Epitheliale weefsels en hun functies

Epithelial tissues are sheets of closely-packed cells covering the body and compartmentalizing specific environments to protect the body from pathogenic invasion, fluid loss, or mechanical injuries.

They occur in two forms, covering or lining epithelia, and glandular epithelia.

Covering or lining epithelia function as gatekeepers. They cover exposed body surfaces and line internal tracts of organs, allowing selective substances to enter and exit the body.

For example, the epithelial lining of the kidney tubules allows the reabsorption of nutrients from the urine and the release of waste products from the nearby capillaries.

Glandular epithelia are arranged into specialized structures or glands, which can be a single cell or a group of cells. They produce and release different secretory substances, such as mucus, sweat, and hormones.

Epithelial tissues are richly supplied with sensory nerves that quickly relay information between the external and internal environments, producing an immediate response.

For instance, a mosquito bite instantly stimulates nerves under the skin epithelium and triggers the body to swat at the location.