0.2 Integumentary system module 3: accessory structures of the  (Page 3/33)

Nails

Sweat glands

When the body becomes warm, sweat glands produce sweat to cool the body. Sweat glands develop from the epidermis and extend into the dermis. The sweat passes from the gland out to the skin via a structure called a duct . A duct is a hollow tube that channel secretions from the gland and in this case, to the skin's surface. There are two types of sweat glands, each secreting different products for different purposes.

An merocrine sweat gland (sometimes called an eccrine gland) is type of gland that produces a watery sweat for thermoregulation. This sweat is more that 99% water and the remaining percentage is made up of various salts. This is why sweat tastes salty. These glands are found all over the skin’s surface, but are especially abundant on the palms of the hand, the soles of the feet, and the forehead ( [link] ). Eccrine glands are a primary component of thermoregulation in humans and thus help to maintain homeostasis.

Eccrine gland

An apocrine sweat gland    is usually associated with hair follicles in densely hairy areas, such as armpits and genital regions. Apocrine sweat glands are larger than eccrine sweat glands and lie deeper in the dermis, sometimes even reaching the hypodermis, with the duct normally emptying into the hair follicle. In addition to water and salts, apocrine sweat includes organic compounds that make the sweat thicker and subject to bacterial decomposition and subsequent smell. The release of this sweat is under both nervous and hormonal control, and plays a role in the poorly understood human pheromone response. Human pheromones are believed to play a role in sexual attraction. Most commercial antiperspirants use an aluminum-based compound as their primary active ingredient to stop sweat. When the antiperspirant enters the sweat gland duct, the aluminum-based compounds form a physical block in the duct, which prevents sweat from coming out of the pore. A deodorant simply affects the sweat that has come to the surface of the skin. Regular cleansing helps to minimize the number of bacteria, greatly reducing the unpleasant smell associated with this type of sweat.

Sebaceous glands

A sebaceous gland    is a type of oil gland that is found all over the body and helps to lubricate and waterproof the skin and hair. Most sebaceous glands empty into hair follicles. They generate and excrete sebum    , a mixture of lipids, onto the skin surface, thereby naturally lubricating the dry and dead layer of keratinized cells of the stratum corneum, keeping it pliable. The fatty acids of sebum also have antibacterial properties, and prevent water loss from the skin in low-humidity environments. The secretion of sebum is stimulated by hormones, many of which do not become active until puberty. Thus, sebaceous glands are relatively inactive during childhood.

Chapter review

Accessory structures of the skin include hair, nails, sweat glands, and sebaceous glands. Hair is made of dead keratinized cells, and gets its color from melanin pigments. Nails, also made of dead keratinized cells, protect the extremities of our fingers and toes from mechanical damage. Sweat glands and sebaceous glands produce sweat and sebum, respectively. Each of these fluids has a role to play in maintaining homeostasis. Sweat cools the body surface when it gets overheated and helps excrete small amounts of metabolic waste. Sebum acts as a natural moisturizer and keeps the dead, flaky, outer keratin layer healthy.