131, T21, Ch5 Integument _12.pdf - Skin Integument Chapter...

This preview shows page 1 - 4 out of 19 pages.

11/8/12 1 Integument Chapter 5 IB 131 Instructor: Tom Carlson Dept of Integrative Biology University of California, Berkeley 1 Skin Skin is our largest organ and accounts for 7% of body weight Varies in thickness from 1.5–4.4mm Divided into two distinct layers Epidermis Dermis 2 Hypodermis Hypodermis —lies deep to the dermis 3 Skin & underlying tissue 4 Skin Structure Figure 5.1 Epidermis Hair shaft Dermis Reticular layer Papillary layer Hypodermis (superficial fascia) Dermal papillae Pore Subpapillary vascular plexus Appendages of skin Eccrine sweat gland Arrector pili muscle Sebaceous (oil) gland Hair follicle Hair root Nervous structures Sensory nerve fiber Lamellar (Pacinian) corpuscle Hair follicle receptor (root hair plexus) Dermal vascular plexus Adipose tissue 5 Functions of Skin (epidermis & dermis) & Hypodermis Protection —cushions organs and protects from bumps, chemicals, water loss, UV radiation Regulation of body temperature Excretion —urea, salts, and water lost through sweat Production of vitamin D in deep epidermis Sensory reception —keeps us aware of conditions at the body’s surface 6
11/8/12 2 Embryologic origin of skin Epidermis – Develops from embryonic ectoderm Dermis and hypodermis – Develop from mesoderm Melanocytes – Develop from neural crest cells which are ectoderm in origin 7 Skin = epidermis + dermis 8 Epidermis 9 Epidermis is a keratinized stratified squamous epithelium with four distinct cells types : Keratinocytes: most common cell type in epidermis Melanocytes: Location—basal layer; manufacture and secrete pigment Tactile epithelial cells: Location—basal layer; attached to sensory nerve endings Dendritic cells: Location—stratum spinosum; part of immune system; macrophage-like 10 Keratinocytes vs. keratocytes Keratinocytes: predominant cell-type in skin epidermis Keratocytes: specialized fibroblasts in the cornea 11 Keratinocytes in Epidermis Most abundant cell type in epidermis Present in all epidermis layers Cells are tightly connected by a large number of desmosomes Produce antibodies and enzymes that detoxify chemicals that are exposed to our skin • Produce keratin , a tough fibrous protein that gives skin epidermis its protective properties 12
11/8/12 3 Keratinocytes in Epidermis Arise from deepest layer of epidermis (stratum basale) from cells that undergo continuous mitosis As these cells are pushed up by the production of new cells beneath them, they make keratin that fills their cytoplasm 13 Keratinocytes in Epidermis By the time they reach the surface of the skin they are dead flat sacs full of keratin Keratinocytes are dead at skin's surface Millions of these dead cells rub off from our skin every day 14 Keratinocytes in Epidermis 35-45 days is average time from the birth of a keratinocyte until it sloughs off of the exterior skin We form an entirely new skin epidermis every 35-45 days

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture