How does the food change in consistency and form?
Food is first shredded and cut into smaller pieces through mechanical digestion that happens in the mouth with the help of the teeth. Salivary Amylase present in the saliva in the oral cavity also plays a role in chemically digesting the food. The food is now transformed into bolus which is easier to swallow.
Moving on, the bolus now travels into the stomach where gastric juices breaks down the bolus turning it into a semi-liquid substance called chyme. As it travels down the small intestine, chyme undergoes further changes as nutrients are absorbed in the small intestine. Lastly, consistency is altered as it travels down the large intestine where waters, ions, and vitamins are absorbed, forming feces which is to be eliminated through the anus.
How could the body absorb the nutrients from the foods we eat?
Mainly, the absorption of nutrients happens mostly in the small intestine with the help of the villi and microvilli. Glucose, amino acids, and minerals can be absorbed via active or passive transport, while fats are absorbed through diffusion.