Poison Apparatus and Biting Mechanism in Snakes скачать в хорошем качестве

Poison Apparatus and Biting Mechanism in Snakes

Most of the snakes are non poisonous and there are four poisonous genera of snakes, In India every year 20000-30000 persons die of the Snake bite. Snakes do not chew their food but swallow its whole food. All the poisonous snakes have poison apparatus in their heads, which is not found in non–poisonous snakes. The poison and venom both substances are toxic in nature but the difference are; if the plants and animals produce toxic reaction after eating them than the plants and animals supposed to be poisonous. When substance injected into the body of enemy or organism by those animals having poisonous apparatus it is called venomous. Poisonous apparatus of snakes include the following parts; A pair of poison glands  Poison ducts  Fangs  Muscles . Poison Glands The poison apparatus of snakes consists of a pair of poison glands, their ducts and a pair of fangs. In poisonous snakes the poison glands are situated one on either side of the upper jaw. The poison glands are possibly the superior labial glands or parotid glands. Each poison gland is sac-like and provided with a narrow duct at its anterior end. The gland is provided with a narrow duct at its anterior end. The duct passes forward along the side of the upper jaw and loops over itself just in front of the fang and opens either at the base of the fang or at the base of the tunnel on the fang. 3. Fangs: The fangs of snakes evolved to inject venom into the pray of various snakes that possess them. the term fangs refers to a grooved or tubular tooth that is used to inject venom. It has pared pointed and hook like teeth, which are the modified form of maxillary teeth. They are long, curved, sharp and pointed. Fangs are divided into three types on the basis of structure and position which are given bellow; (a) Proteroglyphous (protero, first): Proteroglyphous types of fangs are small, grooved and articulated and permanently erect at the anterior end of maxillae. Such fang is found in cobras, kraits, coral snakes and sea snakes, (b) Opisthoglyphous (opistho, behind): Opisthoglyphous fangs are also small, grooved but remain associated with the posterior end of maxillae. (c) Solenoglyphous (solen, pipe + glyph, hollowed): Solenoglyphous fangs in vipers and rattle snakes, a large functional fang occurs on the front of each maxilla. This contains a narrow hollow poison canal with enamel, which opens at the anterior end of the fang. The fangs are movable and turned inside to lie in the roof of mouth when it is closed. 4. Muscles : The poison apparatus is associated with specialized bands of three types of muscles viz. i. digastrics ii. Sphenopterygoid iii, anterior and posterior temporalis i. Digastric muscle – Attached to the squamosal of the skull at one end and articular of the lower jaw at the other end. It helps in opening jaws. ii. Sphenopterygoid – attached anteriorly to the spheroidal region and posteriorly to the dorsal surface of the pterygoid. It assists in pulling the pterygoid forward. iii. Anterior and posterior temporalis – attached to the side walls of the cranium and the lower jaw. They help in closing the lower jaw.