Digestive System

Food is taken and passes from the mouth to the thoracic cavity in the esophagus and goes into the stomach. The stomach is located ventrally to the liver in the abdominal cavity. The intestines constitute the small intestines which are called the duodenum which are then followed by the jejunum and ileum. The ileum connects to the caecum which is like an enlarged pouch. From the caecum food then proceeds to the colon which ascends and descends before entering the rectum to leave the body via the anus. From looking at this anatomical information about mice and rats, you will find that mice and rats are monogastric just like humans with intestines that are similarly lined up as in humans.

Urogenital System

Just as with humans mice and rats have a urogenital system that comprises of two systems, which are the excretory and reproductive systems. These two systems have some common ducts which are shared.

The main aim of the excretory system is to eliminate nitrogen containing compounds to maintain homeostatic conditions in body fluids. The kidneys play the crucial role of balancing ion concentration. Blood containing nitrogenous waste enters the kidneys via the renal artery at a surface called the hilus. After removal of nitrogenous waste, the blood leaves the kidneys via the renal vein. The ureter also leaves the kidney, carrying urine to the bladder. At the cranial position of the kidneys are adrenal glands. These glands release hormones which affect metabolism and sexual development.

The Kidney

Blood is filtered in the renal cortex before entering a tubular system. The filtered blood is then passed into the medulla in which ions and essential nutrients are reabsorbed back into the body by capillaries. The remaining filtrate moves to the renal papilla, the point where collecting ducts meet. This is the point where urine drips into the renal pelvis which looks like a funnel. The urine then enters the ureter and moves towards the bladder and is taken outside via the urethra. From the information on the urogenital systems of mice and rats, it is evident that these systems closely resemble those of humans. That is why experiments involving hormones or any other drugs that can affect metabolism are tested on mice and rats because the way they absorb, utilize and excrete substances in and out of the body is very similar to humans.

Genetically Modified Mice and Rats

Mice and rats can easily be manipulated through genetic engineering to produce homologous mice. These mice can be produced from injecting blastocysts with embryonic stem cells from mice that have been selected for specific traits. This results in the production of offspring that have uniform traits. These uniform animals are very important in experiments in order to have results that are not biased by differences in traits and phenotype. Such genetic manipulations are not easy with other kinds of animals and the fact that mice and rats are very small and have a short reproductive cycle they are much favored for scientific experiments.

Production Of Transgenic Mice and Rats

Scientists are now capable of breeding genetically engineered mice and rats which are called transgenic mice or transgenic rats. These mice and rats are made to carry genes that are similar to the ones that cause human diseases. In experiments these genes can be activated or inactivated to see their effects on the animal. This has led to scientists being able to assess the effects of carcinogens and see how results from such animal experiments can be used to promote drug safety in humans.

Mice can naturally be born without an immune system. These mice are then used as models for research on human diseases. Some of the diseases that mice are used as models for, include; cancer, obesity, diabetes, hypertension, muscular dystrophy, spinal cord injuries, HIV and Aids, Hearts disease and many other human diseases.

Mice and rats are often used in labs because they share many genes with humans and their body systems such as the digestive system, endocrine system and respiratory system are very similar to those of humans. Because of their short reproductive cycle, experiments with mice take a very short time to come up with results.