Epithelial Tissue: Squamous, Cuboidal, Columnar

• Epithelial Tissue is the topic

Simple Squamous Epithelium

• Includes Mesothelium and Endothelium
• Allows rapid diffusion across the epithelium
• The tissue has cell boundaries, cytoplasm, and nuclei
• Can be found lining of vessels (endothelium) and serous lining of cavities: pericardium, pleura, peritoneum (mesothelium)
• Facilitates the movement of the viscera (mesothelium)
• Active transport by pinocytosis (mesothelium and endothelium)
• Secretes biologically active molecules (mesothelium)
• The glomerulus and Bowman's capsule in the kidney contain Simple Squamous Epithelium

Simple Cuboidal Epithelium

• Lines small excretory ducts in different organs
• Functions in Covering and Secretion
• Can be found in the thyroid, kidney tubules, or ovary
• This tissue is responsible for covering the ovary, thyroid, and secretion in those locations

Simple Columnar Epithelium

• Covers the digestive organs including the stomach, small and large intestine, and gallbladder
• Functions in Lubrication, absorption, protection, and secretion
• May have apical microvilli or cilia
• Microvilli are present in the intestines and gallbladder
• Ciliated Simple Columnar Epithelium is present in the fallopian tube and uterus
• Functions in protection, lubrication, absorption, and secretion
• Can be found in the lining of the intestine and gallbladder

Pseudostratified Columnar Epithelium

• Lines the upper respiratory passages such as the trachea and bronchi, and the lumina of the epididymis and vas deferens
• Frequently Ciliated
• Functions in protection, transport, and secretion
• Can be found in the lining of the trachea, bronchi, and nasal cavity
• Responsible for protection and secretion
• Responsible for cilia-mediated transport of particles trapped in mucus out of the air passages

Transitional Epithelium

• Found exclusively in the excretory passages of the urinary system
• Covers lumina of renal calyces, pelvis, ureters, and bladder
• Epithelium change shape in response to stretching, fluid accumulation, or contraction during voiding of urine
• Functions in Protection and Distensibility
• Can be found in bladder, ureters, and renal calyces

Stratified Squamous Epithelium

• Multiple cell layers exist
• Basal cells are cuboidal to columnar, cells toward the surface become squamous
• Has protective functions
• Two types: nonkeratinized or keratinized

Nonkeratinized (moist) Stratified Squamous Epithelium

• Exhibits live surface cells and covers moist cavities such as the mouth, pharynx, esophagus, vagina, and anal canal
• Can be found in the mouth, esophagus, larynx, vagina, and anal canal
• Functions in Protection and Secretion; Prevents water loss

Keratinized (dry) stratified squamous epithelium

• Lines external surfaces of the body
• Contains non-living surface keratinized cells known as skin
• Found in the epidermis
• Its main function is protection and prevention of water loss

Stratified Cuboidal Epithelium

• Limited distribution
• Lines larger excretory ducts of salivary and sweat glands
• Functions as protection and secretion
• Found in sweat glands and developing ovarian follicles

Stratified Columnar Epithelium

• Is of limited distribution
• Seen in the conjunctiva lining the eyelids
• Functions in protection and secretion
• Conjunctiva is where it can be located

An overview of epithelial tissues, including simple squamous, cuboidal, and columnar types. Covers location, function, and identifying factors such as cell boundaries and nuclei.