Epithelial Tissue Quiz

Epithelial Tissue

• Avascular tissue covering external body surfaces and lining internal closed cavities.
• Forms the secretory portion of glands and their ducts.
• Forms the receptors of certain sensory organs.
• Composed of tightly packed cells arranged in sheets, with specialized intercellular junctions (junctional complexes).
• Cells exhibit distinct apical (free), lateral, and basal surface domains, whose properties are determined by specific membrane proteins.
• Rests on an underlying basal lamina, a non-cellular layer rich in proteins and polysaccharides.

Epithelial Tissue Functions

• Transport: Moves particles and mucus via motile cilia (e.g., trachea, bronchi).
• Sensory Reception: Detects stimuli (e.g., neuroepithelia, taste buds, retina, smell receptors, hearing receptors).
• Lubrication: Secretes mucus and serous fluids.
• Excretion: Filters substances like blood, urine, and sweat.
• Reproduction: Involved in producing sex cells (e.g., ovary and testis).

Epithelial Tissue Classification

• Classified by cell arrangement (single/multiple layers) and cell shape (squamous, cuboidal, columnar), not by function.

Epithelial Cell Shapes and Arrangement

• Simple Epithelium: One cell layer thick.

  • Simple Squamous: Flattened cells, involved in exchange (e.g., blood vessels, Bowman's capsule, respiratory spaces in lungs). Also a barrier (e.g., central nervous system, between compartments in other locations). Exhibits exchange and lubrication.
  • Simple Cuboidal: Cube-shaped cells, found in glands, ducts, kidney tubules, parts of the thyroid gland (follicle walls), and surface of the ovary, walls of kidney tubules, collecting ducts.
  • Simple Columnar: Tall, narrow cells, involved in absorption and secretion (e.g., intestines, uterus, gall bladder). Also acts as a barrier.
  • Pseudostratified: Appears stratified but is one layer; all cells contact the basement membrane (e.g., respiratory tract, trachea, bronchi—ciliated; epididymis—stereocilia; ductus deferens).

• Stratified Epithelium: Two or more cell layers thick.

  • Stratified Squamous: Multiple layers; superficial cells are flattened. Provides protection. Keratinized (skin) or Non-Keratinized (lining of oral cavity, esophagus, vagina, tongue).
  • Transitional: Cells change shape in response to tension (e.g., urinary bladder, part of urethra, ureter, renal calyces).

Staining

• Tissues are often stained with hematoxylin and eosin (H&E). Hematoxylin stains purple; Eosin stains pink.

Epithelial Cell Shapes

• Squamous: Width of cell is greater than its height.
• Cuboidal: Width, depth, and height are approximately the same.
• Columnar: Height of cell greatly exceeds its width.
  • Low Columnar: Height only slightly exceeds width.

Test your knowledge on epithelial tissue, its functions, and classifications. Understand the various characteristics of epithelial cells and their roles in the body. This quiz will cover key concepts essential for biology and anatomy studies.