Chapter 9 Flashcards
List and describe the four stages of the digestive process.
The four stages of the digestive process are:
1) Ingestion occurs when the mouth takes in food.
2) Digestion involves the breakdown of larger pieces of food into smaller pieces that digestive enzymes can act on.
3) Absorption occurs as subunit molecules cross the GI tract wall and enter cells.
4) Elimination removes indigestible molecules and discharges them from the body.
Briefly describe the structure of the mouth. What is the function of the mouth? Distinguish between
mechanical digestion and chemical digestion. What is the function of salivary amylase?
The mouth, pharynx, and esophagus are in the first part of the GI tract.
The Mouth
A roof, formed by the hard and soft palates, separates the mouth from the nasal cavities. The mouth receives food and begins the process of mechanical and chemical digestion. Three pairs of salivary glands secrete saliva (containing salivary amylase for digestion of starch) into the mouth.
What is a bolus?
Mechanical digestion begins when the teeth chew the food and the tongue forms a bolus for swallowing.
Name the two parts that each tooth has. Distinguish among enamel, dentin, and pulp
Each tooth has a crown and a root. The crown has a layer of enamel, dentin, and an inner pulp. The root has dentin and pulp. Blood vessels and nerves are in the pulp
What are some ailments associated with the teeth?
Gum disease and dental caries are two ailments associated with the teeth.
What type of muscle composes the tongue? What are the sensory receptors of the tongue?
The tongue is composed of skeletal muscle, and it is covered by a mucous membrane that contains the sensory receptors called taste buds.
What is the pharynx? What is the function of the esophagus?
The air and food passages, two tubes that run parallel to one another, cross in the pharynx, which is a hollow space at the back of the throat. The esophagus is the long tube that takes food to the stomach.
What does the epiglottis do when we swallow? Can we breathe and swallow at the same time? Why or why not?
When one swallows, the air passage is usually blocked off by the epiglottis and food must enter the esophagus. We do not breathe when we swallow.
What is peristalsis? Where does it occur in the digestive tract?
A rhythmic contraction called peristalsis pushes food along the esophagus and continues in all the organs of the digestive tract.
What are sphincters? What is their function?
Sphincters are muscles that encircle tubes and act as valves. The tubes close when the sphincters contract and open when they relax.
What is heartburn and what causes it?
When food moves from the stomach back into the esophagus, heartburn occurs.
What happens physically in the digestive system that causes vomiting?
When strong contractions of the abdominal muscles and the diaphragm force the stomach contents into the esophagus and oral cavity, vomiting occurs.
What is the function of the stomach? What is chyme? What are rugae?
The stomach expands and stores food. While food is in the stomach, the stomach churns, mixing the food with its acidic gastric juices (containing HCl and pepsin for the digestion of protein) to produce chyme. Few materials are absorbed through the stomach lining. Besides the circular and longitudinal layers of stomach smooth muscle, the oblique layer allows the stomach to stretch and mechanically break down food. Deep folds called rugae disappear when the stomach fills. Peristaltic waves move food toward the pyloric sphincter.
What is the function of the small intestine?
The small intestine is smaller in diameter than the large intestine but is actually longer.
Why do you suppose pancreatic juice is alkaline (basic)? What are the functions of: lipase, pancreatic amylase, and pancreatic trypsin?
Digestion Is Completed in the Small Intestine
The small intestine contains enzymes to digest all types of foods. The duodenum receives bile from the gallbladder and pancreatic enzymes. Pancreatic juice is basic because of the presence of NaHCO3. Lipase is a pancreatic enzyme that hydrolyzes fat, and pancreatic amylase digests carbohydrates. Pancreatic trypsin and other intestinal proteases complete protein digestion.