Epithelial Tissue

Epithelial tissue serves as a covering for external structures (skin) and internal organs.  There are many categories of epithelial cells that many beginning anatomy students must learn to identify.   Generally, epithelial tissue is classified as either simple or stratified.  Stratified tissue consists of many layers of cells and simple tissue is a single layer.  In both cases, the cells are attached to a basement membrane.   To further identify tissue types, they are classified as squamous (flat),  cuboidal (square), and columnar (columns).   Combining these terms gives the specific names of the tissues.

epithelial tissue

1. Simple Squamous      –  found in respiratory cells and capillaries, specialized for diffusion

2. Simple Cuboidal     –  found in kidneys and ovaries, secretion and absorption

3. Stratified Squamous – found lining body cavities like the mouth and vagina and the outer layer of skin; protection

4. Simple Columnar –  found in the digestive tract; absorbs nutrients and often contains goblet cells and microvilli

5.  Stratified Cuboidal – found in mammary glands and salivary glands, functions in secretion

6.  Stratified Columnar – rare, found in the conjunctiva of the eye

7. In addition to these basic shapes, epithelial cells can also be pseudostratified, where there is a single layer of cells, but the position of the nuclei gives it the appearance of having multiple layers.   These cells are often found in the respiratory tract and can also contain cilia that help move mucus.

pseudostatified

8.  Transitional Epithelium – found in the urinary bladder, tissue that can stretch and is waterproof

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