chapter 6 skin and its appendages. introduction skin (integument) is body’s largest organ...
DESCRIPTION
Structure of the Skin Skin classified as a cutaneous membrane Two primary layers: 1)epidermis 2)dermis Hypodermis lies beneath dermisTRANSCRIPT
Chapter 6Skin and its Appendages
Introduction
• Skin (integument) is body’s largest organ• Approximately 1.6 to 1.9 m2 in
average-sized adult• Integumentary system describes the skin
and its appendages—the hair, nails, and skin glands
Structure of the Skin
• Skin classified as a cutaneous membrane• Two primary layers:1) epidermis 2) dermis• Hypodermis lies beneath dermis
Structure of the Skin
• Thin and thick skin – “Thin skin”—covers most of body surface
(1 to 3 mm thick)– “Thick skin”—soles and palms
(4 to 5 mm thick)
Epidermis
– Three Cell types:• Keratinocytes—constitute over 90% of cells
present; principal structural element of the outer skin
• Melanocytes—pigment-producing cells (5% of the total); contribute to skin color; filter ultraviolet light
• Langerhans cells—dendritic (branched) antigen-presenting cells (APCs), they play a role in immune response
Cell Layers
• There are 6 layers to your epidermis:1) Stratum germinativum (growth layer)2) Stratum basale (base layer)3) Stratum spinosum (spiny layer)4) Stratum granulosum (granular layer)5) Stratum lucidum (clear layer)6) Stratum corneum (horny layer)
Structure of the Skin
• Stratum germinativum (growth layer)—describes the stratum spinosum and stratum basale together
Structure of the Skin Stratum basale (base layer)—single layer of
columnar cells; only these cells undergo mitosis, then migrate through the other layers until they are shed
Structure of the Skin– Stratum spinosum (spiny layer)—cells
arranged in 8 to 10 layers with desmosomes that pull cells into spiny shapes; cells rich in RNA
Structure of the Skin
• Stratum granulosum (granular layer)—cells arranged in two to four layers and filled with keratohyalin granules; contain high levels of lysosomal enzymes
Structure of the Skin• Stratum lucidum (clear layer)—cells filled with
keratin precursor called eleidin; absent in thin skin
Structure of the Skin• Stratum corneum (horny layer)—most superficial
layer; dead cells filled with keratin (barrier area)
Epidermal growth and repair
• Turnover or regeneration time refers to time required for epidermal cells to form in the stratum basale and migrate to the skin surface—about 35 days
• Shortened turnover time will increase the thickness of the stratum corneum and result in callus formation
• Normally 10% to 12% of all cells in stratum basale enter mitosis daily