Integumentary chap 1

• INTEGUMENTARY SYSTEM

  • Consists of the skin, hair, glands, and nails

  • Functions:

  1. Protection

  – Against abrasion and UV light

  – Prevents entry of microorganisms

  – Prevents dehydration

  2. Sensation

  – Sensory receptors that can detect heat, cold, touch, pressure, and pain

  3. Temperature regulation

  by controlling:

  – Blood flow through the skin

  – Sweat gland activity

  4. Vitamin D production

  5. Excretion of small amounts of waste products
• Sweat glands


  • Produce sweat, which evaporates and lowers body temperature
• Nails


  Protect the ends of the digits
• Protection - Skin


  • Protects against abrasion and UV light
  • Prevents the entry of microorganisms
  • Helps regulate body temperature
  • Prevents water loss
• Sensation - Skin

  • Heat
  • Cold
  • Touch
  • Pressure
  • Pain
• Excretion - Skin


  • Skin glands remove small amounts of waste products but are not important in excretion
• Protection - Hair


  • Protects against abrasion and UV light
  • Acts as a heat insulator
• Vitamin D Production


  • UV light stimulates the production of a precursor molecule in the skin that is modified by the liver and kidneys into vitamin D
  • Vitamin D increases calcium uptake in the intestines
• Temperature Regulation - Skin


  Controls heat loss from the body by dilation and constriction of blood vessels
• SKIN

  Consists of three major regions:

  – Epidermis: outermost region (superficial)

  • Resists abrasion

  • Reduces water loss

  – Dermis: middle region (bulk of skin)

  • Responsible for most of the structural strength of the skin

  • Leather is produced from the dermis of animals

  – Subcutaneous tissue (hypodermis): deepest region

  • Not really part of the skin

  • Connects the skin to underlying muscle or bone
• Melanocytes


  • Produce the brown pigment melanin
  • Found in the deepest layers of the epidermis
• Cell types

  • Keratinocytes
  • Melanocytes
  • Merkel cells
  • Langerhans’ cells
• Thin skin


  • Contains fewer cell layers per stratum
  • Stratum lucidum is usually absent
  • Hair is found only in thin skin
• Merkel cells


  Touch receptors in association with sensory nerve endings
• Langerhans’ cells


  • Epidermal macrophages
  • Help activate the immune system
• Keratinocytes


  • Most abundant cell type
  • Produce the fibrous protein keratin
  • Gives skin its protective properties
• Thick skin


  • Has all five epithelial strata
• Epidermis


  Composed of keratinized stratified squamous epithelium, consisting of four distinct cell types and four or five layers
• Skin Color

  • Melanocytes produce melanin inside melanosomes and then transfer the melanin to keratinocytes

  – The size and distribution of melanosomes determine skin color

  – Melanin production is determined genetically but can be influenced by UV light

  (tanning) and hormones

  • Increased blood flow produces a red skin color (Erythema), whereas a decreased flow

  causes pale skin

  – Decreased oxygen content in the blood results in a bluish color called cyanosis

  • Carotene, an ingested plant pigment, can cause the skin to appear yellowis
• Papillary layer


  Areolar connective tissue with collagen and elastic fibers
• Dermis


  Second major skin region containing strong, flexible connective tissue
• Dermal papillae


  Contain blood vessels that supply the overlying epidermis
• Components of the papillary layer

  • Dermal papillae
  • Blood vessels
  • Nutrients
  • Waste products
  • Regulation of body temperature
• Cell types in the dermis

  • Fibroblasts
  • Adipose cells
  • Macrophages
• Functions of the reticular layer


  • Collagen fibers add strength
  • Elastin fibers provide stretch-recoil properties
  • Striae (stretch marks) are caused when skin is overstretched, the dermis ruptures and leaves visible lines
• Dermal papillae


  Peg-like projections on the superior surface of the papillary layer
• Reticular layer


  Dense irregular connective tissue
• • Reticular layer

  – Dense irregular connective tissue

  – Accounts for approximately 80% of the thickness of the skin
• Subcutaneous Tissue

  • Deep to the skin

  • Composed of adipose and areolar connective tissue

  • Not really part of the skin

  • Mostly adipose tissue

  • Stores fat and connects the skin to the underlying structures (mainly muscles)

  • Shock absorber and insulator

  • Increases greatly as you gain weight
• Sebaceous Glands

  • Simple or compound alveolar glands found all over the body except on the palms and soles

  • Soften skin when stimulated by hormones

  • Secrete an oily secretion called sebum

  • Acne is an active inflammation of the sebaceous glands.
• Sweat Glands

  • Different types prevent overheating of the body

  • Secrete cerumen and milk

  • Up to 3 million/person

  – Merocrine sweat glands: produce sweat, which cools the body: most numerous in the palms and soles of the feet

  – Apocrine sweat glands: Found in axillary and genital areas. Ducts empty into hair follicles. Produce an organic secretion that can be broken down by bacteria to cause body odor

  – Ceruminous glands: modified merocrine glands in external ear canal that secrete cerumen (ear wax)

  – Mammary glands: specialized sweat glands that secrete milk
• Effects of Aging on the Integumentary System

  • Epidermal replacement of cells slows and skin becomes thinner

  • Decreased elasticity and loss of subcutaneous tissue leads to wrinkles

  • Subcutaneous fat layer diminishes, leading to intolerance of cold

  • Skin becomes dry and itchy

  • Sweat and sebaceous glands are less active, and the number of melanocytes decreases
• HAIR

  • Lanugo (fetal hair) is replaced near the time of birth by terminal hairs (scalp, eyelids, and eyebrows) and vellus hairs

  • At puberty, vellus hairs can be replaced with terminal hairs

  • Hairs are columns of dead, keratinized epithelial cells

  – Each hair consist of

  • A shaft above the skin

  • A root below the skin

  • A hair bulb the site of hair formation

  • Hairs have a growth stage and a resting stage

  • Contraction of the arrector pili, which are smooth muscles, causes hair to “stand on end” and produces “goose flesh”.
• Kwashiorkor

  Severe protein deficiency

  The hair color is faded, and appears reddish or bleached and the texture is coarse and dry.

  Alopecia

  • Hair loss
• Cyanosis


  Bluish tinge, most evident in the nail beds, lips, and buccal mucosa
• Generalized edema is most often an indication of impaired venous circulation and in some cases reflects cardiac dysfunction or venous abnormalities
• Erythema


  Skin redness associated with a variety of rashes and other conditions
• Edema


  The presence of excess interstitial fluid. Appears swollen, shiny, taut, and tends to blanch the skin color or, if accompanied by inflammation, may redden the skin
• Jaundice


  Yellowish tinge, may first be evident in the sclera of the eyes and then in the mucous membranes and the skin
• Pallor


  Result of inadequate circulating blood or hemoglobin and subsequent reduction in tissue oxygenation