Question

What are some examples of mechanical digestion?

Answer 1

Hint: The process of mechanical digestion involves mechanically breaking down the food into smaller chunks. When the food is chewed, mechanical digestion starts in the mouth. Chemical digestion is the process of breaking down food into simpler nutrients that the cells can use which involves the use of chemicals and enzymes in ideal conditions.

Complete answer:
Some examples of mechanical digestion are:
- Mastication
- Swallowing
- Peristalsis
- Absorption
- Defecation

i) The actual act of mastication (chewing) starts mechanical digestion in the mouth. When the food is sliced by the incisors, ripped by the cuspids, and ground by the molars, the advanced teeth break it down.
ii) The tongue and cheeks combine to blend and moisten the food in the mouth, producing a bolus or ball that is forced to the back of the tongue.
iii) The tongue slips back and locks the epiglottis over the larynx, causing the bolus to be forced into the oesophagus which causes swallowing to occur.
iv) The bolus is then forced towards the stomach by peristalsis, which is a wave-like muscle contraction.
v) Peristalsis churns the food in the stomach so that it can mix with the gastric juices to be pushed to the pyloric sphincter at the bottom of the stomach. The food is passed through the pylorus into the duodenum, the first loop of the small intestine, as a paste called chyme.
vi) Peristalsis forces the chyme into the small intestine, causing the villi that line the intestinal walls absorption of the nutrients from the food.
vii) Both the small and large intestines are involved in peristalsis and absorption. In the large intestine, osmosis removes the majority of the water. The remaining waste, known as faeces, is collected in the sigmoid colon until it is released into the rectum and anus in a mass movement known as defecation.

Note: Since foods such as bread, meat, and vegetables are not in a shape that the body can use as nourishment, digestion is essential. Before food and drink are consumed into the bloodstream and transported to cells in the body, they are broken into smaller nutritional molecules.