Snakes, however, play important environmental roles in the fragile ecosystems and can play a very important role in agriculture. They control the population of harmful rodents and pests, thus helping people. Though sometimes dangerous, snakes can be useful, and, as any living creature, they have the right to exist.

Anatomy of Snake

Although snakes are characterized by having neither limbs nor eyelids, several lizards share one of these characteristics, and the origin of snakes lies with lizards. As efficient hunters, prey are located by sight, as well as via chemical cues, which are collected with the aid of their bifid tongues and carried forward to a special sensory organ, located in the roof of the mouth, called Jacobson's organ. Pit vipers and pythons, in addition to this oral organ, have thermal receptors on or near their lips, which permit them to detect the body heat of warm blooded prey in darkness. more info soon... Snakes are ectothermic: which means they get their body heat from external sources. Must avoid extremes in temperatures and hunt preferably during mild conditions.

Life Span: The age to which snakes can survive under wild conditions is virtually unknown. In captivity, their natural life-span are probably exceeded in many cases, given the fact that they are protected against diseases, parasites and predators, and that they have access to a more predictable food supply. Most colubrid species, such as king-snakes and rat-snakes, will live for twelve to fifteen years or more in captivity, and breed right up until the end of their lives. Species with a more active lifestyle probably fall slightly short of these ages.

Sense Organs: The sense organs of snakes are uniquely different than those of mammals and other animals. Unlike mammals, snakes rely primarily on their senses of smell and touch. They do not have moveable eyelids, but transparent caps called "brille" as protective eye coverings. Their eye movement is fairly limited. They also do not have an external ear. Instead, they use a small ossicle (ear bone), called the "columella," to detect vibrations of sound waves conducted through the ground. They are able to pick up some sound waves conducted through the air, but only at very low frequencies. Snakes also smell in a very different way than mammals. Snakes have both nostrils and nasal cavities, but they are not used to smell. Instead, the flicking tongue is actually a smelling device. A small organ on the roof of the oral cavity called the "vomeronasal organ", or "Jacobson's organ." The forked tongue is used to carries scent particles this organ, and the snake then perceives and identifies the smell as prey, predator, or otherwise. So, unlike mammals, the tongue is not used to taste or aid in swallowing, but simply as an accessory smelling organ. In fact, while prey is being swallowed, the tongue is flickering continuously, which is in a sheath like covering.

Some snakes also have a "sixth sense" that mammals and even other reptiles cannot boast. Vipers, rattlesnakes, and other members of the family of snakes known as the 'pit vipers' have special pits located between their eyes and nostrils. Th e pits are used to sense minute temperature changes, as an aid in locating warm-blooded prey such as rodents. This system is so accurate that pit vipers are actually able to detect temperature changes as little as 0.002° Celsius.

Integument: Snakes, like all reptiles, are covered in scales that protect them from abrasion or dehydration. The scales on the top and sides of the snake are smaller and thinner than those found on the belly side. The thick, large scales on the belly are called "scutes," and they help to protect and support the tissues that are in contact with the ground. The scales can be very colorful and organized into interesting patterns.

Though snakes are often described as being "slimy," their skin is actually very dry, In fact, they only have two skin glands -- a pair of anal scent glands that secrete a substance used to attract a mate, provide protection from predators, and mark territory. Unlike other animals, snakes continue to grow until the day they die. Consequently, snakes periodically shed their skin in a process called "ecdysis." Before shedding the skin, the snake takes on a slightly bluish hue and the eyes appear cloudy. This is caused by fluid located between the layers of skin.

The skin is normally shed all in one piece, including the brille. The exception is if the snake has a rattle. The rattle is retained as the snake grows, and a new segment is added each growth period. It is often falsely assumed that the number of rattle segments can indicate the age of the snake, like rings on a tree trunk. This is not accurate, because snakes often shed more than once a year. Young, rapidly growing snakes may even shed as much as once every two months. Also, as a rattlesnake ages, it may lose some of the posterior segments of the rattle. It is not therefore, accurate to judge the age of a snake by the number of segments of its rattle.

How Snakes Move : Musculature and Locomotion

The muscles of the snake are utilized both to move ingested prey internally and for general body movement, or locomotion. There are four basic types of locomotion in snakes:

Serpentine or lateral progression: This form of locomotion is the undulating crawl, commonly called 'slithering,' and the most common form of movement amongst snakes. It allows the snake to reach maximum speeds and is employed by all water snakes to swim.

Rectilinear or Caterpillar Movement: Large and heavy snakes use the caterpillar movement or "inchworm", keeping their bodies in a fairly straight position while successive groups of belly scales are erected, angled forward, then pressed back against the ground. This functions as a lever to move the snake smoothly along. Large size boas, pythons, and vipers use this type of movement because their weight gives them a better grip on the ground.

Sidewinding: Snakes that live in hot deserts on loose sand use this type of adaptive locomotion, hurling their bodies in a sideways looping motion, called "sidewinding." Basically, to achieve the least body contact with hot ground at one point of time. So, the main thrust is sideways rather than backwards. Only three parts of a sidewinder's body are in contact with the ground at any one time. This prevents the snake's belly from resting on the desert sand long enough to become painfully hot. Sidewinding snakes will leave an "S" trail in the sand. photo

Concertina: Some snakes apply the concertina technique when climbing trees. The body bunches up forming horizontal loops and then the head moves forward and the body straightens, similar to an accordion or spring. A "concertina" movement is also used in narrow tunnels, vertical pipes in buildings or burrows. In this movement the snake wedges his coils against the sides of the tunnel and extends the rest of his body.

A snake's flexibility depends upon its many muscles. These are long chains of muscles along the vertebrae, connecting the vertebra, from rib to rib, and from rib to vertebrae. Their skin muscles allow the ribs to pull scales forward and backward, which help the snake to move. Snakes are incapable of significantly lengthening and shortening their total body length because they do not have a hydrostatic skeleton. They get the same effect by throwing their bodies into coils. The wider the coils, the faster they move.

Common Krait

Saw Scaled Viper side winding on sand dune

Skeleton and Teeth: Snake skeleton is not very complex because it does not have any appendages (limbs). A few species, such as boas and pythons, retain some vestigial structures similar to pelvic bones. In some species, these can be seen externally and are called "spurs." All other snakes simply have vertebrae, ribs, and a skull. Snakes can have between 130-500 vertebrae, with ribs attached to each one. This does not include the bones in the tail section.

Adaptations in the skull allow snakes to eat prey much larger than themselves. The bones are connected by elastic ligaments, allowing a lot of stretch and the joint of the upper and lower jaws is placed very posterior (far back) in the skull, allowing the mouth to open as wide as possible. Also, the bones of the lower jaw are not fused together at the front, which means, which can move laterally when the snake is swallowing its prey. In addition, a snake has an additional loosely-attached bone called a "quadrate" on each side. This provides a "double hinge" at the joint and as a snake swallows, it alternately moves the jaws on each side of the face and "walks" over the prey into its mouth. Also, the backwards curve of the teeth helps the snake to swallow prey, as these act as hooks to prevent live prey from escaping free. Snake teeth are both acrodont (attached to the bone) and polyphydont (able to grow back when lost), and a snake may have several sets of teeth throughout its lifetime. This is necessary, because teeth are often lost while feeding. The type of teeth a snake has differs depending on the method used to capture and kill prey. There are three kinds of snake dentition:

Constrictor dentition: Most snakes have two rows of teeth on each upper jaw and one row on each lower jaw. All of the teeth are short and hook-like. All non-poisonous snakes have constrictor dentition, regardless of whether or not they actually constrict their prey. Poisonous snakes have either grooved fangs or hollow fangs.

Groove fanged: Venomous snakes have only one row of teeth on each upper jaw, plus a pair of fangs. The fang has a groove that serves as a path for the venom to flow into the prey through the puncture.

Hollow fangs: The teeth of the hollow-fanged snakes serve the same purpose as grooved fangs, but the fangs are more like a hypodermic needle through which the venom flows and fangs can be either erectile or fixed. The erectile teeth are retracted into a groove on the roof of the mouth and extend when the mouth opens to strike, but fixed fangs are always extended.

Single Fang, red shows venom flow

Snake Skeleton

Fangs and venom gland, red shows venom flow

Respiratory System:The respiratory system of snakes includes the trachea (windpipe), bronchi, lungs, and air sac. The anterior portion of the lungs is vascular (with blood vessels) and functions in gas exchange, but the second half of the lung is an avascular (without blood vessels) air sac that extends into the tail region. The air sac performs a hydrostatic function in most snakes, regulating pressure inside the body cavity. Because snakes do not have a diaphragm, air enters and leaves the lung due to action of the body muscles and movement of the ribs.

Digestive System: The digestive system is composed of the esophagus, stomach, small intestine, colon, and glands. In snakes, the esophagus has very little muscle and food is moved to the stomach more by movement of the entire body. The junction between the esophagus and the stomach is not well defined, and the stomach itself is not very advanced. The small intestine is relatively simple. There may be a few loops or folds, but for the most part it is a long tube that receives food from the stomach, absorbs nutrients from it, and transports it to the colon, or large intestine. The colon then carries the fecal matter to the cloacal opening where it is disposed. The cloaca is a common chamber, receiving products from the digestive, urinary, and reproductive systems.

The liver is the largest internal organ in a snake, filling the space between the heart and stomach. One of the many functions of the liver is to produce bile, a digestive enzyme. The gall bladder and spleen are found near the posterior tip of the liver. The gall bladder stores bile produced by the liver and releases it into the small intestine when needed. The pancreas also secretes digestive enzymes into the small intestine, as well as producing hormones that regulate blood sugar.

Cardiovascular System: Two atria and one ventricle make up the three-chambered heart of a snake. The right and left atria receive blood from the lungs and body, respectively, and pass it to the ventricle to be circulated again. Encased in a sac, called the "pericardium," the heart is located at the bifurcation of the bronchi. The heart is able to move around, however, due to the lack of a diaphragm. This adjustment protects the heart from potential damage when large ingested prey is passed through the esophagus. The spleen is attached to the gall bladder and pancreas and functions to filter the blood and recycle old red blood cells. The thymus gland is located in fatty tissue above the heart and is responsible for the maturation of special immune cells in the blood.

Endocrine System: The endocrine system is made up of glands that secrete hormones essential to normal body function. Snakes have the same endocrine glands as mammals. A few examples are the thyroid, parathyroid, and adrenal glands. The thyroid gland located in the throat area is responsible for proper growth and development, such as normal shedding of the skin. The parathyroid is a paired structure located near the thyroid and helps in the metabolism of calcium. The two adrenal glands are located in the tail region, suspended in a mesentery (membrane sheet attaching organs to the body wall) near the reproductive organs. They secrete the hormone epinephrine (adrenaline) that increases heart and respiratory rates when the animal is in a dangerous situation.

Genitourinary System: The kidneys are the organs responsible for urinary output. In the snake, the kidneys are elongated, and the right kidney is situated closer to the head than the left. These organs filter the blood and remove waste products, which are then concentrated and transported, via the ureters, to the cloaca. The ureters are hollow tubes for transporting urine. In mammals, the ureters empty into the urinary bladder where the urine is stored and later expelled through another tube called the "urethra." Because snakes do not have a urinary bladder, the urine is not stored, and the ureters empty directly in the cloaca.

The paired gonads, testes in the male and ovaries in the female, are situated in a similar fashion, with the right being closer to the head than the left. They are also located closer to the head than the kidneys. In the female, the ovaries are near the oviducts, which carry eggs to the uterus before they enter the cloaca. Some snakes are oviparous (egg-laying) and some are viviparous (having live birth). In mammals, males have two ducts associated with each teste -- the epididymis and ductus deferens. Snakes lack epidiymides and the sperm are simply transported from the teste through the ductus deferens to the cloaca. The male also has organs called "hemipenes" that are located posterior to the cloacal opening. The hemipenes are paired copulatory organs, and they are both fully functional, though only one at a time is used to transfer sperm to the female. The hemipenes are closely associated with the scent glands, or musk glands, which are also present in the female.