More cards

• Tissues are defined as collections of specialized cells and their products that will perform very specific functions or jobs
• Tissues that group together will form organs like the heart or liver or lungs
• Histology is the study of tissues
• Four main types of tissues in the human body

  • Epithelial tissue
  • Connective tissue
  • Muscle tissue
  • Nervous tissue
• Epithelial tissue lines or covers the human body and it can also form glands
• Connective tissue fills spaces inside your body, supports other tissues, transports materials and also stores energy, mostly in the form of fat
• Muscle tissue is specialized to contract and includes three main types: skeletal, heart/cardiac, and smooth muscle
• Nervous tissue carries electrical signals from one part of the body to another
• Cells secrete extracellular material and fluid, which helps the cells stick to each other to form tissues
• Epithelial tissue


  Tissue that lines and covers body surfaces
• Functions of epithelial tissue

  • Protection
  • Control permeability
  • Provide sensation
  • Produce specialized secretions
• Polarity of epithelial tissue

  Having an apical (top) and basal (bottom) surface
• Uneven distribution of organelles in epithelial tissue

  Organelles are not equally distributed, but rather packed to one area of the cell
• Characteristics of epithelial tissue

  • Cellularity (cells connected by junctions)
  • Attaches to basement membrane
  • Can regenerate and be continuously replaced
  • Can become specialized
  • Can move fluids
• Apical surface


  The surface of epithelial cells exposed to the external or internal environment
• Basal surface


  The surface of epithelial cells that attaches to the basement membrane
• Basal lateral surface


  The sides of epithelial cells that connect to neighboring cells
• Intercellular connections in epithelial tissue

  • Gap junctions (for communication)
  • Tight junctions (prevent passage of water and solutes)
  • Desmosomes (link cells together)
• Basement membrane


  Structure that epithelial cells attach to, consisting of basal lamina and reticular lamina
• Epithelial cells are replaced by continual division of stem cells located near the basement membrane
• Epithelial tissue classification by cell shape

  • Squamous (thin, flat, irregular)
  • Cuboidal (square/box-shaped)
  • Columnar (tall, rectangular)
• Epithelial tissue classification by number of cell layers

  • Simple (single layer)
  • Stratified (multiple layers)
• Two-step process to name cell shapes and layers

  1. Name based on cell shapes

  2. Name based on number of layers
• Cell shapes


  • Squamous (thin, flat, flaky)
  • Cuboidal (square, box-shaped)
  • Columnar (tall, slender rectangles)
• Epithelial layers


  • Simple (one layer)
  • Stratified (two or more layers)
• Simple squamous epithelium


  • Lining of peritoneal cavity
• Stratified squamous epithelium


  • Surface of tongue
• Simple cuboidal epithelium


  • Lining of kidney
• Stratified cuboidal epithelium


  • Ducts of sweat glands, mammary glands
• Transitional epithelium


  Tolerates stretching without tearing, found in bladder
• Simple columnar epithelium


  • Lining of stomach, small intestine, large intestine
• Stratified columnar epithelium


  • Pharynx, anus, urethra
• Pseudo-stratified columnar epithelium


  Looks stratified but is actually simple, found in respiratory system
• Epithelial tissues are avascular (no direct blood supply)
• Types of glands


  • Endocrine (release hormones into bloodstream)
  • Exocrine (release secretions through ducts)
• Methods of exocrine secretion

  • Merocrine (secretion by exocytosis)
  • Apocrine (secretion with cytoplasm)
  • Holocrine (secretion by cell bursting)
• Types of exocrine secretions

  • Serous (watery)
  • Mucus
  • Mixed (serous and mucus)
• Connective tissue is highly vascular (has blood vessels)
• Connective tissue is made up of specialized cells, extracellular protein fibers, and ground substance
• Cycle of secretions produced by exocrine glands

  1. Cycle will continue again and again and again

  2. Exocrine glands have ducts

  3. Serous glands produce watery secretions

  4. Mucus glands produce mucus secretions

  5. Mixed exocrine glands produce both serous and mucus