1. Chpt 14

2.  Ingestion – taking in of food  Digestion – breaking down of food, both physically & chemically  Absorption – movement of nutrients throughout the bloodstream  Defecation – ridding the body of indigestible wastes  Alimentary canal – true “digestive tract” – the path food takes once it enters the mouth and exits the anus  Accessory organs – help with the process of digestion, but food does not actually travel there  Teeth, salivary glands, pancreas, liver, gallbladder

3.  Lips (labia)—protect the anterior opening  Cheeks—form the lateral walls  Hard palate—forms the anterior roof  Soft palate—forms the posterior roof  Uvula—fleshy projection of the soft palate  Vestibule—space between lips externally and teeth and gums internally  Oral cavity proper—area contained by the teeth  Tongue—attached at hyoid bone and styloid processes of the skull, and by the lingual frenulum to the floor of the mouth

4.  Mastication = chewing  Saliva is released once food is masticated  Initiation of swallowing by the tongue  Allows for sense of taste

5.  About 10 inches long (3 lengthwise fists)  Runs from the pharynx to the stomach, through the diaphragm  Moves food to the stomach through rhythmic contractions called peristalsis  Passageway for food only  Respiratory system branches off after the pharnyx (hence the larnyx only serves a respiratory function)

6.  All alimentary canal organs have many layers  Mucosa  Innermost, moist membrane ▪ Surface epithelium ▪ Small amount of connective tissue & smooth muscle  Submucosa  Just beneath the mucosa layer ▪ Soft connective tissue containing ▪ Blood vessels, nerve endings & lymphatic tissue  Muscularis externa  Two layers of smooth muscle  Serosa  Outermost wall containing fluid producing cells ▪ Parietal peritoneum: lines the abdominopelvic cavity ▪ Visceral peritoneum: outermost layer that is connected to parietal peritoneum

7.  Located on the left side of the abdominal cavity  Food enters at the cardioesophageal sphincter  Food empties into the small intestine at the pyloric sphincter (valve)  Regions of the stomach  Cardiac region—near the heart  Fundus—expanded portion lateral to the cardiac region  Body—midportion  Pylorus—funnel-shaped terminal end  Rugae—internal folds of the mucosa

8.  Temporary storage tank for food  Site of food breakdown  Chemical breakdown of protein begins  Delivers chyme (processed food) to the small intestine  Mucosa is simple columnar epithelium  Mucous neck cells—produce a sticky alkaline mucus  Gastric glands—situated in gastric pits and secrete gastric juice  Chief cells—produce protein-digesting enzymes (pepsinogens)  Parietal cells—produce hydrochloric acid  Enteroendocrine cells—produce gastrin

9.  All the hormones below are made by the stomach mucosa & stimulated by food entering the stomach.  Gastrin:  Stimulates the emptying of the stomach, stimulates contraction of intestinal muscles  Relaxes ileocecal valve  Stimulates mass movement of the contents of the large intestine  Serotonin:  Causes contractions of the stomach muscle  Histamine:  Activates the parietal cells to release HCl (starting the digestion process)  Somatostatin  Inhibits secretion of all gastric products (important for negative feedback)  Slows down blood flow to intestines & decreases intestinal absorption  Inhibits the release of bile from the gallbladder

10.  The body’s major digestive organ  Site of nutrient absorption into the blood  Muscular tube extending from the pyloric sphincter to the ileocecal valve  Suspended from the posterior abdominal wall by the mesentery  Duodenum  Attached to the stomach  Curves around the head of the pancreas  Jejunum  Attaches anteriorly to the duodenum  Ileum  Extends from jejunum to large intestine

11.  Chemical digestion begins in the small intestine  Enzymes are produced by ▪ Intestinal cells ▪ Pancreas  Pancreatic ducts carry enzymes to the small intestine  Bile, formed by the liver, enters via the bile duct

12.  Three structural modifications that increase surface area  Microvilli—tiny projections of the plasma membrane (create a brush border appearance)  Villi—fingerlike structures formed by the mucosa  Circular folds (plicae circulares)—deep folds of mucosa and submucosa

13.  All hormones listed below are produced by the duodenal mucosa  Intestinal gastrin: stimulated by acidic & partially digested foods entering the duodenum  Stimulates secretion of gastric products & intestinal motility  Secretin: stimulated by acidic chyme  Inhibits secretion of gastric products  Increases output of pancreatic juices to breakdown carbohydrates and proteins  Increases bile output  Cholecystokinin (CCK): stimulated by fatty chyme  Aids in the effectiveness of bile  Increases output of pancreatic juice  Stimulates the gallbladder to expel bile  Relaxes the hepatopancreatic sphincter to allow entry of bile into duodenum

14.  Gastric inhibitory peptide (GIP): stimulated by fatty or glucose-containing chyme  Inhibits gastric gland secretion & motility  Vasoactive inhibitory peptide (VIP): chyme containing all kinds of partially digested foods  Stimulates buffer secretion  Dilates intestinal capillaries to prepare for absorption of nutrients  Inhibits HCl production (stops further digestion)  Relaxes the intestinal smooth muscle to increase surface area for absorption

15.  Larger in diameter, but shorter in length, than the small intestine  Frames the internal abdomen  Cecum—saclike first part of the large intestine  Appendix  Accumulation of lymphatic tissue that sometimes becomes inflamed (appendicitis)  Hangs from the cecum

16.  Colon  Ascending—travels up right side of abdomen  Transverse—travels across the abdominal cavity  Descending—travels down the left side  Sigmoid—enters the pelvis  Rectum and anal canal—also in pelvis  Anus—opening of the large intestine  External anal sphincter—formed by skeletal muscle and under voluntary control  Internal involuntary sphincter—formed by smooth muscle  These sphincters are normally closed except during defecation

17.  No villi present  Goblet cells produce alkaline mucus which lubricates the passage of feces  Muscularis externa layer is reduced to three bands of muscle called teniae coli  These bands cause the wall to pucker into haustra (pocketlike sacs)

18.  Work together to create & store bile  The liver ejects bile directly into the duodenum to emulsify fats  When fats are broken down into tiny particles, they are more easily digested  Liver – appx. 3 lbs  Extends from the right hypochondriac to epigastric regions  Divided into 4 lobes with its own specific circulation (hepatic portal)  Entire liver is covered by serosa (visceral peritoneum), which attaches the liver to the diaphragm  Gallbladder is chiefly responsible for storage of bile

19.  Thin walled, green, muscular sac  About the size of a kiwi (4 inches)  Gland that extends from the interior margin of the liver  Stores bile that is not needed immediately for digestion  Since it is not needed immediately, the gallbladder concentrates that bile by absorbing some of its water content  When empty or only containing a small amount of bile, it can fold up like the rugae of the stomach to allow for quick expansion and expulsion of bile when needed

20.  Extends across the abdomen  Lies deep to the greater curvature of the stomach  Produces a broad spectrum of enzymes to breakdown foodstuffs  Pancreas delivers pancreatic juice directly to the duodenum  Usually fuses with the bile duct from the liver/gallbladder  Pancreatic juice mainly consists of water, electrolytes, and enzymes  Has a high pH – enables neutralization of acidic chyme  Pancreatic enzymes include:  Amylase, lipases, nucleases  Carboxypeptidase: broad range of functions: mainly protein digestion  Chymotrypsin: breaks down proteins: specifically: tyrosine (cheese protein), tryptophan & phenylalanine  Enterokinase – a serine protease – breaks bonds between peptides