ANAPHY

• The integumentary system consists of the skin, hair, oil and sweat glands, and nails
• Components of the integumentary system

  • Skin
  • Hair
  • Oil and sweat glands
  • Nails
  • Sensory receptors
• General functions of the integumentary system

  • Helps maintain a constant body temperature
  • Protects the body
  • Provides sensory information about the surrounding environment
• Skin (Cutaneous membrane)


  Covers the external surface of the body and is the largest organ in weight
• Parts of the skin

  • Epidermis
  • Dermis
  • Subcutaneous layer (hypodermis)
• Epidermis


  Thin, simple, keratinized stratified squamous epithelium and it gives rise to most derivatives of the integument
• Principal types of cells in the epidermis

  • Keratinocytes
  • Melanocytes
  • Intraepidermal macrophages
  • Tactile epithelial cells
• Keratinocytes


  They make up 90% of the epidermis and accumulate keratin, a tough and fibrous protein, in their cytoplasm. They also release a water-repellent sealant.
• Melanocytes


  They make up 8% of the epidermis and their long, slender projections extend between the keratinocytes to transfer melanin granules. Melanin is a pigment that absorbs damaging UV radiation.
• Intraepidermal macrophages (Langerhans cells)

  They provide an immune response against microbes.
• Tactile epithelial cells (Merkel cells)


  They are in contact with sensory neurons (tactile discs) to detect touch sensations.
• Types of skin


  • Thin skin (4 layers)
  • Thick skin (5 layers)
• Thick skin is found in areas with the greatest exposure to the skin, such as the fingertips, palms, and soles.
• Dermis


  The second, deepest part of the skin which is composed of dense irregular connective tissue containing collagen and elastic fibers. It contains fibroblasts, macrophages, adipocytes, blood vessels, nerves, glands, and hair follicles.
• Regions of the dermis

  • Papillary region
  • Reticular region
• Papillary region


  Contains dermal papillae that project into the epidermis, capillary loops, blood vessels, and touch/sensory receptors.
• Reticular region


  Attached to the subcutaneous layer, contains large collagen fibers that help the skin resist stretching, as well as blood vessels, nerves, hair follicles, sebaceous glands, and sweat glands.
• Epidermal ridges


  • They create a strong bond between the epidermis and dermis in regions of high mechanical stress, increase the surface area of the epidermis to improve grip and tactile sensitivity.
• Skin pigments


  • Melanin
  • Hemoglobin
  • Carotene
• Melanin


  A pigment synthesized by melanocytes from the amino acid tyrosine, it comes in two forms (pheomelanin and eumelanin) and serves a protective function against UV radiation.
• Hemoglobin


  Skin color ranges from pink to red depending on the oxygen content of blood moving through capillaries in the dermis.
• Carotene


  A yellow-orange pigment that is a precursor of vitamin A and is stored in the stratum corneum, fatty areas of the dermis, and subcutaneous layer.
• Accessory structures of the skin

  • Hair
  • Skin glands
  • Nails
• Hair


  Present on most skin surfaces except palms, soles, and some other areas. Functions include protecting the scalp, decreasing heat loss, protecting the eyes, and providing sensory input.
• Anatomy of the hair

  • Shaft
  • Root
  • Hair follicle
  • Dermal root sheath
  • Bulb
• Layers of the hair shaft and root

  • Medulla
  • Cortex
  • Cuticle
• Hair papilla


  Contains areolar connective tissue and blood vessels that nourish the growing hair follicle and hair matrix.
• Hair matrix


  Contains a germinal layer of cells that arise from the stratum basale and are the site of cell division for hair growth.
• Arrector pili


  Smooth muscle with autonomic nerve endings that contracts during cold or fright to cause hairs to stand up.
• Hair root plexus


  Dendrites of neurons that are sensitive to touch.
• Stages of hair growth

  • Growth stage
  • Regression stage
  • Resting stage
• Types of hair


  • Lanugo
  • Terminal hairs
  • Vellus hairs
• Hair follicle


  Housed by the bulb containing areolar connective tissue and blood vessels nourishing the growing hair follicle and hair matrix
• Hair matrix


  Contains a germinal layer of cells that arise from stratum basale, the site of cell division
• Arrector pili


  Smooth muscle, autonomic nerve endings stimulate this to contract during cold or fright
• Hair root plexus


  Dendrites of neurons, sensitive to touch
• Hair growth


  Cells of the matrix divide and are added to the base of the hair root, existing cells are pushed upward and hair grows longer
• Regression stage


  Cells of the hair matrix stops dividing, the hair follicle shrinks, and the hair stops growing
• Resting stage


  A new growth cycle begins, the old hair root falls out or is pushed out of the hair follicle, and a new hair begins to grow
• Types of hair


  • Lanugo (very fine, nonpigmented, downy hairs that cover the body of the fetus)
  • Terminal hairs (long, coarse, heavily pigmented hairs of the eyebrows, eyelashes, and scalp)
  • Vellus hairs (short, fine, pale hairs of the rest of the body that are barely visible to the naked eye)