integumentary system study

• Wound Healing in the Skin

  Fibroblasts from the dermis form an unusually dense mass of new connective fibers for wounds where there is damage to the epidermis, dermis (and possibly hypodermis); if not replaced by normal tissue, this mass remains a scar
• First Layer of the dermis

  • Papillary Layer
  • Made of dermal papillae that project into the epidermis
  • Contains fine collagenous and elastic fibers
  • Papillae make ridges to which the epidermis conforms = fingerprints
• The term integument refers to the skin only
• Nails

  • Made of very hard, tightly-packed plates of keratinized cells; functions include protection (from abrasion of fingers & toes); manipulation of small objects
• Functions of the integumentary system

  • Protection from infection and environmental damage (e.g. UV radiation)
  • Skin is the most effective barrier against microbial invasion
  • Temperature regulation
  • Sensation (temperature, pain, pressure & touch)
  • Production of some chemicals and hormones
  • Excretion of some wastes
• Glands

  • Sebaceous – produce sebum (oil); keeps skin soft and waterproof, prevents hair from drying out; almost always associated with hair follicles
  • Ceruminous – produce cerumen (ear wax) in external ear; prevents dehydration and traps foreign particles
  • Sweat: merocrine – produce sweat (regulate body temperature) and eliminate some wastes (e.g. ammonia and urea); cover most of body, apocrine – produce secretions colonized by bacteria; found in armpits and pubic region
• Accessory structures of the skin

  • Hair
  • Nails
  • Glands
• Layers of the skin

  • Epidermis – outermost epithelial layer (= stratified squamous keratinized epithelium)
  • Dermis – middle layer of connective tissue (= dense connective tissue)
• Integumentary system includes

  • Skin
  • Hair
  • Nails
  • Cutaneous glands
• Melanocytes

  • Produce melanin
• Disorders Affecting the Hair:

  -Alopecia – Thinning of the hair

  -Pattern Baldness - Hair loss from select regions of the scalp & Hormonally/genetically driven

  -Hirsutism - Excessive hairiness & caused by masculinizing ovarian tumors or overactive testosterone production
• Hair

  • Made of hard, dead, keratinized cells; produced by cells located deep in the dermis
  • Functions include: protection (from light, heat loss and foreign particles); sensation (touch)
  • Growth occurs in cycles: Anagen, Catagen, Telogen
  • Color depends on type and amount of melanin present
• Second layer of Dermis

  Reticular Layer

  • Denser area of connective tissue with extensive collagen and elastic fibers (make the skin tough yet flexible)
  • Contains hair follicles, voluntary muslces (facial expressions), involuntary muscles (e.g., goosebumps = activation of piloerector muscles)
• Subcutaneous layer (hypodermis)


  not technically part of the skin; deepest connective tissue layer (contains adipose [fat])
• The Epidermis (five layers)


  keratinized (hardened) stratified squamous epithelium

  1. stratum corneum (outermost) -> up to 30 layers of dead (keratinized) cells; resistant to abrasion, penetration and water loss
  2. stratum lucidum -> found only in areas with thick skin (just above the stratum granulosum)
  3. stratum granulosum -> three to five layers of flat keratinocytes
  4. stratum spinosum -> lower layers keep dividing
  5. stratum basale (innermost) -> layer with melanocytes, stem cells and tactile cells; only layer with stem cells that divide to replace cells that are lost at the surface (via exfoliation)
• Four cell types

  Keratinocytes - majority of skin cells

  • produces keratin: tough, fibrous protein; makes skin water resistant; protects underlying tissues from microbes and the environment

  Melanocytes

  • produce melanin -> dark pigment, transferred to keratinocytes; protects nuclei of underlying cells from damage induced by UV light exposure

  Merkel cells

  • special receptors that detect very light touch

  Langerhans cells

  • help white blood cells with immune response
• Thick vs. Thin Skin

  Thick Skin

  • found on the palms, soles of the feet
  • thick stratum corneum layer (dead cells)
  • sweat glands but no hair follicles or sebaceous (oil) glands

  Thin Skin

  • found everywhere in the body
  • thin stratum corneum
  • hair follicles, sebaceous glands and sweat glands
• Vitamin D production

  UV light activates a precursor molecule in epidermal cells that is converted to calcitriol (the active form of Vitamin D) by other cells in the liver and kidneys
• Skin Color

  Depends on melanocytes; number is about the same in all races, but amount of melanin varies considerably
• Skin Disorders

  Skin cancer; three types:

  • Basal cell carcinoma (least dangerous); arises from stratum basale and invades dermis
  • Squamous cell carcinoma; arises from keratinocytes in stratum spinosum
  • Malignant melanoma (most deadly); arises from melanocytes of a preexisting mole
• Factors that should be monitored

  Asymmetry, Border irregularity, Color mixed and Diameter over 6 mm
• Burns

  • First degree: epidermis only
  • Second degree: epidermis and part of dermis
  • Third degree: epidermis and dermis

  Burns can lead to infection and dramatic dehydration, both of which can be deadly
• Abnormal hues (shades)

  1. Cyanosis: blue tinge resulting from insufficient oxygen in the circulating blood
  2. Erythema: redness due to dilated cutaneous vessels (e.g., following sunburn)
  3. Jaundice: yellowing of skin and sclera (eyes) due to excess of bilirubin in blood (liver disease)
  4. Bronzing: golden-brown color of Addison disease (deficiency of glucocorticoid hormone)
  5. Pallor: pale color from lack of blood flow
  6. Albinism: a genetic lack of melanin
  7. Hematoma: bluish/purple bruise (visible clotted blood)