Bio1 Integ System

• Integumentary system


  The body system that forms the body's outer covering and primarily functions in protecting the body from the threats of outside environment
• The integumentary system is composed of the skin and its derivatives: the hairs, nails, and glands
• Skin and its secretions form the first line of barrier defense of the body by providing an intact organ preventing pathogens to enter the body and maintaining an acidic environment which is not suitable for the growth of pathogens
• Functions of the integumentary system

  • Protection
  • Covering
  • Sensation
  • Thermoregulation
  • Vitamin D synthesis
  • Excretion
  • Osmoregulation
• Skin


  The largest external organ of the body
• Functions of skin


  • Protection
  • Covering
  • Sensation
  • Thermoregulation
  • Vitamin D synthesis
  • Excretion
  • Osmoregulation
• Skin


  • Has three main layers: epidermis, dermis and hypodermis (subcutaneous)
• Functions of epidermis


  • External surface protection
  • Waterproofing
  • Formation of hair and nails
  • Responsible for natural skin color
• Layers of epidermis


  • Stratum Corneum
  • Stratum Lucidum
  • Stratum Granulosum
  • Stratum Spinosum
  • Stratum Basale
• Stratum Corneum


  The uppermost multi-layer of dead, keratinized, cornified squamous cells
• Exfoliation


  The process of the stratum corneum continuously shedding off
• Stratum Lucidum


  A layer only found in the thick skin, providing additional thickness to areas prone to shock and pressure
• Stratum Granulosum


  A layer with active keratinocytes, which are cells producing keratin
• Stratum Basale


  The lowermost layer made up of one layer of columnar cells, where cells are actively dividing to give rise to cells that will comprise the upper layers
• Melanocytes


  Cells in the stratum basale that produce melanin, the substance responsible for skin pigmentation
• Higher melanin production results in a darker skin color while lower melanin production results in a lighter skin color
• Melanin


  Acts as a protection of the skin against harmful UV rays by scattering UV rays and consuming free radicals which are induced by light
• Vitamin D synthesis


  1. Epidermis synthesizes cholecalciferol from a steroid cholesterol in the skin when exposed to UV rays

  2. Cholecalciferol is converted into calcidiol in the liver

  3. Calcidiol is further converted into calcitriol in the kidney

  4. Calcitriol is the active chemical form of the vitamin used by the body for the absorption of calcium and phosphorus needed for bone nourishment and repair
• Dermis


  The second layer of the skin found between the epidermis and hypodermis, acting as the skin glue
• Functions of dermis


  • Provides elasticity of the skin
  • Nourishes the epidermis
  • Receives sensory stimulation
  • Forms the unchanging fingerprint and footprint for unique identity and for easy grasping without slippage
• Structures found in the dermis

  • Abundant areolar connective tissue
  • Blood vessels
  • Sensory receptors
• Areolar connective tissue


  Contains elastin fibers which provide elasticity to the skin
• Blood vessels


  Provide nourishment to the skin cells and have thermoregulatory functions
• Types of sensory receptors in the dermis

  • Mechanoreceptors
  • Thermoreceptors
  • Pain receptors or nociceptors
• Hypodermis


  The lowermost layer of the skin made up of fats and adipose tissue, found between the dermis and muscle
• Functions of hypodermis


  • Provides a high energy reserve
  • Provides insulation
  • Provides cushion
  • Gives body contour
• Hair


  Structure produced by the basale cells of the skin, made up of keratin protein and cuticle
• Functions of hair


  • Thermoregulation
  • Protection
  • Sensation
• The main function of nails is to protect the toes and fingers, and they are also used in grasping small objects and modified into defensive structures
• Types of skin glands

  • Sebaceous glands
  • Sweat glands
• Sebaceous glands


  Sac-like type of exocrine gland that secrete oil or sebum to lubricate the skin and hair, prevent dryness, and contribute to the acidity of the skin
• Sweat glands


  Coiled tubule-like type of exocrine gland that secrete sweat, a mixture of water, ions, nitrogenous wastes and sometimes proteins
• Types of sweat glands

  • Eccrine sweat glands
  • Apocrine sweat glands
• Eccrine sweat glands


  Found almost everywhere, secrete sweat mainly for thermoregulation and minor excretion
• Apocrine sweat glands


  Found only in some areas like the armpit and ano-genital area, active during puberty, emotional stress, and sexual stimulation, may contribute to body odor if left unchecked
• Other modified sweat glands

  • Ceruminous glands
  • Ciliary glands
  • Mammary glands
• Effects of aging on the skin


  • Becomes rougher and drier
  • May develop benign tumors and lesions
  • Becomes slack or soggy
  • Becomes more transparent
  • Becomes more fragile
  • Becomes more easily bruised
  • Losses fat in the hypodermal region
  • Develops discoloration
  • Hair becomes gray
• Middle layer of the skin that contains blood vessels, nerves, hair follicles, and sweat glands. Responsible for providing strength and elasticity to the skin.

  Dermis
• Epidermis


  Outermost layer of the skin that serves as a barrier to protect the body from the external environment. Made up of dead skin cells that are constantly being shed and replaced by new ones.
• Hypodermis (Subcutaneous)


  Innermost layer of the skin made up of fat and connective tissue. Helps to regulate body temperature and protect vital organs.