Integumentary System : The Classical World

Introduction

The Integumentary System is composed of the skin (integument is the Latin word for covering) and the other things that cover the outside of the body, hair, nails, sweat and oil.

The skin in the largest organ in the body, and can weigh up to 20 pounds. In the skin are the nerves or sensory receptors that relay to the brain information about temperature, pain, touch and pressure, and the brain in response through its motor nerves can direct appropriate commands, such as an increase or decrease in the activity of the sweat glands or sebaceous glands.

It is the first line of defense in the immune system, and protects the body from bacteria, chemicals, injury and water; and it also keeps things in the body that otherwise would escape. The sweat, or sudoriferous, glands regulate body temperature, and also secrete some metabolic wastes. The sebaceous glands produce sebum, an oil that lubricates the skin and prevents it from drying out, or the growth of bacteria. An overproduction in adolescents leads to acne, pimples and pustules, whereas in later life a reduced production creates wrinkles and dry skin.

The skin itself has three main layers. The dermis (or corium or cutis, “the true skin”) is the middle layer, which contains hair follicles, sweat and sebaceous glands, blood and lymph vessels, and nerves and nerve endings. On top of the dermis is an avascular layer that has no blood supply, which is called, appropriately, the epidermis. Constantly cells of the epidermis are pushed up from the basal layer of the epidermis to the outer layer, where they harden and slough off. Melanocytes in the basal layer produce melanin, the dark skin pigment that protects against ultraviolet light. Albinism (a white condition) results from a lack of melanin. The subcutaneous layer under the dermis contains blood vessels and fatty tissues, lipocytes, and it protects the inner tissues of the body, and acts as an insulator for heat and cold. The hair likewise protects the head from heat and cold, while the nails provided protection – prior to man’s development of other weapons of self-defense!