Reptile Physiology

Integumentary System—Scales

• Scales formed from epidermis

  • dry, scaly, multiple layers, prevents water loss

  • number and arrangement of epidermal scales species-specific

  • snakes—size, shape of scales related to locomotion

  • squamates—continual growth, shedding

    • outer layer—stratum corneum—replaced gradually or all at once (ecdysis)

  • Turtles—shield or scutes on shells

    • scales develop separately, not a solid sheet

Integumentary System—Glands

• musk—scent

• femoral—pheromones to attract mates or mark territory

• pre-anal—reproductive hormones

• cloacal—scent marking

• nuchodorsal—near neck, defense against predators

Integumentary System—epidermal modifications

• Claws—keratinized, climbing

• Rattles—part of stratum corneum, but stays after ecdysis

• Horns—bony projections of skull covered with scaly integument or just modifications of integument

• Shell—large, bony, dermal plates

  • carapace—dorsal

  • plastron—ventral

  • lateral bridges—unite the two shell parts

• Chromatophores—cells that disperse pigment granules

  • camouflage

  • sex recognition

  • breeding

  • thermoregulation

Skeletal System

• temporal fenestrae—surface area for muscle attachment

  • turtles—anapsids, no fenestrae

  • crocodilians, snakes, and lizards—diapsids—two fenestrae

• Vertebrae

  • snakes—up to 500 vertebrae

  • precaudal—before vent with ribs

  • postcaudal—after vent without ribs

• Lizards

  • thoracic—have ribs

  • lumbar—reduced or absent ribs

• Sacrum—two fused sacral vertebrae that support the pelvic girdle, allows some to stand on 2 legs

Cardiovascular and Respiratory Systems

• 3 chambered heart—ventricles incompletely divided

• Double circulation

• only one functional lung in snakes and some lizards

• lungs located in the pleuroperitoneal cavity

• faveoli—sub-chambers of lungs

• force pump system to get air in lungs or suction/pressure

• some species absorb oxygen through pharynx, cloaca, and skin

Digestive System—oral cavity

• most have teeth, turtles have beaks

• acrodont dentition—marginal teeth attached to biting edges of jaws

• pleurodont dentition—jaw teeth are attached to the inner sides of the jawbone

• thecodont dentition—teeth rooted in sockets (crocodilians)

• snake teeth recurved

• sides of many snakes’ mandibles joined only by stretchy ligament → large prey

• Some snakes have extra folding strut that suspends the lower jaw on a hinge → even larger prey

• Most reptiles have polyphyodont dentition = constant and steady replacement of teeth

Digestive System—venomous snakes

• Proteroglyphs—rigid fangs that fit into pockets in the outer gum of the lower jaw. Eastern coral snake, venom is neurotoxin

• Solenoglyphs—highly specialized fangs that fold back into the mouth. Pit vipers, venom is hemolytic

• Venom glands—modified labial salivary glands

Digestive System—Oral cavity

• Reptilian tongue—more developed than amphibians

• Turtles—attached to floor of the oral cavity, can’t stick it out

• Snakes and some lizards—long, skinny, flexible, forked

• Flicking—chemoreceptors on tongue allow snakes to locate food or mates

Digestive System

• Esophagus

  • long esophagus to accommodate large prey

  • some have esophageal “teeth “ to cut shell

• Stomach

  • elongated in lizards and snakes

  • cecum to help digest plant matter in herbivores

  Separate compartments for intestinal and urogenital tracts, but open into common outlet=vent

Nervous System

• Cutaneous receptors—pain and heat

  • pit vipers—loreal pits—heat sensing

• Ears—equilibrium, and hearing

• Snakes—no external ear openings

• other reptiles—exposed tympanum

• eyes—nictitating membrane in turtles and some lizards

• lacrimal glands—secrete tears

• parietal eye—third eye in some lizards regulates body temperature