integumentary system

• In 1 square inch of skin there are millions of cells
• Things found in 1 square inch of skin

  • 500 sweat glands
  • 1000 nerve endings
  • Yards of blood vessels
  • 100 oil or sebaceous glands
  • 150 pressure sensors
  • 75 sensors for heat
  • 10 sensors for cold
• Skin weighs about 20 lbs or 16% of total body weight
• Thick skin


  Devoid of hair and found only on the plantar (foot) and palmar surfaces (hands)
• Thin skin


  Covers most of the body except for the palmar and plantar surfaces of the hands and feet, respectively
• The thickness of skin varies from 0.5mm thick on the eyelids to 4.0mm thick on the heels of your feet
• Capecitabine: hand and foot syndrome


  Small amount of drug leaks into palms of the hands and soles of the feet, causing damage to surrounding tissues
• Symptoms of hand and foot syndrome

  • Tingling or burning
  • Redness
  • Flaking
  • Swelling
  • Small blisters
  • Small sores on the palms of the hands or the soles of the feet
• 62 year old patient with long term use (3 years maintenance dose) of head and neck cancer had mild hand and foot syndrome and loss of finger prints
• Main layers of skin

  • Epidermis
  • Dermis
  • Hypodermis
• Other structures in skin

  • Sweat glands
  • Hairs
  • Sebaceous glands
  • Smooth muscle
• Epidermis


  Thin outer portion, keratinised stratified squamous epithelium of skin
• Keratin


  Threadlike protein with a protective role
• The epidermis is important for the protective function of skin
• The basal layers of the epidermal epithelium are folded to form dermal papillae
• Layers of thin skin epidermis

  • Stratum corneum
  • Stratum lucidium
  • Stratum granulosum
  • Stratum spinosum
  • Stratum basale
• Layers of thick skin epidermis

  • Stratum corneum
  • Stratum lucidium
  • Stratum granulosum
  • Stratum spinosum
  • Stratum basale
• Stratum corneum


  Layers of flattened keratinised (dead) cells, with space between cells full of lipids that cement the cells together
• Cells are constantly lost from the stratum corneum (exfoliation)
• Variation in skin thickness of the epidermis are due to the varying thickness of the stratum corneum
• Stratum lucidum


  Highly reflective, only seen in thin skin
• Stratum granulosum


  In thick skin, a few layers of flattened cells with cytoplasmic granules; in thin skin only 1 layer may be visible
• Stratum spinosum


  Keratinocytes attached to each other by desmosomes on spiny processes, several layers of polyhedral cells
• Stratum basale (also known as stratum germinativum)


  Single layer of germinal cells resting on the basement membrane which is attached to the dermis - low columnar or cuboidal cells at the base of the epidermis, these are the stem cells of the epidermis
• Renewal of the epidermis takes about 3-4 weeks
• Langerhans cells


  Phagocytic cells in the epidermis that engulf foreign materials, migrate out of the epidermis and skin to lymph nodes when they contact an antigen
• Merkel cells


  Granular basal epidermal cells, attached to a free (Non-myelinated nerve ending-mechanoreceptor), mostly found in thick skin on the palms of hands and soles of feet, slow adapting, type I mechanoreceptors
• Epidermal glands


  • Sweat glands
  • Sebaceous glands
• Encapsulated nerve endings in the dermis

  • Pacinian corpuscles
  • Meissner's corpuscles
  • Ruffini endings
  • Free nerve endings
• Need for protection against UV radiation

  Destroys folate (vitamin B), causes skin cancer
• Need UV to produce vitamin D for calcium absorption


  Balances need for protection against UV radiation
• Albinism - melanocytes completely fail to secrete melanin, resulting in white hair, skin, and iris
• Vitiligo - loss of pigment in certain areas of the skin producing white patches
• Freckles (ephelides) and moles (naevi) are formed when melanin becomes concentrated in local areas
• Malignant melanoma - a cancerous change in a mole that may metastasize (spread) rapidly and is most difficult to treat
• In Addison's disease, the pituitary gland produces more corticotropin which stimulates melanin production, causing dark pigmentation of the skin and lining of the mouth
• Blushing


  Governed by the sympathetic nervous system, causing more local blood flow in the cheeks
• Primary skin lesions


  Variations in colour or texture that may be present at birth or acquired during a person's lifetime
• Secondary skin lesions


  Changes in the skin that result from primary skin lesions, either as a natural progression or as a result of a person manipulating a primary lesion
• Secondary skin lesions


  • Separation of a nail plate from nail bed
  • Bed sores