Poisonous apparatus in snakes

Poison apparatus includes- 

               a. A pair of poison gland
               b. Their ducts
               c. Fangs and
               d. Muscles

a. Poison gland

Two sac-like poison glands are situated one on either innerside of the upper jaw, below the eye. These are possibly modified superior labial or parotid glands. The glands may be small and oval (sea snakes) or large and tubular (vipers). Each gland is covered by fan shaped constrictor muscle, often referred to as temporal. It’s stretching during biting squeezes poison from gland into its duct.

b. Poison duct
A narrow poison duct leads anteriorly from each poison gland to the base of a poison fang to enter its groove or canal.

c. Fangs
Fangs are certain specialized teeth attached to maxillary bones. They are long curved, sharp and pointed. They serve for injecting poison into the body of victim. When a functional fang is lost, it is replaced by one of the reserved fangs. On the basis of structure and position 3 types of fangs occur in poisonous snakes: Solenoglyphous, Proteroglyphous and Opisthoglyphous.