Anatomy of Rat

Rat is a common rodent of the order Rodentia. Rat belongs to class Mammalia of subphylum Vertebrata and is often studied as a representative organism for mammals. As the structural organization of rats and humans are similar, it is widely used in medical research to evaluate the effects of medications, before releasing them for human use. Other research fields that involve rats include carcinogenic and toxic experiments, microbiological analysis and preclinical tests for treatment methods. Since rat is small in size and readily available, it is advantageous to use as a dissection animal. Among the many laboratory experiments, rat dissection is a compulsory exercise for science students.

Rat Dissection: Anatomy of Rat

The anatomy of rat can be classified into two parts, namely, external and internal. The external anatomy encompasses the head (cranial region), neck (cervical region), chest (thoracic portion), pectoral (portion where forelegs attach), abdomen, pelvic (portion where hindlegs attach) and tail. Though both sexes have teats, you can differentiate the male and female rat. The male rat possesses a pair of large scrotal sacs next to the last pair of teats.

In order to observe the internal anatomy of rat, it is necessary to dissect the rat carefully. For dissection, you will require dissecting tools such as scalpel, scissor, forceps, pins and tray. Before dissecting the rat, pin the animal (at the legs) with the ventral side up in the dissection tray. Prior to cutting, you can lift the structures by using forceps so that the underlying organs are not disturbed. Follow the procedure cautiously and dissect only the required structures.

When you dissect the neck region, the salivary glands (soft tissues) can be located on the side of the neck; anterior to the salivary gland is the lymph node. The thyroid glands are present on each side of the trachea. Coming to the thoracic portion, you can locate the diaphragm (a thin muscle layer), under which lies the heart in the center. On top of the heart, the thymus glands are present, which regulates the immune responses of the rat. You can observe the bronchial tubes and the large-sized lungs in the thoracic part.

Below the thoracic region, is the abdomen. The major organs of abdomen include liver (dark colored organ), stomach (beneath the liver), spleen (attached to the lower side of stomach), small intestine (highly coiled digestive organ), pancreas (between stomach and small intestine), large intestine or colon (continuation of small intestine that leads to anus), cecum (intermediate structure between small and large intestine) and rectum (just before anus).

While studying the internal anatomy of rat, the excretory and reproductive systems are studied together, which is referred to as the urogenital system. The excretory system of rat consists of kidneys, ureter (tube that connects kidney to bladder) and urinary bladder. The male reproductive organs of rat are testes (enclosed in the scrotal sac), epididymis (tube present on the upper side of testes), vas deferens (tubular structure originating from testes), seminal vesicles (at the side of urinary bladder), prostrate gland (below the urinary bladder) and penis. The female reproductive organs of rat are uterine horns (below kidney), oviduct (tiny tube that connects uterine horn to ovary) and ovary.

Well! This is in brief the external and internal anatomy of rat, which is similar to that of a mouse. Taxonomically, rat and mouse are not different species; the former differs from the latter by its larger size. Rats are carriers of various microorganisms that are transmissible to humans, resulting in diseases and disorders. In addition, rat is also a carrier of microbes that causes severe diseases in swine.