heces

Heces, or feces, are the solid waste expelled from the digestive tract during defecation. In humans and many other animals, they consist largely of water, bacteria, undigested food residues, cells shed from the intestinal lining, and bile pigments that give the usual brown color. The water content is highly variable, contributing to differences in consistency.

Formation and transit: Most processing occurs in the large intestine where water and electrolytes are absorbed. The remaining material is shaped into stool and transported by peristaltic movements to the rectum over a period of roughly 12 to 48 hours, though this can vary with diet, health, and age. Normal stools are brown due to stercobilin, a breakdown product of bilirubin.

Color and consistency: Stool color ranges from light to dark brown; colors outside this range can indicate dietary factors or medical issues, such as black or tarry stools indicating bleeding, pale stools indicating bile flow problems, or green stools from rapid transit or high chlorophyll content. Consistency is commonly classified with the Bristol Stool Chart, ranging from hard pellets to soft, sausage-like forms.

Health relevance and testing: Stool appearance and tests can reflect gastrointestinal health. Medical tests include fecal occult blood tests for bleeding, stool cultures for infections, and molecular assays for pathogens. Calprotectin or fecal elastase tests assess inflammation and pancreatic function, respectively. Proper collection, handling, and timing are important for accurate results.

Ecology and animal use: In animals, feces vary with species and diet and are used in ecological studies to assess health, diet, and habitat use. Fecal matter can also impact environmental health if not properly managed.