Procedure: Obtained your rat. Rinse it off with water and place it in your dissecting panto observe the general characteristics. Make sure you know each of the highlighted words. The rat's body is divided into six anatomical regions:
cranialregion - head
cervical region - neck
pectoral region - area where front legs attach
thoracic region - chest area
abdomen - belly
pelvic region - area where the back legs attach
1. Note the hairy coat that covers the rat and the sensory hairs (whiskers) located on the rat's face, called vibrissae. 
2. The mouth has a large cleft in the upper lip which exposes large front incisors. Rats are gnawing mammals, and these incisors will continue to grow for as long as the rat lives.
3. Note the eyes with the large pupil and the nictitating membrane found at the inside corner of the eye. This membrane can be drawn across the eye for protection. The eyelids are similar to those found in humans.
4. The ears are composed of the external part, called the pinna, and the auditory meatus, the ear canal.
5. Locate the teats on the ventral surface of the rat. Check a rat of another sex and determine whether both sexes have teats.
6. Examine the tail, the tails of rats do not have hair. Though some rodents, like gerbils, have hair on their tails.
7. Locate the anus, which is ventral to the base of the tale.
8. On female rats, just posterior to the last pair of teats, you will find the urinary aperture and behind that the vagin*l orifice which is in a small depression called the vulva.
9. On males, you will find a large pair of of scrotal sacs which contain testes. Just anterior to the scrotal sacs is theprepuce, which is a bulge of skin surrounding the penis. The end of the penis has a urogenital orifice, where both urine and sperm exit.
The Muscular and Skeletal System of the Rat
The Muscular and Skeletal System of the RatProcedure: Skinning the Rat
Youwill carefully remove the skin of the rat to expose the muscles below. This taskis best accomplished with scissors and forceps where the skin is gently liftedand snipped away from the muscles. You can start at the incision point where thelatex was injected and continue toward the tail. Use the lines on the diagramto cut a similar pattern, avoiding the genital area. Gently peel the skin fromthe muscles, using scissors and a probe to tease away muscles that stick to theskin.
Musclesare attached to bones by connective tissue called tendons that adhere tospines, knobs, and ridges on bones. You will need to refer to the rat skeletonto determine where the muscles are attached to bones. The end attached to thebone that does not move during contraction is called the origin. The endof the muscle that attaches to the bone that does move is called the insertion.The movement caused by the contraction of the muscle is called the action.Muscles can be easily identified from one another by their shape and overlap.
Identify thefollowing muscles:
1.Biceps brachii - located on the anterior surface of the humerus.
2. Triceps brachii - located on the sides and backof the upper arm.
3. Spinotrapezius - locatedacross the dorsal thoracic region of the rat.
4. Latissimus dorsi - located posterior (and partially covered) by thespinotrapezius.
5. Biceps femoris - locatedon the side of the thigh, in two bundles
6.Tibialis Anterior - located on the front of the leg.
7.Gastrocnemius - located on lower leg, bulk of the calf muscle. Attachesto heel by the Achilles Tendon.
8. ExternalOblique - located on the sides of the abdomen.
9. Gluteus Maximus - located on the lower back and rear.
10. Pectoralis Major/Minor - located in chest
Pin the muscles listed above on a skinned rat.
đProcedure:
Carefullytease away the biceps femoris and gastrocnemius to expose the 3 leg bones: Tibia,Fibula, and Femur and the small patella (kneecap). You canalso see the ligaments around the knee that attach the bones of the lowerleg to the femur and the achilles tendon which attaches the the gastrocnemiusto the ankle.
Note that the joint of the hip is called a ball and socket
Related Resources
Rat Pages:
Rat Introduction and Guide | Rat External Anatomy
Head and Abdominal Region | Circulatory System | Urogenital System
Other Resources: Virtual Rat Dissection | Rat Dissection with Photo Submission
Coloring: Comparing a Human to a Rat Skeleton
