How does the food change in consistency and form?
Change in consistency and form of the food we consume occurs throughout the entire digestive process and starts when food enters our mouth. Mastication occurs in the mouth and grounds the food with use of the tongue, the teeth and saliva to altogether transform the food into a softer mass known as bolus. When the bolus arrives into the stomach, it undergoes propulsion and retropropulsion, which is a squeezing of the food back tot he body of the stomach, as to ensure that the food particles are not too large and able to fit through the pyloric sphincter. The food is then thoroughly mixed with the gastric juices and takes the form and consistency of a soupy liquid known as chyme. Chyme is further broken down with the use of several enzymes and secretions in the stomach and later the small intestine. In the small intestine, chyme is sloshed back and forth for further absorption and the completion of carbohydrate, protein and lipid digestion. In the large intestine, the chyme becomes semisolid or solid and is now called feces.
How could the body absorb the nutrients from the foods we eat?
The body mainly absorbs nutrients in the small intestine. The small intestine has absorptive epithelial cells that line the mucosa and into the underlying blood and lymphatic vessels. These allow transport of digested nutrients into the bloodstream or lymph via absorption which may occur through diffusion, facilitated diffusion, active transport and osmosis. Absorption of nutrients also occurs in the stomach and large intestines, though is both significantly less than in the small intestine. The stomach only absorbs small amounts of nutrients including certain drugs, some water, ions and short-chain fatty acids, while the large intestine only absorbs those left unabsorbed by the small intestine such as some vitamins and ions but mainly deals with water absorption.
Reference:
Tortora, G. J., & Derrickson, B. (2017). Principles of anatomy and physiology (15th ed.). Wiley.