Exotics - rodents Flashcards
Is the maxilla or mandible narrower in rabbits and rodents?
Rodents - Maxilla is narrower, mandible is wider
Rabbits - maxilla is wider, mandible is narrower
How many pairs of incisors do rodents have?
One pair of upper and one pair of lower
How many pairs of incisors do lagomorphs have?
Two pairs of upper incisors
How many teeth do lagomorphs have?
28
What do rabbits and rodents share about their mouth>
Diastema and philtrum
What is a diastema and a philtrum?
Gap between incisors and molars
Cheek folds separating the grinding and gnawing compartments of the mouth
What are guinea pigs and chinchillas classed as?
Hystricomorphs
In rodents is the distance between cheek teeth greater in the upper jaw or lower jaw?
Lower jaw
What is a different between rodent and lagomorph limbs?
Lagomorphs have no foot pads, hair covered toes and metatarsals
What is different about lagomorph and rodent mouths?
Rodents have no bony symphysis between mandible whereas lagomorphs do
Rodents have a cartilaginous symphysis instead
What are rats, gerbils, hamsters and mice classed as?
Myomorphs
How many teeth do myomorphs have?
16
How many teeth do hystricomorphs have?
20
What type of teeth do myomorphs have and number of each?
4 aradicular incisors, no premolars, 12 brachdont molars
What are brachydont teeth?
Closed rooted teeth, enamel above the gumline in a crown
What type of teeth do hystricomorphs have and number of each?
4 incisors, 4 premolars, 12 aradicular teeth
What are aradicular teeth?
Open rooted teeth, hypsodont so constantly grow, enamel extends below the gum line
How are rodents adapted for gnawing?
Loose articulation of jaw
Incisors are in apposition when the molars are not and vice versa
Large masseters
What is an identifying feature of rat teeth?
Yellow/orange pigmented teeth
What is the gland called that rats and gerbils have that produces red pigment and what is the red pigment called?
Harderian gland
porphyrin
Where does the medial masseter pass in myomorphs and why?
Passes through the infraorbital foramen to the rostral muzzle
Gives a stronger lever to make a stronger bite
Which teeth are longer - upper or lower incisors?
Lower incisors
What is a feature on a myomorph tongue?
torus linguae
What feature do hamsters have that other rodents dont have?
Cheek pouches
What is a feature of a hystricomorph tongue?
Palatal ostium - hole in the soft palate that connects with the pharynx - makes intubation difficult
What is the feature of hearing that is very big in rodents?
Tympanic bullae
Which species is the tympanic bullae most pronounced?
Chinchilla
What is different about a myomorph and hystricomorph skull?
Myomorph is more pointy, hystricomorph more rounded
What kind of young do myomorphs have?
Altricial young
What kind of gestation do myomorphs have?
Short gestation
What kind of young do hystricomorphs have?
Precocious young
In what rodents is the anogenital distance useful?
Myomorphs
What are squirrels classed as?
Sciuromorphs
How many digits do myomorphs have?
4/5 on forefoot - digit 1 is very reduced
5 on hindfoot
How many digits do hystricomorphs have?
4 digits on forefoot, 3 on hindfoot
What is different about myomorph and hystricomorph mammary tissue?
Myomorphs - extensive mammary tissue, 6 teat pairs
Hystricomorphs - reduced tissue
How many teats do myomorphs have?
6 pairs
How many teats do guinea pigs have?
2 inguinal teats - 1 pair
How many teats do chinchillas have?
2 thoracic pairs and one inguinal pair
What is different about myomorph and hystricomorph sexing?
Guinea pigs have developed penis - apply pressure rather than anogenital distance like in myomorphs
What are the main features of rodent respiratory system?
They are obligate nasal breathers
They have a high O2 demand
High thoracic wall compliance
What are the features of myomorph lungs?
Only the right lung is divided - 4 lobes
How many lobes does hystricomorph lungs have?
Both lungs are lobulated
3 in left
4 in right
What kind of diet are myomorphs and hystricomorphs?
Myomorphs - omnivores
Hystricomorphs - strict herbivores
What are the areas of a myomorph stomach?
Non glandular area proximally - proventricular region, translucent
Glandular area distally - fundic region
pyloric region
What are the areas in a myomorph stomach separated by? Which animal is it most pronounced in?
Limiting ridge - hamster
What type of stomach do myomorphs have?
Monogastric
Where is the caecum located in myomorphs?
left caudal abdomen
How many lobes does a myomorph liver have?
4
Do myomorphs have a gall bladder?
No
What type of stomach do hystricomorphs have?
Monogastric
What are the features of the hystricomorph stomach?
Entirely glandular
How many lobes does a guinea pig stomach have?
6 lobes
Do hystricomorphs have a gall bladder?
Yes
How many taeniae do guinea pig caecum have?
3
What occurs in the proximal (ascending) colon in guinea pigs?
Separates digesta into faecal pellets and caecotrophs
How is a chinchilla GI tract different to a guinea pig?
Very long colon - for water conservation
Proximal colon has taeniae and haustra whereas guinea pigs dont have any
What kind of uterus do myomorphs have?
Duplex uterus
Two cervices in rats, one in gerbil and mouse
What kind of uterus do hystricomorphs have?
Bicornuate uterus
What is the length of gestation in rats and mice?
21-23 days
What is the length of gestation in hamsters?
15-18 days
What is the length of gestation in guinea pigs?
65 days
What is the length of gestation in chinchillas?
111 days
What is the uterus seal called?
Copulatory plug
What male sex glands are in close proximity and look lumpy?
Vesicular glands - lumpy
Coagulatory glands - underneath
What are found on rodent testes?
Cranial fat bodies
What do guinea pig vesicular glands look like?
Curved, tubular
What do chinchilla vesicular glands look like?
Scrunched up long tubularW pale structures
What is important to note about castration?
Open inguinal canal
