called hair follicle Hair growth begins from hair papilla Hair root lies hidden in follicle and visible part of hair
called shaft Arrector pili —specialized smooth muscle that produces
Stratum corneum— outermost layer of keratin-filled cells
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)
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
THE SKIN (cont.)
Accessory structures of the skin
Hair Soft hair of fetus and newborn is called lanugo Hair growth requires epidermal tubelike structure
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
Dermal-epidermal junction—specialized area between two skin layers Blisters can caused if this junction is damaged or destroyed
THE SKIN (cont.)
Dermis Deeper and thicker of the two primary skin layers and
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
“goose bumps” and causes hair to stand up straight
THE SKIN (cont.)
Accessory structures of the skin (cont.)
Receptors Specialized nerve endings—make it possible for skin
Basis of fingerprinting Improves grip for tool use and walking
Dermis
THE SKIN (cont.)
Deeper reticular layer of dermis : filled with network of tough, interlacing, collagenous and stretchable elastic fibers
to act as a sense organ Tactile (Meissner’s) corpuscle /Merkel cell—capable
of detecting light touch Close to the skin surface Pacini corpuscle—capable of detecting pressure Located deep in the dermis Free nerve endings –pain Krause end bulbs (bulboid corpuscles) – lowfrequency vibration
Байду номын сангаас
THE SKIN (cont.)
Accessory structures of the skin (cont.)
Nails Produced by epidermal cells over terminal ends
of fingers and toes Visible part is called nail body Root lies in a groove and is hidden by cuticle Crescent-shaped area nearest root is called lunula Nail bed may change color with change in blood flow
The Integumentary System and Body Membranes
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