The<unk>  is the set of organs forming the outermost layer of an animal's body. It comprises the skin and its appendages, acting as a physical barrier between the external environment and the internal environment that it serves to protect and maintain the body of the animal. The<unk>  includes hair, scales, feathers, hooves, and nails. It has a variety of additional functions; it may serve to maintain water balance, protect the deeper tissues, excrete wastes, and regulate body temperature, and is the attachment site for sensory receptors to detect pain, sensation, pressure, and temperature.
Integumentary system
Nervous system
Endocrine system
Peripheral nervous system
Cranial nerves
Immune system
Motor system
Urinary system