- During the digestion process, food goes through many consistency and form modifications. Food is first mechanically broken down into smaller pieces in the mouth by chewing, then combined with saliva to form a semi-liquid mass known as a bolus. After passing down the esophagus and into the stomach, the bolus mixes with digestive fluids and enzymes to generate chyme, a more liquid-like substance. It then travels to the small intestine, where it comes into contact with pancreatic enzymes and bile from the liver, which further breaks it down into a semi-liquid form that is more watery to aid in the absorption of nutrients. The remaining undigested material eventually travels to the large intestine, reabsorbing water and forming feces.
- The small intestine is where nutrients are mainly absorbed. Villi and microvilli, which are finger-like projections on the inner lining of the small intestine, greatly increase the surface area that is available for absorption. After food has been digested, nutrients enter the bloodstream or lymphatic system through the small intestine's walls. Water, vitamins, minerals, proteins, lipids, carbs, and other nutrients are absorbed through various mechanisms. These nutrients are needed by the body's cells for energy production, development, repair, and different metabolic processes once they are absorbed and are delivered to them through circulation.
References
Tortora, G. J., & Derrickson, B. H. (2020). Principles of Anatomy and Physiology (16th ed.). John Wiley & Sons, Inc.