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Reptile Anatomy

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What are the four orders of the class Reptilia?
- Chelonia
- Crocodilia
- Sphenodonta
- Squamata
What does the order 'Chelonia' include?
Tortoises and turtles
What does the order 'Crocodilia' include?
Caimans, crocodiles, alligators
What does the order 'Sphenodonta' include?
Tuataras

Considered to be the most primitive and endemic to New Zealand. The two species of tuatara, Sphenodon punctatus (common) and S. guntheri (Brothers Island), are the only surviving members of their order, which flourished around 200 million years ago.
What does the order 'Squamata' include?
Amphisbaenians (worm-like lizards), lizards, and snakes
Reptiles evolved from fish 250 million years ago. True or false?
False.

Reptiles evolved from amphibians 250 million years ago.
All reptiles are ectothermic. Define ectothermic
Derive heat from the environment
Which reptiles are mainly carnivorous?
Snakes

Lizards and chelonians have a more varied diet.
UV light and photoperiods are important for reptile health and reproductivity, but what is a common reason for UV lights being detrimental when it comes to husbandry?
Burns
As well as a hepatic portal system (second capillary bed), what other portal system do reptiles have?
Renal portal system (drains hindlimb and/or tail)

As venous return from the hindlimb goes straight to the kidney tubules via the renal portal system, injecting drugs in the caudal half of the body could theoretically result in lower serum concentrations. This could lead to underdosing and also renal toxicity from nephrotoxic drugs.

Fish and birds also have a renal portal system.
Reptiles do not have diaphragms, true or false?
True
Reptiles and snakes have a kinetic skull, but chelonians don't. True or false?
False

All reptiles have a kinetic skull (cranial kinesis), like fish and birds. Unlike mammals that can only move their bottom jaw, they are also able to move their maxillary jaw/beak => wider gape.

A large part of the reptile skull fails to ossify and elastic cartilage allows for movement between different regions of the skull. Consequently, reptiles are able to raise their upper jaw like a hinge to increase gape during feeding. The quadrate bone that articulates between the upper and lower jaw can also move freely.
What allows a greater degree of movement of the head relative to the neck in reptiles?
Only one occipital condyle, which articulates with the axis.

(Same as birds).
Which order have a well developed third/parietal eye?
Tuatara

It is located midline between the two proper eyes. It doesn't form images but it is sensitive to changes in light and dark (photosensitive).

Less well developed parietal eyes are also found in lizards, frogs and lampreys, as well as some species of fish, such as tuna and pelagic sharks.
What is the third/parietal eye of the tuatara also known as?
Pineal eye

It connects to the pineal gland and has a role in circadian rhythms.
Which layer of integument are reptiles scales located?
Epidermis

(Fish - dermis)
How many chambers do reptiles hearts have?
3

Two atria and one common ventricle.
Where do the distal ends of the ribs attach in the snake?
Via muscles to the inside surface of the integument.

They don't have a sternum. Allows expansion.
How many species of snake are there?
~ 2500

However, veterinary data is available on only a few.
What is the suborder for snakes?
Serpentes
How many families are found in the suborder 'serpentes'?
11

The 2 most diverse families are colubrids and boids.

Colubrids form about 75% of the 2500 species of snake, they are generally non-venemous, except the Boomslang.

Boids includes pythons and boa constrictors (the constrictor snakes).
Do some species of snakes have limbs?
No, snakes are limbless!

Snakes don't have a pectoral limb girdle but some, particularly in the boid family, have pelvic spurs, which are external remnants of the pelvic girdle.
Do snakes have an external ear?
No

Snakes have no external evidence of an ear. There is no tympanic membrane or middle ear cavity either. The columella, an ossicle, extends from the inner ear to the quadrate bone and may detect vibrations from the ground through the jaw.
Do all snakes lay eggs?
Not all snakes lay eggs (oviparous), some also have live young (viviparous).
The scales of a snake are formed by thickened parts of epidermis between which are foldings of thin skin, what does this allow for?
Allows great expansion when consuming prey

The scales are different to fish where they can easily be scraped off, snakes scales are an integral part of the skin (snakes = epidermis, fish = dermis).
What do snakes eyelids fuse to form?
Transparent spectacle or brille

It is continuous with the epidermis and protects the cornea. It is shed with the other scales during ecdysis.

Birds, tortoises and most lizards have eyelids.
Why does the skin and spectacle develop a blue appearance prior to ecdysis?
Lymph fluid builds up between the old and new epidermal layers, causing the markings to become obscure and giving a blue appearance to the skin and spectacle (remember the spectacle, eye covering, is continuous with the epidermis).

Snakes cannot see clearly around this time so may become more irritable than usual. Just before the shed takes place the spectacle clears and the skin cir- culation then becomes engorged, stretching the old skin and causing it to split.
In snakes, what are scales located ventrally and cranial to the vent called?
Gastropeges

They are single, wide scales. Unique to snakes they support the underside and aid in locomotion.
In snakes, what are scales located ventrally and caudal to the vent called?
Subcaudal scales

They are paired.
What is the process of shedding the skin known as?
Ecdysis

Snakes shed their
Do snakes shed their skin piecemeal or in one piece?
One piece

Snakes normally shed their complete skin, 2-4 times per year.

Each time a Rattlesnake sheds its skin, a new rattle segment is added. However, since Rattlesnakes may shed their skins several times a year depending on food supply and growth rates and since the rattle can and does break, there is little truth to the claim that one can tell a rattlesnakes age from the number of beads in its rattle.
Which suborder of reptiles do not have a mandibular symphysis?
Serpentes (snakes)

Instead they have an elastic ligament that allows for a wide gape in order to eat large prey.

Each half of the skull works separately and this independence allows the snake to literally walk its jaw along large prey. The left half of the upper and lower jaw can be moved and then clamped allowing the right side to advance forwards. Snakes often yawn after a meal to allow their jawbones to reposition themselves.
How is the braincase of snakes adapted to suit their lifestyle?
The braincase is heavily ossified to protect it from protesting prey.
Which bones allow snakes to 'hear' vibrations?
Quadrate and columella

Snakes have no external aural structures, no tympanic membrane, and only a narrow tympanic cavity. The columella (stapes) is directly attached to the quadrate bone and the inner ear appears to be well developed and sensitive to ground vibrations. Snakes hear by literally having "an ear to the ground". They pick up sensitive vibrations via the quadrate bone (which acts like an eardrum) and direct them to the inner ear and brain.
How many rows of teeth do most snakes seen in veterinary practice have?
6

One row on each lower jaw (mandible) and two rows on each upper jaw (maxilla).
Why are snakes teeth retrograde?
Help prevent the escape of prey
Do snakes have acrodont, pleurodont or thecodont?
Pleurodont

Snakes have a rudimentary socket and teeth are attached to the medial side of the jaw.

Lizards - acrodont and pleurodont
Crocodiles - thecodont
Why do snakes and lizards regularly shed and replace their teeth?
Due to their eating habits and simple structure means frequent replacement is necessary to keep them sharp.
Do reptiles have molars and incisors?
No
What are the modified teeth in venomous snakes known as?
Fangs
What are the classifications for snake dentition?
- Aglyph
- Opisthoglyph (o-pis-tho-glyph)
- Proteroglyph (pro-ter-o-glyph)
- Solenoglyph (sol-en-o-glyph)
Do aglyphous snakes have fangs?
No

"Aglyph" means "without a grooved channel". These snakes have no fangs with the characteristic groove necessary to transport venom.

Teeth are homodont and they are mostly non-venomous.
Where are the fangs located in opisthoglyphous snakes?
Rear-fanged

Opisthoglyphous snakes are found in family Colubridae. Fangs are grooved for the venom to trickle down. Venom is weak except the Boomslang and Twig snake. The main aim of the venom is actually to incapacitate the prey so that it cannot damage the mouth while being eaten.
Where are the fangs located in proteroglyphous snakes?
Front fangs

Hollow fangs and highly venomous. Includes spitting cobras. Fangs remain erect and cannot fold.
Where are the fangs located in Solenoglyphous snakes?
Front fangs

Each maxilla is reduced to a nub supporting a single hollow fang tooth. They are so long that when the mouth is closed the fangs lie folded backwards in a sheath along the roof of the mouth. This form of dentition is unique to vipers.
In snakes, which vertebrae have ribs?
There are about 400 pre-cloacal vertebrae and all but the first 2 have ribs.

Post-cloacal vertebrae do not have ribs.
Which reptiles don't have a sternum?
- Snakes

Each rib pair attaches by muscles to the inner surface of the ventral scales, which allows for great expansion.

- Chelonians
What happens to the snakes glottis during feeding?
It is laterally extended to allow breathing

The glottis (entrance to airway) is easy to visualise and very mobile.
In the snake, when the mouth is shut what does the glottis sit against?
Internal nares (choanae)
Do snakes have good or poor vision?
Poor

They rely more on olfaction.
Apart from the usual olfactory epithelium in the nostrils, what else do snakes possess to help with olfaction?
Highly developed vomeronasal organ of Jacobsen

This is a pair of domed cavities or vomeronasal pits lined with sensitive epithelium. The forked tongue is flicked out through a groove in the mouth called the lingual notch or fossa where it picks up scent particles from its surroundings. It then inserts the fork in the vomeronasal pits and sends information via the olfactory nerves to the brain.
In snakes, which side, right or left, are the organs cranial and larger?
Right

Can also be missing completely from the left. Elongation has led to asymmetrical viscera.
What three regions can a snake be divided into?
- Cranial third
- Middle third
- Caudal third
In the snake, what organs can be found in the cranial third?
- Trachea
- Thyroid gland
- Heart
- Oesophagus (extends into middle third)
- Lung (extends into middle third)
- Liver (mainly middle third)
In snakes, where does they thyroid gland lie in relation to the heart?
Cranial
What shape are the tracheal cartilages in snakes?
'C'-shaped

They extend into the entrance of the lung.
In the snake, does the trachea pass dorsally or ventrally to the heart?
Dorsally

The trachea is easily identified by the cartilaginous rings.
Are snakes lungs short or elongated?
Elongated
In snakes, where does the heart lie in relation to the tracheal bifurcation?
Cranioventral

The heart is not fixed in position and is very mobile, which is advantageous for when eating large prey.
Why is blood shunting/diving reflex important in reptiles?
- Bypass the evaporative process of the lungs completely and shunt blood systemically to avoid cooling.

- Bypass the lungs during periods of oxygen starvation (e.g., when turtles dive or snakes swallow large prey).

The 3-chambered heart with two atria and one common ventricle allows reptiles to bypass the lungs. A sphincter at the bottom of the pulmonary artery can close and divert blood away from the pulmonary circulation when not needed/desired.
What venepuncture sites are used in snakes?
- Ventral coccygeal vein
- Cardiac puncture
- Dorsal palantine vein
- Jugular cutdown

■ Ventral coccygeal vein - Insert the needle caudally to avoid the hemipenes in males.

■ Cardiac puncture - This is usually recommended in species over 300 g in weight. The needle is inserted into the ventricular apex and the syringe allowed to fill passively according to the cardiac cycle. There is little danger of leakage post sampling due to the slow heart rate and low blood pressure.

■ Dorsal palatine vein - This can be easily visualized in medium to large sized snakes. It lies on the dorsal oral cavity, medial to the palatine row of teeth. Hematoma formation is common post sampling and saliva may contaminate blood samples.

■ Jugular cutdown - This is possible on collapsed or anesthetized animals.
What venepuncture sites are used in lizards?
- Ventral coccygeal vein
- Axillary venous plexus
- Ventralabdominalvein

• Ventral coccygeal vein - The vein must be accessed caudal to the cloaca to avoid damaging the hemipenes in males. Access is usually about one third of the way from the vent and the needle is inserted ventrally in the midline. In some species a lateral approach may be used by inserting the needle perpendicular to the tail and ventral to the lateral vertebral processes.

• Cardiac - as the heart cannot be held this is not as safe
in lizards as in snakes.

• Axillary venous plexus - this is located near the
shoulder joint at the caudal aspect of the humerus.
Lymph dilution can occur.

• Ventralabdominalvein-thisveinisveryfragileso
anesthesia is advisable to avoid lacerating it. The vein is approached two thirds of the distance caudally on the midline where it lies superficially just under the skin and muscle and is useful for lizards, like geckos,
with short tails
Do reptiles have lymph nodes?
No

Although they lack lymph nodes, reptiles have vast plexiform lymphatic networks and large dilated reservoirs (cisternae) that occur at the sites of mammalian lymph nodes.

Fish do not have lymph nodes either.
How many functional lungs do snakes have?
Normally one (normally the right)

The viperids have only one lung; the colubrids have one functional lung (the left lung is vestigial) and the more primitive boids have two saccular lungs, although the right lung is slightly longer.

Lizards and chelonians have two functional lungs.
Where does gas exchange occur in the reptilian lung?
Faveoli

Cranial (faveolate) part of the lung and honeycomb in appearance.

They don't have a highly branched airways like mammals.
In snakes, the caudal third of the lung is like an air sac, what is its function?
- Buoyancy aid
- Ventilation of lungs

The caudal (membranous) third is non-respiratory and functions like an airsac. Aquatic snakes have an airsac that extends caudally to the cloaca and acts as a buoyancy aid.

Some snakes also use the avascular airsac like bellows in order to ventilate the lungs when the passage of food compresses them.
If reptiles don't have a diaphragm, how do snakes draw air into their lungs?
Intercostal muscles and rib movements

Respiration is controlled by the dorsal and ventrolateral sheet of intercostal muscles, which extend along almost the entire length of the trunk. The intercostal muscles contract, decreasing intrapulmonary pressure and resulting in active inspiration. Passive expiration then occurs as these muscles relax and the lung recoils.
In the snake, what organs are associated with the middle third?
- Liver
- Stomach
- Spleen
- Gallbladder
- Pancreas
- Small Intestine (extends into caudal third)
In the snake, what marks the boundary between the oesophagus and stomach?
There is no obvious difference

Often the stomach may be slightly wider, but is indistinct.
In the snake, in some species which two digestive organs are fused?
Spleen and pancreas = splenopancreas
In the snake, which organs form the 'organ triad'?
Spleen, pancreas and gallbladder

They are located near the pyloric region of the stomach.
Why do snakes often have a large gall bladder?
Fat absorption

As snakes consume large meals infrequently a gall bladder is essential to help digest fat.
Snakes have a very complex digestive system, true or false?
False

They are mainly carnivorous and have a simple digestive system. They carry out mechanical and chemical digestions, as for mammals.
In snakes, the oesophagus is tough, true or false?
False

The oesophagus is fragile, be aware if carrying out assisted feeding.
In snakes, what is a necessary feature of the stomach considering their diet?
Very distensible

Oesophagus is also expandable.
Describe the structure of the snake liver
Elongated and divided into 2-3 lobes.
Which organs are found in the caudal third of snakes?
- Small intestine
- Large intestine
- Kidney (right organs always cranial to left)
- Urogenital tract
In some boids, where can a caecum be found?
Junction of the small intestine and large intestine
Which reptiles have a bladder?
Only chelonians and most lizards have a urinary bladder, snakes do not.

In snakes, the ureters come out of the ventral surface of the kidneys and enter the dorsal urodeum, the middle chamber of the cloaca.

When a bladder is present it is connected to the cloaca by a short urethra. Urine empties from the ureter into the urodeum and is then refluxed into the bladder.

Species with no bladder reflux the urine into the distal colon for water absorption.
What do reptiles excrete via their urinary system?
Mainly uric acid

Terrestrial species need to conserve water so they excrete uric acid, which precipitates from solution in the bladder or cloaca to form pasty, white urates.

Aquatic reptiles excrete ammonia and urea and relatively small amounts of uric acid, as water loss is not crucial.
Describe the structure of the snake kidneys
- Reddish-brown
- Highly lobulated
- Right more cranial than left
Reptiles do not have subcutaneous fat, where do they store their fat?
Store fat as "fat bodies" in the caudal celom (surrounds and contain the digestive tract and other organs) or in the tail.

Fat bodies may obscure organs on radiographs.
The cloaca is a 3-chambered pouch which the rectum empties into, what are the names of the 3 chambers?
- Coprodeum
- Urodeum
- Proctodeum
Which chamber of the cloaca does copulation occur?
Proctodeum

Also, all the wastes collects here prior to excretion.
Which chamber of the cloaca collects feces?
Coprodeum
What empties into the urodeum?
- Gonads
- Ureters (uric acid)
In the male snake and lizards, are the testes found caudal or cranial to the kidneys?
Cranial

The fusiform testis enlarge and regress as season changes.
In males snakes and lizards, what organ has a sexual segment?
Kidneys

Male snakes and lizards have a renal sexual segment in the caudal half of the kidney. Secretions from this segment are transported to the cloaca where they are mixed with sperm. Enlargement of the kidneys is also seen during the breeding season.
Which reptiles have hemipenes?
Snakes and lizards

They are paired and saclike. Some have barbs/ridges to help them remain in the female. These become engorged and evert from their cavity for mating.

Chelonians have a single phallus, while this is protruded during copulation it is not turned inside out.
Where are the hemipenes stored?
Ventral tail base, caudal to the cloaca.

Can be seen as a bulge, proximal to the tail, in lizards.

The hemipenes are not used for urination and can be removed if they become necrotic.
What retracts and inverts the hemipenes after mating?
Retractor muscle
Describe the pathway of sperm in reptiles with hemipenes
1. Testicle
2. Ductus deferens
3. Cloaca/Urodeum
4. Hemipene, travels down sulcus spermaticus (groove)
5. Proctodeum of female
What is the groove in the hemipenes called?
Sulcus spermaticus

Sulcus, Latin: "furrow"
The sex of a snake can be identified by gentle probing distal to the cloaca, what depth would be expected for both males and females?
- Over six subcaudal scales may be reached if the snake is male.

- Less than two to three scales will indicate it is female.
In female snakes, where are the ovaries located?
- Cranial to the kidneys and near the pancreas
- Right more cranial than left (asymmetrically placed)

Lizards ovaries are also cranial to the kidneys.
In female snakes, what is the structure of the ovaries?
Saccular, covered in follicles
Why might a female snakes become unexpectedly pregnant?
Some females can store sperm up near their ovaries, possible for years.
In females snakes, describe the structure of the oviducts
- Pleated
- Ribbonlike
- Prominent

Lizards oviducts are also pleated.
What are the functions of the oviducts?
- Egg transport
- Secrete albumin, protein and calcium
Which species of lizard does not have legs?
Slow worm
Which reptiles have an external ear opening
Lizards

Snakes and chelonians do not
Where are the chromatophores located?
Beneath the epidermis

This is why when snakes shed their skin it is colourless.

Chromatophores not only help in camouflage and sexual display but in thermoregulation. They also provide the elaborate range of skin coloration, most particularly notable in the chameleon.
Which reptiles may have a gular pouch?
Lizards

From Latin gula 'throat'

Can be inflated to look threatening or used in sexual display and courtship behaviour.
In lizards, the integument may form crests, where are these located?
- Nuchal (nape of neck) crests
- Dorsal crests
In the lizard, during ecdysis is the skin shed in one piece or pieces?
Pieces
What function does the tail serve in lizards?
- Climbing/prehensile (chameleons)
- A site of fat storage (Leopard gecko)
- Defence (monitors)
- It can function as a counterbalance
- Rudder-like and used for swimming (Marine iguanas)
- Autonomy, provides a distraction allowing escape
What is it referred to as when a lizard 'drops' their tail?
Autotomy, "Self-amputation"

It is a mechanism to escape from predators. When the animal is attacked the brightly colored tail will break off and wriggle for a few minutes to distract the attacker, allowing the lizard to escape. It occurs in many lizards, such as the iguana, skink, and gecko species.

Should never be stitched and bleeding is minimal, owing to the action of sphincter muscles in the caudal arteries and valves in the veins.
Which reflex is unique to lizards, which can be used to lower their heart rate and blood pressure?
Vasovagal reflex

Larger lizards (and crocodiles) have a vasovagal reflex whereby pressure on the eyeballs decreases the heart rate and blood pressure. This can be used by clinicians to perform non-painful procedures like radiography
If reptiles don't have a diaphragm, how do reptiles draw air into their lungs?
Lizards breathe by expansion and contraction of the ribs
What type of diet do most lizards eat?
Most are omnivorous/herbivorous
Which reptiles chew their food?
Lizards

Unlike snakes and chelonians, lizards do chew their food and will tear off pieces if the food item is too big to swallow. Chelonians have no teeth so are unable to chew. Snakes swallow their food whole.
Are reptiles kidneys smooth or lobulated?
Lobulated
Ovulatory problems are common in lizards, what are the preovulatory and postovulatory problems?
Pre - ovulation does not occur and the mature follicle remains causing preovulatory retention or follicular stasis.

Post - the ova lies within the oviduct and the lizard is egg bound causing postovulatory retention.

Ovaries are located cranial to the kidneys and are saccular.
What are the 2 suborders of chelonia that depend on mode of head retraction?
- Pleurodira (side-neck)
- Cryptodira (hidden-neck)

The Pleurodira or sideneck turtles have three main points of neck flexure so the neck forms a horizontal "s" shape. They are more primitive than the Cryptodira, being unable to retract their head inside their shell, instead placing it sideways. These are mainly aquatic or semi- aquatic turtles and are only found in the southern continents.

The Cryptodira or hidden-neck turtles have two points of neck flexure that form a vertical "s" bend, allowing the head to be completely withdrawn inside the shell. This has enabled them to be more successful and includes the majority of chelonian species (11 families).
What allows chelonians to withdraw their necks?
Retractor muscle

Very strong muscle attached to the dorsal head.
In chelonians, what is the dome of the shell called?
Carapace
In chelonians, what is the flat underpart of the shell called?
Plastron
What is the joint between the carapace and plastron called?
The bridge
In chelonians, what is the cranial aperture and caudal aperture of the shell called?
- Cranial aperture: axillary aperture

- Caudal aperture: inguinal aperture
In chelonians, what is the shell formed from?
Dermal bone

Consists of about 60 bones formed from the modified pectoral and pelvic limb girdles, trunk vertebrae, sacrum, and ribs (highlighted on upper half of image).
In chelonians, what is the shell covered by?
Scutes

Keratinized (horny) epidermal scales known as scutes (lower half of image).

The outer layer of the shell is part of the skin; each scute (or plate) on the shell corresponds to a single modified scale. The remainder of the skin is composed of skin with much smaller scales, similar to the skin of other reptiles.

Some turtles do not have horny scutes. For example, the leatherback sea turtle and the soft-shelled turtles have shells covered with leathery skin, instead.
The chelonians undergo ecdysis, including the scutes, is the piecemeal or in one piece?
Piecemeal

During ecdysis the skin becomes more permeable and more vulnerable to parasites and infection.

Changes in feeding behavior and activity occur prior to ecdysis and the reptiles become very susceptible to dehydration.
Do the shapes of the scutes and the dermal bones correspond?
No

The scutes do not correspond with the underlying bone, adding greater protection and strength to the shell
Do chelonians have moveable eyelids?
Yes
Do lizards have eyelids?
Present in most species

They are usually present. The lower lid is movable, moving upwards to close the eye; in some lizards, this lid might be transparent, allowing vision even when the lids are closed.

In some chameleon species as well as some geckos and the oscellated skink (Ablepharus sp.) the eyelids have fused.

In chameleons, the upper and lower eyelids are joined, with only a pinhole large enough for the pupil to see through.

All geckos, excluding the Eublepharidae family (Leopard gecko), lack eyelids and instead have a transparent membrane, which they lick to clean.
Which reptiles do not have a nictitating membrane (third eyelid)?
Snakes

Lizards and chelonians do.
Do chelonians have teeth?
No, they have a beak

Chelonians have no teeth so are unable to chew. Instead, like birds, they have a short horny beak with sharp edges. Most herbivorous species have a row of hard chewing ridges on the palate to allow more precise biting of food.
There are 13 Chelonia families, what is the most commonly seen in the UK?
Testudinidae

- Testudo graeca (spur-thighed tortoise or Mediterranean/Greek tortoise), right image. Plastron dark centrally and spur-thighed.

- T. hermanni (Herman's tortoise), left image. Spurs at the end of the tail, central area of plastron yellow/orange.
What are the 4 types of carapace scutes?
- Vertebral
- Pleural
- Marginal
- Cervical/nuchal
What are the 5 types of carapace dermal bones?
- Nuchal (1)
- Neural (8)
- Costal (8)
- Peripheral (11)
- Suprapygal/pygal (1)
What are the 6 types of plastron scutes?
- Gular
- Humeral
- Pectoral
- Abdominal (usually accessed for surgery)
- Femoral
- Anal
What are the 5 types of plastron dermal bones?
- Epiplastron (1st lateral)
- Entoplastron (medial)
- Hyoplastron (2nd lateral)
- Hypoplastron (3rd lateral)
- Xiphiplastron (4th lateral)
Which reptiles have a quadrate bone?
Lizards, snakes and chelonians

Helps allow for a wider gape.
How many cervical vertebrae do chelonians have?
8

The eight cervical vertebrae are flexible and allow for bending of the neck sideways (Pleurodira) or inside the shell (Cryptodira).
How many trunk vertebrae do chelonians have?
10

The trunk vertebrae each have rib (small and slender) attachments which fuse with the dermal bone plates. The dorsal spinous processes are also fused with the carapace. The trunk vertebrae are part of the dermal bone structure.
What is unique about the placement of the chelonians pectoral and pelvic girdles?
Located inside the ribs

They act like vertical pillars giving extra strength to the shell.

These two bony girdles are attached to the plastron and carapace by fan-shaped pectoral and pelvic muscles. These limb muscles constitute the largest muscle mass and are surprisingly powerful.
In chelonians, which 3 bones from the tripartite shoulder?
- Scapula
- Acromion process
- Coracoid

The scapula fuses dorsally with the carapace via a ligamentous attachment and ventrally articulates with the humerus at the glenoid cavity. A prominent acromion process projects medially, almost touching its counterpart and is fused to the plastron via connective tissue bands. The third strut is the coracoid bone, which extends caudomedially and also articulates with the glenoid fossa.
How many body cavities do chelonians have?
3

- Dorsal cavity
- Ventral cavity
- Pericardial cavity
In the chelonians, what is found within the dorsal cavity?
Lungs
In the chelonians, what is found within the ventral cavity?
Viscera
In the chelonians, what is found within the pericardial cavity?
Heart
In the chelonians, what separates the dorsal and ventral cavity?
Postpulmonary septum

Sometimes called the diaphragmatic membrane, but reptiles don't have membranes.
What are the internal nostrils also known as?
Choanae
In chelonians, where does the trachea bifurcate?
Immediately caudal to the head

The trachea is very short, be aware of intubating.
In chelonians, where are the lungs attached?
Dorsally - periosteum of carapace

Ventrally - Postpulmonary septum

Cranially and caudally - mass of muscles associated with limbs
Do chelonians have a pleural cavity?
No

They are not surrounded by a pleural cavity and are only separated from the ventral cavity and viscera by a thin non-muscular post pulmonary septum. If the dorsal cavity is punctured the lungs do not collapse.
Can chelonians expand and contract their ribcage?
No
Describe how chelonians breath
Movement of the head and limbs

Inspiration
- Lungs connected to postpulmonary septum
- Ventral cavity can be moved outwards by serratus and abdominal oblique muscles
- Pulls viscera and hence septum, drawing in air

Expiration
- Lungs connected to postpulmonary septum
- Ventral cavity can be compressed by rotating the limbs into shell using pectoralis and transverse abdominis
- Compresses viscera and hence septum, expelling air

Only small movements are require and chelonians can switch over to anaerobic respiration.

Some semi-aquatic freshwater turtles possess the ability to absorb oxygen via a well vascularized cloacal bursae, which they can use during periods of hibernation underwater. Others, like the softshelled turtles can remain submerged for hours in the mud, utilizing oxygen in the water by breathing through the skin and pharyngeal mucosa.
In chelonians, what effect does retraction of the head and limbs have on the dorsal part of the body cavity?
Can't move pectoral girdle so must breath-hold. Reduces size of dorsal cavity to a fifth.
How many chambers do chelonians hearts have
3, like all reptiles.
What are the chelonian venepuncture sites?
- Jugular vein
- Dorsal coccygeal vein
- Dorsal occipital venous plexus
- Toenail vein (least recommended)

■ Jugular vein - This lies very superficially on the lateral side of the neck and runs from the tympanic membrane at the angle of the jaw to the base of the neck (Fig. 3.17).
■ Dorsal coccygeal vein - The coccygeal vertebrae lack dorsal spines and the vein runs quite superficially.
■ Dorsal occipital venous plexus - This sinus cannot be visualized. The head is extended and needle inserted lateral to the cervical vertebrae, just cranial to the carapace. It is the best location in marine turtles.
■ Toenail - This is least recommended as it is painful and samples can be contaminated with urates.
What type of diet do chelonians eat?
- 75% omnivores
- 25% herbivores
In chelonians, what is the pancreas associated with?
The duodenum
In chelonians, how do you distinguish between the oesophagus and stomach?
Stomach widens
Do chelonians have a large or small caecum?
Relatively small indent well developed, even though most are herbivores

Wide large intestine is site for microbial digestion.
How many lobes do chelonians livers have?
Bi-lobed

Also curved dorsally to fit the carapace.
In chelonians, where does the gallbladder lie?
Right love of liver
In chelonians, is the caecum located on the right or the left?
Right
In chelonians, which organ are the testes attached to?
The kidneys

The testes are long, yellow and oval and attached to the cranioventral pole of the kidneys.

Note: the epididymis is covered by pigmented peritoneum.
Do chelonians have hemipenes?
No

The ventral proctodeum is modified and thickened into a single phallus. This consists of two pairs of fibrous tissue separated by a central trough that, unlike in snakes and lizards, cannot be inverted. This tissue is highly vascular and when inserted into the cloaca of the female it becomes engorged. Semen is conveyed down the central sulcus. A retractor muscle then returns the phallus back into the cloaca.
In chelonians, are the ovaries located cranial or caudal to the kidneys?
Cranial

The paired ovaries lie symmetrically.
In chelonians, what four parts is the oviduct divided into?
- Infundibulum
- Magnum
- Uterus
- Vagina
Which part of the oviduct secrets albumin?
Magnum

Looks like a pleated ribbon.
Which part of the female reproductive tract is also known as the shell gland?
Uterus

Holds the egg during shell formation and the majority of time (80%) is spent here.
Where is the muscular sphincter located that must relax in order to lay an egg?
Vagina
What pre and post ovulatory problems may a female chelonian experience?
Pre-ovulatory egg stasis: no ovulation
- egg follicles are formed on the ovaries but not
ovulated

Post-ovulatory egg stasis: eggs stuck
-"egg bound": eggs stuck due to damage/disease of reproductive tract or stress
How do you distinguish between male and female chelonians?
Male
- Plastron slightly concave caudally
- Longer thicker tail
- Vent beyond carapace
- Scute over tail hooked/curved

Female
- Plastron flattened
- Shorter, thinner tail
- Vent at tail base
- Scute over tail flattened
How can you sex a snake?
- A probe can be inserted distal to the cloaca for ~6-10 subcaudal scales in the male, whereas it will only reach 2-3 scales in the female.

- Hemipenes may be everted by gently squeezing the tail base.

- In boidae, spurs are larger in males, and the tail is longer (measure by counting subcaudal scales).
How can you sex a lizard?
-Many species are sexually diamorphic (males more brightly coloured, have crests and throat fans, more prominent femoral pores etc).

- Probing may be used but is less accurate than in snakes.

- Use of endoscopy, radiography, ultrasonography.
What can complicate anaesthesia in chelonians?
Dive reflex and anaerobic metabolism
Do chelonians have poor or good eyesight?
Good

Good smell/vision, but poor hearing.
How does the general shape of a snake differ from that of a lizard?
-Snake: long body, short tail.
-Lizard: short body, long (sometimes prehensile) tail.
How many claws on found the fore and hindlimbs of tortoises?
- 5 claws on the forelimb
- 4 on the hindlimb

Note that the limbs project sideways in these terrestrial chelonians, so their muscles tire easily, making progress arduous.
How may euthanasia be carried out for snakes, chelonians and lizards?
- Deep frozen if under 40g
- Chemically euthanised
- Subjected to an inhalant
- Physically euthanised (exsanguination, pithing, concussion, captive bolt, decapitation)
In chelonians, the caudal two trunk vertebrae have swellings for attachment to which structure?
The ilia of the pelvic girdle

The caudal 2 vertebrae can be considered sacral due to their association with the pelvic girdle.