Question

1. Trace the pathway in the digestive system from ingestion to elimination of a cheeseburger with “the works”. Describe the effects of each GI tract structure on the components of the cheeseburger as they pass along. Include motility, digestive processes including enzymes, absorption of nutrients and elimination.

Answer 1

1. The process starts with ingestion of cheeseburger into mouth where it is chewed into pieces which stimulates the exocrine glands. The exocrine glands release digestive enzymes such as salivary amylase which helps in breaking down carbohydrates in the cheeseburger. The saliva in the mouth helps to condense the food into a bolus which can be easily passed through esophagus.

2. The esophagus is an organ where no digestion takes place but the food is pushed down by peristalsis movement which is a wavelike contraction of smooth muscle tissue.

3. The food enters the stomach through the cardiac splincter where the food is churned and mixed with digestive fluids like hydrochloric acid and other digestive enzymes. It decomposes the food chemically for few hours and after that the acidic level changes and more enzymes are activateed or deactivated to extract and proces various nutrients.

4. The food moves and is passed to the intestine through peristalsis. It paases through the pyloric sphincter and goes into the first 10 inches of the small intestine called as duodenum. In duodenum, the food is mixed with bile juices (which helps in fat digestion), pancreatic juice and intestinal juices. Bile contains pigments by red blood cells that leave with the feces.

5. The food passes through the small intestine whose walls contain small hair like structures called villi. The villi helps in the increasing the surface area for the food absorption and most nutrient absorption takes place in the small intestine.

6. The nutrients are absorbed into the blood and is carried away from the small intestine through the hepatic portal vein to the liver. In the liver, the nutrients are processed to separate the toxins.

7. After small intestine, the food goes into the large intestine which consists of three parts namely cecum, colon and rectum. The water is reabsorbed, food (like fiber) that cannot go through the villi can be stored in large intestine. Fiber helps in food movement through the GI tract. The food that cannot be broken down is called feces which is stored in rectum until it is expelled through the anus.