convoluted tubule, U-shaped hair pin loop, the loop of Henle and the distal convoluted tubule. The distal convoluted tubule opens into the collecting tubule. The nitrogenous wastes are drained into renal pelvis of kidney which leads to ureters and stored in the urinary bladder. Urine is expelled out through the urethra.

Starch      - Glucose
Proteins    -Amino acids
Fats Fatty -acids and glycerol

Permanent teeth are of four types (Heterodont), according to their structure and function namely incisors, canines, premolars and molars.