Digestive part B Flashcards

Question

what are the 3 phases of gastric secretion?

Answer 1

– Cephalic (reflex) phase – Gastric phase – Intestinal phase

Answer 2

– Conditioned reflex triggered by aroma, taste, sight, thought

Answer 3

– Lasts 3–4 hours and provides two-thirds of gastric juice released

Answer 4

 Distension activates stretch receptors, initiating both long and short reflexes  Chemical stimuli, such as partially digested proteins, caffeine, and low acidity, activate enteroendocrine G cells to secrete gastrin – Stimulation of gastric phase  Release of gastrin then initiates H C l release from parietal cells and activates enzyme secretion – Prods parietal cells to secrete H C l by: * Binding to receptors on parietal cells * Stimulating enteroendocrine cells to release histamine – Buffering action of ingested proteins causes p H to rise, which activates more gastrin secretion

Answer 5

 Low p H inhibits gastrin secretion – Occurs between meals – Occurs during digestion as negative feedback mechanism * The more protein, the more H C l acid is secreted, causing decline in p H, which inhibits gastrin secretion

Answer 6

– Begins with a brief stimulatory component followed by inhibition

Answer 7

 Partially digested food enters the small intestine, causing a brief release of intestinal (enteric) gastrin – Encourages gastric glands of stomach to continue secretory activities – Stimulatory effect is brief and overridden by inhibitory stimuli as intestine fills

Answer 8

 Four main factors in duodenum cause inhibition of gastric secretions: – Distension of duodenum due to entry of chyme – Presence of acidic chyme – Presence of fatty chyme – Presence of hypertonic chyme  Inhibitory effects protect intestine from being overwhelmed by too much chyme or acidity  Inhibition is achieved in two ways: enterogastric reflex and enterogastrones

Answer 9

– Duodenum inhibits acid secretion in stomach by: * Enteric nervous system short reflexes * Sympathetic nervous system and vagus nerve long reflexes

Answer 10

– Duodenal enteroendocrine cells release two important hormones that inhibit gastric secretion * Secretin * Cholecystokinin (C C K)

Answer 11

* Parietal cells pump H+ (from carbonic acid breakdown) into stomach lumen via H+/K+ A T Pase (proton pumps) – As H+ is pumped into stomach lumen, H C O3− is exported back to blood via C l− and H C O3− antiporter  Resulting increase of H C O3− in blood leaving stomach is referred to as alkaline tide – C l− is pumped out to lumen to join with H+, forming H C l

Answer 12

– Stretches to accommodate incoming food – Two factors cause pressure to remain constant until 1.5 L of food is ingested  Receptive relaxation: reflex-mediated relaxation of smooth muscle coordinated by swallowing center of brain stem  Gastric accommodation: intrinsic ability of smooth muscle to exhibit stress-relaxation response, which enables hollow organs to stretch without increasing tension or contractions

Answer 13

– Peristaltic waves move toward pylorus at rate of three per minute – Basic electrical rhythm (B E R) is set by enteric pacemaker cells (formerly interstitial cells of Cajal)  Pacemaker cells are linked by gap junctions so that entire muscularis contracts – Distension and gastrin increase force of contraction – Contractions are most vigorous and powerful near pylorus region – 30 ml of chyme produced is either:  Delivered in ~3 m l spurts to duodenum, or  Rest of 27 m l forced backward into stomach – Only liquids and small particles are allowed to pass through pyloric valve

Answer 14

– Duodenum can prevent overfilling by controlling how much chyme enters  Duodenal receptors respond to stretch and chemical signals  Enterogastric reflex and enterogastrones inhibit gastric secretion and duodenal filling – Stomach empties in ~4 hours, but increase in fatty chyme entering duodenum can increase time to 6 hours or more  Carbohydrate-rich chyme moves quickly through duodenum

Answer 15

– Extreme stretching – Intestinal irritants, such as bacterial toxins, excessive alcohol, spicy food, certain drugs * Chemicals and sensory impulses stimulate emetic center of medulla * Excessive vomiting can lead to dehydration and electrolyte and acid-base imbalances (alkalosis)

Answer 16

* Liver, gallbladder, and pancreas

Answer 17

digestive function is production of bile – Bile: fat emulsifier

Answer 18

chief function is storage of bile

Answer 19

supplies most of enzymes needed to digest chyme, as well as bicarbonate to neutralize stomach acid

Answer 20

– Largest gland in body; weighs ~3 l b s – Consists of four primary lobes: right, left, caudate, and quadrate

Answer 21

 Separates larger right and smaller left lobes  Suspends liver from diaphragm and anterior abdominal wall

Answer 22

 Remnant of fetal umbilical vein along free edge of falciform ligament – Lesser omentum anchors liver to stomach – Hepatic artery and vein enter liver at porta hepatis – Bile ducts

Answer 23

leaves liver

Answer 24

connects to gallbladder

Answer 25

formed by union of common hepatic and cystic ducts

Answer 26

 Hexagonal structural and functional units  Composed of plates of hepatocytes (liver cells) that filter and process nutrient-rich blood  Central vein located in longitudinal axis

Answer 27

 Branch of hepatic artery, which supplies oxygen  Branch of hepatic portal vein, which brings nutrient-rich blood from the intestine  Bile duct, which receives bile from bile canaliculi

Answer 28

leaky capillaries located between hepatic plates  Blood from both hepatic portal vein and hepatic artery proper percolates from triad regions through sinusoids and empties into central vein

Answer 29

in liver sinusoids remove debris and old R B Cs – Hepatocytes have increased rough and smooth E R, Golgi apparatus, peroxisomes, and mitochondria – Hepatocyte functions  Produce ~900 m l bile per day  Process bloodborne nutrients – Example: store glucose as glycogen and make plasma proteins  Store fat-soluble vitamins  Perform detoxification – Example: converting ammonia to urea

Answer 30

- Composition and enterohepatic circulation – Yellow-green, alkaline solution containing:  Bile salts: cholesterol derivatives that function in fat emulsification and absorption  Bilirubin: pigment formed from heme – Bacteria break down in intestine to stercobilin that gives brown color of feces  Cholesterol, triglycerides, phospholipids, and electrolytes

Answer 31

 Recycling mechanism that conserves bile salts  Bile salts are: – Reabsorbed into blood by ileum (the last part of the small intestine) – Returned to liver via hepatic portal blood – Resecreted in newly formed bile  About 95% of secreted bile salts are recycled, so only 5% is newly synthesized each time

Answer 32

 Usually viral infection, drug toxicity, wild mushroom poisoning

Answer 33

 Progressive, chronic inflammation from chronic hepatitis or alcoholism  Liver → fatty, fibrous → portal hypertension

Answer 34

* Gallbladder is a thin-walled muscular sac on ventral surface of liver * Functions to store and concentrate bile by absorbing water and ions * Contains many honeycomb folds that allow it to expand as it fills * Muscular contractions release bile via cystic duct, which flows into bile duct

Answer 35

caused by too much cholesterol or too few bile salts – Can obstruct flow of bile from gallbladder – Painful when gallbladder contracts against sharp crystals – Obstructive jaundice: blockage can cause bile salts and pigments to build up in blood, resulting in jaundiced (yellow) skin  Jaundice can also be caused by liver failure – Gallstone treatment: crystal-dissolving drugs, ultrasound vibrations (lithotripsy), laser vaporization, or surgery

Answer 36

mostly retroperitoneal, deep to greater curvature of stomach – Head is encircled by duodenum; tail abuts spleen

Answer 37

produce pancreatic juice

Answer 38

clusters of secretory cells that produce zymogen granules containing proenzymes

Answer 39

secrete to duodenum via main pancreatic duct; smaller duct cells produce water and bicarbonate

Answer 40

secretion of insulin and glucagon by pancreatic islet cells

Answer 41

– 1200–1500 m l/day is produced containing:  Watery, alkaline solution (p H 8) to neutralize acidic chyme coming from the stomach  Electrolytes, primarily H C O3− Digestive enzymes – Proteases (for proteins): secreted in inactive form to prevent self-digestion – Amylase (for carbohydrates) – Lipases (for lipids) – Nucleases (for nucleic acids)

Answer 42

– Proteases are secreted in an inactive form; they are activated after they reach duodenum  Enteropeptidase, enzyme bound to plasma membrane of duodenal epithelial cells, activates pancreatic protease trypsinogen to trypsin  Once trypsin is activated, it can then activate: – More trypsinogen – Procarboxypeptidase to active carboxypeptidase – Chymotrypsinogen to active chymotrypsin

Answer 43

in wall of duodenum – Fuse together in bulblike structure called hepatopancreatic ampulla

Answer 44

controls entry of bile and pancreatic juice into duodenum

Answer 45

smaller duct that empties directly into duodenum

Answer 46

– Bile and pancreatic juice secretions are both stimulated by neural and hormonal controls – Hormonal controls include:  Cholecystokinin (C C K)  Secretin

Answer 47

– Bile secretion is increased when:  Enterohepatic circulation returns large amounts of bile salts  Secretin, from intestinal cells exposed to H C l and fatty chyme, stimulates gallbladder to release bile  Hepatopancreatic sphincter is closed, unless digestion is active – Bile is stored in gallbladder and released to the small intestine only with contraction

Digestive part B Flashcards

(72 cards)