Internal Organs
The anatomy of reptiles enables them to live on land. Thanks to their dry, scaly skin and their excretion of uric acid instead of urea, they minimize water loss. The heart distributes blood in a double circuit. Crocodiles were the first vertebrates to have a four-chambered heart; the separation of the ventricles is incomplete in all other reptiles. The lungs, developed beyond those of amphibians, contribute to cardiac efficiency by allowing for greater exchange of gases. •
Weight: more than 1 ton
NILE CROCODILE
Crocodylus niloticus
Diet
Carnivorous
Longevity 45 years in the wild and 80 years in captivity
SKIN
Reptiles have chromatophores that modify their color to a small degree. Two unique traits of crocodiles are that the skin on the head has glands that regulate the body's ionic balance, and the cloaca has glands that secrete substances crucial for mating and defense.
Jugular Region
Neck
PLACEMENT OF THE SCALES
Longitudinal Lines
Jugular Region
Neck
PLACEMENT OF THE SCALES
Longitudinal Lines
- The flanks and the stomach are lighter and shinier than the dorsal surface.
DORSAL AORTA
transports oxygenated blood throughout the body.
OLFACTORY BULB
LUNGS
contain air sacs called alveoli.
STOMACH
contains rocks that help break down food.
64 to 68
TEETH
ESOPHAGUS
PITUITARY GLAND
TRACHEA
TEETH
retain prey. They do not chew but cut prey into pieces, which are swallowed whole.
HEART
LIVER
MAMMAL REPTILE AMPHIBIAN
4 Chambers 3 Chambers 3 Chambers
DORSAL AORTA
transports oxygenated blood throughout the body.
OLFACTORY BULB
MESENCEPHALON
MEDULLA CEREBELLUM OBLONGATA
LUNGS
contain air sacs called alveoli.
STOMACH
contains rocks that help break down food.
64 to 68
TEETH
ESOPHAGUS
Circulatory System
Nile crocodiles have double t^t circulation. A minor circuit brings deoxygenated blood to the lungs and transports oxygenated blood from them, and a major circuit transports the oxygenated blood to the rest of the body and returns deoxygenated blood to the heart. Reptile hearts have two auricles (atria) and a single ventricle, which is partially divided by an incomplete ventricle partition.
PITUITARY GLAND
TRACHEA
THE HEART
The flow patterns inside the heart prevent the mixing of pulmonary and systemic blood.
MAMMAL REPTILE AMPHIBIAN
4 Chambers 3 Chambers 3 Chambers
MOUTH
is closed by strong muscles. The rear portion contains a membrane that prevents water from entering while the animal is diving.
TEETH
retain prey. They do not chew but cut prey into pieces, which are swallowed whole.
HEART
BLOOD CIRCULATION An ample and efficient network of blood vessels extends throughout the bodies of reptiles.
LIVER
CORAL SNAKE
Micrurus altirostris
It is characterized by its smooth and brightly colored scales.
GROWTH OF THE SCALES
Epidermis
NEW SKIN
is smooth and bright
OLD SKIN
is fragile. It rips easily.
Melanophores
A Question of Skin
The absence of extremities and the friction produced during movement give snakes the ability to slide and to shed their skin in one motion. Other reptiles must shed their skin by tearing it off in pieces. Reptiles shed their skin regularly and continue to do so even in the last years of their lives.
CORAL SNAKE
Micrurus altirostris
It is characterized by its smooth and brightly colored scales.
NEW SKIN
is smooth and bright
OLD SKIN
is fragile. It rips easily.
Melanophores
1 Osteoderms x Flexible Joint
GROWTH OF THE SCALES
Epidermis
Dermis
□ The dermal layer is found below the epidermis.
□ Differentiation takes place during dermal cell growth.
0The epidermis secretes large amounts of keratin.
The new scales overlap each other and cover the skin.
SPLEEN TESTICLES
Lobuled. Their ducts empty in the cloaca.
KIDNEYS Metanephric. The ureters empty in the cloaca.
DOUBLE CAUDAL CREST
SPLEEN TESTICLES
Lobuled. Their ducts empty in the cloaca.
KIDNEYS Metanephric. The ureters empty in the cloaca.
DOUBLE CAUDAL CREST
n EXHALING
■■ Internal organs are compressed. This, in turn, compresses the lungs and causes them to expel air.
The liver compresses the lungs.
Respiratory System
^^ is completely pulmonary. Most reptiles M^M possess a pair of functional lungs, with the exception of snakes, which have only one functional lung. Bocly-wall muscles generate the pressure differences necessary to circulate air through the airways from the nasal cavities to the pulmonary alveoli.
BREATHING
n EXHALING
■■ Internal organs are compressed. This, in turn, compresses the lungs and causes them to expel air.
INHALING
The pelvic bones rotate downward, the abdomen stretches, and the muscles cause the lungs to expand.
The liver compresses the lungs.
- expelled.
- The pressure difference causes the lungs to expand and take in air.
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