Epithelial Tissue Types

Epithelial Tissue

Simple Squamous Epithelium

• Includes the mesothelium and endothelium.
• Allows rapid diffusion across the epithelium.
• Mesothelium is the lining of vessels.
• Serous lining of cavities include the pericardium, pleura, and peritoneum (mesothelium).
• Lining of vessels is endothelium.
• Active transport by pinocytosis occurs in the mesothelium and endothelium.
• Secretion of biologically active molecules occurs in the mesothelium.

Simple Cuboidal Epithelium

• Lines small excretory ducts in different organs, covers, and secretes.
• The covering is located in the ovary and thyroid.

Simple Columnar Epithelium

• Covers the digestive organs including the stomach, small and large intestine, and gallbladder.
• Functions include lubrication, absorption, protection, and secretion.
• It may have apical microvilli or cilia.
• Microvilli are located in the intestines and gallbladder.
• Ciliated examples are the fallopian tube and uterus.
• Lines the intestine and gallbladder.
• Functions to provide protection, lubrication, absorption, and secretion.

Pseudostratified Columnar Epithelium

• Lines the upper respiratory passages, which are the trachea and bronchi.
• Also lines the lumina of the epididymis and vas deferens.
• Frequently ciliated and provides protection, transport, and secretion.
• Located in the lining of the trachea, bronchi, and nasal cavity.
• Functions in protection and secretion: cillia-mediated transport of particles trapped in mucous out of the air passages.

Transitional Epithelium

• Exclusively in the excretory passages of the urinary system.
• Covers lumina of renal calyces, pelvis, ureters, and bladder.
• The epithelium changes shape in response to stretching, fluid accumulation, or contraction during voiding of urine.
• Bladder, ureters, and renal calyces are lined with transitional epithelium.
• Provides protection and distensibility.

Stratified Squamous Epithelium

• Consists of multiple cell layers.
• Basal cells range from cuboidal to columnar while surface cells become squamous.
• Functions for protection.
• Includes nonkeratinized and keratinized types.

Stratified Squamous Nonkeratinized Epithelium

• Exhibits live surface cells.
• Covers moist cavities like the mouth, pharynx, esophagus, vagina, and anal canal.

Stratified Squamous Keratinized Epithelium

• Lines external surfaces of the body.
• Contains non-living surface keratinized cells, like skin.

Stratified Cuboidal Epithelium

• Has limited distribution.
• Lines larger excretory ducts of salivary and sweat glands.
• Located in sweat glands and developing ovarian follicles.
• Functions in protection and secretion.

Stratified Columnar Epithelium

• Distribution is limited.
• Observed in the conjunctiva lining the eyelids
• Located in the conjunctiva.
• Provides protection.

Specific Locations

• Kidney tubules have simple cuboidal epithelium.
• Bowman's capsule has simple squamous epithelium.
• Thyroid follicles exhibit simple cuboidal epithelium.
• Ileum has simple columnar epithelium with microvilli and goblet cells.
• Jejunum has simple columnar epithelium with microvilli and goblet cells.
• Trachea has ciliated pseudostratified columnar epithelium with goblet cells.
• Olfactory epithelium has ciliated pseudostratified columnar epithelium.
• Epididymis has pseudostratified columnar epithelium with stereocilia.
• Esophagus has non-keratinized stratified squamous epithelium.
• Vagina has non-keratinized stratified squamous epithelium.
• Thick skin on the palm has keratinized stratified squamous epithelium.