Chapter 11 - Skin
Skin covers the outer surface of the body and is the largest organ. Skin and it's accessory structures (hair, sweat glands, sebaceous glands, and nails) make up the integumentary system. Its primary functions are to protect the body from the environment and prevent water loss.
Skin is classified into two types:
- Thick skin - covers the palms of the hands and the soles of the feet
- Thin skin - covers the rest of the body
Skin consists of two layers:
- Epidermis - outer layer of stratified squamous keratinized epithelium
- Dermis - underlying layer of dense, irregular connective tissue that contains other structures (such as hair follicles and sweat glands)
Deep to the dermis is the hypodermis, a layer of varying thickness of loose connective tissue and adipose tissue.
Thick skin is only found on the palms of the hands, and the soles of the feet, locations subjected to considerable abrasion. It has a thick epidermis and contains sweat glands, but lacks hair follicles and sebaceous glands.
Thin skin covers most of the body except for the palms of the hands and the soles of the feet. It has a relatively thin epidermis and contains hair follicles, sweat glands, and sebaceous glands.
Melanin is the most important substance in determining the color of skin.
Scalp hairs arise from hair follicles extending deep into the dermis. Hair follicles are invaginations of the epidermis that form multilayered cylinders of cells.
Meissner and Pacinian Corpuscles
Meissner and Pacinian corpuscles are two types of touch/pressure receptors that are found in skin.