Lesson 112 - Reptile Basics

What are the characteristics of the class reptilia?

1. internal fertilization

2. amniotic development

3. epidermal scales

4. ectotherms

What are the four orders of reptiles?

1. squamata

2. testudines

3. crocodilia

4. rhynchocephalia

What animals are in the squamata order?

1. lizards

2. snakes

What is another name for testudines?

chelonians

What animals are in the testudines order?

1. turtles

2. tortoises

3. terrapins

4. sliders

What animals are in the crocodilia order?

1. crocodiles

2. alligators

What animals are in the rhynchocephalia order?

tuatara

What animals are ectotherms?

1. amphibians

2. fish

3. reptiles

What are characteristics of ectotherms?

1. metabolic rate is low

2. metabolism does not generate enough thermal energy to maintain stable body temperature

3. rely on thermoregulatory behaviors for body temperature

What are some physiological mechanisms of thermoregulation that reptiles do have?

1. thermal panting

2. changes in heart rate

3. changes in blood vessel diameter

What is all involved with keeping a reptile within its optimum temperature zone?

1. physiologic mechanisms

2. behavior mechanisms

3. health

How does immune response change with temperature?

lower in winter or outside POTZ

What reptiles can substantially elevate and maintain their body temperature above the environmental temperature?

1. leatherback sea turtle

2. Burmese python

How do leatherback turtles have unique thermoregulation mechanisms?

1. maintain temp up to 18 Celsius higher than surrounding water

2. through muscle activity, large body size, insulation, vascular

What is a unique thermoregulation feature of burmese pythons?

coils around its eggs and generates heat by shivering

What are some adaptations of reptiles that allow them to live in dry environments compared to amphibians?

1. keratinized skin

2. internal fertilization and amniotic eggs

3. water-efficient excretion

What are all reptiles covered in?

scales made of keratin

What determines if it is an osteoderm?

mineralisation of the dermis

What is ecdysis?

shedding of the outer keratinized layer to allow for growth

What animals have complete ecdysis?

1. snakes

2. some lizards like geckos

What animals have patchy ecdysis?

1. chelonians

2. most lizards

What do chameleons have present in their skin?

chromatophores

What helps with sexing of lizards?

femoral or prefemoral pores in males

What glands do snakes have in their skin?

cloacal scent glands

Where is water efficiently reabsorbed in reptiles?

1. colon

2. cloaca

3. urinary bladder

What can reptiles do during dehydration?

decrease glomerular activity to reduce filtrate production

What is a function of the renal portal system in reptiles?

maintains tubular perfusion to prevent damage

What determines what type of nitrogenous waste gets excreted in reptiles?

how much water they need to conserve

What nitrogenous waste do lizards excrete?

uric acid

What nitrogenous waste do snakes excrete?

uric acid

What nitrogenous waste do tortoises excrete?

uric acid and urea

What nitrogenous waste do freshwater and sea turtles excrete?

urea and ammonia

What nitrogenous wastes do crocodiles and alligators excrete?

ammonia, urea, uric acid

What is the flow of the renal portal system?

blood from the hind limbs and tail to the kidneys before returning to the heart

What is the flow of the hepatic portal system?

blood from both the GI tract and parts of the caudal body to the liver

What is the clinical importance of the hepatic portal system?

anesthetics, opioids, oxytocin, and other hepatic metabolism drugs have reduced systemic drug levels when injected into the hind limbs

What structure is near the beginning of the respiratory tract in the mouth in reptiles?

simple glottis at base of tongue

What type of tracheal rings do squamates have?

incomplete rings

What type of tracheal rings do chelonians have?

complete rings

Do reptiles have a diaphragm?

no

What cavity are the organs contained in with reptiles?

single coelemic cavity

What is unique about the act of respiration in reptiles?

1. active and conscious

2. requires striated muscle contraction

What reptile has a membrane resembling a diaphragm that aids in respiration?

crocs

Where does oxygen exchange occur mostly in with reptiles?

cranial portions of lungs in squamates

What is the function of the caudal portions of lungs in squamates?

air sacs

What are some other areas of respiration in reptiles?

1. cutaneous

2. buccopharyngeal

3. cloacal

What stimulates breathing in reptiles?

hypoxia

What suppresses ventilation in reptiles?

high oxygen levels

What are reptiles less responsive to with respiration?

elevated carbon dioxide

Where is the heart in lizards?

cranial thorax in the thoracic girdle

Where is the heart in chelonians?

caudal to the thoracic girdle

Where is the heart in snakes?

typically 1/4 to 1/3 down the body length

How many chambers do reptiles have in their heart and what are they?

1. three

2. two atria

3. one ventricle

What prevents blood mixing in the ventricle in reptiles?

1. muscular ridge

2. coordinated contractions

How many chambers do crocodilians have in their heart?

four

How do crocodilians shunt blood in their heart?

foramen of Panizza connects right and left aortas at the base of the heart

How many aortic arches do reptiles have?

two that connect caudal to the heart

What is the function of a right-to-left cardiac shunt?

diverting blood away from the lungs during periods of apnea, diving, or thermoregulation

What is the function of a left-to-right cardiac shunt?

improve oxygenation and CO2 elimination

When can snakes have an increase in heart rate?

after a large meal to support the high metabolic demands of digestion

What seals the glottis in crocs?

soft palate and gular fold

What reptiles have tail autonomy?

1. true lizards

2. geckos

3. skinks

4. young iguanas

5. some colubrids

What reptiles have prehensile tails?

chameleons

What is the scientific name for true lizards?

Lacertidae

How do we describe the orientation of lizard legs?

four legs in the same plane as the body

What is the outer structure associated with hearing in lizards?

visible tympanic membrane

How many toes do lizards have?

five on each foot

What do geckos, anoles, and chameleons have under their toes?

adhesive pads made of modified scales

What is a unique feature of chameleon toes?

zygodactyl in order to perch

What does zygodactyl mean?

toes divided into two opposed groups on each foot

What type of teeth do lizards have?

simple conical teeth that lack tooth sockets or alveoli

What is a parietal eye?

third eye with rudimentary retina and lens on top of the head in some lizards

What is the importance of lizards having a reduced hard palate?

allows airflow from the inner nasal opening to the glottis

What is important about trachea in lizards?

1. incomplete tracheal rings

2. bifurcates just cranial to the heart

What is the role of the thyroid gland in lizards and snakes?

control of ecdysis

What is important about the thymus in lizards?

remains present throughout life and has one or two lobes

What are iguana lungs like?

sac-like structures attached to bronchii

What is the color of the liver in lizards?

dark brown and heavily pigmented

What is the main bile pigment in lizards?

biliverdan

What is the difference in the pancreas with lizards compared to mammals?

alpha and beta cells are not grouped into islets

What is the function and structure of the spleen in lizards?

1. site of possible extramedullary hematopoiesis

2. spindle-shaped

3. located just off greater curvature of stomach

Where are the kidneys in iguanas?

in the pelvis

How is uric acid secreted in the kidney?

tubular secretion rather than glomerular filtration

What are hemipenes?

pair of intromittent organs in males usually held inverted at the base of the tail for reproduction

What is the structure and function of the snake tongue?

forked tongue to sense environment

What allows the jaw of snakes to open 180 degrees?

1. no mandibular symphysis

2. quadrate bone

What is the function of the facial/labial pits in snakes?

infrared receptors

What covers the eye in snakes and geckos?

spectacle

What do male snakes have the stimulate females during copulation?

pelvic spurs in boas and phythons

What is the structure of the urogenital system in snakes?

lack a urinary bladder so two ureters empty into the urodeum of the cloaca

Why would a male snakes caudal kidney be enlarged?

involved in reproduction so can become enlarged during periods of breeding

What part of the nephron do snakes not have?

loop of henle

Where are the testes in snakes?

right is more cranial than the left and both are cranial to the kidneys

What lung do some snakes not have?

left lung

What structure is present before the right atrium in snakes?

sinus venosus

Where is the heart in relation to the esophagus in snakes?

cranioventral to the end of the trachea so it can be displaced if snake eats a large meal

Where is the thymus in snakes?

thin and lies on top of the trachea

What hearing structure is seen on turtles?

visible tympanic membrane

What is the carapace?

dorsal part of the turtle shell with modified ribs and vertebrae

What are the lateral parts of a turtle shell called?

bonny bridges