N3 AY24-25: Activity 1. The Food Journey

The ingested food undergoes an initial consistency transformation in the mouth, where the teeth physically reduce it into smaller pieces through mastication, and saliva lubricates, dissolves, and initiates its chemical breakdown. Enzymes like salivary amylase and lingual lipase play a key role in this chemical digestion, facilitating the alteration of food's consistency to enhance digestion and ease its passage through the digestive system. Subsequently, the food continues to transform in consistency throughout the digestive process. It combines with saliva and gastric juice in the stomach to form the semifluid mass known as chyme. In the small intestine, chyme undergoes further changes as monosaccharides, amino acids, lipids, electrolytes, and other nutrients are absorbed. Finally, in the large intestine, its consistency is altered once more due to chemical digestion as water, ions, and vitamins are absorbed, culminating in the formation of feces.
The body absorbs nutrients from food primarily in the small intestine. Certainly, the absorption of nutrients from food is aided by the other digestive organs to some degree, but in the small intestine specifically, digested food molecules are transported across the intestinal lining into the bloodstream or lymph. This process is facilitated by the large surface area of the small intestine, provided by structures like villi and microvilli. Nutrients like glucose, amino acids, and minerals are absorbed actively or passively, while fats are absorbed through diffusion. The absorbed nutrients are then distributed to cells throughout the body for energy, growth, and repair.

Tortora, G. J., & Derrickson, B. (2011). Principles of anatomy and physiology (13th ed). Wiley.