Final answer:
Digestion is the breakdown of food, while absorption is how its nutrients are taken up by the body, primarily in the small intestine, for use or eventual elimination as waste.
Step-by-step explanation:
Absorption in the Digestive Process
The process of absorption is a vital part of the digestive system where digested food products are transported from the lumen of the small intestine into the bloodstream. Most of the absorption occurs in the small intestine, where nutrients are taken up by the mucosal epithelial cells. Lipids are absorbed differently, through the lacteals, and carried to the bloodstream via the lymphatic system. As the partially digested substances move through the small intestine, most carbohydrates and proteins are absorbed in the jejunum, while bile salts and vitamin B12 are notably absorbed in the terminal ileum. The large intestine then absorbs water, some vitamins, and electrolytes, forming feces with the remaining waste material for removal from the body.
The intestinal villi increase the surface area for absorption, allowing an efficient transfer of nutrients. Each day, the alimentary canal processes a massive volume of food, liquids, and secretions, but it is a testament to the efficiency of absorption that less than one liter of residue reaches the large intestine. By the time the chyme (semi-digested food) reaches the large intestine, it consists mainly of indigestible food residue, excess water, and microflora.
Absorption is the critical phase of digestion where digested nutrients enter the bloodstream from the small intestine, and any remaining undigestible residue is processed into feces for elimination.