Venom can be described as a highly adapted form of saliva. Usually, the venom is released via specialized teeth for the purpose of immobilizing a prey and defending against aggression. The injection mechanism, the producing glands and the venom itself form a special adaptive feature in venomous snakes. There are different types of snake venom that are basically categorized as cytotoxic, neurotoxic and hemotoxic venom.
The venom production and injection system differs considerably in different types of snakes. Usually, venom is synthesized in special salivary glands that are often located in the head of the snake. The venom glands are usually differentiated into true and false venom glands. The false venom glands (less dominant) are composed of mucus secreting suprabial glands that are situated on both sides of the head and extend downwards into forming a continuous strip. At the lower end near the viper’s jaw, the gland differentiates into multiple ducts that are connected to every tooth base. Studies have shown that Alethinophidians possess the false glands arrangements.
The true venom glands are composed of dense connective tissue and have a lumen with separate muscle and a duct that goes to each fang on either side of the jaw. The true glands are found in all viperids and elapids and are also present in some atractaspidids.
The majority of the colubrid snakes possess a different arrangement. Instead of utilizing specialized salivary glands, they use bigger glands that are referred to as the Duvernoy’s gland. The Duvernoy’s gland is located immediately under the skin, and right above and in close proximity to the angle of the jaw. There is a duct that originates from the glands to one or more enlarged posterior fangs. The Duvernoy’s glands lack a storage chamber (lumen) and the fangs are groove-less. Therefore the snake must hold onto its prey as it injects sufficient venom for envenomation.
Venomous snakes have heads that appear to be shaped like a heart due to the large venom glands that are located in them.
There are four types of teeth that are used by venomous snakes to deliver the venom to its prey or aggressor. There are those that have a groove and those that lack a groove and therefore the venom usually runs down on the surface of the teeth. The different tooth forms seem to indicate a continuous progression to perfection but do not reflect the actual morphological variations that are seen in snake families.
Snake venoms are 90 to 95% composed of proteins, which are in most cases responsible for all the effects that are caused by venom. Venom consists of both toxic and non-toxic proteins.