The Integumentary System

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The Integumentary System

  1. 1. The Integumentary System
  2. 2. Introduction An organ consists of a group of tissues that performs a specific function. The tissues comprising the skin are the epithelium of the epidermis and the connective tissues of the dermis. A system is a group of organs working together toward common goals. The organs that make up the integumentary system are the skin and its derivatives, such as hair, nails, glands and nerve endings; many interrelated factors (nutrition, hygiene, circulation, age, immunity, genetic traits, psychological traits, psychological state and drug use) affect both appearance and health of the skin.
  3. 3. Skin The skin is one of the largest organs of the body. Dermatology is the medical specialty that deals with diagnosing and treating skin disorders. Structurally, skin consists of two principal parts: the epidermis (the outer, thinner portion composed of epithelium) and the inner or thicker dermis which is composed of connective tissue. It overlies the subcutaneous or SubQ layer. This is also called the superficial fascia or hypodermis.
  4. 4. Functions of the Skin Regulation of body temperature Protection Sensation Excretion Immunity Blood Reservoir Synthesis of Vitamin D
  5. 5. Epidermis The epidermis is composed of stratified squamous epithelium and contains four principal types of cells: keratinocytes, melanocytes, Langerhans cells and Merkel cells. Four or five (soles or palms) distinct layers form the epidermis.
  6. 6. Epidermis The layers of the epidermis (from deepest to most superficial) are: stratum basale (also known as the stratum germinitivum), stratum spinosum, stratum granulosum, stratum lucidum (which is only in the palms and soles) and the stratum corneum.
  7. 7. Epidermis The basale layer undergoes continuous cell division and produces all other layers. The cells in the multiple layers of the stratum corneum are continuously shed and replaced by the cells from the deeper strata. Keratinization: replacement of cell contents with the protein keratin, occurs as the cells move to the skin surface over 2 to 4 weeks.
  8. 8. Epidermis Epidermal Growth Factor or EGF is a hormone that stimulates growth of epithelial and epidermal cells during tissue development repair and renewal.
  9. 9. Dermis The dermis is composed of connective tissue containing collagen and elastic fibers. It has two regions: papillary and reticular layers.
  10. 10. Papillary Layer The papillary layer is areolar connective tissue containing fine elastic fibers, dermal papillae and corpuscles of touch or Meissner’s corpuscles.
  11. 11. Reticular Layer The reticular layer is irregular connective containing collagen and elastic fibers, adipose tissue, hair follicles, nerve, sebaceous (oil) glands and ducts of sudoriferous (sweat) glands Strength, extensibility and elasticity are provided to the skin by the combination of collagen and elastin fibers. Lamellated or Pacinian corpuscles found in the subcutaneous layer (hypodermis or superficial fascia) are sensitive to pressure. Lines of cleavage (tension lines) indicate the direction of collagen fibers bundles in the dermis and are considered in making surgical incisions.
  12. 12. Skin Color The wide variety of colors in skin are due to three pigments: melanin, carotene and hemoglobin (in blood capillaries) in the dermis. The color of skin and mucous membranes can provide clues for diagnosing certain problems such as cyanosis, jaundice and erythema.
  13. 13. Skin Color Epidermal ridges increase friction for better grasping ability and provide for the basis of fingerprints and footprints. The ridges typically reflect contours of the underlying dermis.
  14. 14. Skin Grafts When the germinal portion of the epidermis is destroyed, new skin cannot regenerate without a skin graft. The most successful type of skin graft comes from the individual himself or from an identical twin. Another type of self donation is autologous skin transplantation in which sheets of skin are grown in the laboratory from a small amount of the patient’s epidermis, synthetic materials may be used to simulate dermis and epidermis while this skin is being grown.
  15. 15. Epidermal Derivatives Epidermal derivatives are structures developed from the embryonic epidermis. Examples of epidermal derivatives are hair, skin glands (sebaceous, sudoriferous and ceruminous) and nails.
  16. 16. Hair Hairs or pili are epidermal growths that function in protection and reduction in heat loss. Hair consists of a shaft above the surface, a root that penetrates the dermis and subcutaneous layer and a hair follicle. Associated with hairs are sebaceous (oil) glands, arrectores pilorum muscles and root plexuses in a cyclic pattern. The color of hair is primarily due to melanin. Hormones—particularly androgens—can stimulate hair growth in both males and females or somehow inhibit it in genetically predisposed males (male pattern baldness). Drug treatment can occasionally stimulate regrowth of some lost hair.
  17. 17. Glands Sebaceous (oil) glands are usually connected to hair follicles; they are absent in the palms and soles. Sebaceous glands produce sebum which moistens hairs, waterproofs and softens the skin. Enlarged sebaceous glands may produce blackheads, pimples and boils.
  18. 18. Sudoriferous Glands Sudoriferous glands or sweat glands are divided into apocrine and eccrine types. Eccrine Sweat Glands: have an extensive distribution, their ducts terminate at pores at the surfaces of the epidermis. Apocrine: Limited in distribution to the skin of the axilla, pubis, and areolae their ducts open into the hair follicles. Sudoriferous glands produce perspiration (sweat) which assists in maintaining proper body temperature and also carries small amounts of washes to the surface.
  19. 19. Ceruminous Glands Ceruminous glands are modified sudoriferous glands that produce a waxy substance called cerumen. The are found in the external auditory meatus (ear canal).
  20. 20. Nails Nails are hard keratinized epidermal cells over the dorsal surfaces of the terminal portions of the fingers and toes. The principal parts of a nail are: body, free edge, root, luncuna, eponychium and matrix. Cell division of the matrix cells produce new nails. Functionally, nails help in grasping and manipulating small objects in various ways and provide protection against trauma to the ends of the digits.
  21. 21. Skin and Homeostasis Epidermal Wound Healing: wounds are repaired by enlargement and migration of basal cells, contact inhibition and division of migrating and stationary basal cells.

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