A columnar cell is a type of epithelial cell that is shaped like a column. It's named for its elongated, rectangular shape, with a nucleus usually located at the base. These cells are commonly found in the lining of the passages of the respiratory, digestive, and genitourinary (reproductive and urinary) systems.
Here's a breakdown of what columnar cells do:
- Barrier: Columnar cells form a protective barrier, separating the body's internal environment from the external world.
- Secretion: They can secrete substances like mucus, enzymes, and hormones, depending on their location and function.
- Absorption: In the digestive tract, columnar cells play a vital role in absorbing nutrients.
- Transportation: They can move fluids or substances across the epithelial layer.
Examples of Columnar Cells:
- Intestinal epithelium: Columnar cells with microvilli on their apical surface (the side facing the lumen) aid in nutrient absorption.
- Respiratory epithelium: These cells secrete mucus to trap foreign particles, contributing to the body's defense mechanisms.
- Gallbladder epithelium: This epithelium helps concentrate bile, which is essential for digestion.
Columnar cell lesions: These are abnormal changes in the breast tissue, where the usual cuboidal cells lining the milk glands are replaced by columnar cells. They can be a marker for potential breast cancer risk.
Note: It's important to understand that "columnar cell" refers to a specific type of epithelial cell and can be further classified based on its structure and location.
