Structure of Skin

Structure of Skin

1. Epidermis

   • Integumentary System
   • contains keratinocytes, melanocytes, Langerhans cells and Merkel Cells
     • Keratinocyes: Produce lamellar granules and keratin (a fibrous protein
       • Integumentary System
       • Lamellar Granules: secrete a fatty substance that waterproofs the skin, prevents dehydration and invading bacteria from entering
       • Keratinization: more and more keratin is accumulated when cells move to deepest layer to the surface
         • Dandruff occurs when an excess of keratinized cells shed from the scalp
     • Melanocytes: produce melanin--> Albinism: cant produce melanin---> Vitiligo: partial/ complete loss of melanoctyes from patches of skin
     • Langerhans Cells: Arise from Red Bone Marrow and migrate to epidermis
     • Merkel Cells: contact sensory neurons and function in touch sensations
   • Epidermal Layers (Deep to Superficial) include Stratum Basale, Stratum Spinosum, Stratum Granulosum, Stratum Lucidum, Stratum Corneum,
     • Stem cells in STRATUM BASALE are constantly undergoing cell division to produce keratinocytes for the other layers
     • Spinosum: contain Langerhans Cells and projections of melanoctyes
     • Granulosum: contain Lamellar Granules
     • Lucidum: present in thick skin (fingertips, palms and soles)
     • Corneum: lamellar secretion between the cells waterproofs this stratum

2. Hypodermis links underlying tissues and organs to the dermis

   • It is not part of the Skin

3. Dermis: Connective Tissue with fibroblasts, adipocytes, macrophages, mast cells and is embedded with fibers . Contains blood vessels, hair follicles, glands and nerves

   • Integumentary System
   • Divided into Papillary and Reticular Regions
     • Papillary: contains thin collagen and elastic fibers, dermal papillae and Meissner's Corpuscles
     • Reticular: consists of dense irregular connective tissue, collagen and elastic fibers and Pacinian Corpuscles
       • Collagen fibers: give strength and resiliency
       • Elastic Fibers: provide stretch- recoil properties
         • Extensibility is provided by collagen fibers and is the ability to stretch
         • Elasticity: provided by elastic fibers (goes back to original shape and size after being stretched
       • Stretch marks appear if dermis is pushed past its point

4. Skin Colour is due to Melanin, Carotene and Hemoglobin

   • Melanin:pigment produced by melanocytes, which is present in equal amounts in all individuals, but amount of melanin produced is not the same in everyone. --> UV light exposure increases melanin production and melanin absorbs UV Radiation
   • Carotene: yellow- orange pigment located in strat. corneum, adipose tissue and Hypodermsi
   • Hemoglobin: Located in Red Blood Cells F: Gives skin a pink colour as blood moves through capillaries