Digestive System


Q1.Identifyand describe the six major processes involved in gastrointestinalactivity.

  • Ingestion- this is intake of food

  • Propulsion- this is the process of passing the food down the gastrointestinal (GI) tract

  • Mechanical digestion- this is the process of preparing the food for chemical digestion. It involves chewing and mixing the food with saliva.

  • Chemical digestion- these are catabolic steps in which food molecules are broken down into simple sugar, fatty acids, and amino acids by enzymes

  • Absorption- this is the movement of food particles from the gastrointestinal (GI) tract to the blood.

  • Defecation- this is elimination of waste (indigestible food) via anus

Q2.Whatrole do hormones play in hunger and satiety?

Ghrein,leptin, and obestatin are the three hormones that control hunger andsatiety (Martini,Nath, and Bartholomew, 2015).The stomach produces Ghrein hormone while the fat cells producesleptin hormone. The main role Ghrein is to turn on the hunger cell inthe brain, as well as turn off the satiety cell. On the other hand,the leptin hormone turns on the satiety cell in the brain, as well asturn off the hunger cell. Obestatin hormone is produced in thestomach and in the small intestine. It primary role is to decreasethe appetite.

Q3.Outline the usual pathway for digestion and absorption oftriglycerides (fats).

Lipasebreaks down triglycerides into monoglyceride and fatty acids. Next,bile salts combines with lipids to transport them to the smallintestine. The gall bladder secretes them. Next, the triglyceridesare digested by pancreatic lipase to fatty acids. Later, theintestinal epithelial cells absorbs them and resynthesize them intotriacyglycerols. Eventually, the small lipids enter the apicalmembrane and form chylomicrons that are released into lymphaticsystem (Martiniet. al., 2015).At the same time, fatty acids are transported to peripheral tissuesby chylomicrons, and adipose tissue stores the excess fat.

Q4.Explain the role of the hormones cholecystokinin and secretin inregulating the release of bile and pancreatic juices.

Cholecystokininand secretin hormones travel through bloodstream to liver, pancreas,and gallbladder. When fat gets into the duodenum, its acid stimulatesthe secretion of Cholecystokinin. The pancreas reacts tocholecystokinin and releases enzyme-rich pancreatic juice (Johnson,2015).Here, the secretin hormone causes bicarbonate-rich pancreaticsecretion and the liver reacts to secretin and releases bile. On theother hand, cholecystokinin stimulates the gallbladder to releasebile. In addition, the Cholecystokinin stimulates pancreatic enzymesuch as lipase and amylase to break down food. Further, it causescontraction of the gallbladder, and correspondingly releases bileinto the duodenum.

Q5.Why is it necessary for the stomach contents to be so acidic? Howdoes the stomach protect itself from digestion?

Thestomach contents should be acidic to help digestion and kill thebacteria (Johnson,2015).A stomach protects itself from digestion by use of bicarbonate-richmucous that protect the stomach from digestion. The tight junctionsin the epithelial cells stop leaking, as well as quickly replacedamages cells. In addition, the stomach lining releases enzymes thatbreak down the digested food. It also secretes an acid that create anideal condition for enzymes to work. This acid also kills bacteriaas well as protects the stomach from harmful microbes.

Q6.Identify three ways the small intestine is modified to increase thesurface area for digestion and absorption.

  • Plicae circulars- these are circular folds of the submucosa and mucosa. They facilitate spirally movement of chyme through lumen.

  • Villi- these are projections of the mucosa. Their purpose is to increase absorptive surface area.

  • Microvilli- these are projections of plasma membrane. Their purpose is to enhance absorption and increase surface area.


Johnson,R. L. (2005).&nbspThedigestive system.Minneapolis: Lerner Publications Co.

Martini,F., Nath, J. L., &amp Bartholomew, E. F. (2015).&nbspFundamentalsof anatomy &amp physiology.San Francisco: Benjamin Cummings.