There are a variety of unique terms used to refer
to turtles and their anatomy - here's what some of
a member of the order of reptiles called Chelonia,
made up turtles.
common term for primarily terrestrial turtles.
common term for largely aquatic turtles.
group of turtles which lack the ability to pull their
heads back into their shells; they retract their
heads under their shells by turning them sideways
under the margin of their shells.
large scale like structures made up of keratin (like
fingernails) that cover the shells of turtles.
They do have nerve endings, and the turtle can detect
something touching its shell. Turtles can regenerate
damaged scutes, and on some turtles the have rings
similar to growth rings on trees and can be used to
The ventral (bottom) portion
of a turtle's shell (under the abdomen/chest).
It is made up of bony plates and covered with scutes.
In some turtles, the some of the bony plates making
up the plastron are hinged.
The dorsal (top) portion of
the turtle shell (over the back). The carapace
is also made up of bony plates, that are fused to
the ribcage and backbone of the turtle. The
seams of the bony plates do not necessarily coincide
with the seams between scutes.
common opening of the digestive,
urinary and reproductive tracts.
turtles share a physical feature with all other turtles
and tortoises; they have a shell that protects their
soft organs. Box turtles can also retract their head
and limbs into their shells and close the shell for
added protection. There are two parts to the shell.
The top part of the shell, or the carapace, is a dome
made from the actual back bones and ribs, which have
expanded and fused together. The shoulders and pelvic
bones are within the ribcage instead of outside it,
as is the case with humans and other animals with
arms and legs. The lower part of the shell is called
the plastron and connects to the carapace on both
sides by the bridge. The plastron has a hinge that
divides the bottom shell into two halves which can
be drawn up to the carapace and close the shell up
like a box. Hatchling box turtles do not have a hinge,
but develop one after a year or two.
bony part of the shell is covered with a thin layer
of keratin. The keratin layer is divided into segments
called scutes. These scutes and the underlying bones
grow incrementally, thus allowing the box turtle to
expand and get larger. Turtles have had over 200,000,000
years to evolve this body type and itís obviously
served them well. Turtles have outlived the dinosaurs
and many other prehistoric creatures to become one
of the oldest living families in the animal kingdom.
are several differences between turtle internal organs
and what we are used to in mammals. For one thing,
they have a three-chambered heart instead of four-chambered
heart. Consequently, oxygenated blood from the lungs
and veinous blood are in the heart chamber at the
same time. However, a partial wall in the heart called
an incomplete septum helps to keep the blood apart.
Also, there is a pressure difference between the two
blood types and little mixing occurs.
location of internal organs are also different. The
lungs, for example, are situated right under the bony
shell and above all the other organs. Muscles in the
abdomen push the other organs against the lungs and
move them in and out like bellows.
turtle brain has highly developed sight and smell
centers, so we know turtles depend on them greatly.
In fact, a turtle who has lost its sight or cannot
smell due to pneumonia will not eat. These turtles
may need force-feeding if their recuperation takes
too long. The turtle brain can also withstand longer
periods of oxygen depletion than mammal brains. For
this reason never assume a box turtle that has been
submerged in water to be dead. Try to resuscitate
it by pumping its back legs in and out while it is
lying on its plastron with its head pointed slightly
downwards. The legs are used to push against the lungs
and expel water.
Oxygen is needed for metabolism, during which harmful
carbon dioxide is produced. It is the job of the respiratory
system to take in oxygen and dispose of carbon dioxide.
Turtles have lungs and must breathe oxygen from the
air. Even sea turtles, which are the most aquatic
reptiles, must surface from time to time to get air.
Marine turtles also inflate their lungs to keep themselves
afloat when basking. Some turtles, such as softshell
turtles, snapping turtles, and maybe marine turtles,
can exchange gases through areas of their skin, cloaca,
and throat. The amount of oxygen obtained is slight,
but is enough to keep them alive during times of low
oxygen need (such as hibernation).
inside the skull where food, water, and air enter.
opening behind the tongue. It connects the pharynx
and larynx. It closes when the turtle is underwater
upper end of the respiratory duct. It is connected
to the glottis and leads into the trachea.
trachea is a long hollow tube between the lungs and
the larynx. Halfway down, it divides into two tubes,
called bronchii (singular: bronchus). One bronchus
enters the left lung, the other the right lung.
and Left Lungs
reddish, spongy organs lying underneath the carapace.
Air passes from the bronchii into smaller tubes in
the lungs called bronchioles. The bronchioles get
progressively smaller until they end into a small
cluster of air sacs. These air sacs, known as alveoli
(singular: alveolus), located at the end of the bronchioles
are where gases are exchanged. Oxygen from the air
disolves into the blood, while carbon dioxide diffuses
out of the blood into the air.