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Integument (SKIN) By Dr. Abdullah Aldahmash

Integument (SKIN) By Dr. Abdullah Aldahmash. The single largest organ. About 16% of the human body weight. Its about 1.2- 2.3 m 2. Has two layers 1. epidermis : epithelial tissue 2. dermis: connective tissue Two types

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Integument (SKIN) By Dr. Abdullah Aldahmash

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  1. Integument(SKIN)By Dr. Abdullah Aldahmash

  2. The single largest organ. • About 16% of the human body weight. • Its about 1.2- 2.3 m2. • Has two layers1. epidermis : epithelial tissue 2. dermis: connective tissue • Two types • thick skin (glabrous): Palms and soles (400-600µm, 0.8-1.4 mm)- dermatoglyphs • thin skin: the hairy: every where (75-150µm , 0.07-0.12 mm) • hypodermis (subcutaneous tissue) as a pad for the skin (the superficial fascia of gross anatomy), helps the skin to slide over underlying organs. • Panniculusadiposus

  3. Dermis epidermis junction • irregular • dermis and epidermis interdigitate though • dermis projection into the epidermis- dermal ridges {papillae (P) papilla (s)}. • epidermis evaginations - basement membrane

  4. Epidermis • consist MAINLY of a stratified sequamous keratinized epithelium. • 0.07 to 0.12 mm in thickness • Epidermal layers • stratum basale (stratum germinativum). • stratum spinosum • stratum granulosum • stratum lucidum • stratum corneum

  5. stratum basale • Mitotically active • Cuboidal /low columnar • Large nucleus stratum Spinosum Thickest layer Mitotically active (less!!) Has more tonofilaments

  6. Stratum granulosum • 3-4 layers • The most superficial layer with nucleated cells • Has keratohyalin granules • Membrane-coating granules (exocytosis) Stratum Lucidum Only in thick skin No nuclei and organelles Stratum Corneum • Flattened cells. • Has two layers • squames or horny • desquamated

  7. Epidermal specialized cells • Melanocyte melanin producing cells • Lengerhans • star-shape cells • bone marrow derivative • play important role in skin immunology • decrease in number after exposure to UV • Merkel’s • present mainly in thick skin most abundant in the fingertips • serve as mechanoreceptors??

  8. Melanocytes Located under or within the basal layer (stratum basale) Produce melanin Derived from neural crest cells Attached to basement membrane by hemidesmosomes

  9. Developmental stages of mature melanin granule • Tyrosine is synathesized in the RER then accumulated in vesicles (melanosomes) by Golgi • Tryrosine; (inside melanosomes), activated by UV and after series of activation, will be converted into melanin • Melanosomes (containing melanin only) travel through melanocyte projections to be deposited (Cytocrine secretion)

  10. Dermis 1- Development regulator (mesodermal derivative). 2- Has two layer with indistinct boundaries: 1- papillary layer 2- reticular layer

  11. - papillary layer • mainly of loss connective tissue, fibroblasts and other connective tissue cells (Mast, macrophages and leukocytes). • collagen mainly type III, elastic and Anchoring fibrils • Mechanoreceptors (Meissner corpuscles & Krause end bulb) • - reticular layer • dense connective tissue • more fibers and less cells • thick elastic fibers. • Type I collagen fibers. • Some smooth muscles. • Mechanoreceptors (pacinian corpuscles & Ruffini corpuscles )

  12. Vessels &skin sensorial receptors • Two arterial plexuses, located between - papillary and reticular layer - dermis and subcutaneous • three veins plexuses, located between - two in the same location as the arterial - the 3rd in the middle of the dermis • Extensive sensory receptors are found in the skin: - free nerve ending (touch-pressure) - encapsulated: Vater-Pacini,Meissner and Krause corpuscles - expanded: include Ruffini endings

  13. Skin appendages or derivatives • Hair • Nails • Gland • Sebaceous glands • Sweet glands • Mammary glands

  14. Sweat gland Eccrine: 1- Simple 2- Embedded in the dermis 3- two cell types in the secretory part: -dark (pyramidal) lining the lumen & they have secretory granules in their apical surface. -clear devoid of secretory granules and accumulate glycogen. 4- surrounded by myoepithelial Apocrine 1- present in axillary, areolar and anal region. 2- hair associate. 3- their product is initially odorless.

  15. Sebaceous glands • Acinar glands, i.e. have several acini opening into a short duct. • holocrine gland. • in some regions they open directly into the epidermal surfaces, e.g lips, penis and clitoridis. • secret sebum • Controlled by testosterone in men and by ovarian and adrenal androgens in women.

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