StudyLoop

INTEGUMENTARY SYSTEM

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by

luna
in

Integumentary System

 “covering” Composed of:

  • Cutaneous membrane:

–       Epidermis – superficial epithelium

–       Dermis – underlying “cutaneous tissue” with blood supply

  • Accessory structures:

–       Hair

–       Nails

–       Exocrine glands

Functions:

  • Protect underlying tissues from infection, exposure and dehydration.
  • Excrete salts, water, and organic waste.
  • Maintain normal body temp (conserve and radiate heat).
  • Synthesize Vitamin D3 for calcium metabolism.
  • Store nutrients (fat).
  • Sensory detection: touch, pressure, pain, and temp.

Epidermis:

  • The corrugated border between dermis and epidermis helps bond epidermis to the dermis (increased surface area for attachment):

–       In thick skin, epidermal ridges show on the surface as fingerprints: function to enhance gripping.

  • Epidermis water resistant but notwaterproof:

–       Insensible perspiration: water loss through epidermis: ~500ml (1 pint)/day (more if damaged, e.g. burn).

–        Callus: thickening of the epidermis, due to repeat friction

–       Blister: separation of epidermal layers of epidermis from dermis, space fills with interstitial fluid.

Skin color:

  • Pigment-based: epidermal pigments and blood pigments contribute to the color.
  • Epidermal Pigmentation:

–        Carotene: yellow-orange, from diet.

–        Melanin: brown, from melanocytes.

Sensory perception in integument:

  • Skin highly innervated for sensory perception, mostly in the dermis:
  • Tactile discs/Merkel cells:

–       deep layers of epidermis, superficial touch.

  • Free nerve endings:

–       the superficial dermis, pain, and temperature.

  • Tactile/Meissner’s corpuscles:

–       the superficial dermis, light touch.

  • Lamellated/Pacinian:

–       corpuscles -deep dermis, pressure and vibration.

Accessory Structures of the Integument:

  • Hair follicles and hair
  • Sebaceous glands
  • Sweat glands
  • Nails

v   All these structures are anchored in the dermis but are derived from epidermal tissue.

Hair Functions:

  • Head:

–        UV protection

–        Cushion from trauma

–        Insulation Nostrils, Ears canals, Eyelashes: -prevent the entry of foreign material.

  • Body hair:

–       Sensory detection

Integumentary Glands:

v  All are exocrine glands (secrete product onto skin surface via a duct).

  • Sebaceous glands:

–       Holocrine secretion

–        Secrete sebum into hair follicle

Sebum: lipids +cholesterol + proteins + electrolytes.

  • Function:

–       lubricate and protect keratin.

–       Prevent evaporation.

–       Inhibit bacterial growth.

v   Sebaceous glands active in the fetus, then off until puberty, on whole adult life.

Sudoriferous glands / Sweat glands:

Merocrine/Eccrine sudoriferous glands:

  • Produce sensible perspiration: 99% water + electrolytes + organic nutrients + antibodies + antimicrobial agents + organic wastes.

–       Functions:

    • Evaporative cooling of the surface of the skin to reduce body temp
    • Excrete waste electrolytes and drugs
    • Protection:
        •  Prevent adherence of microbes (antibodies).
        •  Physically wash off microbes.
        •  Antimicrobial agents to kill microbes dermcidin (antibiotic).
    •  Merocrine secretion.
    •  Small coiled tubular glands.
    •  Located in the superficial dermis.
    •  Open directly on the surface of the skin.
    • Secrete in response to high temp or stress.
  • Merocrine secretion
  • Armpits, nipples, groin
  • Secrete into the hair follicle
  • Secretion is sticky and cloudy:

–       sensible perspiration + proteins + lipids

  • Microbes eat it → wastes: body odor
  • Glands deep in the dermis
  • Surrounded by myoepithelial cells: a contract in response to sympathetic nervous system stimulation
  • Active only after puberty
  • Special apocrine sweat glands:

–        Mammary glands:

  • located in female breast -secrete milk during lactation.

–       Ceruminous glands:

  • located in external ear canal-secrete cerumen.

Nails:

  • Scale like projections on the dorsal surface of distal digits.
  • Functions:

–       Protect tips from mechanical stress, assist gripping.

–       Consists of dead cells containing hard keratin.

–       New nail formed at nail root -nail growth is continuous.

Injury and Repair:

  • Integument can function independently of nervous and endocrine systems to maintain own homeostasis.
  • Mesenchymal cells of the dermis can regenerate connective tissue.
  • Germinative cells (basal cells) of the epidermis can regenerate epithelial tissue.