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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
What type of uterus do rodents have? Which species is the exception?
Duplex - 2 cervices | Guinea pigs can be bicornuate OR duplex
26
How do litters vary between myomorphs and hystricomorphs (guinea pig is included in hystricomorphs)?
Myomorphs - altricial, short gestation, large litter | Hystricomorphs - smaller litters, long gestation, precocial young
27
How long is the oestrus cycle in mice/rats/hamsters, gerbils, guinea pigs and chinchillas?
Mice/rats/hamsters = 4-5 days Gerbils = 4-7 days Guinea pigs = 15-16 days Chinchillas = 30-50 days
28
What type of ovulators are rodents? Which species is the exception?
Polyoestrus spontaenous Chinchillas polyseasonal
29
Do rodents have a postpartum oestrus or not?
Yes
30
What age do myomorphs sexually mature?
6-8 weeks
31
What is the age of sexual maturity in guinea pigs and chinchillas?
Guinea pigs = 4-6 wks | Chinchillas = 8 months
32
What is the gestation period for mice, rats hamsters?
``` Mice = 20 days Rats = 22 days Hamsters = 17 days ```
33
Most rodents have many litters per year, with large numbers of offspring. What species is the exception?
Chinchillas Have 2 litters per year Only 2 offspring
34
What is the most reliable method to sex rodents? Why?
Anogenital distance - males longer | Stress inducing, absence of nipples/testes/penis in some species
35
Do all mice and rats have nipples?
Only females
36
Rodents have large testes. Can they be retracted?
Yes
37
Do all gerbils have nipples?
Yes but more prominent in females
38
Do all hamsters have nipples?
Yes - more obvious in females
39
Which species have nipples in both sexes?
Hamster, gerbils, guinea pigs
40
Which species only has nipples on females?
Rats, mice
41
What shape are the genitals in guinea pigs?
``` Female = Y Male = i ```
42
Do both sexes of guinea pigs have nipples?
Yes | Obvious inguinal
43
Why are chinchillas particulary difficult to sex?
External genital look similar - mistake penis for clitoris | Testes in inguinal canal
44
How can you determine the stage of oestrus in rats and mice?
Cytology of vaginal secretions
45
What is the method for cytology of vaginal secretions?
Flush vagina with distilled water Air dry side Stain Count lymphocytes and epithelial cells - do they have nuclei
46
What are the 4 stages of the female repro cycle and how can they be distinguished?
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
What do female rodents often have after copulation? What is this? How long is it there?
Copulatory plug Ejaculate which hardens within the cervix - seals vagina so mating more successful 8-12 hrs
48
High surface area to body ratio means that rodents are susceptible to what?
Hypothermia Dehydration Hypoglycaemia
49
Why are rodents obligate nasal breaths in terms of anatomy?
Larynx high up in oropharynx
50
Rats are nocturnal. Why are their incisors yellow? What is interesting about rat eyes?
Yellow incisors due to iron pigmentation (normal) | Prominent harderian gland - increased secretion when stressed/ill
51
What is unique about female rats and hamsters genitalia?
Urehral orifice separate from vulva in rats
52
Where can be used for venupuncture in rats? How much blood should be taken?
Lateral tail vein Ventral tail artery Lateral saphenous vein
53
Rats have extensive mammary glands. How many pairs do they have? What is a problem with this?
6 pairs | Prone to mammary tumours
54
How far do the cheek pouches extend in the hamster? What is often a problem with this?
Extend caudally to shoulder blades - store transport/flood, float in water Often impaction Site of immunological privilege
55
What is different about the stomach in hamsters?
Stomach separated like ruminants into forestomach and glandular stomach
56
Why are hamsters sensitive to antibiotics?
Disrupt normal gut flora
57
Which rodent has the shortest gestation?
Hamsters
58
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?
Bilateral vagina pouches Plug is deep Vaginal discharge
59
What glands are found on the dorsal hamster? What hormones are they responsive to? Are they in both sexes?
Flank glands Androgen responsive Yes but more prominent in males
60
Do hamsters hibernate?
Yes if <5 degrees
61
Why is venipuncture difficult in a hamster? What sites should be used?
No tail vein | Jugular, cephalic or cranial vena cava
62
Like hamsters, gerbils have a deep vaginal plug. What is interesting about post-mating behaviour in gerbils?
Form monogamous pairs | Dad helps raise young
63
What large gland is found in gerbils of both sexes?
Ventral midline sebaceous gland
64
How do hamsters and gerbils differ in terms of water consumption?
Hamsters drink lots | Gerbils drink little
65
Why should gerbils not be handled by their tail?
Autonomy - can slough
66
What is unique about guinea pigs vitamin requirements?
Vitamin C essential | If not - scurvy within days
67
Male guinea pigs have prominent caudal sebaceous glands and large seminal vesicles. Why should females be bred before 7-8 months old?
Pubic symphysis dilates for parturition | If bred after - pubic symphysis fuses and dystocia
68
What can be used for venupuncture in a guinea pig?
Cranial vena cava Jugular Femoral or lateral saphenous vin
69
Where is the thymus in the guinea pig?
Cervical - surrounds trachea
70
Chinchillas are usually nocturnal but can be diurnal if needed. What ratio of light to dark period do they need?
12 hrs light | 12 hrs dark
71
Chinchillas have very dense fur, 50-60 hairs from each follicle. What is significant about the coat?
Tolerant of cold Sensitive to heat and wet Drop coat if stressed Require dust baths
72
Where can be used for chinchilla venupuncture?
Cranial vena cava | Lateral saphenous

Exotics and random anatomy (23 decks)

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