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Exotics and random anatomy > Rodents > Flashcards

Rodents Flashcards

1
Q

What order are rodents in? What is the main characterisation of rodents?

A

Rodentia

Continuously growing incisors

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2
Q

What are the smallest and largest rodents?

A

Pygmy mouse

Capybara

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3
Q

What are the 2 main suborders of rodents (actually 5)?

A 
Myomorpha = mouse like
Hystricomorpha = porcupine like
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4
Q

What is the life expectancy of a mouse/rat/hamster/gerbil?

A 
Mouse = 1-2.5 years
Rat = 3 years
Hamster/gerbil = 1.5-2 years
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5
Q

What is the life expectancy for a guinea pig/chinchilla?

A

Guinea pig = 4-7 years

Chinchilla = 10-15 years

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6
Q

What is the dental formula for a myomorph?

A

I 1/1
C 0/0
PM 0/0
M 3/3

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7
Q

What is the dental formula for a hystricomorph?

A

I 1/1
C 0/0
PM 1/1
M 3/3

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8
Q

Why is it possible to reduce the crown length using a dental burr, without anaesthetic? (Rodents)

A

Incisor pulp cavity is small and beneath the gumline

Never use nail clippers on teeth

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9
Q

Describe the root and growth of incisors, premolars and molars

A

All open rooted
All incisors continuously grow
Molars and premolars continuously grow in guinea pigs and chinchillas

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10
Q

What is the purpose of the large diastema in rodents?

A

Cheeks drawn in

Enables gnawing without wearing molars or swallowing

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11
Q

What is the lower to upper incisor crown ratio in myomorphs?

A

3:1

Normal to have much longer lower incisors

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12
Q

Rodent teeth are open rooted and incisors continuously grow, with most molars/premolars stopping growing. What are the terms for this?

A

Aradicular
Elodont - continuous growth
Anelodont - stop growing

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13
Q

What results in rodents having chisel shaped incisor teeth?

A

Hard enamel on rostral surface only

Softer dentine wears away quickly to form chisel shape

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14
Q

Why is dental disease common in guinea pigs and chinchillas?

A

Have elodont premolars/molars

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15
Q

Describe the stomach of rodents

A

Monogastric - simple stomach

Glandular stomach separated from fore stomach by ridge

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16
Q

Do rodents have a caecum? What shape is their colon?

A

Yes - large caecum

Elongated

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17
Q

What behaviour do rodents exhibit to enhance uptakes of essential minerals? Which minerals in particular is this for?

A

Coprophagy

Vitamin B and K

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18
Q

Are rodents able to vomit? Do they need starving before surgery? Why?

A

No

Don’t need starving as high metabolic rate and fast gut transit time

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19
Q

What type of breathers are rodents?

A

Obligate nasal

Mouth breathing = distress

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20
Q

How many lung lobes do rodents have?

A

Left - 1

Right - 4 (except hamster has additional)

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21
Q

For their size, rodents have high oxygen requiremens. How do they maximise their respiratory intake?

A

Short airways
Increased RR
Many alveoli of thin diameter
High chest wall compliance (increases vital capacity, decreases residual capacity)

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22
Q

Which way does the O2 haemoglobin saturation curve shift in smaller animals?

A

Right

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23
Q

Rodents are homeothermic endotherms. How do they manage thermogenesis in cold?

A

Behavioural - nest building
Shivering
Peripheral vasoconstriction
Non-shivering thermogenesis - brown fat for life

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24
Q

How do rodents manage to cool down when over heating?

A

Evaporation of saliva groomed over body
Arteriovenous shunts in ears, tails and feet
Sweat glands on feet

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25
Q

What type of uterus do rodents have? Which species is the exception?

A

Duplex - 2 cervices

Guinea pigs can be bicornuate OR duplex

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26
Q

How do litters vary between myomorphs and hystricomorphs (guinea pig is included in hystricomorphs)?

A

Myomorphs - altricial, short gestation, large litter

Hystricomorphs - smaller litters, long gestation, precocial young

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27
Q

How long is the oestrus cycle in mice/rats/hamsters, gerbils, guinea pigs and chinchillas?

A

Mice/rats/hamsters = 4-5 days
Gerbils = 4-7 days
Guinea pigs = 15-16 days
Chinchillas = 30-50 days

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28
Q

What type of ovulators are rodents? Which species is the exception?

A

Polyoestrus spontaenous

Chinchillas polyseasonal

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29
Q

Do rodents have a postpartum oestrus or not?

A

Yes

30
Q

What age do myomorphs sexually mature?

A

6-8 weeks

31
Q

What is the age of sexual maturity in guinea pigs and chinchillas?

A

Guinea pigs = 4-6 wks

Chinchillas = 8 months

32
Q

What is the gestation period for mice, rats hamsters?

A 
Mice = 20 days
Rats = 22 days
Hamsters = 17 days
33
Q

Most rodents have many litters per year, with large numbers of offspring. What species is the exception?

A

Chinchillas
Have 2 litters per year
Only 2 offspring

34
Q

What is the most reliable method to sex rodents? Why?

A

Anogenital distance - males longer

Stress inducing, absence of nipples/testes/penis in some species

35
Q

Do all mice and rats have nipples?

A

Only females

36
Q

Rodents have large testes. Can they be retracted?

A

Yes

37
Q

Do all gerbils have nipples?

A

Yes but more prominent in females

38
Q

Do all hamsters have nipples?

A

Yes - more obvious in females

39
Q

Which species have nipples in both sexes?

A

Hamster, gerbils, guinea pigs

40
Q

Which species only has nipples on females?

A

Rats, mice

41
Q

What shape are the genitals in guinea pigs?

A 
Female = Y 
Male = i
42
Q

Do both sexes of guinea pigs have nipples?

A

Yes

Obvious inguinal

43
Q

Why are chinchillas particulary difficult to sex?

A

External genital look similar - mistake penis for clitoris

Testes in inguinal canal

44
Q

How can you determine the stage of oestrus in rats and mice?

A

Cytology of vaginal secretions

45
Q

What is the method for cytology of vaginal secretions?

A

Flush vagina with distilled water
Air dry side
Stain
Count lymphocytes and epithelial cells - do they have nuclei

46
Q

What are the 4 stages of the female repro cycle and how can they be distinguished?

A

Pro-oestrus - round, nucleated cells, few lymphocytes
Oestrus - few lymphocytes, few round nucleated cells
Metoestrus - mostly leucocytes (lots more than nucleated cells)
Diestrus - mostly leucocytes (more than nucleated cells)

47
Q

What do female rodents often have after copulation? What is this? How long is it there?

A

Copulatory plug
Ejaculate which hardens within the cervix - seals vagina so mating more successful
8-12 hrs

48
Q

High surface area to body ratio means that rodents are susceptible to what?

A

Hypothermia
Dehydration
Hypoglycaemia

49
Q

Why are rodents obligate nasal breaths in terms of anatomy?

A

Larynx high up in oropharynx

50
Q

Rats are nocturnal. Why are their incisors yellow? What is interesting about rat eyes?

A

Yellow incisors due to iron pigmentation (normal)

Prominent harderian gland - increased secretion when stressed/ill

51
Q

What is unique about female rats and hamsters genitalia?

A

Urehral orifice separate from vulva in rats

52
Q

Where can be used for venupuncture in rats? How much blood should be taken?

A

Lateral tail vein
Ventral tail artery
Lateral saphenous vein

53
Q

Rats have extensive mammary glands. How many pairs do they have? What is a problem with this?

A

6 pairs

Prone to mammary tumours

54
Q

How far do the cheek pouches extend in the hamster? What is often a problem with this?

A

Extend caudally to shoulder blades - store transport/flood, float in water
Often impaction
Site of immunological privilege

55
Q

What is different about the stomach in hamsters?

A

Stomach separated like ruminants into forestomach and glandular stomach

56
Q

Why are hamsters sensitive to antibiotics?

A

Disrupt normal gut flora

57
Q

Which rodent has the shortest gestation?

A

Hamsters

58
Q

Why is vaginal cytology hard to interpret in a hamster? Why is the vaginal plug difficult to see in hamsters? What can be seen instead?

A

Bilateral vagina pouches
Plug is deep
Vaginal discharge

59
Q

What glands are found on the dorsal hamster? What hormones are they responsive to? Are they in both sexes?

A

Flank glands
Androgen responsive
Yes but more prominent in males

60
Q

Do hamsters hibernate?

A

Yes if <5 degrees

61
Q

Why is venipuncture difficult in a hamster? What sites should be used?

A

No tail vein

Jugular, cephalic or cranial vena cava

62
Q

Like hamsters, gerbils have a deep vaginal plug. What is interesting about post-mating behaviour in gerbils?

A

Form monogamous pairs

Dad helps raise young

63
Q

What large gland is found in gerbils of both sexes?

A

Ventral midline sebaceous gland

64
Q

How do hamsters and gerbils differ in terms of water consumption?

A

Hamsters drink lots

Gerbils drink little

65
Q

Why should gerbils not be handled by their tail?

A

Autonomy - can slough

66
Q

What is unique about guinea pigs vitamin requirements?

A

Vitamin C essential

If not - scurvy within days

67
Q

Male guinea pigs have prominent caudal sebaceous glands and large seminal vesicles. Why should females be bred before 7-8 months old?

A

Pubic symphysis dilates for parturition

If bred after - pubic symphysis fuses and dystocia

68
Q

What can be used for venupuncture in a guinea pig?

A

Cranial vena cava
Jugular
Femoral or lateral saphenous vin

69
Q

Where is the thymus in the guinea pig?

A

Cervical - surrounds trachea

70
Q

Chinchillas are usually nocturnal but can be diurnal if needed. What ratio of light to dark period do they need?

A

12 hrs light

12 hrs dark

71
Q

Chinchillas have very dense fur, 50-60 hairs from each follicle. What is significant about the coat?

A

Tolerant of cold
Sensitive to heat and wet
Drop coat if stressed
Require dust baths

72
Q

Where can be used for chinchilla venupuncture?

A

Cranial vena cava

Lateral saphenous

Exotics and random anatomy (23 decks)

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