12.3.1 Introduction to the Digestive System

Question 1

Introduction to the Digestive System

Answer 1

• The three major roles of the digestive system include ingestion, digestion, and absorption. Ingestion involves the intake of food. Digestion involves the breakdown of food into small absorbable molecules. Absorption is the uptake of small molecules from the digestive system into the bloodstream.
• Food travels through the digestive system from the mouth, down the esophagus, into the stomach, and through the small and large intestines before exiting the body

Question 2

ingestion

Answer 2

• The first major role of the digestive system involves the ingestion of food.
• Ingestion begins in the mouth. The teeth grind and rip food, thus increasing the surface area of the food and making it easier to swallow. The tongue is able to move food around in the mouth and compact it into a ball called a bolus. The salivary glands secrete saliva, which contains the enzyme salivary amylase. Salivary amylase is able to hydrolyze starch and glycogen forming smaller polysaccharides.
• A bolus is pushed to the back of mouth into the pharynx. The bolus will travel from the pharynx, down the esophagus and enter the stomach.
• Swallowed food enters the stomach where it is stored and undergoes mechanical and chemical digestion. The stomach is lined with smooth muscles, which help liquefy the contents of the stomach, by a churning action.
• A sphincter is a ring-shaped modified muscle that is able to open and close. The cardiac sphincter acts as a valve and prevents food from backing up to the esophagus. The pyloric sphincter regulates the passage of food into the small intestine.
• Food enters the small intestine from the stomach through the pyloric sphincter. Most of the chemical digestion of food occurs within the small intestine.
• Accessory organs produce digestive juices, which are squirted into the small intestine and take part in chemical digestion.
• The appendix is a small extension at the end of the human small intestine. The appendix serves no apparent purpose, and is thought to be a relic of a herbivorous lifestyle.
• Materials that remain after passing through the small intestine will then enter the large intestine. The large intestine functions in the absorption of water and the production of feces.

Question 3

For humans, digestion begins in the mouth. Which of the following occur(s) in the mouth as part of digestion?

i. mechanical digestion
ii. enzymatic digestion
iii. peristalsis
iv. destruction of some bacteria

Answer 3

• i, ii, iv

Question 4

Which of the following is not a function of the digestive system?

Answer 4

• synthesis of glucose

Question 5

Which of the following is not a part of the digestive process?

Answer 5

• respiration

Question 6

If the stomach’s structure suggests its function as an organ of storage, and chemical and mechanical digestion, how does the small intestine’s structure suggest its function?

Answer 6

• The great length of the small intestine provides an enormous surface area across which products of digestion may be absorbed into the rich blood supply of the mesentery.

Question 7

Movement of food through the digestive tract is facilitated by

Answer 7

• the tongue.
• peristalsis.
• swallowing.

Question 8

Which structure keeps the acid chyme from spurting up the esophagus as the stomach undergoes muscular contractions?

Answer 8

• cardiac sphincter

Question 9

The actions of the stomach and selected enzymes convert ingested food into

Answer 9

• chyme