Integumentary system

• Integumentary system


  The organs of the integumentary system include the skin and its accessory structures including hair, nails, and glands, as well as blood vessels, muscles and nerves
• Dermatology


  The medical specialty for the diagnosis and treatment of disorders of the integumentary system
• Skin


  • Covers the body and is the largest organ of the body by surface area and weight
  • Its area is about 2 square meters (22 square feet) and weighs 4.5-5kg (10-11 lb), about 16% of body weight
  • It is 0.5 – 4 mm thick, thinnest on the eyelids, thickest on the heels; the average thickness is 1 – 2 mm
• Epidermis


  The outer, thinner layer of the skin, consists of epithelial tissue
• Dermis


  The inner, thicker layer of the skin
• Subcutaneous (subQ) layer


  Also called hypodermis, attaches the skin to the underlying tissues and organs
• Types of cells in the epidermis

  • Keratinocytes
  • Melanocytes
  • Langerhans cells
  • Merkel cells
• Keratinocytes


  • Produce keratin which is a tough fibrous protein that provides protection
• Melanocytes


  • Produce the pigment melanin that protects against damage by ultraviolet radiation
• Langerhans cells


  • Involved in immune responses, arise from red bone marrow
• Merkel cells


  • Function in the sensation of touch along with the adjacent tactile discs
• Layers of the epidermis (thin skin)

  • Stratum basale
  • Stratum spinosum
  • Stratum granulosum
• Layers of the epidermis (thick skin)

  • Stratum basale
  • Stratum spinosum
  • Stratum granulosum
  • Stratum lucidum
  • Stratum corneum
• Stratum basale


  Deepest layer, where continuous cell division occurs which produces all the other layers
• Stratum spinosum


  1. 10 layers of keratinocytes
• Stratum granulosum


  Includes keratohyalin and lamellar granules
• Stratum lucidum


  Present only in thick skin (the skin of the fingertips, palms, and soles)
• Stratum corneum


  Composed of many sublayers of flat, dead keratinocytes called corneocytes or squames that are continuously shed and replaced by cells from deeper strata
• Keratinization


  The accumulation of more and more protective keratin, occurs as cells move from the deepest layer to the surface layer
• Dandruff


  An excess of keratinized cells shed from the scalp
• Dermis


  • Composed of connective tissue containing collagen and elastic fibers
  • Contains two layers: the papillary region and the reticular region
• Papillary region


  Consists of areolar connective tissue containing thin collagen and elastic fibers, dermal papillae (including capillary loops), and corpuscles of touch and free nerve endings
• Reticular region


  Consists of dense irregular connective tissue containing collagen and elastic fibers, adipose cells, hair follicles, nerves, sebaceous (oil) glands, and sudoriferous (sweat) glands
• Striae


  Stretch marks can appear if the skin is stretched too much
• Lines of cleavage


  "Tension lines" in the skin indicate the predominant direction of underlying collagen fibers
• Epidermal ridges


  Reflect contours of the underlying dermal papillae and form the basis for fingerprints (and footprints); their function is to increase firmness of grip by increasing friction
• Dermatoglyphics


  The study of the pattern of epidermal ridges
• Skin color


  • Variations arise from variations in the amounts of three pigments: melanin, carotene, and hemoglobin
• Melanin


  A yellow-red or brown-black pigment produced by melanocytes (located mostly in the epidermis, where it absorbs UV radiation)
• Nevus


  A benign localized overgrowth of melanocytes, or a mole
• Albinism


  An inherited inability to produce melanin
• Vitiligo


  A condition in which there is a partial or complete loss of melanocytes from patches of skin
• Carotene


  A yellow-orange pigment (found in the stratum corneum, dermis, and subcutaneous layer)
• Hemoglobin


  A red color (located in erythrocytes flowing through dermal capillaries)
• Lamellated (pacinian) corpuscles


  Located in the subcutaneous layer (and sometimes the dermis), detect external pressure applied to the skin
• Accessory structures of the skin

  • Hair
  • Skin glands
  • Nails
• Hair

  • Has functions of protection, reduction of heat loss, and sensing light touch
• Hair shaft


  The part of the hair that mostly projects above the surface of the skin
• Hair root


  The part of the hair that penetrates into the dermis
• Hair follicle


  Consists of an epithelial root sheath (Internal) and a dermal root sheath (External)