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Anatomical
Road Map:
Because snakes are
basically one long tube, it is possible to partition their main anatomical
parts into sections. If you lay the snake out straight on a table with its head
on your left, going from left to right, the first 25 percent of the snake
consists of the head, the esophagus and trachea, and the heart. Those are the
major organs and parts.
In the second quarter,
about 26 to 50 percent of the snake, are the top of the lungs, the liver, and
then three-fourths of the way down the liver, the stomach.
In the third quarter,
about 51 to 75 percent of the snake, you encounter the gall bladder, the spleen
and the pancreas (or the splenopancreas depending on the species). Following this
triad of organs you will find the gonads (testes or ovaries). Coursing between
these structures is the small intestine, and adjacent to them is the right lung
(and in some species the left lung, as well).
In the last quarter, the
last 76 to 100 percent of the snake, you’ll find the junction between the small
and large intestine, the cecum (if present), the kidneys (right in front of the
left) and the cloaca.
Please click image below for larger view.
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| Photo: Douglas Mader |
Outer
structure:
Most reptiles have four
legs. Snakes, however, do not have legs. They also lack a pectoral girdle
(shoulder bones) and — with the exception of the boids, which retain a
vestigial pelvis and external spurs — they also lack a pelvic girdle (rear leg
support).
Scales and Shedding / ecdysis: As with all reptiles,
snakes are covered with scales, which offer protection from desiccation and
injury. They can be smooth and shiny, such as a python’s scales, or rough and
dull, such as a hognose snake’s scales. The outer, thin layer is the epidermis,
which is shed on a regular basis. The inner, thicker, more developed layer is
the dermis. This dermal layer is filled with chromatophores, the pigment cells
that give snakes their color. Scales
are formed
largely of keratin derived from the epidermis. As the snake grows, which they
do their entire lives (growth just slows as they get older), this outer layer
of epidermis sheds off. New scales grow beneath the older outer scales.
Eventually, the outer layer sheds off, usually in one piece and inverted as if
it were a sock pulled from the top down. This shedding process is called
ecdysis. In general, if the shed
skin comes off in shards, it may be a sign of some underlying problem. The
snake’s health or husbandry issues, such as improper environmental
temperatures, humidity or caging furniture, might be to blame. Scales are attached to
each other by soft skin — generally not noticed from the outside — that folds
inward between each adjacent scale. Scales cannot stretch, but when a snake
eats a large meal, the skin folds are pulled out straight to expand the surface
area. Basically two types of
scales are on a snake. Its top and sides are generally covered by smaller
scales. These can juxtapose or overlap like shingles on a roof. The bottom of
the snake is covered by short but very wide scales that look like rungs on a
ladder. These special scales are called scutes. They form the belly of the
snake and are integral in the snake’s ability to move. Snakes have two eyes,
but they do not have eyelids. A spectacle, a transparent scale that is actually
part of the skin, protects each eye. When a snake undergoes ecdysis, it sloughs
this spectacle off along with its skin. Spectacles turn a light, semiopaque
blue as the snake prepares to shed. Herpetologists call this condition “in the
blue.” This is normal, but snakekeepers who have never seen it happen before
may mistake it for a problem. Immediately before the actual shed, spectacles
again become clear. This means that the shed is imminent.
It is imperative that
shed skin be examined every time a snake sheds to make sure these spectacles
come off. Occasionally one does not, and this results in a retained eye cap.
Like other shedding problems, a retained spectacle can be a sign of a health or
husbandry problem. In addition, if a retained spectacle is not removed, it can
cause problems with the animal’s vision and can potentially damage the eye. If you are experiencing poor or incomplete sheds; please refer to our care and maintenance section that addresses this issue. If snake has retained eye caps, please refer to the care and maintenance section that addresses this issue.
Head Features:
A
snake’s head contains the eyes, nostrils, mouth (and structures within), brain,
and a special sensory structure called the vomeronasal or Jacobson’s organ. Its
paired openings are just in front of the snake’s choana, the open slitlike structure
on the upper inside of the reptile’s mouth. All snakes have a forked tongue.
When they flick their tongue, the tips pick up minute scent particles in the
air and place them in direct contact with this organ. In essence, this is how a
snake smells.
Snakes’
teeth line the inner surfaces of the upper and lower jawbones (maxilla and
mandible, respectively). Nonvenomous snakes have four rows of upper teeth: two
rows attached to the maxillary (outer) bones, and two rows attached to the
palatine and pterygoid (inner) bones. Only two rows are on the lower jaw; one
is attached to each mandible. Most venomous snakes substitute fangs for the
maxillary teeth. These fangs can either be in the front of the mouth, such as
in a rattlesnake, or the back of the mouth, such as in a hognose snake.
Snakes
use their teeth for grasping, not chewing. Their teeth are recurved, so once a
prey item is bitten, the only direction for it to move is toward the snake’s
stomach.
Snakes have two eyes, but they do not have
eyelids. A spectacle, a transparent scale that is actually part of the skin,
protects each eye.
Snakes lack an external
ear, but they do have an internal ear, and they are capable of detecting low
frequency sounds ranging from 100 to 700 hertz. (A young person with normal
hearing can hear frequencies between approximately 20 and 20,000 hertz.) A
snake’s inner ear also allows it to detect motion, static position and sound
waves traveling through the ground.
Another external feature
found in boids and crotalids are the labial pits, a series of openings along
the upper and lower lips that contain heat-sensing organs. These pits help
snakes acquire prey, and they warn them of possible predators nearby.
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| Photo: Douglas Mader Desription: Living Art Reptiles |
Vent / Cloaca:
All
snakes have a single vent, which is an excretory opening. This vent opens on
the bottom of the snake near the tail and leads into a compound structure
called the cloaca. The picture below shows the cloaca as well as the snakes
spurs. This is an example of a healthy cloaca which directly ties into our care and maintenance page on selecting a healthy Ball Python.
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| Photo: Living Art Reptiles |
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| Photo: Living Art Reptiles |
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