解剖学英文皮肤Skin课件.ppt

The Integumentary System and Body Membranes THE SKIN THE SKIN ? Structure — two primary layers called epidermis and dermis ? Epidermis ? Outermost and thinnest primary layer of skin ? Composed of several layers of stratified squamous epithelium ? Stratum germinativum — inner layer of cells that continually reproduce; new cells move toward the surface ? As cells approach the surface, they are filled with a tough, waterproof protein called keratin ; eventually cells flake off ? Stratum corneum — outermost layer of keratin-filled cells THE SKIN THE SKIN ? Skin pigment — deepest epidermal layer is responsible for production of pigment, which gives color to the skin ? The brown pigment melanin is produced by specialized cells in this layer (melanocytes) ? Dermal-epidermal junction — specialized area between two skin layers ? Blisters can caused if this junction is damaged or destroyed THE SKIN (cont.) THE SKIN (cont.) ? Dermis ? Deeper and thicker of the two primary skin layers and composed largely of connective tissue ? Upper papillary layer of dermis characterized by parallel rows of tiny bumps called dermal papillae ? Ridges and grooves in dermis form pattern unique to each individual ? Basis of fingerprinting ? Improves grip for tool use and walking THE SKIN (cont.) THE SKIN (cont.) ? Dermis ? Deeper reticular layer of dermis : filled work of tough, interlacing, collagenous and stretchable elastic fibers ? Number of elastic fibers decreases with age and contributes to wrinkle formation ? Dermis also contains nerve endings, muscle fibers, hair follicles, sweat and sebaceous glands, and many blood vessels THE SKIN (cont.) THE SKIN (cont.) ? Accessory structures of the skin ? Hair ? Soft hair of fetus and newborn is called lanugo ? Hair growth requires epidermal tubelike structure called hair follicle ? Hair growth begins from hair papilla ? Hair root lies hidden in follicle and visible part of hair called sh