Ch6 Ppt Lect


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Ch6 Ppt Lect

  1. 1. Chapter 6 Skin and the Integumentary System PowerPoint Presentation to accompany Hole’s Human Anatomy and Physiology, 10 th edition , edited by S.C. Wache for Biol2064.01
  2. 2. You are responsible for the following figures and tables : Fig. 6.1 - skin consists of CT and ET. ET - stratified squamous epithelium CT - irregular dense connective tissue ET - glandular epithelium CT - adipose tissue Read TB, p.159-164 on 'epidermis', 'dermis', 'subcutaneous layer'. Tab. 6.1 - Layers of the Epidermis Fig. 6.2 - Skin. Fig. 6.4 - Melanocytes. Fig. 6.7 - Nails. Fig. 6.9 - Eccrine and apocrine sweat glands. Hair. Read on cuts and burns, TB, pp. 173-175. Which epidermal layer has regenerative function ? Fig. 6.13 - Wound Healing. Fig. 6.14 - Extent of skin damage.
  3. 3. Epithelial Membranes (EM) <ul><li>There are three types of EM : </li></ul><ul><li>Serous / Mucous / Cutaneous </li></ul><ul><li>The skin or cutaneous epithelial membrane, consisting of layers of ET called the epidermis and a layer of CT called the dermis, is an organ of the integumentary system . </li></ul>
  4. 4. Cutaneous Membrane = Skin <ul><li>Skin contains two layers, the epidermis and the dermis . </li></ul><ul><li>The hypodermis is the layer underneath the skin. </li></ul>Figure 6.2
  5. 5. Cutaneous Membrane <ul><li>Beneath the dermis is loose connective and adipose tissue that binds the skin to underlying organs. This is the hypodermis / subcutaneous layer . </li></ul>
  6. 6. Cutaneous Membrane Function <ul><li>Skin is a protective covering that prevents harmful substances from entering the body. </li></ul><ul><li>It helps regulate body temperature and water loss. </li></ul><ul><li>It houses sensory receptors and contains immune system cells. </li></ul><ul><li>It synthesizes chemicals and excretes some wastes. </li></ul>
  7. 7. Epidermis <ul><li>It is composed of stratified squamous epithelium (ET). </li></ul>Figure 6.3
  8. 8. Epidermis <ul><li>It is composed of stratified squamous epithelium (ET) and a simple basal layer of cuboidal cells. </li></ul><ul><li>It lacks blood vessels, but the deepest layer, the stratum basale, is close to the dermis and receives nutrients. </li></ul><ul><li>The thickness of the epidermis varies with region of the body. </li></ul>
  9. 9. Layers of the Epidermis from deepest to top layer <ul><li>Stratum basale : deepest layer, single row of cells that divide and grow </li></ul><ul><li>Stratum spinosum : flat cells specialize and synthesize keratin </li></ul><ul><li>Stratum granulosum : flat keratinized cells mature and nuclei appear shriveled </li></ul><ul><li>Stratum lucidum : clear cells </li></ul><ul><li>Stratum corneum : many layers of flat, dead, keratinized, nonnucleated cells that are shed </li></ul><ul><li>* The epidermis, like most epithelial tissues, regenerates. Epidermal c ells exhibit high mitotic activity. They divide, grow, and die, while the new cells are already progressing through the same process. </li></ul>
  10. 10. Melanin – A Pigment <ul><li>It is a dark pigment produced by melanocytes in the basal layer . </li></ul><ul><li>Melanin absorbs UV light and prevents mutations and damage to cells . </li></ul>Figure 6.4 basal layer
  11. 11. Skin Cancers Clinical Applications 6.1 (textbook p. 163) Problem : Need balance between too much UV and skin cancer and too little UV and Vit. D deficiency due to lack of Vit. D synthesis in the absence of sunlight. Types of Skin Cancers: Squamous cell carcinoma Basal cell carcinoma Malignant melanoma
  12. 12. Carcinoma: a malignant tumor of epithelial origin Melanoma: a benign or malignant skin tumor containing dark pigment; sometimes it is a tumor of high malignancy that starts in melanocytes of normal skin or moles and metastasizes rapidly and widely -- called also malignant melanoma, melanocarcinoma, melanoepithelioma, melanosarcoma Sarcoma: a malignant neoplasm arising from connective tissue, bone, cartilage, or striated muscle that spreads by extension into neighboring tissue or by way of the bloodstream From: Skin Cancers and Other Cancers
  13. 13. Dermis Structure <ul><li>The dermis is separated from the epidermis by the basement membrane . </li></ul><ul><li>Epidermal ridges = dermal papillae project into the dermis. These dermal papillae are responsible for fingerprints. </li></ul><ul><li>The dermis binds the epidermis to the underlying tissues. </li></ul><ul><li>The dermis is composed of irregular dense connective tissue with collagen and elastin in a gel-like ground substance. </li></ul>
  14. 14. Dermis Function <ul><li>Dermis contains muscle fibers. Smooth muscles are associated with follicles and glands. </li></ul><ul><li>Motor and sensory nerves and sensory receptors are found throughout the dermis. </li></ul><ul><li>The dermis contains blood vessels , hair follicles, sebaceous and sweat glands. </li></ul>
  15. 15. Subcutaneous Layer <ul><li>The subcutaneous layer or hypodermis is made up of loose connective tissue and adipose tissue . </li></ul><ul><li>Collagenous and elastic fibers are continuous with those in the dermis. </li></ul><ul><li>The adipose tissue conserves body heat . </li></ul><ul><li>The subcutaneous layer contains the major blood vessels that supply the skin with oxygen, nutrients, and immune cells. </li></ul>
  16. 16. Accessory Organs: Hair Follicles <ul><li>Hair develops from epidermal cells at the base of the hair follicle. </li></ul><ul><li>Epidermal cells keep dividing continuously, grow, and die. </li></ul>Figure 6.6
  17. 17. Hair Follicles <ul><li>Hair develops from epidermal cells at the base of the hair follicle. </li></ul><ul><li>Epidermal cells keep dividing continuously, grow, and die. </li></ul><ul><li>The dead cells make up the shaft of the hair. </li></ul><ul><li>The arrector pili muscle is a smooth muscle attached to the follicle. </li></ul><ul><li>It causes hair to stand upright on the skin. </li></ul>
  18. 18. Accessory Organ: Nails <ul><li>consist of nail plate over a growing epithelium of the nail bed on the skin surface. </li></ul>Figure 6.8
  19. 19. Nails <ul><li>Nails consist of a nail plate over a growing epithelium of the nail bed on the skin surface. </li></ul><ul><li>The white lunula at the base of the nail is the region of most active growth. </li></ul><ul><li>Epithelial cells divide and become keratinized. </li></ul>
  20. 20. Sweat Glands <ul><li>These glands respond to increased body temperature and </li></ul><ul><li>function in evaporative cooling. </li></ul>Figure 6.10 – Eccrine Sweat Gland
  21. 21. Sweat Glands <ul><li>Sweat or sudoriferous glands are epithelial glands widespread in the skin. </li></ul><ul><li>Eccrine sweat glands respond to increased body temperature and function in evaporative cooling. </li></ul><ul><li>Apocrine sweat glands become active at puberty and secrete sweat that produces body odor when metabolized by bacteria. </li></ul><ul><li>They can respond to pain, fear, and emotions. </li></ul><ul><li>Modified sweat glands : </li></ul><ul><li>Ceruminous glands secrete ear wax. </li></ul><ul><li>Mammary glands secrete breast milk. </li></ul>
  22. 22. Sebaceous Glands <ul><li>Sebaceous glands are holocrine glands associated with hair follicles. </li></ul><ul><li>Sebum , a mixture of fatty material and cellular debris, is secreted to keep hair and skin soft and waterproof. </li></ul><ul><li>Acne results from excess sebum secretion. </li></ul>
  23. 23. Figure 6.11
  24. 24. Problems in Temperature Regulation <ul><li>Hypothermia or lowered body temperature is a dangerous condition resulting from cold exposure. </li></ul><ul><li>Hyperthermia or increased body temperature can result from inadequate body cooling during exercise or in extreme heat. </li></ul><ul><li>* Clinical Application 6.4 </li></ul>
  25. 25. Skin Color <ul><li>Heredity and environment determine skin color. </li></ul><ul><li>The number of melanocytes is the same in all races, but more melanin is released in darker skinned individuals. </li></ul><ul><li>People who inherit mutant melanin genes do not produce this pigment and have nonpigmented skin and hair, albinism . </li></ul>
  26. 26. Other Factors Influencing Skin Color <ul><li>Ultraviolet light and X-rays stimulate melanocytes to synthesize melanin. </li></ul><ul><li>Oxygenated blood creates a pink tint to skin while lack of oxygen results in cyanosis where the skin appears bluish. </li></ul><ul><li>Carotene , found in yellow vegetables, can create a yellow or sallow tint to skin. </li></ul><ul><li>Jaundice due to liver malfunction can create a bright yellow color in the skin. </li></ul>
  27. 27. Skin Healing <ul><li>Superficial cuts heal due to increased epithelial cell division. </li></ul><ul><li>Dermal cuts involve clotting and scab formation. Growth factors stimulate cell division and growth and scars may form. </li></ul>
  28. 28. Skin Healing - Burns <ul><li>Superficial partial-thickness ( first degree ) burns involve redness of the epidermis. </li></ul><ul><li>Deep partial-thickness ( second degree ) burns destroy the epidermis and some of the dermis. Fluid escapes causing blisters. </li></ul><ul><li>Full-thickness ( third degree ) burns destroy the epidermis, dermis, and accessory skin organs. </li></ul><ul><li>Treatment of burns involves estimating the burn surface area by the “rule of nines” (Fig. 6.14) </li></ul>