In animals, the integumentary system is the largest organ system of the body. It makes up about 16% of the body’s weight. It includes the hair, skin and nails, and it serves as the body’s main protection from the elements. Some animal integumentary systems include feathers or scales. The integumentary system serves various purposes in different animals but is a vital line of defense against environmental threats for all species.
The integumentary system’s primary function is to maintain homeostasis, which is the body’s regulation process. Integumentary systems in different animals have some things in common as compared to the human integumentary system. For instance, primates and horses have similar sweat glands. Sweating is a way of cooling the body when it begins to overheat. Cats and dogs have different cooling mechanisms where sweat glands play only a minor role in cooling their bodies. Dogs normally pant when they are hot, while cats can sweat through their paws.
Being the largest organ system, the integumentary system serves a variety of vital functions. It protects the body’s other organs and tissues from infection, dehydration, sunburn and sudden changes in temperature. The skin contains nerve receptors that pick up senses of touch, pain and temperature. Also, any disturbance in homeostasis and subsequent damage to the integumentary system can affect different organ systems in the body, most notably through dehydration, extreme changes in temperature and vitamin D deficiency.
The epidermis contains four layers of cells: keratinocytes, melanocytes, langerhans and merkel cells. Keratinocytes form a protective barrier. Melanocytes produce melanin, the pigment that gives skin and hair its color. Langerhans cells regulate the skin’s immune function. Merkel cells are responsible for sensitive touch, such as the sensations detected by a cat’s whiskers.
In the dermis, motor nerves stimulate the arrector pilli muscles, which are tiny muscle fibers attached to each hair follicle that cause “goose bumps” on a person’s skin in response to cold or excitement. Sensory nerves also are found in the dermis; these nerves are responsible for sense of touch, temperature and pain. Although not considered a part of the integumentary system, the subdermis located under the dermis provides protection, energy storage and insulation.
Basement Membrane Zone
The basement membrane zone is found between the epidermis and the dermis and it serves as a protective layer between the two. The epidermis does not contain blood vessels, so when an animal bleeds this means the entire epidermis has been penetrated. This area is vulnerable to damage through skin disease and autoimmune disorders. Vesicles or bubbles of liquid are examples of damage. One common instance of a vesicle is a blister.
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