Biology and Anatomy of
Mouse
A brief history of rodent welfare
The word mouse in the
English language can
be traced back to the
Latin mus, then to the
Greek mys,and finally
to the ancient Sanskrit
mush meaning "to
steal”.
Taxonomy
Order: Rodentia
Sub-Order: Myomorpha
Family: Muridae
Sub-Family: Murinae
Genus: Mus
Species: Mus musculus
21st century rodents: pets or pests?
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•fancy breeds
nuisance animals
Human values determine animal welfare
When a mouse is being used for research on cancer,
it is highly valued and a range of standards and
legislation governs its care and management.
Once a mouse escapes from its cage, invades human
space or presents a threat to economically important
crops, its status changes and it becomes a pest that
can be trapped or poisoned with little concern for its
welfare.
The value of the animal determines the way in which
people treat animals, and what constitutes an
acceptable level of welfare.
Animal value factors
Factors about animals that may affect how
people regard them:
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A species that gets high media coverage,
publicity
Cute and cuddly
Similar to humans, so that we relate to it
Of use to us
A danger to us or to other animals
A species that is endangered or near
extinction
Animal values: mice in research
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Today, the mouse is
recognized by the
scientific community
as the most important
model for human
diseases and
disorders
Mice account for the
majority (98%) of
procedures involving
genetically modified
animals.
Reasons for use
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Inexpensive
Small size
Short life span (2-3
years
Can study many
generations in
short time period
Reasons for use
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Rapid Reproduction
(G.P. 19-21 days)
Large litter size
Mice uses
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These mice are glowing because
scientists inserted a gene found in
certain bioluminescent jellyfish into
their DNA
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Genetic Research
Breeding research
Cancer
Drug testing
Cosmetics
Virology
Histocompatability (tissue
transfer)
Congenital defects
Aging
Radiobiology
Diabetis
Behavior
Physiology
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Life span:
 2 to 3 years
Adult weight:
 20 to 40 gm
Birth weight/condition:
 1 to 5 gm
 blind
 naked
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Weaning age:
 21 to 28 days
Temperature:
 97.5 – 100.4 F
HR:
 325-780 beats/min
RR:
 60-220/min
Urine pH is 7.3-8.5, with a mean specific gravity of 1.08
“highly concentrated”
Reproduction
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Puberty:
 6-8 weeks
Estrous cycle:
 4-5 days
Spontaneous ovulation:
 polyestrus
Gestation:
 19-21 days
Litter size:
 1-20 (average is 6-12)
Eyes open:
 12-13 days
Vaginal plugs persist for 18-24 hou
Reproduction cont.
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Breeding duration 7-9 months
Breeding onset
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Male 50 days
Female 50-60 days
Breeds
Mus musculus
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The laboratory strains of
mice used today are
descendants of the western
European house mouse
(Mus domesticus), with
some genes from
Asianspecies.
The taxonomic designation
Mus musculus, as
commonly applied, is a
composite designation for
several interbreeding
species.
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As early as the 17th and 18th
centuries, mice were already
being used in studies of
anatomy and respiration.
The breeders and fanciers of
19th century Europe developed
the albino and color mutants,
and they began the
investigations of varietal
characteristics and inheritance
that provided stocks for later
research.
This yellow mutant is used in
studies of pigmentation,
implantation, obesity, and
sterility.
Rex (Frizzie)
Spotted
Inbred mouse strains
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From left to right in this
photograph are the BALB/c,
DBA/2, and C3H strains. In
1907 Clarence Cook Little, then
a Harvard undergraduate,
began studying the inheritance
of coat color in mice.
Two years later he began
inbreeding mice. Little was also
interested in studying neoplastic
diseases. He recognized that
inbreeding mice eliminated the
genetic diversity in unrelated
animals and facilitated his study
of tumors.
Mouse strains*
(inbred, mutant, and genetically engineered mice)
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http://www.informatics.jax.org/external/festin
g/mouse/STRAINS.shtml
A genetically defined strain is any strain in
which the genetic background is known, is
similar or identical from one mouse to
another, and can be faithfully reproduced
over time (Davisson, 1999)
Where previously there were only 140,000
variations in DNA sequence described, it
turns out there are 8.3 million.
*inbred animal used for experimental purposes
Albino mouse
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This image shows a
Swiss mouse. In 1926
Dr. Clara Lynch of the
Rockefeller Institute
obtained two male and
seven female albino
mice from a colleague
in Switzerland. These
were the ancestors of
the so-called “Swiss
mice” widely used
today in research.
Anatomy
External
Vibrissae.
Harderian Gland behind eye
Left forepaw
Right hind paw.
Genitalia
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External genitalia.
Female
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External genitalia.
Male.
Skull.
Right mandible
Dental formula is 2(I 1/1, M 3/3) = 16.
The incisors are open-rooted and grow
continuously. Mice will bite or "pinch" with
their sharp incisors if mishandled
Viscera - Neck dissected
Ventral
aspect of female.
Mammary tissue
in situ
Thoracic Cavity
Abdominal Cavity
Sexing
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Ano-genital distance
Females closer than male
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Adult male testes below tail but retractable
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Female
Male
Female
Male