Simple Squamous Epithelium
Identification: Small, flat cells arranged around large, empty spaces (air sacs). May be confused with Adipose Tissue, but note the multiple cells and nuclei (arrows).
Features to Know: Nuclei.
Where Located: Lungs (air sacs called alveoli); glomeruli of kidneys; lining of the heart, blood and lymphatic vessels; lining of ventral body cavity (serosae).
Function: Diffusion (e.g. gas exchange) and filtration. The top image is what you would see with a transverse section through the tissues. The bottom image is from a cheek smear and shows a cluster of four cells viewed if they were laid out flat.
Simple Cuboidal Epithelium
Identification: Squarish cells with round nuclei in a single row (arrows), usually arranged in a circle (tubule).
Features to Know: nuclei.
Where Located: Kidney tubules; ducts and secretory portions of small glands (can be seen in sweat glands of skin slide); surface of ovaries.
Function: absorption and secretion.
Simple Columnar Epithelium
Identification: Tall rectangular cells, with single, neat row of oval nuclei, usually more towards the base (in the bracketed row, the base is towards the top), leaving an apical region of nucleus-free cytoplasm. Note also goblet cells, found only here and in Pseudostratified Columnar Epithelium.
Features to Know: Goblet cells (1), nuclei (2), microvilli (3).
Where Located: Jejunum of small intestine.
Function: Absorption (microvilli), secretion of mucus (goblet cells).
Pseudostratified Columnar Epithelium
Identification: Tall rectangular cells, with multiple irregular rows of nuclei (bracketed; compare to simple columnar, above). Note also goblet cells, found only here and in Simple Columnar Epithelium.
Features to Know: Cilia (1), goblet cells (2), nuclei (3).
Where Located: Trachea and most of the upper respiratory tract.
Function: Secretion and movement of mucus.
Stratified Squamous Epithelium
Identification: Many layers (6 or more) of small, flattened cells. The only other epithelial tissue with so many layers is transitional (below), but note that stratified squamous epithelium typically has a more evenly contoured surface with the uppermost layers of cells flattened.
Features to Know: Nuclei, if evident.
Where Located: Lining of mouth, esophagus, and vagina; epidermis of skin.
Function: Protection from abrasion and infection.
Identification: Numerous layers of cells of varying and often irregular shape, though generally not squamous (when unstretched as in the slides). Surface of tissue is folded (inside of ureter) or bumpy appearing (urinary bladder).
Features to Know: Nuclei.
Where Located: Lining the ureters, urinary bladder, and part of the urethra.
Function: Distend (stretch) and retract.