Rodent Body Systems

Question 1

Why are rodents obligate nasal breathers?
What would be concerning to see a rodent do?
Why do rodents have such a high oxygen demand? How do they meet this? (3)
What sense can be affected by respiratory infection?

Answer 1

Larynx place high in oropharynx
Concern to see rodent mouth breathing.
High O2 demand due to high metabolic rate due to small body weight.
Meet demands with high chest wall compliance and low residual lung capacity so can expand lungs well. Also have a high RR.
Sense of smell can be affected.

Question 2

Which lung is divided and which lung is not in myomorphs?
How many lobes does the divided lung have in myomorphs?

Answer 2

Right lung divided, left lung not.
4 loves of the right lung.

Question 3

How many lobes does each hystricomorph lung have?

Answer 3

3 left lobes. 4 right lobes.

Question 4

Are myomorphs herbivores, omnivores or carnivores?
Are hystricomorphs herbivores, omnivores or carnivores?
How do hystricomorphs digest such large amounts of fibre?
What is caecotrophy?

Answer 4

Myomorphs are omnivores.
Hystricomorphs are strict herbivores.
Large caecum
Passing of food through the alimentary tract twice.

Question 5

What type of stomach do myomorphs have? — what animal stomachs are myomorph stomachs similar to? — how?

Answer 5

Mono gastric stomachs — similar to horse stomach. — divided into non glandular area proximally and glandular fundic area distally.

Question 6

What are the 2 areas of the myomorph stomachs separated by?

Answer 6

A limiting ridge.

Question 7

What section of the abdomen does the caecum sit in in the rat?
How many loves does the myomorph liver have?
What structure is not present among the liver of the rat?

Answer 7

Left caudal abdomen
4 liver lobes
Gall bladder

Question 8

Hystricomorphs are crepuscular. What does this mean?
What type of stomach do hystricomorphs have?
What areas is the hystricomorph stomach split into?

Answer 8

Appear at dusk and dawn.
Mono gastric stomachs.
Not split — entirely glandular so no limiting ridge

Question 9

How many lobes of the Guinea pig liver?
What do Guinea pigs have among the liver that rats do not?

Answer 9

6 lobes.
Gall bladder (well developed)

Question 10

What side is the caecum on in the Guinea pig?
How many taenial bands of the Guinea pig caecum?
What are these taenial bands important for?

Answer 10

Left side (fills majority)
3 taenial bands
Taenial bands important for churning of fiber.

Question 11

What parts is the colon separated into in the Guinea pig?
Where does caecotrophy occur in the Guinea pig?
Describe shape of colon.

Answer 11

Proximal and distal colon.
Caecotrophy in the proximal/ascending colon.
Flattened spiral.

Question 12

What is the longest part of the GI tract in the chinchilla?
Why is this?
What does the proximal colon have in the chinchilla that the Guinea pig does not have?

Answer 12

The colon (2x length of small intestine)
An adaptation for water conservation as chinchillas are desert animals.

Chinchillas have taenial bands and haustra in the proximal colon.

Question 13

How many openings are there at the perineum of a rodent? — What are these?

Answer 13

3 openings — urethra from urinary, vagina or penile opening from repro, rectum from digestive

Question 14

What is the lump present on the perineal surface of both males and females?
In which sex is this larger?
In what species is the testicular size variable? And in which season are they larger?

Answer 14

Genital papilla
Larger in males
Testicular size variable in hamsters.
Larger in summer.

Question 15

How would you differentiate the sex of Guinea pigs?

Answer 15

Anogenital distance not always helpful. Genital orifice not always patent and may have membrane covering.

Perineum of female inverted Y

Males have well developed penis and a total swelling when older.

Question 16

Sex differentiation on chinchillas

Answer 16

Anogenital distance helpful

Can’t use testes as chinchillas don’t have scrotal sac so testes sit more inguinally.

Vagina mostly closed apart from for copulation and parturition.

Question 17

Comment on gestation period and young of myomorphs
Myomorph litter size
Myomorph gestation periods — days and mice, hamsters, gerbils

Answer 17

Short gestation and altricial young
Large litters
Gestation of rats and mice = 21-23 days
Hamsters = 15-18 days
Gerbils = 22-26 days

Question 18

What type of uterus does a rat have?

Answer 18

Duplex uterus — 2 completely separate horns, with each horn having its own cervix entering into the vagina. No uterine body.

Question 19

What are copulatory plugs?

Answer 19

Produced by the male coagulating glands and seal entrance to uterus to prevent fertilisation of another male shortly after mating.

Question 20

What is found cranial to the testicles in myomorphs.
Where do these structures project?

Answer 20

Fat bodies — project through open inguinal canal.

Question 21

What accessory sex glands do make myomorphs have?

Answer 21

Large vesicular glands (a pair).
Paired coagulating glands sit in the curve of the large paired vesicular glands.
Ampullae
Prostate
Bulbourethral glands

Question 22

What is the name for the is penis in small mammals?

Answer 22

Baculum

Question 23

What type of uterus do hystricomorphs have?

Answer 23

Bicornuate

Question 24

Comment of hystricomorph gestation period and young

What is the average Guinea pig gestation?
What is the average chinchilla gestation?

Answer 24

Long gestation and precocial young

Guinea pig gestation = 65 days
Chinchilla gestation = 111 days

Question 25

What structure lie cranial to the hystricomorph testes?
What do these structures protect through.
What type of castration should be performed on hystricomorphs ?

Answer 25

Fat bodies.
Large open inguinal canal.
Closed castration.

Question 26

What accessory sex glands are present in hystricomorphs?

Compare the vesicular glands in g-pigs and chinchillas

Answer 26

Coagulating glands
Prostate
Bulbourethral glands
Vesicular glands
NO ampullae

G-pig twisted cylinders
Chinchillas more tubular

Question 27

Baculum in hystricomorphs?

Answer 27

Yes

Question 28

What family do ferrets belong to?
Give examples of other animals in this family

Answer 28

Mustelids
Weasels, skunks, otters, badgers

Question 29

Are ferrets herbivores, omnivores or carnivores?
How is this shown in their dentition?
What anatomical feature gives ferrets their characteristic smell?

Answer 29

Carnivores — predators
Very pronounced canine teeth
Well developed anal scent glands

Question 30

Name of male ferret
Name of female ferret

Answer 30

Male Hobs
Females Jills

Question 31

Comment of ferret bodies and legs

How are they able to move around in homes and burrows when hunting?

Answer 31

Long, tubular bodies, short legs.

Their very flexible spines allow their movement in burrows

Question 32

What allows for an acute sense of hearing and smell in ferrets?

Comment on eyesight

Answer 32

Elaborate turbinate system.

Relatively poor eyesight but reasonable in low light levels as nocturnal and underground hunters

Question 33

Thoracic cavity size in ferrets? How is this beneficial?
Comment on lungs
Comment on thoracic inlet

Answer 33

Large for body size — increases lung capacity
Lungs anatomically human-like.
Narrow thoracic inlet

Question 34

What structures are absent in the ferret GU tract

Answer 34

Caecum and appendix

Question 35

How many teats does a female ferret have?
What animal is the external genitalia likened to?

Answer 35

4 teats.
Dog/bitch — prepuce and os penis
Male ferret scrotum is positioned same as in cat.

Question 36

What type of ovulators are Jills?
What can occur if female ferrets are not mated?
What should be done if a female is kept alone as a pet?

Answer 36

Induced ovulators

Persistent oestrogen stimulation causes bone marrow suppression and anemia.

Ovariohysterectomy should be performed.

Question 37

What type of uterus do female ferrets have?

Answer 37

Bicornuate uterus

Question 38

What may be done if males are kept with females?

Answer 38

Vasectomy — so testosterone still produced and can mate with female and induce ovulation without risk of pregnancy.