Chapter 23 Digestive System Flashcards

Question

Gastic Glands

Answer 1

* Produce Gastric Juice * Cell types * mucus neck cells, Parietal cells, chief cells, entroendocrine cells * Glands in fundus and body produce most of the stomach secretions * Prietal Cell Secretions * Hydrochloric Acid (HCl) pH 1.5-3.5. Denatures protein, activates pepsin, breaks down plant cell walls, kills bacetia * Intrensic factor) glycoproteinen required for B12 absorption * Cheif cell secretions * Pepsinogen) Inactive form of pepsin activted by HCl and peprsin itself * Lipases) digest about 15% of lipids * Enteroendocrine cells ("gut endocrine") * secrete chemical messengers * Act as paracrines (seratonin and histamine) * Somatostatin Hormone) acts as a paracrine * Gastrin Hormone) regulates stomach secretion and mobility.

Answer 2

* Harsh digestive enzymes can digest stomach itself but it has mucosal barrier to protect itself * three factors * Thick layer of bicarbonate-rich mucus * Tight Junctions between epithelial cells * prevents juice from seeping into tissue * Damaged epithelial cells quickly replaced by division of stem cells. * Surface cells replaced every 3-6 days

Answer 3

* Inflammation caused by anything that breaches mucosal barrier * Persistent damage to undelying tissues can cause * peptic ulcers, specifically called gastric ulcers when it is stomach wall is eroding. Cause Hemmorage * Caused mostly by Helicobacter Pylori Bacteria, * NSAID's, smoking, spicy food, alcohol, coffee or stress also can cuase.

Answer 4

* Propulsion) Peristalsis * Mechanical Breakdown) churning of stomach during peristalsis * Digestion * Denaturation of protiens by HCl * Proteins digested by pesin * milk protein is digested by rennin in infants * Fat) mostly digested in small intestine byt gastric and lingual lipases help. * Absorbtion) not much abosrbed in stomach * Secretes Intresnsic Factor for intestinal absption of B12 * prodices mature red blood cells (pernicious anemia)

Answer 5

* Gastric mucosa secretes three L of gastric juice a day * Nural Control) * Vagus nerve stimulation (parasympathetic) \> secretion up * Sympathetic stimulation \> Secretin Down * Hormonal control) largly Gastrin * Stimulates secretion of acid by stomach and secretion of hormones (gastrin antagonists) by small intestine * ACh and Histamine also stimulate pareiteal cells.

Answer 6

1. Cephalic (reflex) phase) before food enters the stomach * Triggered by aroma, sight, or though of food * triggers vagus nerve 2. Gastric Phase) when food reaches the stomach * lasts 3-4 hours; 2/3 of gastric juice release * Ditension) activates streach receptors for both short and long term reflxes * Protein in stomach \> rises pH of gastric content \> stimulates gastrin secretion \> HCl release. * Low ph Inhibits gastrin 3. Intestinal Phase) partially digested food enters the small intestine * Stimulated by food entering the duodenim. Intestinal (enteric) gastrin release stimuates intestinal activity * Inhibition) Dissention of the duodenum or presensce of acidic, fatty or chyme all tell stomach to stop (decrease gastric emptying)

Answer 7

* Inhibits acid secretion in the stomach by short and long reflexes * Enterogastrones) hormones release by a scattering of enteroendocrine cells in duodenal mucosal epithelium. * Secretin and Cholecystokinin (CCK) * all inhibit gastric secretion

Answer 8

* Peristaltic waves * move toward pylorus at a rate of 3 per min; more vigurous near pylorus. * each wave squirts 3 ml or less of chyme into the small intestine * the rest (~27 or so) is propelled backward where it it mixxed more *

Answer 9

* Larger meal = faster absorption of liquid componats * stomach needs longer to absorb solid compnants * As Chyme enters Duodenum * receptors repond to streatch and chemical signals * Initiates entrogastric reflex and hormonal mechanisms to inhibit secretion and duodenal filling * Carb Rich chyme moves quickly through duodenum * Fat chyme remains in duodenum 6 hours or more

Answer 10

* Causesed by * Extreme stretching of stomach or intestine * Intestinal irritants, e.g., bacterial toxins, excessive alcohol, spicy food, certain drugs * Excessive vomiting \> dehydration, electrolyte and acid-base imbalances (alkalosis)

Answer 11

* Bile Production * bile) fat emulsifier that breaks fat into tiny particles * Largest Gland in the body * Four lobes) left right, cudate and quadreate * Lesser Omentum) anchors liver to lesser curvate of the stomach * Hepatic artery/ vein enter at porta hepatis * Bile leaves the liver through the left and right hepatic ducts * fuse to form large common hepatic duct \> cystic duct \> bile duct in gall bladder

Answer 12

* Liver Lobules) Structural and functional units * Hepatocytes) liver cells. Radiate outward from a centeal vein running longitudallly to axis of the lobule * Portal Triad) corner of each lobule * Branch of hepatic artery) supplies O2 * Hepatic Portal Vein) brings in nutrient ruch blood * Bile Duct) recives bile from bile canaliculi * Liver Sinusoids) behind hepatic plates * heavily fenestrated * Hepatic/ Stellate macrophages) remove debris and old RBC's

Answer 13

* Yellow-Green, alkaline solution containing * Bile salts) cholesterol dericatives that function in fat digestion and absorption. * Bilirubin) cheif bile pigment. Yellow waste from the heme- part of hemoglobin

Answer 14

• Thin-walled muscular sac on inferior surface of liver • Stores and concentrates bile • Muscular contractions release bile via cystic duct, which flows into bile duct

Answer 15

* Deep to Greater Curvature of the stomach. Head encircled by Duodenum; tail next to the spleen * Produces enzymes that break down all categoreis of food * Endocrine) secrerete insulin and glucagon (pancreatic inluts) * Exocrine) secrete pancreatic juice (acini and ducts) * Zymogen Granules) of acini cells contain digestive Proenzymes * Pancreatic Juice) 1200-1500 ml per day * Electrolytes (HCO3-) * pH 8. Alkaline nutralizes chyme for intestinal enzymes * Amlyase (starch) Lipase (lipids) Nucleases (nucleaic acids) Proteases (Proteins; secreted in inactive form to protect pancreas) * Trypsinogen \> activated trypsinogen \> activtaes carboxipeptidase and chymotrypsin.

Answer 16

* Bile Duct (liver) and Main Pancreatic Duct * Join a in the wall of Duodenunm at Hepatopancreatic ampulla * Opens into Duodnum at Major Duodenal Papillla * Controled by Hepatopancratic Spinchter * Acessory Pancratic Duct) empties directly into duodenum just proximal to midn duct. Just Pancreeas

Answer 17

* Hormonal and Nueral Stimuli both regulate secretion of bile/ Pancreatic juice * CCK * Stimulated by proteins and Fats in the Chyme * Induces secretion of Pancreatic Juice from Acinar cells of pancreas * Causes gall bladder constriction * Causes Hepatopancratic Sphincter to Relax (release of bile/pancreatic enzymes) * Secretin * Stimulated by acidic chyme * Causes secretion of HCO3- fom duct cells of pancreas * Minor stimilus for Bile production * Bile * Bile Salts returning from enterohepatic circulation stimulate more bile secretion. * Vagus Nerve * Weakley stimulates pancreas and gallbladder during cephalic and gastric phases.

Answer 18

* Major Organ of Digestion and Absorption * 2-4 m long (7-13ft) Half of the diameter of the large intstine * Longest part of alamentary canal * Duodenum * Mostly a Retroperitonial Organ * about 25 cm long (10 in) * Jejunum) Extends from duodenum to ileum * about 2.5 m (8ft) long * Illeum) Joins large intstine at ileocecal valve. * about 3.6 m (12ft) long. * Fan Shaped Mesentary) supports jejunum and ileum from posterior wall. * Innervation * Parasympatetic) vagus * Sympatetic) Thoracic Splanchnic Nerves * Both relayed through superior mesentatic and celiac plexuses' * Blood Vessels) * Mesentaric Arteries * Mesentatic Veins \> Hepatic Portal Vein\> Liver

Answer 19

* Increase surface area of proximal part for nutrient absorption * Circular Folds) * Permanent folds that force chume to spiral through lumen * Slows movment which allows more time for nutrient absorption * Vili * Fingerlike projections of mucosa * Each vilus has a capilary bed and Lacteal (lymphatic) capilary for absorption * Microvilli (Brush boarder) * Long, cytoplasmic extensions of absorptive cells of mucosa * Contain encymes for Carb and Protein digestion (Brush Boarder Enzymes)

Answer 20

* Intestinal Crypts) Tubular Glands located between the Vili in the mucosa * decrease in number the further down the small intestine you go * Five Major cell types * Enterocytes) * Villi) Primary responsibility is absortion in the villi * Crypts) they produce intestinal juice which serves as a carrier fluid for absorbing nutritnes * Goblet Cells) secrete mucus in villi and crypts * Enteroednocrine Cells) * secrete Enterogastrones (secretin, Cholecysotokinin) * Paneth Cells * Located deep in the crypts * Secrete antimicrobial agents (defensins and lysozyme) * Stem Cells * Divide in the bottom of crypts * daughter cells differentiate to become all other types of cells * most cells migrate up, paneth cells migrate to the bottom of the crypts.

Answer 21

* Mucosa-Associated Lymphoid Tissue (MALT) * Included induivudual lymphoid Follicles and Aggregated Lymphoid Nodules (Peyer's Patches) * Peyer's Patches are more abundent in the distal part of small intestine (more bacteria)

Answer 22

* 1-2L Secreted Daily; Major Stimulus for production comes from hypertonic or acidic chyme * Slightly alkaline * Isotinic with blood plasma (7.35-7.45 pH)

Answer 23

* Chyme from stomach contains partially diegested Carbs, Proteins and undigested Fats * spends 3-6 hours in small intestine * Most water and all nutrients are absorbed * Enymes for digestion * Most substances for digestion; bile, enzymes except brush boarder, and bicarbonate ions, are imported from the liver or pancreas * If either organ's function is impeded our ability to digest food goes down. * Regulating Chyme Entry * Chyme is hypertonic = if a bunch rushes into the duodenum and small intestine it would pull water away from the capalaries of Villi * Low pH of chyme must be adjusted and chyme must be well mixed * Enterogastric reflex and enterogastrones carfully controls food movement into the small intestine.

Answer 24

* After a meal * Small intesine has contracting rings of smooth muscle which simply move the chyme back and forward. * Stomach Peristalsis initates these movments * Segmentation * Most common motion of small intestine; Initated by intrnsic pacemaker cells * Mixes/ Moves contents to the end * Increased by Parasumpatetic tone * Bewteen Meals * True Peristalsis occurs only after most nutrients have been absorbed * Segmenting movements wane and duodenal mucosa begins to release Motilin

Answer 25

* Illeocecal Valve is closed most of the time * Two mechanisms cause it to relax and let chyme to the small intesine * Gastorieal Reflex * Long nueral reflex triggered by stomach activity * Increases force of segmentation in ileum and relaxes the valve * Gastrin) * Hormone released by stomach * Increases mobility of ileum and relaxes the valve * Flaps close when chyme exerts backwards pressure

Answer 26

* Ileoceal Valve to anus \> Diameter is 7cm and is about 1.5 m * Teniae Coli "ribbons of the colon" * three bands of longicudinal smooth muslce in muscularis * Hausta (Singular hasturm) * Pocketlike sacs cause by tone of teniae coli * Epilolic Appendages (membrane covered) * Fat-filled pouches of visceral peritoneum

Answer 27

* Cecum) First Part of the larfe intestine * Appendix) masses of lymphoid tissue; contains MALT * storehouse of bacteria; recolonize the gut when needed * Suseptiable to blockage * Ascending Colon) Right side to level of kidney * Right Colic \> (hepatic) flexure * Transsverse colon * Hepatic Flexure \> Transverse Colon \> Left colic (splenic) flexure * Descening colon * Splenic flexure \> Descending colon * Sigmoid colon * in the pelvis * Rectum * Thre folds called rectal valves (stop feces being passed with gas) * Anal Canal * Last segemt of large intestine, opens to body exterior * Internal Anal Sphincter) smooth muscle * External Anal Sphincter) skeletal muscle * Colon is Retroperitonal * Except for transverse and sigmoid parts. (Anchored to mesenary sheets called mesocolons)

Answer 28

* Wall of Large Intsinte differs in several ways from the small intestine * Deeper Crypts with termendous globlet cells * Mucus eses the passage of feces * Thicker mucose of simple columnar epithelium * Anal Canal) stratified squamous to withstand abrasion * No absorbtion. * Folds are called anal colums * Anal sinuses) are recesses between anal columns

Answer 29

* Consists of over a thousand types of bacteria * couple pounds of body weight * Most colanize colan via the anus * Some enter from small intestine * Metabolic Functions * recover energy from otherwise indgestible foods and syntethizize some vitamens * Fermentation * bacetria ferment indigestible carbohydrates. Can be absored by body cells afetwards * Produces gases (more when we eat indigesable carbs) * Vitamin Syntesis * B complex vitamins and some vitamin K are produced by gut bacteria

Answer 30

* Residue remains in large intesine 12-24 hours * No food breakdown except for gut bacteria * Vitamns, water, and electrolytes reclaimes

Answer 31

* Haustral Contactions * Slow segmenting movments that last about one min * Occur every 30 min or so * Contrat in respone to distension * Mass Movments * Presence of food in stomach activates gastroieal reflex in the small intesinte and gastrocholic rflex in colon * Activates three to four slow powerful peristaltic waves. * Fiber in diet makes colon movments easier

Answer 32

* Diverticula (herniations of colon mucose dure to a low fiber diet. * Narrowed colon \> stonger contractions \> more pressure \> hernia * Affects sigmoid colon * IBS) Reoccuring abdominal pain, stool changes, bloating, flatuence, nause and depression

Answer 33

* Mass Movments force feces toward Rectum * initited spinal Defication Reflex * Contraction of sigmoid colon and rectum * Relax internal anal sphincter * Assisted by vasalva's manuever