FELASA Module 3: Basic Biology
Animals are arranged into: Kingdom, Phylum, Class, Order, Family, Genus and Species
(Kind parrots can only fly going south)
Rodents are part of the rodentia order
Mice are from the Muridae family
The two most common species are mus musculus (house mouse) and rattus
norvegicus (brown rat)
Mongolian gerbil (meriones unguiculatus) is also part of the Muridae family
The cricetidae family contains Chinese hamsters (cricetulus griseus) and Syrian golden
hamsters (mesocricetus auratus)
The Caviidae family contains guinea pigs (cavia porcellus)
Directions in anatomy
Cranial in anatomy relates to directions towards the head and caudal refers to
directions towards the tail
To the sides is lateral and to the centre is proximal
Towards the back is dorsal and towards the stomach is ventral
Most rodents have fur which is determined by multi-loci genes which leads to many
different coat colours
Each loci can have alleles for multiple colours
Long Evans rat
Non-agouti- hairs are white at the bottom and pigmented on the tip
Has black fur so is not albino and has full pigmentations
Hooded means it only has coloured hair on its head and thorax
In nature most rodents have a phenotype from a fully dominant genotype
i.e they will be full agouti all over the body with variation in coat colour on the back and
belly
May have a lighter appearance due to agouti triple hair colouring
Muridae have long tails which are naked in mice and rats
Gerbils have hairy tails
Under the skin there are two lateral and one dorsal vein and to the ventral side there is
an artery
Muridae ears are naked
Rodents use whiskers to touch their environment and rely on them to recognize food,
objects and other animals
Vision doesn’t help orientation in rodents like it does in humans
The nose and smelling sense is used for identifying other animals, finding food and
being stimulated by pheromones
Teeth
Mice and other rodents have 18 teeth
4 incisors, 2 premolars, 12 molars
They have no canines
The have 2 dorsal and 2 ventral incisors which grow continuously
The Danish name for rodents is gnavere (gnawers) from these teeth
If rodents do not have something to gnaw on these teeth overgrow
Salivary glands
Submandibular glands are the largest glands in rodents
This is different to humans which have the parotid glands as the largest
, Larynx
Respiratory air from the nose and mouth passes in and out of the larynx
The larynx fixes the trachea to the caudal part of the mouth
On the outer surface of the laryngo-tracheal surface we find the thyroidea and
parathyroideal glands
These secrete endocrine hormones of importance for metabolism and calcium
regulation
Food passes from the mouth through the thorax via the eosophagus
The esophagus runs along the thorax with the trachea
The left lung has one lobe and the right lung has four lobes
The lungs oxygenate blood and end it to the heart
The thymus is located in the cranial opening of the thorax
The thymus is the body’s T-cell generator
It is large in young rodents but decreases in size with age
The entire thorax and all its organs are covered by a membrane called the pleura
Arteries
Blood flows through arteries from the heart to capillaries in the most distant parts of
the body
The aorta is the largest artery and follows a dorsal path through the thorax and
abdomen
Caudally the aorta divides into the ischiadic arteries to bring blood to the legs
Blood flows cranially through a brachiocephalic trunk to the fore-legs and to the
head through the carotid arteries
Veins
When leaving the capillaries blood flows back through the veins
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