Correlate individual structural features of epithelial cell surfaces with their specific functions, & the overall function of the tissue of which they are a part

Epithelial cells are one of the four basic types of animal tissue, along with connective tissue, muscle tissue, and nervous tissue. They line the cavities and surfaces of structures throughout the body, and have many functions including protection, secretion, absorption, and sensation.

1. Protection: The primary function of epithelial tissue is to protect the underlying structures from physical damage, infection, and dehydration. This is achieved through the tightly packed nature of the cells, which form a barrier that is difficult for pathogens to penetrate. The outer layer of the skin, known as the epidermis, is a prime example of protective epithelial tissue.

2. Secretion: Some epithelial cells are specialized for secretion and are part of glands. For example, in the stomach, epithelial cells secrete gastric juices that aid in digestion. The structure of these cells includes a large amount of cytoplasm, which allows for the production and storage of the substances to be secreted.

3. Absorption: Epithelial cells in the small intestine, for example, have a structure that includes microvilli. These are small, finger-like projections that increase the surface area of the cell, allowing for greater absorption of nutrients.

4. Sensation: Epithelial cells in sensory organs like the nose, eyes, and ears are specialized to detect and transmit signals related to smell, sight, and sound. These cells have structures like cilia (hair-like projections) that help in the detection of these signals.

The overall function of the tissue depends on the specific functions of the individual cells. For example, the epithelial tissue in the small intestine is primarily involved in absorption, while the epithelial tissue in the skin is primarily involved in protection.