Tissue

• Cells


  The most basic building blocks that make up the body
• Tissues


  Groups of similar cells that come together to perform a common function
• Organs


  Two or more tissues combined
• Primary tissues

  • Nervous tissue
  • Muscle tissue
  • Epithelial tissue
  • Connective tissue
• Primary Tissues

  • Nervous tissue provides control and communication
  • Muscle tissue gives movement
  • Epithelial tissue lines body cavities and organs, and protects the body
  • Connective tissue provides support
• Microscopes invented by Hans and Zacharias Jansen


  1590s
• Anton van Leeuwenhoek develops high-power microscopes


  Late 1600s
• Stains and dyes


  Used to enhance contrast and visibility of cellular structures under a microscope
• First true histological stain developed by Joseph von Gerlach


  1850s
• Nervous tissue


  Consists of neurons and glial cells<|>Neurons generate and conduct electrical impulses<|>Glial cells provide support, insulation, and protection
• Neurons

  • Cell body, dendrites, and axon
• Muscle tissue types

  • Skeletal
  • Cardiac
  • Smooth
• Skeletal muscle tissue


  • Attaches to bones, supports posture, voluntary movement
• Cardiac muscle tissue


  • Forms heart walls, involuntary contractions
• Smooth muscle tissue


  • Lines walls of blood vessels and hollow organs, involuntary contractions
• Epithelial tissue


  Tissue that lines, covers, and generally organizes the body, creating order from what would be chaos
• Two types of epithelial tissue

  • Proper epithelium
  • Glandular epithelium
• Proper epithelium


  • Covers and lines the outer and inner body
  • Partitions everything into separate but connected units
• Epithelial tissue


  • Protects deeper layers of tissue from injury or infection
  • Avascular - doesn't have a blood supply, relies on surrounding connective tissue
• Three basic shapes of epithelial cells

  • Squamous
  • Cuboidal
  • Columnar
• Squamous cells

  Flat, scale-like
• Cuboidal cells


  Cube-shaped, absorb nutrients and produce secretions
• Columnar cells


  Tall and thick, cushion underlying tissues
• The shape of epithelial cells correlates with their function
• Types of epithelial tissue based on layering

  • Simple epithelium (single layer)
  • Stratified epithelium (multiple layers)
  • Pseudostratified epithelium (mostly single layer, cells of different shapes and sizes)
• When describing epithelial tissue, we cite both its shape and layering
• Simple squamous epithelium


  • Lining of air sacs in lungs
• Stratified cuboidal epithelium


  • Lining of ducts that secrete sweat and saliva
• Squamous cells


  • Small, cheap to make, form dense protective layers that can regenerate quickly
• Epithelial cells

  • Polar - have distinct apical and basal sides
  • Selectively permeable - allow for absorption, filtration, and excretion
• Functions of epithelial tissue

  • Protect body from outside world
  • Create order among organs
  • Facilitate secretions (sweat, mucus, hormones, enzymes)
• Types of glands formed by glandular epithelium

  • Endocrine glands (secrete hormones into bloodstream)
  • Exocrine glands (secrete into ducts leading to body surfaces)
• Endocrine secretion


  • Thyroid gland secreting thyroxin
• Exocrine secretions


  • Sweat, saliva, mucus, stomach acid, milk
• Marfan Syndrome


  A genetic disorder of the connective tissue that weakens it over time
• Connective tissue


  The most abundant and diverse tissue type in the body, that keeps you looking young, makes up your skeleton, and delivers oxygen and nutrients
• Main classes of connective tissue

  • Proper
  • Cartilage
  • Bone
  • Blood
• Connective tissue


  Develops from mesenchyme, a loose and fluid type of embryonic tissue<|>Has different degrees of blood flow<|>Is mostly composed of non-living extracellular matrix
• Extracellular matrix


  The inert material between connective tissue cells that is more important than the cells themselves
• Components of extracellular matrix

  Ground substance - a watery, rubbery, unstructured material<|>Proteoglycans - proteins that anchor the framework<|>Glycosaminoglycans (GAGs) - long, starchy strands radiating from the proteoglycans<|>Fibers - including collagen, elastic, and reticular fibers that provide support and structure