Tracking Digestion

Topics: Digestion, Stomach, Digestive system Pages: 2 (768 words) Published: August 23, 2011
As a part of my breakfast on Day 1, I ate a peanut butter and jelly sandwich. The creamy peanut butter provided both protein and fat for my diet while the multigrain bread provided me with carbohydrates. As I take a bite of the peanut butter and jelly sandwich I crush all three of the macronutrients with my teeth. The role of saliva helps moistens the food while a digestive enzyme in the saliva called salivary amylase (ptyalin) helps breaks down the complex carbohydrates mostly contained in the bread into simple sugars. Once the food has been sufficiently chewed, the tongue rolls it into a ball known as a bolus and pushes it into the pharynx. In a combination of voluntary and automatic movements, swallowing propels the food downwards into the upper esophagus using a peristaltic contraction. The epiglottis blocks the trachea (windpope) to prevent food particles from entering the trachea and interfering with respiration. The esophagus is then able to move the bolus downwards. At the bottom of the esophagus there is the cardiac sphincter which then opens to food can enter the stomach. The sphincter then recloses to prevent regurgitation of stomach contents into the esophagus. The bolus of food stimulates the secretion of gastrin by the cells of the stomach wall. The gastrin cells secrete gastrin which stimulates HCl production in the parietal cells of the gastric glands, gastrin also stimulates muscular contractions fo the stomach to further churn the food and produce an acidic, semi-fluid, partially digested of my peanut butter and jelly sandwich called chyme. Mucous cells in the stomach secrete mucus to protect the stomach lining from acidic pH of the stomach (pH 2). The chief cells secrete pepsinogen, the precursor to pepsin. The parietal cells of the stomach secrete hydrochloric acid which kills bacteria in the stomach and helps break down intercellular links in food tissues and aids in the conversion of pepsinogen to pepsin; they also secerete intrinsic factor...
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