Epithelium tissue

• Tissues


  The four basic types of tissue that make up the human body: epithelial, connective, muscular, and nervous
• Epithelial tissue


  • Covers body surfaces, lines body cavities, hollow organs, and ducts, and forms glands
• Connective tissue


  • Protects and supports the body and its organs, binds organs together, stores energy reserves as fat, and provides immunity
• Muscular tissue


  • Generates the physical force needed to make body structures move
• Nervous tissue


  • Detects changes inside and outside the body and initiates and transmits nerve impulses that coordinate body activities to help maintain homeostasis
• Epithelial tissue


  May be divided into two types: covering and lining epithelium, and glandular epithelium
• Covering and lining epithelium


  • Forms the outer covering of the skin and the outer covering of some internal organs, and lines body cavities, blood vessels, ducts, and the interiors of the respiratory, digestive, urinary, and reproductive systems
• Epithelial tissue cells


  • Have an apical surface, lateral surfaces, and a basal surface
• Simple epithelium


  A single layer of cells that functions in diffusion, osmosis, filtration, secretion, and absorption
• Stratified epithelium


  Consists of two or more layers of cells that protect underlying tissues in locations where there is considerable wear and tear
• Pseudostratified epithelium


  Appears to have multiple layers of cells because the cell nuclei lie at different levels and not all cells reach the apical surface
• Transitional cells


  Change shape, from flat to cuboidal and back, as organs such as the urinary bladder distends
• Squamous cells


  Are thin, allowing for the rapid passage of substances through them
• Cuboidal cells


  Are as tall as they are wide and are shaped like cubes or hexagons, may have microvilli at their apical surface and function in either secretion or absorption
• Columnar cells


  Are much taller than they are wide, like columns, and protect underlying tissues, their apical surfaces may have cilia or microvilli, and they often are specialized for secretion and absorption
• Types of simple epithelium

  • Simple squamous epithelium
  • Simple cuboidal epithelium
  • Simple columnar epithelium (nonciliated/ciliated)
  • Pseudostratied columnar epithelium (nonciliated/ciliated)
• Types of stratified epithelium

  • Stratified squamous epithelium (keratinized and non-keratinized)
  • Stratified cuboidal epithelium
  • Stratified columnar epithelium
  • Transitional epithelium
• Gland


  Consists of one cell or a group of highly specialized epithelial cells that secrete substances into ducts, onto a surface, or into the blood
• Endocrine glands


  Enter the interstitial fluid and then diffuse into the bloodstream without flowing through a duct, their secretions are called hormones
• Exocrine glands


  Secrete their products into ducts that empty at the surface of covering and lining epithelium such as the skin surface or the lumen of a hollow organ, their secretions include mucus, perspiration, oil, earwax, milk, saliva, and digestive enzymes
• Goblet cells


  Their role is to protect the surface of epithelium, lubricate it, and catch harmful particles, although protective, they may be involved in pathophysiology of certain respiratory diseases, such as chronic bronchitis
• Connective tissue


  One of the most abundant and widely distributed tissues in the body, with a variety of functions including binding, supporting, and strengthening other tissues, protecting and insulating internal organs, compartmentalizing structures, transporting substances, storing energy reserves, and facilitating immune responses
• Connective tissue


  • Consists of cells and extracellular matrix
  • Extracellular matrix contains protein fibers and ground substance
• Types of connective tissue cells

  • Fibroblasts
  • Macrophages
  • Plasma cells
  • Mast cells
  • Adipocytes
• Ground substance


  Component of connective tissue between cells and fibers that supports cells, binds them together, and provides a medium for substance exchange
• Types of fibers in extracellular matrix

  • Collagen fibers
  • Elastic fibers
  • Reticular fibers
• Collagen fibers


  • Branched and form network
  • Resist pulling forces
  • Often in parallel bundles
• Elastic fibers


  • Elastin surrounded by fibrillin
  • Stretchy (1.5x length)
  • Promote flexibility, allow tissue to expand and recoil
• Reticular fibers


  • Collagen coated with glycoprotein
  • Branched networks around cells
  • Support blood vessel walls, framework for soft organs
• Types of connective tissue

  • Loose connective tissue (areolar, adipose, reticular)
  • Dense connective tissue (dense regular, dense irregular, elastic)
• Cartilage


  • Dense network of collagen or elastic fibers embedded in chondroitin sulfate ground substance
  • Cells called chondrocytes occur singly or in groups in lacunae
  • Has no blood supply, so heals poorly
• Types of cartilage


  • Hyaline cartilage
  • Fibrocartilage
  • Elastic cartilage
• Bone


  • Supports soft tissues, protects delicate structures, generates movement with skeletal muscles
  • Stores calcium, phosphorus, and bone marrow
• Blood and lymph


  Liquid connective tissues with liquid extracellular matrix
• Membranes


  Flat sheets of pliable tissue that cover or line a part of the body, consisting of an epithelial layer and an underlying connective tissue layer
• Types of membranes


  • Connective tissue membranes (including synovial membranes)
  • Epithelial membranes (including mucous, serous, and cutaneous membranes)
• Muscular tissue


  • Consists of elongated muscle fibers specialized to generate force, producing motion, maintaining posture, and generating heat
• Types of muscular tissue

  • Skeletal muscle
  • Cardiac muscle
  • Smooth muscle
• Skeletal muscle


  • Multinucleated structures with actin and myosin proteins arranged in striations, under voluntary control
• Smooth muscle


  • Spindle-shaped, shorter than skeletal muscle fibers, produce connective tissue, lack striations and sarcomeres