integumentary system from study guide

• Integumentary System

  • Consists of the skin, hair, nails, subcutaneous tissue, and assorted glands
  • Most obvious function is protection of underlying tissues and prevention of fluid loss
  • Subcutaneous tissue connects skin to underlying tissues
  • Hair provides insulation, keeps dust and perspiration out of eyes and nasal cavities, and protects fingertips
  • Nails protect fingertips and enhance ability to pick up small objects
• Types of glands in the integumentary system

  • Sudoriferous (sweat) glands
  • Sebaceous glands
  • Ceruminous glands
  • Mammary glands
• Sudoriferous glands

  Sweat producing glands important for maintaining body temperature
• Sebaceous glands

  Oil producing glands that inhibit bacteria, keep skin waterproof, and prevent drying
• Ceruminous glands


  Produce earwax to keep the outer surface of the eardrum pliable and prevent drying
• Mammary glands

  Produce milk
• Skin

  • Organ of the integumentary system that protects against pathogens, provides insulation, regulates temperature, offers sensation, and synthesizes vitamins D and B
  • Contains pigmentation (melanin) provided by melanocytes to absorb radiation and repair UV damage
  • Damaged skin heals by forming scar tissue
  • Considered the largest organ in the human body in terms of surface area and weight
  • Average adult human skin surface area is between 1.5-2.0 square meters, with various components like sweat glands, blood vessels, melanocytes, and nerve endings
• Use of cosmetics to treat the appearance of the face and condition of the skin is common among many cultures
• Layers of the skin

  • Epidermis, Dermis, Hypodermis or subcutaneous adipose layer
  • Epidermis consists of stratified squamous keratinizing epithelium with keratinocytes, melanocytes, and Langerhans cells
  • Epidermis can be subdivided into strata: corneum, lucidum, granulosum, spinosum, basale
  • Cells are formed through mitosis at the innermost layers and move up the strata differentiating in shape and composition
• Keratinization

  Cells are formed through mitosis at the innermost layers. They move up the strata changing shape and composition as they differentiate, inducing expression of new types of keratin genes. They eventually reach the corneum and become sloughed off (desquamation). This process takes place within about 30 days
• Layer of skin responsible for keeping water in the body and keeping other harmful chemicals and pathogens out

  • Corneum, lucidum, granulosum, spinosum, basale
• Blood capillaries are found beneath the dermis


  Linked to an arteriole and a venule
• Arterial shunt vessels may bypass the network in ears, the nose, and fingertips
• Dermis


  • Contains blood vessels, nerves, hair follicles, smooth muscle, glands, and lymphatic tissue. Consists of loose connective tissue (areolar connective tissue) with collagen, elastin, and reticular fibers. Erector muscles can contract, resulting in the hair fiber being pulled upright
• Main cell types in the dermis

  • Fibroblasts, adipocytes (fat storage), macrophages
• Sebaceous glands

  • Exocrine glands producing a mixture of lipids and waxy substances for lubrication, water-proofing, softening, and antibacterial actions
• Sweat glands


  • Open up via a duct onto the skin by a pore
• Hypodermis


  • Not part of the skin, lies below the dermis. Attaches the skin to underlying bone and muscle, supplies it with blood vessels and nerves. Consists of loose connective tissue and elastin. Main cell types are fibroblasts, macrophages, and adipocytes (contains 95% of body fat)
• Functions of the skin

  • Protection, Sensation, Heat regulation
• Types of hair in humans

  • Lanugo, Vellus, Terminal
• The fingernail is an important structure made of keratin
• The fingernail serves as a protective plate and enhances sensation of the fingertip
• Nail structure parts

  • Root, Nail bed, Nail plate, Eponychium (cuticle), Perionychium, Hyponychium
• Parts of the nail structure

  • Root
  • Nail Bed
  • Nail Plate
  • Eponychium
  • Perionychium
  • Hyponychium
• Root of the fingernail

  Also known as the germinal matrix, beneath the skin behind the fingernail, produces most of the volume of the nail and the nail bed, does not have melanocytes, edge seen as a white crescent-shaped structure called the lunula
• Nail Bed


  Part of the nail matrix called the sterile matrix, contains blood vessels, nerves, and melanocytes, important for normal nail growth to be smooth
• Nail Plate


  Actual fingernail made of translucent keratin, pink appearance from blood vessels underneath, underneath surface has grooves to anchor it to the nail bed
• Eponychium


  Also called the cuticle, situated between the skin of the finger and the nail plate, fuses structures together and provides a waterproof barrier
• Perionychium


  Skin that overlies the nail plate on its sides, also known as the paronychial edge, site of hangnails, ingrown nails, and paronychia infection
• Hyponychium


  Area between the nail plate and the fingertip, junction between the free edge of the nail and the skin of the fingertip, provides a waterproof barrier
• Glands

  • Sweat Glands
  • Sebaceous Glands
• In humans, there are two kinds of sweat glands: Eccrine and Apocrine
• Eccrine sweat glands


  • Produce sweat composed chiefly of water (99%) with various salts, distributed over the entire body surface, primary function is body temperature regulation
• Apocrine sweat glands


  • Develop during early- to mid-puberty, produce sweat containing fatty materials, mainly present in the armpits and around the genital area, main cause of sweat odor, serve as scent glands
• Emotional stress increases the production of sweat from the apocrine glands
• Sebaceous glands secrete an oily substance called sebum
• Sebaceous Glands


  Glands found in the skin of mammals that secrete an oily substance called sebum, made of fat (lipids) and debris of dead fat-producing cells
• Sebum

  An oily substance (Latin, meaning fat or tallow) secreted by sebaceous glands to protect and waterproof hair and skin, inhibit the growth of microorganisms, and prevent dryness, brittleness, and cracking
• Locations of sebaceous glands in humans

  • Throughout the skin except in the palms of the hands and soles of the feet, also found in non-haired areas of lips, eyelids, penis, labia minora, and nipples
• Pilosebaceous Unit


  The structure consisting of hair, hair follicle, and sebaceous gland