1 / 27

Skin and Derivatives of Skin

Skin and Derivatives of Skin. Main Layers of Skin. Epidermis (outer layer) Dermis (inner layer). Epidermis. Functions Protection against physical, chemical, and radiation injury.

Télécharger la présentation

Skin and Derivatives of Skin

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.


Presentation Transcript

  1. Skin and Derivatives of Skin

  2. Main Layers of Skin • Epidermis (outer layer) • Dermis (inner layer)

  3. Epidermis • Functions • Protection against physical, chemical, and radiation injury. • Protection against microorganisms (by barrier, by bacterial binding to cells which will be released and by some phagocytosis) • Reduction of fluid loss

  4. Sub-layers of Epidermis • Basal lamina – separates epidermis from dermis • Stratum basale • Deep layer contains living cells that divide to produce new cells • Stratum spinosum • Stratum granulosum • Stratum corneum • Surface layer of dead cells

  5. Stages of Epidermal Cell Development • Synthetic Stage • Most cells found in lower part of spinosum layer • Synthesis of specific proteins and lipids (protein filaments, a polar lipid material that will be released from the cell, and keratohylain granules which will form the protein keratin)

  6. Stages (Continued) • Transformation Stage • Occurs in layers below Stratum corneum • Intracellular enzymes are released that attack and lyse all organelles • Keratohyalin material fills cell

  7. Stages (Continued) • Terminal Stage • Excessive loss of fluid from cells • The narrow intracellular space becomes filled with lipid material • Cells at the end of this stage are found in upper Stratum corneum layer

  8. Dermis of Skin • Thick layer of: • Fibrous connective tissue (anchoring fibers, collagen fibers, elastic fibers) • Muscle tissue • Adipose tissue • Blood vessels • Nerves including sensory receptors

  9. Dermal Structures of Epidermal Origin • Sebaceous Glands • usually associated with hair follicles – serve primarily to lubricate hair • These glands are important in waterproofing the pelage • Secretions are mainly cellular debris and lipids (oils) from cells that breakdown • Androgens stimulated these glands

  10. Structures (Continued) • Sweat Glands • Hypotonic secretions that contain a lot of water • Apocrine Type – open into a hair follicle • Eccrine Type – open onto the surface of the skin independent of a hair follicle • Responsible for most of the sweat that is produced

  11. Structures (Continued) • Sweat functions in • Evaporative Cooling • Improving tactile sensitivity • No sweat glands in – Cetaceans, Sirenians, Elephants, Pangolins, Echidnas, Moles, Rodents

  12. Structures (Continued) • Only apocrine sweat glands in – Bats, some primitive primate species • More eccrine than apocrine sweat glands in – higher primates and humans

  13. Structures (Continued) • Scent glands • May be modified sebaceous glands or modified sweat glands • Used for defense, territory marking, orientation, social interactions

  14. Structures (Continued) • Hair • Hair is a keratinized derivative of the epidermis which is found in all mammals at some point in life cycle • Structure is • Central medulla (continuous or with air spaces) • Cortex which constitutes bulk of hair follicle • Cuticle (layer of outer scales that vary in shape)

  15. Types of Hair • Vibrissae – Long, stiff hairs well well innervated bases, tactile receptors, definitive growth • Guard Hairs – Serve primarily for protection • Spines – enlarged, stiff guard hairs, ex. quills of porcupines, definitive growth, shed and replaced periodically

  16. Types of Hair (Continued) • Guard Hairs (Continued) • Bristles – long, firm hairs with angora growth, ex. horse and lion manes • Awns – firm, expanded distal portion with smaller base, definitive growth

  17. Types of Hair (Continued) • Underhair – primarily for insulation • Wool – long, angora growth • Fur – short, definitive growth • Velli – down or fuzz, first hair on an animal

  18. Color of Hair • Pigment molecules • Eumelanin – provides shades of black and brown • Pheomelanin – produces shades of red and yellow

  19. Pigment in Cells • Contained in melanosomes within melanocytes • Melanosomes are transferred from melanocytes to epithelial cells that become keratinocytes • Pigment in melanocytes and keratinocytes shield stratum basale from UV radiation • Pigment also acts as free radical scavenger, preventing cellular damage

  20. Pigment in Hair • Melanocytes transfer melanosomes to epithelial cells at base of hair shaft • Melanosomes are phagocytized by cells that will form the cortex of the hair shaft

  21. Head Ornaments • Occur only in Orders Artiodactyla and Perissodactyla

  22. True Horns • Found only in Family Bovidae of O. Artiodactyla • An inner core of bone from the frontal bone and a sheath of keratinized epidermis • Grow continuously throughout life of animal • Unbranched • Never shed • Usually in males but can be in females too

  23. Pronghorns • Found only in Pronghorn antelope (F. Antilocapridae, O. Artiodactyla) • Similar in structure to true horns except • Sheath is shed annually • Sheath is branched but bone is not • Occur in males and some females, horn on female may be smaller than on male and could be unbranched

  24. Giraffes Horns • F. Giraffidae of O. Artiodactyla • Derive from separate bony ossifications that fuse to the skull near the junction of the parietal and frontal bones (are not projections from frontal bone!) • Permanently covered by skin and hair • Occur in both sexes

  25. Rhinoceros Horns • O. Perissodactyla • Horn is composed of large mass of elongated, dermal papillae that fuse to form the horn • No core of bone • Horn is really keratinized skin

  26. Antlers • F. Cervidae of O. Artiodactyla • Made entirely of bone • Branched • Outgrowths of frontal bone • Shed annually • Covered by “velvet” while growing • Size cannot be used to directly age and animal, size depends upon nutritional state

More Related