Digestive System Flashcards

Question

What are the regions of the stomach?

Answer 1

* Cardiac region (cardia)—small area within about 3 cm of the cardiac orifice * Fundic region (fundus)—dome-shaped portion superior to esophageal attachment * Body (corpus)—makes up the greatest part of stomach * Pyloric region—narrower pouch at the inferior end – Subdivided into the funnel-like antrum – Narrower pyloric canal that terminates at pylorus – Pylorus: narrow passage to duodenum – Pyloric (gastroduodenal) sphincter—regulates the passage of chyme into the duodenum

Answer 2

– Parasympathetic fibers from vagus – Sympathetic fibers from celiac ganglia

Answer 3

* Stomach has a simple columnar epithelium covers mucosa – Apical regions of its surface cells are filled with mucin – Mucin swells with water and becomes mucus after it is secreted * Mucosa and submucosa are flat when stomach is full, but form longitudinal wrinkles called gastric rugae when empty * Muscularis externa has three layers (instead of the two seen elsewhere) – Outer longitudinal, middle circular, and inner oblique layers

Answer 4

—depressions in gastric mucosa * Cardiac glands in cardiac region * Pyloric glands in pyloric regions * Gastric glands in the rest of the stomach

Answer 5

mucous, regenerative, parietal, chief, enteroendocrine

Answer 6

water, HCl, pepsin

Answer 7

* HCl activates pepsin and lingual lipase * Breaks up connective tissues and plant cell walls – Helps liquefy food to form chyme * Converts ingested ferric ions (Fe3+) to ferrous ions (Fe2+) – Fe2+ absorbed and used for hemoglobin synthesis * Contributes to nonspecific disease resistance by destroying most ingested pathogens

Answer 8

secretion of intrinsic factor to make B12 to synthesize Hb

Answer 9

* Swallowing center of medulla oblongata signals stomach to relax * Soon stomach shows a rhythm of peristaltic contractions controlled by pacemaker cells in longitudinal layer of muscularis extern

Answer 10

small intestine

Answer 11

– Mucous coat: thick, highly alkaline mucus resists action of acid and enzymes – Tight junctions between epithelial cells prevent gastric juice from seeping between them and digesting deeper tissue – Epithelial cell replacement: cells live only 3 to 6 days * Sloughed off into the chyme and digested with food * Replaced rapidly by cell division in gastric pits

Answer 12

secretes bile to contribute to digestion

Answer 13

* Four lobes—right, left, quadrate, and caudate – Falciform ligament separates left and right lobes * Sheet of mesentery that suspends the liver from the diaphragm – Round ligament (ligamentum teres)—fibrous remnant of umbilical vein * Carries blood from umbilical cord to liver of the fetus

Answer 14

—irregular opening between quadrate and caudate lobes – Point of entry for hepatic portal vein and proper hepatic artery – Point of exit for the bile passages – All travel in lesser omentumWha

Answer 15

two vessels and a bile ductule – Other vessel: branch of hepatic portal vein – One vessel: branch of hepatic artery proper – Both vessels supply blood to sinusoids which receive a mixture of nutrient-laden venous blood from the intestines, and freshly oxygenated arterial blood from the celiac trunk 25-68

Answer 16

– After a meal, hepatocytes absorb from the blood: glucose, amino acids, iron, vitamins, and other nutrients for metabolism or storage – Between meals, hepatocytes break down stored glycogen and release glucose into the blood – Remove and degrade: hormones, toxins, bile pigments, and drugs – Secrete into the blood: albumin, lipoproteins, clotting factors, angiotensinogen, and other products

Answer 17

* Bile canaliculi—narrow channels into which the liver secretes bile – Bile passes into bile ductules of the triads – Ultimately into the right and left hepatic ducts – Common hepatic duct: formed from convergence of right and left hepatic ducts on inferior side of the liver – Cystic duct coming from gallbladder joins common hepatic duct – Bile duct: formed from union of cystic and common hepatic ducts * Descends through lesser omentum toward the duodenum

Answer 18

Microscopic Anatomy of the Liver (Continued) – Near duodenum, bile duct joins duct of pancreas – Forms expanded chamber: hepatopancreatic ampulla * Terminates in a fold of tissue—major duodenal papilla on duodenal wall – Major duodenal papilla contains muscular hepatopancreatic sphincter (sphincter of Oddi) * Regulates passage of bile and pancreatic juice into duodenum * Between meals, sphincter closes and prevents release of bile into the intestines

Answer 19

—a pear-shaped sac on underside of liver – Serves to store and concentrate bile by absorbing water and electrolytes – About 10 cm long – Internally lined by highly folded mucosa with simple columnar epithelium – Head (fundus) usually projects slightly beyond inferior margin of liver – Neck (cervix) leads into the cystic duct

Answer 20

—yellow-green fluid containing minerals, cholesterol, neutral fats, phospholipids, bile pigments, and bile acids – Bilirubin: principal pigment derived from the decomposition of hemoglobin – Bacteria in large intestine metabolize bilirubin to urobilinogen * Responsible for the brown color of feces – Bile acids (bile salts): steroids synthesized from cholesterol * Bile acids and lecithin, a phospholipid, aid in fat digestion and absorption

Answer 21

– 80% of bile acids are reabsorbed in the ileum and returned to the liver * Hepatocytes absorb and resecrete them * Enterohepatic circulation—route of secretion, reabsorption, and resecretion of bile acids two or more times during digestion of an average meal – 20% of the bile acids are excreted in the feces * Body’s only way of eliminating excess cholesterol * Liver synthesizes new bile acids from cholesterol to replace those lost in feces

Answer 22

* Endocrine portion—pancreatic islets that secrete insulin and glucagon – Concentrated in the tail of the gland * Exocrine portion—99% of pancreas that secretes 1,200 to 1,500 mL of pancreatic juice per day – Secretory acini release their secretion into small ducts that converge on the main pancreatic duct 25-78

Answer 23

– Pancreatic duct runs lengthwise through middle of the gland * Joins the bile duct at the hepatopancreatic ampulla * Hepatopancreatic sphincter controls release of both bile and pancreatic juice into the duodenum – Accessory pancreatic duct: smaller duct that branches from the main pancreatic duct * Opens independently into the duodenum * Bypasses the sphincter and allows pancreatic juice to be released into duodenum even when bile is not 25-81

Answer 24

– Pancreatic juice: alkaline mixture of water, enzymes, zymogens, sodium bicarbonate, and other electrolytes * Acini secrete the enzymes and zymogens * Ducts secrete bicarbonate – Bicarbonate buffers HCl arriving from the stomach

Answer 25

– Trypsinogen * Secreted into intestinal lumen * Converted to trypsin by enterokinase that is secreted by mucosa of small intestine * Trypsin is autocatalytic—converts trypsinogen into still more trypsin – Chymotrypsinogen: converted to chymotrypsin by trypsin – Procarboxypeptidase: converted to carboxypeptidase by trypsin

Answer 26

– Pancreatic amylase: digests starch – Pancreatic lipase: digests fat – Ribonuclease and deoxyribonuclease: digest RNA and DNA respectively

Answer 27

Ach, cholesystokinin, and secretin 25-86 – Acetylcholine (ACh): from vagus and enteric nerves * Stimulates acini to secrete enzymes during cephalic phase of gastric control even before food is swallowed – Enzymes remain in acini and ducts until chyme enters the duodenum – Cholecystokinin (CCK): secreted by mucosa of duodenum in response to arrival of fats in small intestine * Stimulates pancreatic acini to secrete enzymes * Strongly stimulates gallbladder * Induces contractions of gallbladder and relaxation of hepatopancreatic sphincter to discharge bile into duodenum – Secretin: released from duodenum in response to acidic chyme arriving from the stomach * Stimulates ducts of both liver and pancreas to secrete more sodium bicarbonate * Raises pH to the level required for activity of the pancreatic and intestinal digestive enzymes

Answer 28

– Duodenum: first 25 cm (10 in.) * Begins at pyloric valve – Major and minor duodenal papilla distal to pyloric valve – Receives major and minor pancreatic ducts respectively * Arches around head of the pancreas * Ends at a sharp bend called the duodenojejunal flexure * Most is retroperitoneal – Jejunum: first 40% of small intestine beyond duodenum * Has large, tall, closely spaced circular folds * Its wall is relatively thick and muscular * Especially rich blood supply which gives it a red color – Ileum: forms last 60% of the postduodenal small intestine * Thinner, less muscular, less vascular, and paler pink color * Peyer patches—prominent lymphatic nodules in clusters on the side opposite the mesenteric attachment – Visible to naked eye; become larger near large intestine * Ileocecal junction—end of the small intestine – Where the ileum joins the cecum of the large intestine * Ileocecal valve—a sphincter formed by the thickened muscularis of the ileum – Protrudes into the cecum – Both jejunum and ileum are intraperitoneal and covered with serosa

Answer 29

– Lumen lined with simple columnar epithelium – Muscularis externa is noted for a thick inner circular layer and a thinner outer longitudinal layer – Large internal surface area - great length and three types of internal folds or projections * Circular folds (plicae circulares)—increase surface area by a factor of 2 to 3 * Villi—increase surface area by a factor of 10 * Microvilli—increase the surface area by a factor of 20 * Circular folds (plicae circulares)—largest folds of intestinal wall

Answer 30

– Villus covered with two types of epithelial cells * Absorptive cells (enterocytes) * Goblet cells—secrete mucus – Epithelia joined by tight junctions that prevent digestive enzymes from seeping between them – Core of villus filled with areolar tissue of lamina propria * Contains arteriole, capillaries, venule, and lymphatic capillary called a lacteal

Answer 31

—form a fuzzy brush border on apical surface of each absorptive cell – About 1 μm high – Increases absorptive surface area * Brush border enzymes—contained in plasma membrane of microvilli – Carry out some of the final stages of enzymatic digestion – Not released into the lumen – Contact digestion: chyme must contact the brush border for digestion to occur – Intestinal churning of chyme ensures contact with the mucosa

Answer 32

– To mix chyme with intestinal juice, bile, and pancreatic juice * To neutralize acid * Digest nutrients more effectively – To churn chyme and bring it in contact with the mucosa for contact digestion and nutrient absorption – To move residue toward large intestine 25-100

Answer 33

segmentation set by pacemaker cells

Answer 34

mix and churn

Answer 35

* Peristalsis moves contents of small intestine toward colon * Peristaltic wave begins in duodenum, travels 10 to 70 cm and dies out

Answer 36

usually closed – Food in stomach triggers gastroileal reflex that enhances segmentation in the ileum and relaxes the valve – As cecum fills with residue, pressure pinches the valve shut * Prevents reflux of cecal contents into the ileum

Answer 37

Mouth: starch gets broken up by salivary amylase into oligosaccharide and maltose, sucrose and lactose continue down Stomach: none Small intestine (lumen): pancreatic amylase creates more maltose Small intestine (epithelium): sucrase and lactase break down sugars into fructose and galactose, maltase breaks down maltose into glucose Goes into blood capillary

Answer 38

Mouth: none Stomach: pepsin breaks down into peptides Small intestine (lumen): trypsin, chymotrypsin, and carboxypeptidase create dipeptides Small intestine (epithelium): dipeptidase and aminopeptidase create amino acids goes into blood capilary

Answer 39

mouth: none stomach: lingual lipase activated small intestine (lumen): the lipases create monoglycerides and free fatty acids small intestine (epithelium): monoglyerice + ffa = triglyceride, + cholesterol etc lead to chylomicrons goes into lacteal

Answer 40

nucleases, nucleosidases, and phosphatases

Answer 41

absorb most

Answer 42

small intestine

Answer 43

too little water absorbed

Answer 44

too much water absorbed

Answer 45

– Begins as cecum inferior to ileocecal valve – Appendix attached to lower end of cecum * Densely populated with lymphocytes—a significant source of immune cells – Ascending colon, right colic (hepatic) flexure, transverse colon, left colic (splenic) flexure, and descending colon frame the small intestine – Sigmoid colon is S-shaped portion leading down into pelvic cavity – Rectum: portion ending at anal canal * Has three curves and three infoldings, called the transverse rectal folds (rectal valves) – Anal canal: final 3 cm of the large intestine * Passes through levator ani muscle and pelvic floor, terminates at the anus * Anal columns and sinuses—exude mucus and lubricant into anal canal during defecation * Large hemorrhoidal veins for superficial plexus in anal columns and around orifice * Hemorrhoids—permanently distended veins that protrude into anal canal or bulge outside the anus – Muscularis externa of colon is unusual * Taenia coli—longitudinal fibers concentrated in three thickened, ribbon-like strips * Haustra—pouches in the colon caused by the muscle tone of the taeniae coli * Internal anal sphincter—smooth muscle of muscularis externa * External anal sphincter—skeletal muscle of pelvic diaphragm – Omental appendages—club-like, fatty pouches of peritoneum adhering to the colon; unknown function

Answer 46

transverse colon

Answer 47

Haustral contractions, gastrocolic and duodenocolic reflexes

Digestive System Flashcards

(72 cards)