Small Mammal Anatomy & Physiology Flashcards
how do small mammals thermoregulate in the wild
in wild burrows to avoid extreme temps (hibernate)
how do small mammals adapt to cold
- high activity (shivering)
- brown fat
- peripheral vasoconstriction
how do small mammals adapt to heat
- burrows
- water conservation (urine conc)
- peripheral heat exchanges
- size (high SA:volume), big ears
what are the thermoregulation considerations of small mammals and anaesthesia
high metabolic rate –> susceptible to hypothermia and dehydration
what are lagomorpha
rabbit, hare
what are rodentia
myomorpha (mouse like) –> rat, mouse, hamster
caviomorpha (cavy like) –> guinea pig, chinchilla, degu
sciuromorpha (squirrel like) squirrel, chipmunk
what are carnivora family mustelidae
ferret, weasel, stoat, otter, badger
how many teeth do rodents and lagomorphs have
16-28 teeth
what are the features of rodent and lagomorph incisors
open-rooted –> continual growth
chisel shaped tip
innervation only at root
cheek folds plug diastema to prevent sharp material entering oral cavity
what is the funciton of the cheek teeth
rasp effect
what are the features of the cheek teeth in herbivores
open roots
teeth ground down by plant material
failure to wear –> dental disease
what are the features of omnivore cheek teeth
roots close at ~4 months
how many incisors are there
1/2 pairs of upper incisors
1 pair lower
do rodents and lagomorphs contain canines
no
what is the dental formula for rodents
1-0-0-3/1-0-0-3
do molars have open or closed roots
closed
enamal folds, enamel-free cusps
what is the dental formula for rabbits
2-0-3-3/1-0-2-3
28 total
what are the 2nd upper incisors in rabbits
rudimentary
peg teeth
what do horizontal grooves in enamel of upper incisors suggest in rabbits
dental disease associated with poor diet
do all rabbit teeth continually grow
yes
2mm/week
need fibre for erosion
why is dental exam in rabbits difficult
limited range of jaw opening
what is the dental formula in ferrets deciduous
3(4)-1-3-0/3-1-3-0
what is the dental formula in ferret permanent
3-1-3-1/3-1-3-2
what are hamster cheek pouches
distensible invaginations of lateral buccal endothelium
extend to doroscaudal scapula
what type of digestive tract to rodents and lagomorphs have
monogastric
some have non-glandular areas
simple small intestine
cecum (larger in herbivores)
what are the characteristics of the rabbit hindgut
10x capacity of stomach
40% of GIT content
3 gyral folds
thin walls
mainly bacteroides spp
what is coprophagy
consumption of feces
what is cecotrophy
consumption of cecal pellets (night stools)
why is cecotrophy essential for health and what diets effect consumption
high fibre diet required for produciton (cellulose, lignin)
low-protein diet encourages consumption
high carb diet decreases consumption and allows bacterial overgrowth in cecum
where do cecotrophs form
cecum and in proximal colon
high nutrient content (fibre doesn’t enter cecum)
mucus covering during passage through colon
ingested directly from anus through anal reflex
what type of uterus do small mammals have
duplex
what are the features of the male genitalia in rodents
rounded scrotum at caudal end
copious fat around testes
longer anogenital distance
what are the features of the female external genitalia in rodents
more pointed caudal end
shorter anogenital distance
what are the features of male external genitalia in rabbits
scrotal sacs either side of preputial sheath
genital opening circular
what are the features of female external genitalia in rabbits
triangular vulva
genital opening slit-like
thoracic and inguinal mammary glands
what is the repro cycle of the rabbit (estrus, gestation, litter size, weaning)
estrus: 5-6d (induced ovulation)
gestation: 31-32d
litter size: ~6
weaning: ~4-7wk
high (~30%) embryonic mortality
what is the repro cycle of guinea pig
estrus: 15-17d (polyestrus)
gestation: 59-72d
litter size: 1-6
weaning: 21d
post-partum estrus 2-10h after parturition
what is the repro cycle of the rat
estrus: 4-5d (polyestrus)
gestation: 21-23d
litter size: 3-18
weaning: ~3-6 weeks
what is the repro cycle of the hamster
estrus: 4d (seasonal polyestrus)
gestation: 15-18d
litter size: 5-10
weaning: 21 d
what is the female repro system of ferrets
similar to cat
estrus cycle linked to increasing daylight in spring
coitus-induced ovulation (if unmated estrogen production continues, hyperestrogenism)
post estrus anemia through suppression of bone marrow
what is the gestation period in ferrets
42 d
when are ferret kittens weaned
6-8weeks
what is a male and female ferret called
m = hob
mn = gib
f = jill
fn = sprite
what is the characteristics of the male ferret repro system
similar arrangement to dog
os penis has curved tip –> catheterization difficult
may be castrated or vasectomized (used to take jills out of season prevent post-estrus anemia)
why are rodents/lagomorphs obligate nose breathers
larynx in high position
what causes high oxygen demand in rodent/lagomorphs
lungs not proportionally larger
greater number of alveoli with smaller diameter
compliant chest wall
poor lubulation of lungs in rabbits –> pneumonia can spread quickly
what is the heart size relative to thorax
2-4th intercostal spaces
often larger in proportion to thorax
where are the venupuncture areas
saphenous/cephalic veins
tail vein
jugular if larger sample required
marginal ear vein in rabbits
where are the lymph nodes
- submandibular
- cervical cranial to scapula
what is the rabbit and guinea pig urinary system features
- relatively high water intake (120 ml/day)
- urine alkaline, not very concentrated (often creamy appearance due to calcium carbonate, may be red due to plant pigmentation)
rodent urine also very concentrated
what are the features of calcium metabolism
high circulating calcium
rapid adjustments in parathyroid hormone control absorption from gut (independent of vitamin D) –> tolerant of high Ca intake, Ca:P ratio not as critical as other mammals
excess calcium cleared via urine (up to 60% of ingested Ca) –> phosphorus excreted via feces
chronic vit D deficiency may lead to mild hypocalcemia (important when dietary supply low)
what are the adrenals of the ferret endocrine system
simialr to dog
high incidental of adrenal neoplasia –> possible association with sex hormones produced by the adrenal
may lead to alopecia
possible implication of early neutering coupled with inadequate exposure to daylight
what are the senses of rodents
prey animals
mainly active at low light
acute senses of smell, hearing and touch –> large tympanic bullae, large olfactory bulbs, sensitive vibrissae (whiskers)
odours important in communication and identification (urine, feces, scent glands)
what is the harderian gland
particularly in rats (present in all vertebrates often rudimentary)
behind eye –> secretes lipids and porphyrin red pigment (ocular lubrication and pheromones)
secretion increased when stressed = red-brown deposit –> chromodacryorrhea
what is significant about the rabbit skeletal system
fragile esp compared to muscular system
spine easily fractured if incorrectly held (esp L6-L7)
what is the significance of the rat skeletal system
ossification not complete until ~1 year (poorly developed haversian remodelling system, prox. humerus and distal radius/ulna fuse at 2 y)
what are the features of the rodent skull
skull: cartilagenous mandibular symphysis
what are the spinal features of the rat
spine: C7, T13, L6, S4, Cd 27-31
what are the features of the ferret skull
carnivore skull
what are the vertebrae of the ferret
C7, T15, L5/6, S3, Cd18
flexible spine
support important when carrying (fractures not uncommon, esp in pregnant jills)
how many pairs of sternal ribs are there
12
narrow thoracic inlet
proportionally large chest
