Answer (Explanation)
MOUTH: In the mouth, the teeth helps to chew (crush) the donut into smaller pieces and an enzyme called salivary amylase is secreted from the salivary glad which works as a catalyst to breakdown the carbohydrate present in the donut.
ESOPHAGUS:- The esophagus which is tube-like in nature, helps to transport the chewed (crush) pieces of the donut from the mouth into the stomach, this movement is made possible by controlled muscles and autonomic nerves. The salivary amylase still continue to breakdown the carbohydrate present in the donut at this stage because the pH level in the esophagus is neutral and it's favourable to the enzyme.
STOMACH:- In the stomach lumen, the pH level isn't favourable for salivary amylase to function rather an enzyme called pesin is produce from the gastric glands to help with further breakdown of the donut. The pieces of donut are coated with acid and digestive enzymes which helps to further break it down. This process is fast due the contraction ability of the bottom end of the stomach.
SMALL INTESTINES:- The small intestine receives the break down donut in the duodenum section where enzymes such as pancreatic amylase, maltsas, trypsin, peptidases, nuclease, nucleosidases, lipase help to breakdown fat and protein as well as further breakdown of the carbohydrate present in the donut.
The villi which is a very large surface area in the small intestine and with a finger-like structure helps to absorb the nutrients (fat, carbohydrates, proteins, fats) from the broken-down donut into the blood stream and the remains are passed on to the large intestine.
LARGE INTESTINE:- Also known as colon is the final stage of the digestion process, the large intestine absorb the salt and water present in the remains before it's been passed out of the rectum.
