Final answer:
Absorption refers to the transfer of substances into the bloodstream or lymphatic system, which can occur within the digestive system, primarily the small intestine, or via alternative routes for non-digestive absorption such as intravenous injections.
Step-by-step explanation:
Methods intended to absorb substances outside the digestive system often include administration routes such as intravenous, intramuscular, subcutaneous, inhalation, and transdermal methods, bypassing the gastrointestinal (GI) tract. Absorption is the passage of digested products from the intestinal lumen through mucosal cells and into the bloodstream or lacteals. However, when absorption occurs outside of the digestive system, it means that substances are directly entering the bloodstream or lymphatic system through alternative routes, facilitating their distribution throughout the body without the need for digestion.
The process of absorption within the digestive system primarily occurs in the small intestine where nutrients enter the bloodstream through epithelial cells or into the lymphatic system via lacteals. Essential for the circulatory system to distribute these nutrients to cells throughout the body, absorption ensures that our bodies benefit from the nutrients obtained from food. Conversely, drugs or other substances taken through non-oral routes are designed to get absorbed without passing through the gastrointestinal tract, therefore serving different therapeutic purposes.