1. Two cell types of salivary glands are serous and mucous.
2. Serous cells produce watery fluid that contains amylase.
3. Mucous cells produce mucus.
4. Amylase digests carbohydrates.
5. Salivary glands are innervated by both sympathetic and parasympathetic nerves.
6. Sympathetic fibers stimulate the glands to secrete a small amount of viscous saliva.
7. Parasympathetic fibers stimulate the glands to large amounts of watery saliva.
C. Major Salivary Glands
1. The largest of the major salivary glands is the parotid.
2. The parotid glands are located anterior and inferior to each ear.
3. A parotid duct is located within the buccinator muscle and opens into the inside of the cheek about the level of the second molar.
4. The parotid glands secrete a water fluid rich in amylase.
5. The submandibular glands are located in the floor of the mouth on the inside surfaces of the lower jaws.
6. The submandibular glands secrete primarily serous fluid.
7. Ducts of submandibular glands open inferior to the tongue.
8. The sublingual glands are located inferior to the tongue.
9. The sublingual glands secrete primarily mucus.
10. The ducts of sublingual glands open beneath the tongue.
V. Pharynx and Esophagus
1. The pharynx is a cavity posterior to the nasal and oral cavities.
2. The pharynx and esophagus function in swallowing.
B. Structure of the Pharynx
1. The pharynx connects the nasal and oral cavities with the larynx and esophagus.
2. The three divisions of the pharynx are the nasopharynx, oropharynx, and laryngopharynx.
3. The nasopharynx is located behind the nasal cavity.
4. The nasopharynx provides a passageway for air.
5. The oropharynx is located behind the oral cavity.
6. The oropharynx is a passageway for food and air.
7. The laryngopharynx is located just inferior to the oropharynx.
8. The laryngopharynx is a passageway to the esophagus.
9. Constrictor muscles function to pull the pharyngeal walls inward during swallowing.
C. Swallowing Mechanism
1. The events of the first stage of swallowing are chewing of food and the mixing of food with saliva.
2. The events of the second stage of swallowing are pushing of food toward the pharynx and the triggering of the swallowing reflex.
3. The events of the third stage of swallowing are movements of food through the esophagus and to the stomach.
4. The actions of the swallowing reflex are raising of soft palate, elevation of larynx and hyoid bone, pressing of tongue against soft palate, contraction of pharyngeal muscles, opening of the esophagus, and movement of food into the esophagus.
1. The esophagus is a passageway for food.
2. The esophagus propels food from the pharynx to the stomach.
3. The esophagus descends through the thoracic cavity.
4. The esophageal hiatus is an opening in the diaphragm.
5. Mucous glands are scattered throughout the submucosa of the esophagus.
6. The lower esophageal sphincter is located where the esophagus and stomach join and functions to prevent regurgitation of food.
1. The shape of the stomach is J-shaped.
2. The location of the stomach is just inferior to the diaphragm.
3. Rugae are thick folds in the lining of the stomach.
4. The functions of the stomach are to mix food with gastric juice, begin protein digestion, to begin a small amount of absorption, and movement of food into the small intestine.
B. Parts of the Stomach
1. The four parts of the stomach are cardiac portion, body, fundus, and plylorus.
2. The cardiac region is the region near the esophageal opening.
3. The fundic region is a pouch that extends superior to the cardiac portion.
4. The body of the stomach is the main part of the stomach.
5. The pyloric region is the narrow region that is continuous with the small intestine.
6. The pyloric sphincter is located between the pylorus and the duodenum and functions to control the movement of food into the small intestine.
C. Gastric Secretions
1. Gastric pits are openings of gastric glands.
2. The three cell types of gastric glands are parietal, chief, and mucous.
3. Mucous cells secrete mucus.
4. Chief cells secrete digestive enzymes.
5. Parietal cells secrete hydrochloric acid and intrinsic factor.
6. Gastric juice is a mixture of the secretions of mucous, parietal, and chief cells.
7. Pepsin is an enzyme that digests proteins.
8. The function of pepsinogen is to be converted to pepsin when needed.
9. The function of hydrochloric acid in the stomach is to convert pepsinogen into pepsin and to destroy pathogens.
10. The coating of the stomach is important for protecting the stomach wall from digestive enzymes and acids.
11. The function of intrinsic factor is enhance the absorption of vitamin B12.
D. Regulation of Gastric Secretions
1. Somatostatin is produced in the stomach and functions to inhibit acid secretion.
2. Parasympathetic innervation stimulates the release of gastric juice.
3. Gastrin is produced the stomach and functions to increase the secretory activity of gastric glands.
4. The three stages of gastric secretion are cephalic, gastric, and intestinal.
5. The events of the cephalic phase are secretion of gastric juice before food enters the stomach.
6. The events of the gastric phase are distension of the stomach and the release of more gastric juice.
7. The events of the intestinal phase are the movement of food into the small intestine.
8. Cholecystokinin is produced by the small intestine and functions to inhibit gastric secretions.
E. Gastric Absorption
1. The stomach absorbs alcohol, some drugs, salts, and a small amount of water.
2. Most nutrients are absorbed in the small intestine.
1. A stomachache results from the rise of internal pressure in the stomach.
2. Chyme is food substances that have been mixed with gastric juice.
3. Peristaltic waves push chyme toward the pylorus of the stomach.
4. Stomach contractions push chyme a little at a time into the duodenum
and backwards into the stomach, mixing it further.
5. The lower esophageal sphincter prevents regurgitation of food.
6. The rate at which the stomach empties depends on the fluidity of the chyme and its contents.
7. Liquids usually pass first through the stomach.
8. The enterogastric reflex is a reflex involving the small intestine and the stomach. It is triggered by distension of the small intestine wall and inhibits peristalsis in the stomach to slow down movement of food into the duodenum.
9. Vomiting results from a complex reflex that empties the stomach in the reverse of the normal direction.
A. Structure of the Pancreas
1. The pancreas is located close to the duodenum posterior to the parietal peritoneum.
2. Pancreatic acinar cells produce digestive enzymes and make up the bulk of the pancreas.
3. Acini are clusters of acinar cells.
4. The pancreatic ducts extends the hepatopancreatic ampulla and empties into the duodenum.
5. Hepatopancreatic ampulla is a dilated tube that receives the pancreatic duct and hepatic duct.
6. The hepatopancreatic sphincter is the sphincter that surrounds the hepatopancreatic ampulla.
B. Pancreatic Juice
1. Pancreatic juice contains many enzymes and bicarbonate ions.
2. The function of pancreatic amylase is to digest carbohydrates.
3. The function of pancreatic lipase is digest lipids.
4. The functions of trypsin, chymotrypsin, and carboxypeptidase are to digest proteins.
5. Zymogen granules are granules that store pancreatic enzymes.
6. The function of trypsinogen is to be converted to trypsin.
7. The functions of nucleases are to digest nucleic acids.
C. Regulation of Pancreatic Secretion
1. Parasympathetic fibers cause the pancreas to release pancreatic juice.
2. The function of secretin is to stimulate the pancreas to release pancreatic juice with a high concentration of bicarbonate ions.
3. The release of cholecystokinin is triggered by the presence of chyme in the small intestine.
4. The action of cholecystokinin on the pancreas is to release pancreatic juice that has a high concentration of digestive enzymes.
1. The largest internal organ is the liver.
2. The liver is located in the upper right abdominal quadrant.
B. Liver Structure
1. The two large lobes of the liver are the right and left.
2. The falciform ligament is a fold that separates the lobes of the liver and anchors the liver to the posterior abdominal wall.
3. The two small lobes of the liver are caudate and quadrate.
4. The porta hepatis is where blood vessels and ducts enter or exit the liver.
5. The coronary ligament is a ligament that attaches the liver to the diaphragm.
6. Hepatic lobules are divisions of a liver lobe.
7. A hepatic lobule consists of many hepatic cells radiating outward from a central vein.
8. Hepatic sinusoids are vascular channels in hepatic lobules.
9. Kupffer cells are macrophages of the liver.
10. Bile canals are canals within liver lobules that receive secretions from hepatic cells.
11. Hepatic ducts are formed from bile canals of neighboring hepatic lobules.
C. Liver Functions
1. The liver carries on many important metabolic functions.
2. The liver plays a key role in carbohydrate metabolism by helping maintain the normal blood glucose concentrations.
3. The liver plays a key role in lipid metabolism by oxidizing fatty acids, synthesizing lipoproteins, phospholipids, and cholesterol.
4. The liver plays a key role in protein metabolism by deaminating amino acids, forming urea, synthesizing plasma proteins, and converting amino acids to other forms of amino acids.
5. The liver stores glycogen, iron, and vitamins A,D, and B12.
6. Liver cells help destroy worn out red blood cells.
7. The liver removes toxic substances from the blood.
8. The liver’s role in digestion is to secrete bile.
D. Composition of Bile
1. Bile is secreted by hepatic cells.
2. Bile contains water, bile salts, bile pigments, cholesterol, and electrolytes.
3. Hepatic cells use cholesterol to make bile salts.
4. Bile pigments are products of the breakdown of hemoglobin.
5. Jaundice results from an accumulation of bile pigments in the blood stream.
1. The gallbladder is located inferior to the liver.
2. The cystic duct is the duct of the gallbladder and opens into the common bile duct.
3. The common bile duct is formed from the cystic duct and common hepatic duct and opens into duodenum.
4. Gallstones form when bile is too concentrated.
F. Regulation of Bile Release
1. Cholecystokinin triggers the gallbladder to release bile.
2. Cholecystokinin is released in response to presence of lipids and proteins in the small intestine.
G. Functions of Bile Salts
1. Functions of bile salts are to aid in the absorption of fatty acids, and certain vitamins, and to emulsify fats.
2. Emulsification is the breaking of fat globules into smaller droplets.
3. Lack of bile salts results in poor lipid absorption and vitamin deficiencies.
X. Small Intestine
1. The small intestine extends from the stomach to the large intestine.
2. The small intestine receives secretions from the pancreas, gallbladder, and liver.
3. The functions of the small intestine are to complete digestion, absorption of nutrients, and movement of solid wastes to the large intestine.
B. Parts of the Small Intestine
1. The three parts of the small intestine are duodenum, jejunum, and ileum.
2. The duodenum is located posterior to the parietal peritoneum just beneath the stomach.
3. The jejunum is located in the abdominal cavity between the duodenum and ileum.
4. The ileum is located in the abdominal cavity between the jejunum and large intestine.
5. Mesentery is double-layered fold of peritoneum and supports the blood vessels, nerves, and lymphatic vessels that supply the intestinal wall.
6. The greater omentum is a double fold of peritoneal membrane that drapes like an apron from the stomach, over the transverses colon, and the small intestine.
7. The functions of the omentum are to prevent the spread of infections in the peritoneal cavity.
C. Structure of the Small Intestinal Wall
1. The velvety appearance of the inner wall of the small intestine is due to intestinal villi.
2. Intestinal villi are tiny projections of the mucosa of the small intestine.
3. The functions of villi are to increase the surface area of the lining of the small intestine.
4. Each villus consists of a layer of simple columnar epithelium and a core of connective tissue containing blood capillaries, a lacteal, and nerves.
5. A lacteal is a lymphatic capillary.
6. Microvilli increase the surface area intestinal cells.
7. Intestinal glands are between the bases of adjacent villi.
8. Plicae circulares are circular folds in the mucosa of the small intestine.
D. Secretions of the Small Intestine
1. Brunner’s glands are mucous-secreting glands and are located in the submucosa of the proximal portion of the duodenum.
2. Brunner’s glands secrete alkaline mucus.
3. The enzymes secreted by epithelial cells of the small intestine are peptidase, sucrase, maltase, lactase, lipase, and enterokinase.
4. The functions of peptidases are to digest proteins.
5. The functions of sucrase, maltase, and lactase are to digest sucrose, maltose, and lactose.
6. The functions of intestinal lipase are to digest lipids.
E. Regulation of the Small Intestinal Secretions
1. Mechanical digestion and the presence of gastric juice in the small intestine stimulate the duodenal mucous glands to release large amounts of mucus.
2. Chyme stimulates the goblet cells and intestinal glands to secrete their products.
3. Distension of the intestinal wall stimulates the parasympathetic reflex that causes intestinal secretions.