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Wednesday, January 19, 2011

Rat Dissection

Class Mammalia
Thermoregulation - hair, sweat glands.
Mammary glands - produce milk.
Viviparous development - retained within body of female to keep warm.
Nourishment - blood vessels through placenta (allows exchange of nutrients and wastes).

Our male rat - internal anatomy.

Locomotion - tetrapod (four legs), digitigrade (walks on digits only, with the rest of the foot elevated)

Skeletal System - The skull houses the brain, it's strength is necessary to resist the forces produced by the powerful jaw mucles. The vertebral column supports the body and transfers the weight to the appendages. There are five groups of vertebrae (cervical, thoracic, lumbar, sacral and caudal) although no two vertebrae are exactly alike. The sternum and ribs protecta and incase the organs and help in ventilation of the lungs.

Digestive System - Food enters the mouth where the upper and lower incisors can grind down the food. It then goes down through the esophagus into the cardiac portion (entrance from the esophagus) of the stomach, it then makes its way through the fundic and pyloric portions, through the pyloric sphynctor and into the duodenum. The food makes it's way through the small intestine, then the large intestine where water is absorbed and finally into the rectum where the feces is stored before it is eliminated through the anus.

External Anatomy

Vibrissae (whiskers) - integumentary system, used for tactile sensing.
Mouth - digestive system, food enters into the mouth.
External Nare (nostrils) - respiratory sytem, air enters the nostrils.
Pinnae (external ears) - nervous system, used for hearing.
Eardrums - nervous system, protected within the skull, terrestrial environment.
Scales - integumentary system, on tail, protection.
Claws - sharp, grabs onto things (locomotion, diet).
Anus - digestive system, posterior opening of digestive tract.
Penis - reproductvie system, found in the fur covered prepus (foreskin).
Scrotom - endocrine system, contains testes, anterior to the anus, kept cooler than body temperature (located outside the abdominal cavity) to produce viable sperm.
Tongue - digestive system,
Glottis - respiratory sytem, opens to the rachea (leads to the lungs).
Epiglottis - respiratory sytem, protective covering of the glottis, keeps food out of the trachea when the rat swallows.
Incisors - digestive system, gnawing teeth, grow at a fast rate, constantly worn down.

The tail is covered with scales and hairs.

Eardrums protected within skull.

Body covered in hair - protection.

Whiskers - act as the rat's eyes in it's possibly dimly lit home.

Hind feet - sharp claws.

Teeth for gnawin'.

Male posterior end - notice the scrotum.

Female rat posterior end - no scrotum.

Internal Anatomy

Esophagus - digestive system, leads to the stomach.
Stomach - digestive system, seperates from small intestine by the pyloric sphyncter (a muscular valve).
Large intestine - digestive system, ends the muscular rectum.
Liver - lymphatic system, produces bile (rat has no gall bladder).
Pancreas - located in the loop of the small intestine.
Spleen - lymphatic system, located next to the stomach, break down old red blood cells.
Kidneys - urinary system,
Bladder - urinary system,
Testes - endocrine system,
Urethra - urinary system, reproductvie system, where urin leaves the body, as well as carries sperm.
Seminal Vesicles and Prostate - endocrine system, glands that add fluids to the semen before it passes into the urethra.
Diaphragm - respiratory sytem, sheet seperating abdomen from thorax, when it contracts air is sucked into the lungs.
Heart - circulatory system, four chambers: right atrium, left atrium, right ventricle, left ventricle.
Aorta - circulatory system, artery.
Lungs - respiratory sytem,

Under the skin - muscle.

Rib cage - under the muscle - protects organs.

Three lobes of the liver - below the ribcage.

Intestines - below the liver.

One lung.

The heart.
Stomach - right under the liver.

Stomach of the rat.

Insides of the rat's stomach - rats are omnivores.

Small intestine. 

Small intestine.

Intestines unattached.

Inside the large intestine.

Inside the rectum - waste.
Inside the scrotum - a testicle.

Seminal vesicle - vas deferens. 

Here is what's inside the testes.

Lungs, heart, diaphram, liver, intestines...




  2. Very clear and helpful. Thank-you very much.

  3. Thanks for posting this, our outdoor cat keeps on leaving an organ on the doorstep and now I know it is the stomach. Not sure if she doesn't like it or it is an offering.

  4. Thanks for the information! It is very helpful for me, I always don't understand the process perfectly and I search on internet to understand it beter. So for that I thank you for this post! But I think that is also important to have an good dissection kit to do it, so I recommend to have one. If you don't have one, you can buy one from here: