stomas

Stomas, or stomata, can refer to two related but distinct concepts in biology: surgically created openings on the body's surface and the microscopic pores on plant leaves that regulate gas exchange.

Medical stomas are created to divert fecal flow or urine when normal passage is not possible due to disease, injury, or surgery. Common types include ileostomy (from the ileum), colostomy (from the colon), and urostomy (urinary diversion via a conduit). Stomas can be temporary or permanent, and may be end or loop variants depending on the surgical technique. Care involves an external pouching system attached to the skin around the stoma, stoma hygiene, and skin protection to prevent irritation. Patients need education on appliance management, diet, hydration, and monitoring for changes in stoma output or skin. Complications may include skin irritation around the stoma, blockage, prolapse or retraction of the stoma, parastomal hernia, dehydration (especially with ileostomy), and infection.

Plant stomata are microscopic pores flanked by guard cells that regulate gas exchange between the leaf interior and the atmosphere. When guard cells take in water and swell, the pore opens; when they lose water and shrink, the pore closes. Opening and closing respond to light, carbon dioxide concentration inside the leaf, humidity, temperature, and circadian rhythms. Through stomata, plants take in carbon dioxide for photosynthesis and release oxygen and water vapor during transpiration. The density and distribution of stomata vary by species, leaf side, and developmental stage, influencing water use efficiency and photosynthetic capacity.