General Histology for Level 1 Dentistry

General Histology for Level 1 Dentistry

• Epithelium is a type of tissue

• Basic body tissues include Epithelium, Connective tissue, Muscular tissue and Nervous tissue

• Epithelial tissue has closely aggregated cells

• It has strong adhesions between cells

• Has little intercellular substance

• Cells rest on a basement membrane

• Avascular, meaning no blood vessels run through it

• Nutrition and blood supply come from the underlying connective tissue

• Contains nerves

• Undergoes continuous degeneration and regeneration

• Types of Epithelium:

  • Surface (covering) epithelium
  • Glandular epithelium
  • Neuroepithelium

• Surface epithelium categorized by cell layers

  • Simple: single layer of cells, all cells touch the basement membrane.
  • Stratified: more than one layer of cells, only the basal layer touches the basement membrane. Further categorized by shape of the top layer
    • Simple Squamous: thin, flat cells with bulging nuclei, found in lining of blood vessels (e.g., aorta) and lung alveoli.
    • Simple Cuboidal: cubical shaped cells with central round nuclei, found in thyroid follicles and renal tubules.
    • Simple Columnar: column-like cells with basal and oval nuclei, found in different parts categorized by function:
      • Secretory: in the stomach
      • Absorptive: in the small intestine
      • Ciliated: in the fallopian tube
    • Pseudostratified Columnar: overcrowded columnar cells, all cells reaching the basement membrane. Nuclei at different levels giving a false impression of stratification, types include ciliated(trachea and bronchi) and non-ciliated (large ducts of glands).

• Stratified Squamous: more than one layer of cells, basal layer reaches basement membrane. Can be non-keratinized (mouth cavity, esophagus) or keratinized (epidermis of skin). Describes features according to cell shape and keratin layers

  • Non-keratinized: basal cells columnar or cuboidal, middle layers polyhedral, top layer flat squamous cells.
  • Keratinized: basal cells columnar or cuboidal, middle layers polyhedral, top layer squamous cells, extra layers of keratin protein over upper surface found in epidermis of skin.

• Transitional Epithelium (Urothelium): Found only in the urinary tract (urinary bladder and ureter). Specialized to accommodate a great degree of stretch and withstand urine toxicity, its cells can transition in appearance with a full or empty bladder. in empty bladder it has 4-6 layers, cells are shaped like umbrella cells in the top layer. in distended bladder, it has 2-3 layers and appears thin.

• Glandular Epithelium: forms glands secreting various substances. Categorized by

  • Duct and secretory part
    • Exocrine (salivary glands): have ducts releasing substances outside body
    • Endocrine (thyroid glands): lack ducts, and secrete directly into blood.
    • Mixed (pancreas and liver): share characteristics of both.
  • Shape of secretory part
    • Tubular (tube-like)
    • Alveolar (flask-shaped)
  • Branching of ducts and secretory part
    • Simple (unbranched)
    • Branched
    • Compound (branched)
  • Nature of secretions
    • Mucous (viscid, poor in enzymes): goblet cells
    • Serous (watery, rich in enzymes): parotid gland
    • Mucoserous (both mucous and serous): submandibular gland
    • Oily (e.g., sebaceous glands) secreting fatty substances

• Neuroepithelium: special type of tissue that receives external sensations, located in tongue (taste buds), inner ear (organ of Corti), eye (retina), and olfactory epithelium; has sensory cells with hairlets on free borders, their bases surrounded by free sensory nerves; also supporting and basal cells.

This quiz covers the fundamental aspects of histology relevant to Level 1 Dentistry. It explores different types of epithelial tissues, their characteristics, and their categorization based on cell layers and shapes. Test your knowledge on how these tissues function and their significance in dentistry.