Guided Notes on Accessory Digestive Organs

1. What is saliva, and what are the functions of its 2 components? Saliva is a mixture of mucus and serous fluids Mucus moistens and binds food together into a bolus The serous fluid contains an enzyme called salivary amylase that begins starch digestion

2. List the four types of permanent teeth and their shapes and functions Incisors: chisel-shaped for cutting Canines: fang-like, for tearing or piercing Premolars: (bicuspids) broad crowns for grinding Molars: broader crowns with rounded tips for grinding

3. What do the enzymes produced by the pancreas do? They break down all categories of digestible foods. They are alkaline, so they also neutralize the acidic chyme from the stomach.

4. What is the digestive function of the liver? The liver produces bile, which enters the duodenum through the common hepatic duct.

5. What is bile composed of? What is the function of bile salts? Bile is a yellow-green, watery solution containing bile salts, bile pigments, cholesterol, phospholipids, and electrolytes Bile salts emulsify fats by breaking large fat globules into smaller ones, giving more surface area for enzymes to work

6. When is bile stored in the gallbladder? When food digestion is not occurring, bile backs up into the cystic duct and enters the gallbladder

7. What are gallstones? If bile is stored in the gallbladder too long, the cholesterol it contains may crystallize into gallstones

Functions of the Digestive System Ingestion: an active, voluntary process of placing food in the mouth Propulsion: foods are propelled from one organ to the next by peristalsis and segmentation Mechanical Digestion: mixing of food in the mouth by the tongue; churning of food in the stomach, segmentation in the small intestine.

Functions of the Digestive System Chemical Digestion: large food molecules are broken down to their building blocks by enzymes Absorption: transport of digested end products from the lumen of the GI tract to the blood or lymph Defecation: elimination of indigestible substances from the body

2. What is peristalsis? Peristalsis are involuntary, alternating waves of contractions of muscles in the walls of the alimentary canal. The net effect is to squeeze food along the digestive tract

3. What is the purpose of segmentation? Segmentation moves food back and forth across the internal wall of the organ, serving to mix it with digestive juices

4. Categorize the Sugars Processed by the Stomach: Monosaccharides: Glucose, Fructose, Galactose Disaccharides: Sucrose, Maltose, Lactose Polysaccharides: Starch

5. What is the purpose of cellulose in the diet? Cellulose helps to move foodstuffs along the gastrointestinal tract by providing bulk, or fiber

6. Describe the process of protein digestion Proteins are digested to their building blocks, amino acids, by enzymes in the stomach and small intestine

7. List the stimuli that activate digestive reflexes: Stretch of the organ by food in the lumen pH of the contents Presence of certain breakdown products of digestion

1. How is food broken down in the mouth? Food is physically broken down by chewing Salivary amylase begins the chemical digestion of starch, breaking it down into maltose

2. What regulates the secretion of gastric juice? The sight, smell, and taste of food increase the secretion of gastric juice by the stomach cells 2 to 3 liters of gastric juice is produced every day under normal conditions

3. What causes heartburn to occur? When the cardioesophageal sphincter fails, gastric juice backs up into the esophagus, which has little protection from mucus

4. Compare pepsin and rennin: Pepsin is a protein-digesting enzyme that is activated by hydrochloric acid Rennin is a protein-digesting enzyme that works on milk protein. It is only produced by infants and children Both are produced by the stomach

5. How long does food generally remain in the stomach? 4 hours if the meal is well-balanced 6 hours if it has a high fat content

6. What is vomiting? Vomiting is a reverse peristalsis occurring in the stomach, accompanied by contraction of the abdominal muscles and the diaphragm

7. What four functions do the pancreatic juice enzymes perform? Complete the digestion of starch Carry out protein digestion Totally responsible for fat digestion Digest nucleic acids

8. Why is it important that pancreatic juice contains bicarbonate? Bicarbonate is basic, so that it can neutralize the acidic chyme as they enter the small intestine together

9. How are water and the end products of digestion absorbed? Most substances are absorbed through the intestinal cell plasma membranes by active transport Lipids are absorbed by diffusion

10. What remains from the process of digestion? Water Indigestible food materials (fiber) Large amounts of bacteria

11. What functions do the bacteria perform? They metabolize remaining nutrients and release gas that contribute to the odor of feces

12. What are mass movements? Mass movements are long, slow-moving, powerful contractions that move over the colon 3 or 4 times daily and force the contents toward the rectum. They occur during or just after eating Fiber in the diet causes them to increase in strength

13. What conditions cause diarrhea to occur? When food residue is rushed through the large intestine before sufficient time for water to be absorbed Usually this is caused by irritation from bacteria