Tissues

Kinds of Tissues

• Epithelial

• Connective

• Muscle

• Nervous

Epithelial Tissue

• Grouped based on shape and arrangement• Shape

– Squamous – flat and scalelike– Cuboidal – cube– Columnar – higher than wide

• Arrangement– Simple – single layer of same shape– Stratified – many layers of same shape– Transitional – several layers of different shaped cells

Epithelial Tissue

Simple Squamous EpitheliumIdentification: Small, flat cells arranged around large, empty circles (air sacs).

May be confused with Adipose Tissue, but note the multiple cells and nuclei (arrows).

Features to Know: nuclei. Where Located: lung (air sacs or alveoli).

Function: diffusion (gas exchange

Simple Cuboidal EpitheliumIdentification: Squarish cells with round nuclei in a single row (arrows), usually arranged

in a circle (tubule). Features to Know: nuclei. Where Located: kidney tubules (can also be seen in sweat glands of skin slide).

Function: absorption and secretion

Simple Columnar EpitheliumIdentification: 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 and secretion.

Pseudostratified Columnar EpitheliumIdentification: 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. Function: secretion and movement of mucus

Transitional EpitheliumIdentification: 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: ureter (and urinary bladder). Function: elasticity: stretch and retract.

Stratified Squamous EpitheliumIdentification: 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. Two images are shown to show variation among the slides. Features to Know: nuclei, if evident.

Where Located: lining mouth and esophagus. Function: protection from abrasion and infection