Question

biting machanism in snakes (6marks)​

Answer 1

Answer:

A posterior ligament extends between the gland and the quadrate. Each gland is thickly encapsulated with fibrous connective tissue and mostly covered by a fan-shaped constrictor muscle, often referred to as temporal. Its stretching during biting squeezes poison from gland into its duct.

Answer 2

Answer:

There are four distinct phases when a poisonous snake bites:

(1) The strike;

(2) opening of the mouth and elevation of the fangs;

(3) closing of the jaws and the injection of venom; (4) retraction of the fangs

explanation

I. The strike. –

In this phase the snake throws itself forward with great rapidity and violence,

the distance covered not generally exceeding one-third of its length. Vipers

strike with greater velocity than the colubrids, some of which especially the

hooded species raise the head from the ground thus compensating to some extent

for the limited mobility of the fangs.

II. Opening of the mouth and elevation of the fangs.-

Most poisonous snakes commence the strike with closed jaws, but as the head

approaches the victim the mandibles are depressed by a rapid contraction of the

digastric, cervico-mandibular and vertebro-mandibular muscles and

simultaneously the fangs are elevated or rotated forward by the forward swing of

the pterygo-palatine-transverse arch produced by the contraction of the spheno-

and parieto-pterygoid muscles.

III. Closure of the mouth and the injection of venom.-

Closure of the jaws follows, a result brought about by the simultaneous

contraction of the anterior, middle and posterior temporal muscles which

strongly elevate the mandibles. In the colubrids the venom gland is also

compressed by the superior and inferior portions of the anterior temporal

muscles, producing torsion on its capsule with the expulsion of venom from the

gland along the duct, the papilla of which becomes approximated to the groove

at the base of the fang, but in certain Australian species venom may sometimes

be observed to spurt a considerable distance during a snap bite at a time when no

object is actually being bitten.

IV. Retraction of the fangs.-

Immediately following the insertion of the fangs, and actually accompanying the

discharge of venom, contraction of the retractor muscles which operate on the

pterygo-palatine-transverse arch occurs, dragging the elevated fangs downwards

and backwards through the tissues.