stoma

Stoma is a term with two broad meanings in biology and medicine. In botany, a stoma (plural stomata) is a microscopic pore found primarily on the underside of leaves, but also on stems and other plant organs. Each stoma is formed by two guard cells that control its aperture. When opened, stomata allow carbon dioxide to enter for photosynthesis and enable oxygen to exit; they also permit water vapor to escape, a process called transpiration. Stomatal opening and closing respond to light, carbon dioxide levels, humidity, soil water status, and hormonal signals such as abscisic acid. Stomatal density and distribution vary among species and environmental conditions, influencing a plant’s gas exchange and water balance.

In medicine, a stoma is a surgically created opening on the abdomen that diverts waste from a failing or bypassed section of the intestine or urinary system to an external pouching device. Common types include colostomy (colon), ileostomy (ileum), and urostomy (urinary system). A stoma may be temporary or permanent, depending on the underlying condition. The stoma is usually red and moist and lacks sensation, since it is formed from bowel or urinary tract tissue rather than skin. Care involves protecting the surrounding skin, applying an appropriate ostomy appliance to collect output, and monitoring for irritation, leakage, or retraction. Potential complications include blockage, infection, stoma necrosis, stenosis, or parastomal hernia. Patients typically receive education and follow-up to manage lifestyle adjustments and ostomy-related needs.