Reptiles A&P

Question 1

Describe the eye position of reptiles

Answer 1

Near the front of the skull as predator species

Question 2

Describe the teeth of reptiles

Answer 2

Peg-like teeth arranged in rows along the jaw

Teeth in mandible not attached in sockets unlike mammals.

Question 3

What is a pleurodont?

Answer 3

Teeth are continually shed and replaced

Question 4

What is an Acrodont?

Answer 4

Teeth are not replaced

Question 5

What is the cloaca?

Answer 5

Chamber into which the GI, urinary and reproductive tracts meet

Question 6

Describe the skin of reptiles

Answer 6

Thick keratinised epidermis forming scales. It is thin and fragile post-shed (ecdysis)

Question 7

Describe the respiratory system of reptiles

Answer 7

No diaphragm
Rely on their ribcage for inspiration
Cant cough and therefore more prone to aspiration pneumonia

Question 8

Describe the urinary system of reptiles?

Answer 8

Can produce thick/turbid urine with mineral deposits in it
Have a bladder
No loops of Henle

Question 9

Describe the reproductive system of reptiles

Answer 9

Oviparous - lay eggs
(some eggs dissolve internally and can appear to birth live young - oviviviparous)
2 ovaries, 2 oviducts, 2 infundibulum, 2 magnum, merge at isthmus, shell gland, vagina, urodeum.

Males have 2 testes cranial to kidneys, 2 vas deferens.
Males have hemipenes (inverted sacs at the base of the tail which evert to reproduce). Dorsal groove.

Question 10

Reptiles are ectothermic. What does this mean?

Answer 10

Unable to alter their internal body temperature so use the external environmental temp to do so e.g. basking in the sun

Question 11

Describe the anatomy of snakes body

Answer 11

Coelomic body cavity - no separate thorax or abdomen.

Question 12

Describe the Skull of the snake

Answer 12

Described as kinetic
Solid and complete brain case
Large nasal cavity

Question 13

Describe the Jaw of snakes

Answer 13

Separate left and right lower jaw joined by mandibular symphysis. Each half can move independently and are joined by an elastic ligament. There is no temporomandibular joint, the jaw is attached to a quadrate bone which allows further mobility - allows vertical and horizontal rotation of the jaw.
The maxilla is also only loosely attached tot he rostral aspect of the skull allowing nose to be lifted and making the oral aperture wider.
Yawn after eating to realign jaw.

Question 14

Describe the sensory perception of snakes

Answer 14

Mandible and quadrate bones can pick up vibrations on the ground. Can detect position of prey

Question 15

Describe the dentition of snakes?

Answer 15

Maxilla has 2 rows of teeth on each side (except fanged snakes which only have 1)
Mandible has 1 row of teeth on each side
Non-venomous snakes don’t have fangs.
Fangs point backward to secure prey and have a groove or are hollow for venom to run down.
All teeth are replaced as required
Fangs can be erect or fixed

Question 16

Describe the vestigial limbs in snakes

Answer 16

Do not have thoracic limbs but do posses vestigial pelvic limbs. They are seen as external spurs in the pelvic region of species including boas and pythons.
Boas have the remains of a pelvic girdle and hind limbs, more evolved species don’t have a girdle.

Question 17

Describe the ribs of snakes

Answer 17

Don’t join ventrally - no sternum!
All vertebrae have ribs attached except caudal vertebrae.
Function to protect organs, contribute to respiration and attachment for muscles for movement.

Question 18

Describe the skin surface of snakes

Answer 18

Keratinised folded outer layer of epidermis covers whole surface.
dorsal and lateral scales are smaller; ventral scales are thicker and larger.
Snakes can have ventral scutes - a single row of scales. The more scutes, the faster the snake

Question 19

Describe the eyes of the snake

Answer 19

No moveable eyelids
Eyelids have become fused together and become transparent - forming spectacles over the cornea.
Little or no skin glands

Question 20

Describe the process of ecdysis

Answer 20

Shedding of scales head first.
complete outer layer (including the spectacle) is shed in one section with new skin layer beneath.

Occurs about 1-4 times per year
Snake will be dull and anorexic pre-shed
Protein-rich fluid is secreted between the old and new layers, pushing the old layer off. Once separate, the fluid is reabsorbed and the skin sloughs off.

Question 21

Describe infrared sensitivity in snakes

Answer 21

Pit organs lie just between nostril and eye.
Used to detect prey by heat changes.
Can also help thermoregulation as can detect the surface temperatures in the environment.

Question 22

Describe the ears of snakes

Answer 22

Do not have an external ear drum/ tympanic membrane or middle ear cavity.

Question 23

Describe how snakes smell

Answer 23

Forked tongue provides a directional sense of smell and taste. It is in constant motion and used to detect prey and danger.

Then it passes onto the vomeronasal organ (or Jacobson’s Organ) in the mouth which has many nerve endings.

Question 24

Describe the digestive system of snakes

Answer 24

The tongue can be forced out of the closed mouth via a labial notch.
The oesophagus is extremely distensible
The stomach is strong, elongated and elastic. It has very powerful juices to digest the whole prey.
The majority of digestion takes place in the stomach with a small amount happening in the small intestine.
The only substance that cannot be digested is hair and this is passed in faeces. Small intestine is relatively short, reflecting a carnivorous diet.

Question 25

What effects digestive efficiency in snakes?

Answer 25

Temperature.
Temp between 25 &30 degrees will help. Too cold will slow or stop digestion which will cause problems with regurgitation and fermentation of food.

Question 26

Describe the position of the spleen, pancreas and gall bladder in the snake

Answer 26

Found at the point where the pylorus empties into the small intestine. Some snakes has a splenopancreas - lightly adhered - so close they’re joined together.

Question 27

Name and describe the 3 chambers of the cloaca in snakes

Answer 27

Coprodeum - faeces from LI received
Urodeum - receives urogenital ducts
Proctodeum - general collecting area for digestive and excretory wastes. The hemipenes also open into this portion

Question 28

Describe the urinary system of snakes

Answer 28

Snakes have NO bladder
Snakes have no loops of henle and produce uric acid which is part of their adaption to preserving water.
U and F are passed through the same opening.

Question 29

Describe respiration in snakes

Answer 29

Paired nostrils
No hard palate
Glottis allows breathing whilst eating by extending out of mouth. The glottis is rigid enough to withstand pressure when swallowing and opens when the snakes breathe.
Trachea has C-shaped cartilage rings
Lungs - large right lung and small or absent left lung. Some snakes have an air sac in place of a left lung.
Only anterior part of the lungs are for gas exchange. The posterior part is avascular and functions as an air sac that may act as a reserve during periods of apnoea.
Tracheal lung also present as an out-pouch of the lining of the trachea - helps breathing when the main lungs are being compressed by a large prey item.

Movement of ribs aids respiration as no diaphragm.

Question 30

Describe the heart of a snake

Answer 30

3 chambered - 2 atria and one common ventricle

Heart is long and thin and quite mobile so larger prey items can pass by it.

Question 31

Describe reproduction in male snakes

Answer 31

Testes are cranial to the kidneys. (R more cranial)
They enlarge during the breeding season.
Each has a vas deferens
Empties into the urodeum (where the sperm gets seminal fluid added to it)
Have hemipenes - paired penises. Lie in base of tail just caudal to the vent. Only use one at a time. Have barbs or spines and have a dorsal groove.

Question 32

Describe reproduction in female snakes

Answer 32

Paired ovaries lie cranial to kidneys (R more cranial)
2 oviducts, 2infundibulum, 2 magnum.
Merges into the isthmus then uterus (shell gland) then opens into the vagina. Vagina empties into the urodeum.
They are seasonal breeders mostly

Question 33

Describe sexual dimorphism in snakes

Answer 33

Can differentiate between species in some snake species by looking at colours and markings.
Surgical probe can be used. It will insert further towards the tail in males.
Males usually have a longer tail.
Male’s area around the tail can be swollen.
In some species the female is larger

Question 34

Define oviviviparous

Answer 34

Egg dissolves and absorbed internally and appear to birth live young.

Question 35

Describe the digestive system of reptiles

Answer 35

Caecum present in herbivore species
Variety of tongue shapes. Tongue is used to ‘taste’ the environment in conjunction with the Jacobsen’s organ.
Simple, elongated stomach
Terminates the cloaca

Question 36

On the diagram of the reptile skeleton, what bones are at the front of the forelimbs and hindlimbs?

Answer 36

Radius

Tibia

Question 37

Reptiles can exhibit autotomy. What does this mean?

Answer 37

Can drop body parts e.g. tail