ANATOMY - Reptiles Flashcards
Which central structure regulates temperature in ectotherms?
Hypothalamus
What is the preferred optimal temperature zone (POTZ) for most reptiles?
20 - 38°C
What is the main advantage of being ectothermic?
Lower energy requirements
What is the main disadvantage of being ectothermic?
Activity dependent on ambient temperature
Which species’ does chelonian refer to?
Tortoises
Turtles
What is the chelonian shell made up of?
The chelonian shell is made up of dermal bone
Which four anatomical features is the dermal bone of the chelonian shell fused to?
Spine
Ribcage
Pelvic girdle
Pectoral girdle
What is the name for the top of the chelonian shell?
Carapace
What is the name for the bottom of the chelonian shell?
Plastron
What is the name of the external plates on the chelonian shell?
Scutes
Name the carapace scutes
Name the plastron scutes
What is autotomy?
Autotomy is the self-amputation of the tail of a lizard when they feel as if they are under threat
Which breed of lizard doesn’t grow their tail back following autotomy?
Crested gecko
Which breed of lizard does grow their tail back following autotomy?
Leopard gecko
Why can undergoing autotomy cause further health issues in leopard geckos that are already ill?
Leopard geckos use their tails as a fat store
Why do reptiles only have a single body cavity?
Reptiles only have a single body cavity as they do not have a diaphragm
What is the name of the single body cavity present in reptiles?
Coelomic cavity
What are the three chambers of the reptilian heart?
Left atrium
Right atrium
Ventricle
What are the three functional divisions of the reptilian ventricle?
Cavum arteriosum
Cavum venosum
Cavum pulmonale
What is the function of the cavum arteriosum?
Cavum arteriosum receives oxygenated blood from the left atrium
What is the function of the cavum venosum?
Cavum venosum receives deoxygenated blood from the right atrium
What is the function of the cavum pulmonale?
Cavum pulmonale receives deoxygenated blood from the right atrium via the cavum venosum and directs the flow into the pulmonary circulation
Describe the flow of deoxygenated blood during normal reptilian respiration
Deoxygenated blood flows from the systemic circulation via the hepatic vein, left and right precaval veins and post caval vein into the sinus venosus. Blood flows from the sinus venosus into the right atrium, to the cavum venosum, to the cavum pulmonale, to the pulmonary trunk and into the lungs
Describe the flow of oxygenated blood during normal reptilian respiration
Oxygenated blood flows from the pulmonary veins to the left atrium, to the cavum arteriosum, to the cavum venosum and to the left and right aorta. The blood that flows into the left aorta flows directly into the systemic circulation and the blood that flows into the right aorta is transported to the central nervous system followed by the systemic circulation
What is reptile apnoea?
Reptile apnoea is the suspension of breathing through removing their pulmonary circulation from general circulation
How do reptiles cut off their pulmonary circulation from general circulation during apnoea?
When reptiles enter apnoea, their parasympathetic tone increases causing vasoconstriction of the pulmonary trunk. This leads to increased blood pressure within the cavum pulmonale causing the blood to be pushed back into the cavum venosum and shunted into the left aorta and the systemic circulation - essentially cutting off their pulmonary circulation
How should reptiles be anaesthetised?
Reptiles cannot undergo gaseous induction as they will enter apnoea so intravascular or intramuscular induction should be carried out instead. Once the animal is under general anaesthesia, they can be maintained using gaseous anaesthetic as their parasympathetic tone will be lost and they can no longer enter apnoea
How does the renal portal system maintain renal tubular function in reptiles?
The renal portal system transports blood from the hindlimbs and the tail directly to the kidneys before the systemic circulation
Why should you only inject the cranial half of the body in reptiles?
Injecting drugs at the caudal end of the body can cause drugs with renal excretion or nephrotoxic drugs to have a direct effect on the kidneys due to the renal portal system and thus only cranial injections should be carried out in reptiles
What is the structure of reptile erythrocytes?
Reptiles have large, nucleated erythrocytes
What are the two reasons for using heparin tubes for blood sampling reptiles?
- EDTA tubes cause haemolysis in some species
- Heparin can be used for haematology and biochemistry, reducing the volume of blood required for a full profile
What are the two preferred venepuncture sites for chelonians?
Jugular vein
Subcarapacial sinus
What are the two preferred venepuncture sites for lizards?
Jugular vein
Ventral tail vein
What is the preferred venepuncture site for snakes?
Ventral tail vein
What are the two anatomical features that make reptiles so prone to respiratory infections?
Lack of diaphragm and thus no coughing reflex
Primitive mucociliary lining of the respiratory tract
Which structure separates the lungs from the rest of the coelomic cavity in chelonians (tortoises)?
Horizontal septum
How is respiration achieved in chelonians (tortoises)?
Tortoises cannot expand their body wall when breathing due to the rigidity of their shell so respiration is achieved through muscular movement of the limbs
What are the most important muscles used in chelonian (tortoise) respiration?
Pectoral muscles
What is the main indicator that a chelonian (tortoise) is dyspnoeic (unable to breathe)?
Dyspnoeic tortoises will move their head around as well as their limbs
Why does open mouth breathing in a chelonian (tortoise) indicate a respiratory problem?
Chelonians are obligate nasal breathers so open mouth breathing indicates they are not achieving adequate gaseous exchange
In most breeds of snake, which lung is functional and which lung is absent/rudimentary?
In most snakes, the right lung is functional and the left lung is absent/rudimentary
What are the three respiratory phases seen in snakes?
Inspiratory phase
Expiratory phase
Breath hold phase
How long can the breath hold phase last in snakes?
30 minutes to 33 hours depending on the species
In snakes, what is the function of the cranial portion of the lung?
The cranial portion of the lung is vascularised and undergoes gas exchange
In snakes, what is the function of the caudal portion of the lung?
The caudal portion of the lung is avascular and functions as an air-sac/reserve
What is the cloaca?
The cloaca is the point of exit for the digestive, urinary and reproductive systems in reptiles
What are the three structural divisions of the cloaca?
Coprodeum
Urodeum
Proctodeum
What is the function of the coproduem?
The coproduem is the chamber of the cloaca that collects faeces
What is the function of the urodeum?
The urodeum is the chamber of the cloaca that collects urinary waste and connects to the reproductive tract
What is the function of the proctodeum?
The proctodeum is the final chamber of the cloaca that acts as a collecting area prior to elimination
What is present in the herbivorous lizard gastrointestinal tract that is not present in lizards with other dietary requirements?
Caecum
Where are the venom glands located in some breeds of snake?
Venom glands are modified labial glands located in the upper jaw just below the orbit
Which important process is regulated by the thyroid gland in snake?
The thyroid gland regulates metabolism and ecdysis
Which five major physiological changes occur when a snake ingests a prey item?
Metabolic rate increases 40x the normal rate
Heart size increases by 40%
Liver size increases by 50%
Pancreas size increases by 94%
Gastrointestinal tract and kidney size increase by 72%
How long does it take a snake to fully digest a meal?
4 - 5 days
Which anatomical and physiological changes occur in snakes between meals?
The gastrointestinal tract shuts down and stomach distends to encourage basking to increase their metabolic rate
Why can’t reptiles produce hypertonic urine?
Reptiles cannot produce hypertonic urine as their kidneys do not have a loop of Henle
Describe the structure of a chelonian (tortoise) urinary system
Chelonians have wide, flat and lobulated kidneys and a large urinary bladder
Describe the structure of a lizard urinary system
Lizards have semi-lobulated and semi-elongated kidneys and sometimes have a urinary bladder (depending on the breed)
Describe the structure of a snake urinary system
Snakes have lobulated and elongated kidneys with no urinary bladder
In what form do snakes secrete their urinary waste?
Uric acid
What are the two methods of gestation seen in reptiles?
Oviparity
Viviparity
What is oviparity?
Oviparity is the laying of eggs soon after fertilisation
What is viviparity?
Viviparity is development of the embryo inside the body of the mother
What is the only source of nutrients the developing embryo receives within oviparous species?
The only source of nutrients the developing embryo receives is the yolk sac within the egg
How many clutches per breeding season does oviparity allow for?
2 -3 clutches per breeding season
List four oviparous reptile species
Chelonians
Pythons
Iguanas
Geckos
How long does the gestation period last for viviparous reptiles?
Gestation can last between 6 weeks and 6 months in viviparous reptiles
How many clutches per breeding season does viviparity allow for?
1 clutch per breeding season
What is a common complication associated with viviparity in reptiles?
The developing young compress the maternal gastrointestinal system resulting in a reduced capacity for food and thus a reduced body condition
List two viviparous reptile species
Boas
Chameleons
What are the three functions of the reptilian egg shell?
Gas exchange
Water resistance
Calcium source
Why is the source of calcium within the egg shell so important for developing chelonian embryos?
Chelonian embryos use 80% of the egg shell calcium to develop their own shell
What are the three foetal membranes present in reptilian eggs?
Amnion
Allantois
Chorion
Where are the testes located within the body of male reptiles?
In male reptiles, the right testis is located close to the vena cava, the left testis is located near the left adrenal gland and both are cranial to the kidneys
What are the male copulatory organs found in lizards and snakes?
Male lizards and snakes have paired extracloacal hemipenes
What is the male copulatory organ found in chelonians?
Male chelonians have a single intracloacal phallus
Which substances are secreted by the oviducts in female reptiles and why?
Albumin, protein and calcium and secreted by the oviducts for the formation of eggshells
What are the three reptilian ovarian cycles?
Quiescent
Vitelligenic
Gravidity
Which three anatomical and physiological changes occur during the vitelligenic ovarian cycle?
Hypertrophy of ovaries and oviducts
Transport of yolk sac from liver to ovarian follicles
Increases circulatory calcium levels
What happens during the gravidity ovarian cycle?
Fertilised eggs/embryos are present in the oviducts
What forms the outer margin of the ear in most reptiles?
Tympanic membrane
Which two species of reptile do not have a tympanic membrane?
Snakes
Chameleons
What is the name of the single middle ear bone present in reptiles?
Columella
What are the functions of the Jacobson’s organ in reptiles?
Detection of odour particles and pheromones
Which nerve innervates the Jacobson’s organ in reptiles?
Vomeronasal nerve
What is the purpose of the infrared receptors (heat pits) present on the upper jaw of boas and pythons?
The infrared receptors present on the upper jaw of boas and pythons is to detect warm-blooded prey and strike with precision even in the dark
Identify the following anatomical structures of this lizard coelomic cavity
Evaluate this lizard anatomy
Identify the following anatomical structures of this snake coelomic cavity
Identify the following anatomical structures of this snake coelomic cavity
Evalualte this chelonian anatomy
Evaluate this chelonian anatomy
Identify the following anatomical structures of this sagittal section of this tortoise coelomic cavity
Identify the following anatomical structures of this transverse section of this tortoise coelomic cavity
