UNIT 3 THE INTEGUMENTARY SYSTEM. SKIN (1) copie.pdf

GENERAL CHARACTERISTICS § STRUCTURE Tegumentum = cover Skin Only a few mm thick yet the largest organ in the body. Accessory structures: Hair Nails Glands © Copyright Universidad Europea. Todos los derechos reservados GENERAL CHARACTERISTICS § FUNCTION One of the most active systems in our body...

GENERAL CHARACTERISTICS § STRUCTURE Tegumentum = cover Skin Only a few mm thick yet the largest organ in the body. Accessory structures: Hair Nails Glands © Copyright Universidad Europea. Todos los derechos reservados GENERAL CHARACTERISTICS § FUNCTION One of the most active systems in our body © Copyright Universidad Europea. Todos los derechos reservados • It is the first line of defense against foreign organisms and the external environment. • It helps to regulate body temperature. • It senses changes in the environment (pain, pressure, touch). • It supports the removal of wastes (as sweat). • It aids in the production of vitamin D. SKIN FACTS § CUTANEOUS MEMBRANE Surface: 2m2 surface Weight: 4.5-5 Kg Largest organ Depth: 0.5-4 mm (1-2mm) Acid pH (5.5) Covered by hair (except palmar and plantar region) Pigmentation: melanin. Homeostasis. © Copyright Universidad Europea. Todos los derechos reservados OUTLINE 3.1 General characteristics 3.2 Structure of the skin 3.2.1. Epidermis 3.2.2. Dermis 3.3 Accessory structures of the skin. 3.3.1 Hair 3.3.2 Glands 3.4 Functions of skin © Copyright Universidad Europea. Todos los derechos reservados STRUCTURE OF THE SKIN § CUTANEOUS MEMBRANE TWO LAYERS Epidermis = epithelial tissue Dermis = connective tissue Innervation Vascularization Hypodermis or subcutaneous tissue (adipose tissue + areolar connective tissue) Energy storage / Physical protection © Copyright Universidad Europea. Todos los derechos reservados STRUCTURE OF THE SKIN § CUTANEOUS MEMBRANE Epidermis Dermis Adipose tissue Blood vessel Loose connective tissue © Copyright Universidad Europea. Todos los derechos reservados OUTLINE 3.2 Structure of the skin 3.2.1. Epidermis 3.2.1.1 Cells 3.2.1.2 Layers: thin and thick skin 3.2.1.3 Growth and keratinization of the epidermis 3.2.2. Dermis 3.2.2.1 Structure 3.2.2.2 Papillary region 3.2.2.3 Reticular region © Copyright Universidad Europea. Todos los derechos reservados EPIDERMIS Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum or malpighian stratum Stratum basale Keratinized stratified squamous epithelium •Avascular. •Nervous sensory ends. •4 types of tightly bound cells. •5 distinct strata (layers) of cells. © Copyright Universidad Europea. Todos los derechos reservados OUTLINE 3.2 Structure of the skin 3.2.1. Epidermis 3.2.1.1 Cells 3.2.1.2 Layers: thin and thick skin 3.2.1.3 Growth and keratinization of the epidermis 3.2.2. Dermis 3.2.2.1 Structure 3.2.2.2 Papillary region 3.2.2.3 Reticular region © Copyright Universidad Europea. Todos los derechos reservados CELLs IN EPIDERMIS § Keratinized stratified squamous epithelium 90% © Copyright Universidad Europea. Todos los derechos reservados 8% KERATINOCYTES - The most abundant cell of skin (90%) - Arranged in 5 layers at different developmental stages: continuous renewal. - They produce keratin: fibrous protein _ protection (abrasion, heat, microbes). - They produced lamellar granules (water repellent). © Copyright Universidad Europea. Todos los derechos reservados Primary Human Epidermal Keratinocytes cultured in NHEK-GM were stained for Keratin 14 (pink), Phalloidin (blue) and Ki67 (yellow). MaTek © Copyright Universidad Europea. Todos los derechos reservados 15 MELANOCYTES -They represent 8% of the cells of the skin. -Location: stratum basale. -They produce melanin (granules). -Melanin: colour absorption). © Copyright Universidad Europea. Todos los derechos reservados and protection (UV MELANOCYTES - KERATINOCYTES § MELANIN • Melanin granules form a protective veil over the nucleus of keratinocytes, on the side toward the skin surface. They shield the nuclear DNA from damage by UV light. • Melanin granules = MELANOSOMES. Transferred to keratinocytes by means of a secretion process from the “dendrite like” extensions of melanocytes. © Copyright Universidad Europea. Todos los derechos reservados LANGERHANS CELLS § IMMUNE CELLS - They represent 3-4% of epidermal cells - Located in strata with living cells (most abundant in the spinosum). - Epidermal dendritic cells. - Function: immune response: antigenpresenting cells. - Derive from the bone marrow. © Copyright Universidad Europea. Todos los derechos reservados MERKEL CELLS ANDE MERKEL DISCS (NERVE TERMINALS) § SENSORY CELLS - Located in the stratum basale, associated with sensory neurons. - Function: tactile sensations. © Copyright Universidad Europea. Todos los derechos reservados © Copyright Universidad Europea. Todos los derechos reservados 21