Anatomy

• Tissues

  Group of specialized cells and extracellular substances surrounding them
• Changes in tissue may result

  • Development - progression of a tissue over time
  • Growth - tissue increases its size
  • Aging - becoming more stiff, making organs, blood vessels, and airways more rigid
  • Trauma - soft tissue injuries
  • Disease - hereditary (genetic) connective tissue diseases include Marfan syndrome, homocystinuria, and osteogenesis imperfecta
• Four primary tissue types

  • Epithelial tissues/Epithelium
  • Connective tissues
  • Muscle tissues
  • Nervous tissues
• Epithelial tissue

  • Covers the surfaces of the body, lines cavities and organs, and serves as a protective barrier
  • Can also be involved in absorption, secretion, and sensory functions
• Characteristics common to most types of epithelial tissue

  • Mostly composed of specialized cells
  • Covers body surfaces
  • Has an exposed (free/apical) surface
  • Attaches at the basal surface
  • Has specialized cell connections and matrix attachments
  • Is avascular - blood vessels do not penetrate the basement membrane
  • Is capable of regeneration
• How nonvascular epithelial tissue reaches the basement membrane


  1. Diffusion from nearby blood vessels

  2. Diffusion through interstitial fluid

  3. Diffusion through the basal lamina/basement membrane

  4. Transport proteins actively moving molecules

  5. Cell-to-cell communication using signaling molecules
• Functions of epithelia

  • Protects underlying structures
  • Acts as a barrier
  • Permits the passage of substances
  • Secretes substances
  • Absorbs substances
• Major types of epithelia according to number of cells

  • Simple epithelium - single layer of cells
  • Stratified epithelium - more than one layer of cells
  • Pseudostratified columnar epithelium - appears stratified but is a single layer
• Three types of epithelium based on cell shape

  • Squamous - flat, scale-like cells
  • Cuboidal - cube-shaped cells
  • Columnar - tall, thin cells
• Types of epithelial tissues and their distribution

  • Simple squamous - linings of blood vessels and heart
  • Simple cuboidal - ovaries, nephrons, renal tubules, eye, thyroid, salivary glands
  • Simple columnar - digestive system, may contain goblet cells
  • Pseudostratified columnar - respiratory and male reproductive tracts
  • Stratified squamous (keratinized) - skin, mouth, esophagus
  • Stratified cuboidal - some sweat and urinary glands, conjunctiva
  • Stratified columnar - male reproductive tract
  • Transitional - urinary organs
• Connective tissue

  • Diverse primary tissue type that makes up part of every organ
  • Consists of cells separated by an abundant extracellular matrix
• Major functions of connective tissue

  • Enclosing and separating other tissues
  • Connecting tissues to one another
  • Supporting and moving parts of the body
  • Storing compounds
  • Cushioning and insulating
  • Transporting
• Cells of connective tissue

  • Blast - create the matrix
  • Cytes - maintain the matrix
  • Clast - breakdown for remodeling
• Three major components of the extracellular matrix

  • Protein fibers
  • Ground substance - non-fibrous protein and other molecules
  • Fluid
• Classification of connective tissue

  • Connective tissue proper
  • Loose connective tissue - areolar, adipose, reticular
  • Dense connective tissue - collagenous, elastic
• Loose connective tissue

  • Relatively few protein fibers forming a lacy network, with numerous spaces filled with ground substance and fluid
• Dense connective tissue

  • Has a relatively large number of collagen fibers that form thick bundles and fill nearly all the extracellular space
• Subcategories of dense connective tissue

  • Collagenous - mainly collagen fibers
  • Dense, regular collagenous - tendons, ligaments, dermis
  • Dense, irregular collagenous - dermis, organ capsules
  • Dense elastic - abundant elastic fibers allowing stretching and recoil
  • Dense, regular elastic - blood vessel walls
  • Dense, irregular elastic - artery walls
• Marfan's syndrome is an inability to properly maintain and form elastic fibers
• Integumentary system

  Consists of the skin and accessory structures, such as hair, glands, and nails
• Major functions of the integumentary system

  • Protection - against abrasion and UV light, reduces water loss
  • Sensation - detects heat, cold, touch, pressure, pain
  • Vitamin D production
  • Temperature regulation
  • Excretion - small amounts of waste products
• Cells in the skin

  • Keratinocytes - produce keratin
  • Melanocytes - produce melanin pigment
  • Langerhans cells - immune cells
  • Fibroblasts - produce collagen and elastin
  • Adipocytes - fat cells
  • Mast cells - release inflammatory substances
• The 3 layers of the integumentary system

  • Epidermis - prevents water loss, resists abrasion
  • Dermis - provides structural strength
  • Subcutaneous - connects skin to underlying structures, insulates, stores energy
• Epidermis

  The most superficial layer of the skin, a stratified squamous epithelium
• Keratinization

  Cells change shape and chemical composition as they move to the surface, becoming filled with keratin and forming a rigid, protective outer layer
• Strata (layers) of the epidermis

  • Stratum basale - deepest layer, cells divide and push upward
  • Stratum corneum - outermost layer of dead, keratin-filled cells
• Dermis

  • Composed of dense collagenous connective tissue containing fibroblasts, adipocytes, macrophages, nerves, hair, follicles, smooth muscles, glands, and lymphatic vessels
  • Collagen and elastic fibers provide structural strength
• Skin structure

  1. Epidermis is a continuous process

  2. STRATA (distinct layers) can be seen in the epidermis
• Stratum basale

  The deepest stratum, consists of cuboidal and columnar cells that undergo mitotic cell division about every 19 days, one daughter cell becomes the new stratum basale and can divide again, the daughter cell is pushed to the surface for about 40-56 days
• Stratum corneum

  The most superficial stratum of the epidermis, consists of dead squamous cells filled with keratin, composed of 25 or more layers of dead squamous cells joined by desmosomes, produces thickened area called CALLUS
• Dermis

  • Composed of dense collagenous connective tissue containing fibroblasts, adipocytes, macrophages, nerves, hair, follicles, smooth muscles, glands, and lymphatic vessels
• Collagen and elastic fiber

  • Responsible for the structural strength of the dermis, collagen is oriented in different directions to resist stretch, produces cleavage lines or TENSION Lines, most resistant to stretch
• An incision made across the cleavage lines


  Produces scar tissue
• If skin is overstretched

  The dermis can be damaged, leaving lines that are visible through the epidermis called STRETCH MARKS
• Intradermal injection (ID)

  Administering by tightening the skin and gently inserting a small needle at a 5-15-degree angle into the dermis, example: tuberculin skin test
• Subcutaneous injection (SQ)

  Accomplished by creating a skin tent through pinching and inserting a short needle into the subcutaneous adipose tissue, as exemplified in insulin injections (45 or 90-degree angle)
• Intramuscular injection (IM)

  Accomplished by inserting a long needle at a 90-degree angle in the skin into the muscle deep to the subcutaneous tissue, example: some vaccines and antibiotics
• Intravenous injection (IV)

  Involves delivering medication or fluids directly into a vein (15-30-degree angle), allowing for rapid absorption and systemic distribution throughout the body, example: injecting antibiotics and chemotherapy drugs directly into the vein
• Melanin

  A group of pigments primarily responsible for the skin, hair, and eye color, mostly brown and black, some yellowish or reddish, provides protection against ultraviolet light from the sun
• Melanocytes

  Irregularly shaped cells with long processes extending between deep epithelial cells in the epidermis