The Rat

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INTEGUMENTARY

The rat has an epidermis, dermis, and subcutaneous layer of skin. There is a coating of fur, uncovered skin (hands) and nails. Rats have hair all over their body to conserve heat. Nails are mainly for clawing and catching prey. compared to the other organisms, this is the only organism to have hair.

CIRCULATORY
The rat has an lymphatic system much like the humans. Compared to the other organisms, this is the only organism to have an four chambered heart, therefore making the most efficient.  The circulatory system performs both pulmonary and systemic flow; basically being a double circulation. In other words, the blood circulates between the lungs and heart (pulmonary) and flows between the heart and rest of the body (systemic). There are blood, blood vessels. a heart, and arteries included in this system. This is the only organism to have a pulmonary/systematic blood flow, and an four chambered heart.

DIGESTIVE
This chemical digestive system includes a mouth, esouhphagous, pharynx, stomach, small/large intestine, liver, pancreas, colon, rectum, and anus. Teeth and salivary amylase do a big job of breaking down food for this organism. Being the only organism to have teeth,  a gall bladder, a pancreas, spleen, and a colon. The rat's digestive system is closest to the human, for they are both mammals. The rat has an approximately 1 foot long small intestine. Having a long intestine is an advantage. It allows the organism to absorb more nutrients. Unlike the frog, who has an approximately 2 inch small intestine, clearly cannot absorb as much nutrients as the rat can.

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SKELETAL
Like the frog and human, the rat has an axial skeleton with full limb bones and movement. This is the only organism to have a ribcage. Having a ribcage may be an advantage, for the ribcage may protect internal organs. The rat has nails/claws for grip, prey, etc.

MUSCULAR
The rat has ligaments, cartilage, tendons, and muscles just like humans do. Contracting,flexing, and extending muscles assist in movement just like any of the other animals. Cartilage assists in cushioning and impacts.