Epithelial Tissue Types

• Epithelial Tissue

Simple Squamous Epithelium

• Mesothelium is a type of simple squamous epithelium.
• Endothelium is a type of simple squamous epithelium.
• Allows for rapid diffusion across the epithelium.
• Cell boundaries are visible.
• Nuclei are present.
• Cytoplasm is present within each cell.

Simple Cuboidal Epithelium

• Lines small excretory ducts in various organs.
• Functions in covering and secretion.
• Found in the thyroid, kidney tubules, and ovary.

Simple Columnar Epithelium

• Covers digestive organs such as the stomach, small and large intestine, and gallbladder.
• Functions in lubrication, absorption, protection, and secretion.
• May have apical microvilli or cilia.
• Microvilli are found in the intestines and gallbladder.
• Ciliated columnar epithelium is found in the fallopian tube and uterus.

Pseudostratified Columnar Epithelium

• Lines the upper respiratory passages (trachea, bronchi) and lumina of the epididymis and vas deferens.
• Frequently ciliated.
• Functions in protection, transport, and secretion.

Transitional Epithelium

• Found exclusively in the excretory passages of the urinary system.
• Covers the lumina of renal calyces, pelvis, ureters, and bladder.
• Epithelium changes shape in response to stretching, fluid accumulation, or contraction during voiding of urine.

Stratified Squamous Epithelium

• Contains multiple cell layers.
• Basal cells are cuboidal to columnar; cells toward the surface become squamous.
• Functions to provide protection.
• Can be nonkeratinized (moist) or keratinized (dry).
• Nonkeratinized epithelium exhibits live surface cells and covers moist cavities (mouth, pharynx, esophagus, vagina, anal canal).
• Keratinized epithelium lines external surfaces of the body and contains non-living surface keratinized cells (skin).

Stratified Cuboidal Epithelium

• Limited distribution.
• Lines larger excretory ducts of salivary and sweat glands.

Stratified Columnar Epithelium

• Limited distribution.
• Seen in the conjunctiva lining the eyelids.

Examples of Epithelial Tissue Location

• Kidney tubules: simple cuboidal epithelium.
• Bowman's capsule: simple squamous epithelium.
• Simple cuboidal epithelium is found in the thyroid follicles.
• Ileum contains simple columnar epithelium with microvilli and goblet cells.
• Jejunum contains simple columnar epithelium with microvilli and goblet cells.
• Trachea contains ciliated pseudostratified columnar epithelium with goblet cells.
• Olfactory epithelium is ciliated pseudostratified columnar epithelium.
• Epididymis contains pseudostratified columnar epithelium with stereocilia.
• Esophagus contains non-keratinized stratified squamous epithelium.
• Vagina contains non-keratinized stratified squamous epithelium.
• Thick skin (palm) contains keratinized stratified squamous epithelium.