Differentiate between thick and thin skin, between keratinocytes & melanocytes, & between apocrine & eccrine sweat glands
Thick and Thin Skin
Thick skin is found in the palms of the hands and soles of the feet. Thin skin covers the rest of the body. Thick skin has five layers of epidermis (including the stratum lucidum), thin skin only has four layers (without the stratum lucidum layer of the epidermis). Thick skin lacks hair follicles, sebaceous glands, and sweat glands: Thin skin has all of these. Thick skin is less sensitive due to the thicker epidermis and lack of appendages (hair follicles, sebaceous glands, and sweat glands). Thick skin provides protection against abrasion, pressure, and friction. Thin skin regulates body temperature, produces sweat, and provides a sensory interface with the environment.
Keratinocytes and Melanocytes
Keratinocytes form the majority of the skin’s epidermis, producing keratin which provides structural support and protection. Melanocytes produce melanin, a pigment that gives skn its color. Keratinocytes are found throughout the epidermis, from the deepest layer to the outermost layer. Melanocytes are located in the basale layer of the epidermis, interspersed among keratinocytes.
Keratinocytes and melanocytes interact closely.
Keratinocytes secrete factors that stimulate melanocytes to produce melanin.
Melanocytes transfer melanin granules to keratinocytes, which then store and display the pigment.
Apocrine and Eccrine Sweat Glands
Eccrine sweat glands are the most common sweat glands. They produce fluid: water and NaCl (salt), with some ammonia, urea, uric acid, and lactic acid. In palms and soles. Absent from margins of lips, labia minora, tips of penis, and clitoris.
Regulate body temperature by [roducing a watery, odorless sweat that evaporates and cools the skin.
Apocrine sweat glands are active at puberty. Secretion: organic compounds that are odorless but, when acted upon by bacteria, may become smelly. Found in axillae, genitalia (external labium, scrotum), around anus.
Produce a thicker, more viscous sweat that contains proteins, lipids, and pheromones. This sweat is odorless when secreted but develops a characteristic odor when acted upon by bacteria on the skin.
Eccrine sweat production is controlled by temperature and stress, while apocrine sweat production is influenced by hormones and emotions.