UNIT 3 The Integumentary System. Skin (1) PDF

EPIDERMAL LAYERS § 4 or 5 different layers or strata © Copyright Universidad Europea. Todos los derechos reservados STRATUM BASALE § DEEPEST layer Deepest layer, on top of basement membrane. Monolayer of cuboidal cells. Keratinocytes: present a cytoskeleton of tonofilaments (precursors of kerati...

EPIDERMAL LAYERS § 4 or 5 different layers or strata © Copyright Universidad Europea. Todos los derechos reservados STRATUM BASALE § DEEPEST layer Deepest layer, on top of basement membrane. Monolayer of cuboidal cells. Keratinocytes: present a cytoskeleton of tonofilaments (precursors of keratin). Intercalated Merkel cells, Langerhans cells and melanocytes. Function: germinative, proliferation. Stem cells: high proliferation rate. Function: structural and support. Skin grafts require a healthy stratum basale. © Copyright Universidad Europea. Todos los derechos reservados STRATUM SPINOSUM OR MALPIGHI’S STRATUM § Second DEEPEST layer •8 to 10 layers of (mechanical strength). keratinocytes Ø In histological preparations, cells shrink and appear spiny (where attached to other cells by desmosomes). In live skin they are rounded and big. Ø Langerhans cells and cellular projections from melanocytes (melanin captured by keratinocytes). Function: provides strength and flexibility to skin. © Copyright Universidad Europea. Todos los derechos reservados STRATUM GRANULOSUM 3-5 layers of flat keratinocytes. Keratinocytes contain lamellar granules (secretory organelles with lipids that repel water). •Cells contain dark keratohyalin granules. Ø Keratohyalin is a protein that assembles tonofilaments into keratin. In the top layers the cells degenerate and die. Function: prevents water loss physical barrier to microorganisms © Copyright Universidad Europea. Todos los derechos reservados STRATUM LUCIDUM § ONLY present in THICK SKIN •3 to 5 layers of clear, flat, dead keratinocytes (without nucleus). •Present only in the palms of the hands and soles of the feet. •Cells contain large amounts of keratin. •Function: protection © Copyright Universidad Europea. Todos los derechos reservados STRATUM CORNEUM § Most SUPERFICIAL layer •25 to 30 layers of flat dead keratinocytes filled with keratin and surrounded by lipids. –continuous shedding. •Barrier to light, heat, water, chemicals & bacteria •Lamellar granules in this layer make it water-repellent. •Constant exposure to friction will cause this layer to increase in depth with the formation of a callus, an abnormal thickening of the epidermis. •Functions: •Impermeable •Protection © Copyright Universidad Europea. Todos los derechos reservados LAYERS OF THE EPIDERMIS: THICK AND THIN SKIN Thin skin / Thick skin • Stratum corneum. • Stratum lucidum. • Stratum granulosum. • Stratum spinosum or Malpighi’s. • Stratum basale or germinative. © Copyright Universidad Europea. Todos los derechos reservados http://www.youtube.com/watch?v=OZzYrRf0ICE http://www.youtube.com/watch?v=o3so9gKQItE&feature =relmfu © Copyright Universidad Europea. Todos los derechos reservados