[1] Epithelial Tissues

• EPITHELIAL TISSUES

  • Polyhedral cells adhering strongly to one another and to a thin layer of ECM, forming linings of cavities of organs and cover the body surface
• EPITHELIAL TISSUES

  • Principal functions include:
  • Covering, lining, and protecting surface epidermis
  • Absorption (intestinal lining)
  • Secretion (parenchymal cells of glands)
• • Covering (lining) epithelia
  • Can be classified based on number of cell layers, cell morphology, and presence of surface specialization in the outer layer
• • Secretory glandular epithelia
  • specialized to produce and secrete (release) substances
  • found in your glands, which are specialized organs that can make, store and/or release substances such as hormones, proteins and water.
• Simple (one layer)

  Squamous

  Cuboidal

  Columnar
• Simple Squamous

  • Lining of vessels (endothelium)
  • Serous lining of cavities: pericardium, pleura, peritoneum (mesothelium)
• Simple Cuboidal

  • Covering the ovary
  • thyroid
• Simple Columnar

  • Lining of intestine
  • gallbladder
• Stratified (2+ layers)

  Squamous Keratinized (dry)

  Squamous Non-Keratinized (moist)

  Cuboidal

  Transitional

  Columnar
• Stratified Squamous Keratinized (dry)

  • epidermis
• Stratified Squamous Non-Keratinized (moist)

  • Mouth
  • Esophagus esophagus
  • Larynx
  • Vagina
  • Anal canal
• Stratified Cuboidal

  • Sweat glands
  • Developing ovarian follicles
• Transitional

  • bladder 
  • Ureter
  • Renal calyces
• Stratified Columnar (an example of this):

  • conjunctiva
• Pseudostratified

  layers of cell with nuclei at different levels; not all cells reach surface but all adhere to the basal lamina
• Pseudostatified

  • Lining of trachea, bronchi, nasal cavity
• Simple Squamous Epithelium

  • Single layer, flattened cells
  • In blood and lymphatic vessels (endothelium)
  • body cavities (mesothelium)
  • Forms parietal layer of renal corpuscles
• Simple Squamous Epithelium

  • Functions:
  • Facilitates the movement of the viscera (mesothelium), 
  • active transport by pinocytosis (mesothelium and endothelium), 
  • secretion of biologically active molecules (mesothelium)
• Simple Squamous Epithelium

  • Single layer → Allow passive transport of gasses or fluids
  • Irregular cell boundaries
• Bowman’s Capsule – simple squamous forms Sheath to the thickness of a single layer
• Vein – surrounded by a single layered squamous epithelium without proper boundaries (irregular)
• prominent and oval nuclei distinct to simle squamous
• Simple Columnar

  • Roughly cylindrical-shaped cells
• Simple Columnar

  • Secretion, absorption, propulsion of mucus
  • Microvilli lining of intestines
  • Mucus secretion for protection from corrosive and highly acidic secretions in the stomach
• Epithelial tissues are composed of aggregated polyhedral cells with a small amount of extracellular matrix, and their main functions are lining of surface or body cavities and glandular secretion.
• Connective tissues are composed of several types of fixed and wandering cells, have an abundant amount of extracellular matrix, and their main functions are support and protection of tissues and organs.
• Muscle tissues are composed of elongated contractile cells with a moderate amount of extracellular matrix, and their main function is strong contraction and body movements.
• Nervous tissues are composed of elongated cells with extremely fine processes, have a very small amount of extracellular matrix, and their main function is transmission of nerve impulses.
• Compound acinar glands, such as those in the submandibular salivary gland, are characterized by being both benched acinar and branched tubulo-acinar.
• Simple branched tubular glands of the stomach are secretory portions which converged to a single unbranched duct of a wider diameter.
• Brunner's glands of the duodenum are compound branched tubular.
• These glands empty into an excretory duct which is formed by strati fi ed columnar epithelium.
• Simple acinar glands occur in epithelial pockets, such as the penile urethra.
• Some salivary glands, such as the ones in the left large intestine, have a single straight lumen through which the secretory product is discharged.
• Sweat glands are tubular and coiled.
• The lining of these glands is entirely made up of goblet cells.
• Epithelial tissues are composed of polyhedral cells adhering strongly to one another and to a thin layer of extracellular matrix, forming linings of cavities of organs and cover the body surface.
• Simple Cuboidal Epithelium is also found in kidney ducts, originating from the renal collecting tubule.
• Villi of the Small Intestine are columnar cells with brush border microvilli.
• Cells at the surface of Pseudostratified Columnar Epithelium are often ciliated (ciliated PE).