chp 23 exam 4 Flashcards

Question

periodontitis

Answer 1

Periodontitis (periodontal disease) -Neglected gingivitis can escalate to disease -Immune cells attack bacterial intruders and own tissues destroys periodontal ligaments activates osteoclasts Cells that dissolve bone so tooth falls out -May increase heart disease and stroke two ways: Promotes atherosclerotic plaque formation Bacteria entering blood can cause clot formation in coronary and cerebral arteries -Risk factors: smoking, diabetes mellitus, oral piercings and poor oral hygiene

Answer 2

Food passes from mouth into oropharynx and then into laryngopharynx Allows passage of food, fluids, and air Stratified squamous epithelium lining with mucus-producing glands External muscle layers consists of two skeletal muscle layers Inner layer of muscles runs longitudinally Outer pharyngeal constrictors encircle wall of pharynx

Answer 3

Muscular tube that runs from laryngopharynx to stomach Is collapsed when not involved in food propulsion Goes through the diaphragm at esophageal hiatus Joins stomach at cardial orifice Gastroesophageal (cardiac) sphincter surrounds cardial orifice Keeps orifice closed when food is not being swallowed Mucus cells on both sides of sphincter help protect esophagus from acid reflux

Answer 4

Four tunics Mucosa Stratified squamous epithelium Changes to simple columnar at stomach Submucosa Has esophageal glands that secrete mucus to aid in bolus movement Muscularis externa skeletal muscle at the beginning (superior) mixed in skeletal and smooth muscle in the middle smooth muscle at the end (inferior) Serosa is replaced by adventitia

Answer 5

Heartburn Caused by stomach acid regurgitating into esophagus First symptom of gastroesophageal reflux disease (GERD) Causes excess food/drink, extreme obesity, pregnancy, running Hiatal hernia part of stomach protrudes above diaphragm Can lead to esophagitis, esophageal ulcers, or even esophageal cancer

Answer 6

Reminder The pharynx and esophagus job is to pass food from mouth to stomach Deglutition (swallowing) Requires coordination of 22 muscle groups and two phases: Buccal phase voluntary contraction of tongue Pharyngeal-esophageal phase involuntary phase that primarily involves vagus nerve Controlled by swallowing center in medulla and lower pons

Answer 7

Stomach temporary storage tank that starts chemical breakdown of proteins Converts bolus of food to paste-like chyme Extremely expandable Empty stomach ~50 ml can expand to 4 L when full When empty, stomach mucosa forms many folds called rugae

Answer 8

Major regions of the stomach Cardial part (cardia): surrounds cardial orifice Fundus: dome-shaped region beneath diaphragm Body: midportion Pyloric part: wider and more superior portion of pyloric region, antrum, narrows into pyloric canal that terminates in pylorus Pylorus is continuous with duodenum through pyloric valve (sphincter controlling stomach emptying)

Answer 9

Greater curvature: convex lateral surface of stomach Lesser curvature: concave medial surface of stomach Mesenteries extend from curvatures and hold the stomach to other digestive organs Lesser omentum Runs from lesser curvature to liver Greater omentum: drapes inferiorly from greater curvature over intestine, spleen, and transverse colon Blends with mesocolon, mesentery that anchors large intestine to abdominal wall Contains fat deposits and lymph nodes

Answer 10

Four Tunics Modified muscularis and mucosa Muscularis Externa Modifications Has regular circular and longitudinal smooth muscle layers AND extra third layer, the oblique (diagonal) layer allows stomach to churn, mix, and move chyme Also allows pummeling motion increases physical breakdown and forces chyme into small intestine Mucosa Modifications Simple columnar epithelium entirely composed of mucous cells Secrete two-layer coat of alkaline mucus Surface layer traps a bicarbonate-rich fluid layer beneath it Gastric pits lead into gastric glands gastric glands make gastric juice

Answer 11

Types of gland cells Glands in fundus and body produce most gastric juice Mucous neck cells, Parietal cells, Chief cells, Enteroendocrine cells Mucous neck cells Secrete thin, acidic mucus of unknown function

Answer 12

Parietal cells Secretions include: Hydrochloric acid (HCl) pH 1.5–3.5; denatures protein, activates pepsin, breaks down plant cell walls, and kills many bacteria Intrinsic factor Glycoprotein required for absorption of vitamin B12 in small intestine secrets HCL and intrinsic factor

Answer 13

``` Chief cells Secretions include: Pepsinogen: inactive enzyme that is activated to pepsin by HCl and by pepsin itself (a positive feedback mechanism) Lipases Digests ~15% of lipids ``` secrets Pepsinogen lipase

Answer 14

Enteroendocrine cells Secrete chemical messengers into lamina propria Act as paracrines Serotonin and histamine Hormones Somatostatin (also acts as paracrine) and gastrin secretes hormones and paracrine

Answer 15

``` Mucosal barrier protects stomach thick layer of bicarbonate-rich mucus tight junctions between epithelial cells prevent juice seeping underneath tissue damaged epithelial cells are quickly replaced surface cells replaced every 3–6 days ```

Answer 16

Gastritis Inflammation caused by anything that breaches stomach’s mucosal barrier Peptic or gastric ulcers Can cause erosions in stomach wall If erosions perforate wall, can lead to peritonitis and hemorrhage Most ulcers caused by bacterium Helicobacter pylori Can also be caused by non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin

Answer 17

``` Reminder of what the stomach does: Carries out breakdown of food Serves as holding area for food Delivers chyme to small intestine Denatures proteins by HCl Pepsin carries out enzymatic digestion of proteins Milk protein (casein) is broken down by rennin in infants Results in curdy substance ```

Answer 18

-Denatures proteins by HCl -Pepsin Enzyme that digests of proteins -Milk protein (casein broken down by rennin in infants Makes “curds”

Answer 19

Alcohol and aspirin absorbed into blood through the mucosa both are lipid soluble Intrinsic factor Synthesis and secretion is the only stomach function essential to life Required vitamin B12 absorption Reminder: B12 needed for red blood cells to mature Lack of intrinsic factor causes pernicious anemia Treated with B12 injections

Answer 20

Gastric mucosa secretes >3 L of gastric juice/day Regulated by: Neural mechanisms Parasympathetic (Vagus nerve) stimulation increases secretion Sympathetic stimulation decreases secretion Hormonal mechanisms Gastrin stimulates HCl secretion by the stomach Stimulates gastrin antagonist hormones by the small intestine

Answer 21

Gastric secretions are broken down into three phases Cephalic (reflex) phase Gastric phase Intestinal phase

Answer 22

Cephalic (reflex) phase Conditioned reflex triggered by aroma, taste, sight, thought Varies based on life experience!

Answer 23

Gastric phase Lasts 3–4 hours Releases two-thirds of the gastric juice Stimulation of gastric phase Distension (stretching) activates stretch receptors initiates both long and short reflexes Chemical stimuli i.e partially digested proteins, caffeine, and low acidity activate enteroendocrine G cells to secrete gastrin Release of gastrin initiates HCl release from parietal cells and activates enzyme secretion Buffering action of ingested proteins causes pH to rise, which activates more gastrin secretion

Answer 24

Inhibition of gastric phase Low pH Inhibits gastrin secretion Happens between meals Also occurs during digestion as negative feedback mechanism The more protein, the more HCl acid is secreted, causing decline in pH, which inhibits gastrin secretion

Answer 25

Intestinal phase Brief stimulation followed by inhibition Stimulation of intestinal phase Partially digested food enters small intestine, Causes a brief release of intestinal (enteric) gastrin Causes gastric glands of stomach to continue secretion Stimulatory effect is really short! Overridden by inhibitory stimuli as intestine fills

Answer 26

Inhibition of intestinal phase 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 Protect intestine from being overwhelmed by too much chyme or acidity Two mechanisms enterogastric reflex and enterogastrones

Answer 27

Enterogastric reflex Neural control Duodenum inhibits acid secretion in stomach by: Enteric nervous system short reflexes Sympathetic nervous system and vagus nerve long reflexes ``` Enterogastrones Hormonal control Duodenal enteroendocrine cells release two important hormones that inhibit gastric secretion Secretin Cholecystokinin (CCK) ```

Answer 28

Parietal cells pump H+ (from carbonic acid breakdown) into stomach lumen via H+/K+ ATPase (proton pumps) As H+ is pumped into stomach lumen, HCO3− is exported back to blood via Cl− and HCO3− antiporter Resulting increase of HCO3− in blood leaving stomach is referred to as alkaline tide Cl− is pumped out to lumen to join with H+, forming HCl

Answer 29

Response of the stomach to filling 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 enables hollow organs to stretch without increasing tension or contractions

Answer 30

Gastric contractile activity Peristaltic waves move toward pylorus About 3 waves per minute Basic electrical rhythm (BER) is set by enteric pacemaker cells Pacemaker cells are linked by gap junctions so that entire muscularis contracts (Sounds familiar?) Distension and gastrin increase force of contraction Contractions are strongest near pylorus region 30 ml of chyme produced is either: ~3 ml spurts into duodenum Rest of 27 ml forced backward into stomach Only liquids and small particles are allowed to pass through pyloric valve

Answer 31

Regulation of gastric emptying Regulated by the Duodenum Controls how much chyme enters Prevents overfilling Duodenal receptors respond to stretch and chemical signals Enterogastric reflex and enterogastrones inhibit gastric secretion and duodenal filling Stomach empties in ~4 hours High fatty chyme entering duodenum can increase time to 6 hours or more Carbohydrate-rich chyme moves quickly through duodenum! This means that high carb meals do not keep us feeling full as long!

Answer 32

Vomiting (emesis) is caused by: Extreme stretching Intestinal irritants I.e. 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 33

Liver, gallbladder, and pancreas are accessory organs associated with small intestine Liver: Makes bile Bile emulsifies fats Gallbladder: Stores bileLiver, Gallbladder and Pancreas (Introduction) Pancreas: Produces several digestive enzymes Produces bicarbonate to neutralize stomach acid

Answer 34

Gross anatomy of the liver Largest gland in body weighs ~3 lbs Consists of four primary lobes: right, left, caudate, and quadrate Falciform ligament Separates larger right and smaller left lobes Suspends liver from diaphragm and anterior abdominal wall Round ligament (ligamentum teres) Remnant of fetal umbilical vein along free edge of falciform ligament ``` Gross anatomy of the liver (cont.) Lesser omentum anchors liver to stomach Hepatic artery and vein enter liver at porta hepatis Bile ducts Common hepatic duct leaves liver Cystic duct connects to gallbladder Bile duct union of common hepatic and cystic ducts ```

Answer 35

Microscopic anatomy of the liver Liver lobules Hexagonal structural and functional units Composed of hepatocytes (liver cells) Form hepatic plates Filter and process nutrient-rich blood Central vein located in longitudinal axis Portal triad In each corner of lobule contains: Branch of hepatic artery, which supplies oxygen Branch of hepatic portal vein, which brings nutrient-rich blood from intestine Bile duct, which receives bile from bile canaliculi

Answer 36

Liver sinusoids leaky capillaries located between hepatic plates Blood from the hepatic portal vein and hepatic artery proper enters the sinusoids Empties into central vein Stellate macrophages (hepatic macrophages) in liver sinusoids remove debris and old RBCs

Answer 37

``` Hepatocytes have increased rough and smooth ER, Golgi apparatus, peroxisomes, and mitochondria Hepatocyte functions Produce ~900 ml 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 38

Composition Yellow-green, alkaline solution: Bile salts: cholesterol derivatives that function in fat emulsification and absorption Bilirubin: pigment formed from heme Bacteria break down bile in intestine Makes feces brown Cholesterol, triglycerides, phospholipids, and electrolytes Enterohepatic circulation Recycling mechanism that conserves bile salts Bile salts Reabsorbed into blood by ileum (the last part of 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 39

Hepatitis Usually viral infection, drug toxicity, wild mushroom poisoning Cirrhosis Progressive, chronic inflammation from chronic hepatitis or alcoholism Liver → fatty, fibrous → portal hypertension Liver transplants successful, but livers are scarce Liver can regenerate to its full size in 6–12 months after 80% removal So HIGHLY regenerative

Answer 40

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 41

Gallstones (biliary calculi): 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 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 42

``` Location mostly retroperitoneal deep to greater curvature of stomach head is encircled by duodenum tail ends at the spleen Exocrine function produce pancreatic juice Acini clusters of secretory cells t produce zymogen granules with proenzymes Ducts secretes to duodenum via main pancreatic duct smaller duct cells produce water and bicarbonate Endocrine function secretion of insulin and glucagon by pancreatic islet cells ```

Answer 43

``` Pancreatic juice 1200–1500 ml/day Watery, alkaline solution (pH 8) neutralize acidic chyme Electrolytes, mostly HCO3− Digestive enzymes Proteases (for proteins) secreted in inactive form to prevent self-digestion Amylase (for carbohydrates) Lipases (for lipids) Nucleases (for nucleic acids) ```

Answer 44

Bile duct and pancreatic duct unite in wall of duodenum Fuse together in bulblike structure called hepatopancreatic ampulla Ampulla opens into duodenum via volcano-shaped major duodenal papilla Hepatopancreatic sphincter controls entry of bile and pancreatic juice into duodenum Accessory pancreatic duct: smaller duct that empties directly into duodenum

Answer 45

Regulation of bile and pancreatic secretions neural and hormonal controls Hormonal controls include: Cholecystokinin (CCK) Secretin Bile secretion is increased when: Enterohepatic circulation returns large amounts of bile salts Secretin, from intestinal cells exposed to HCl and fatty chyme, stimulates gallbladder to release bile Hepatopancreatic sphincter is closed, unless digestion is active Bile is stored in gallbladder and released to small intestine only with contraction

Answer 46

Small intestine major organ of digestion and absorption (where most of it happens) 2–4 m long (7–13 ft) Small diameter of 2.5–4 cm (1.0–1.6 inches) Begins at the pyloric sphincter Where the stomach empties in Ends at the ileocecal valve, point at which it joins large intestine Small diameter of 2.5–4 cm (1.0–1.6 inches)

Answer 47

``` Subdivisions Duodenum mostly retroperitoneal ~25.0 cm (10.0 in) long curves around head of pancreas has most features Jejunum ~2.5 m (8 ft) long attached posteriorly by mesentery Ileum ~3.6 m (12 ft) long attached posteriorly by mesentery joins large intestine at ileocecal valve ```

Answer 48

``` Blood supply: Superior mesenteric artery brings blood supply Veins (carrying nutrient-rich blood) drain into superior mesenteric veins, then into hepatic portal vein, and finally into liver Nerve supply Parasympathetic innervation vagus nerve Sympathetic innervation thoracic splanchnic nerves ```

Answer 49

Modifications of small intestine for absorption Modified to have huge surface area for absorption Increased 600× to ~200 m2 (size of a tennis court) Modifications include: Circular folds Villi Microvilli

Answer 50

``` Circular folds Permanent folds ~1 cm deep that force chyme to slowly spiral through lumen allows more time for nutrient absorption Villi Fingerlike projections of mucosa ~1 mm high contain lacteals capillariy bed and lymphatic capillaries for absorption Microvilli Brush border Cytoplasmic extensions of mucosal cell Brush border enzymes membrane-bound enzymes carbohydrate and protein digestion ```

Answer 51

Intestinal crypts Five main types of cells found in villi and crypts enterocytes, goblet cells, enteroendocrine cells, paneth cells, stem cells Enterocytes Most of the epithelial cells Simple columnar absorptive cells bound by tight junctions and contain many microvilli Function Villi: absorb nutrients and electrolytes Crypts: produce intestinal juice, watery mixture of mucus that acts as carrier fluid for chyme

Answer 52

``` Goblet cells mucus-secreting cells found in epithelia of villi and crypts Enteroendocrine cells Produce enterogastrones examples: CCK and secretin Found scattered in villi but some in crypts Paneth cells Deep in crypts Secrete antimicrobial agents defensins and lysozyme Stem cells Continuously divide Produce other cell types Villus epithelium renewed every 2–4 days ```

Answer 53

Mucosa-associated lymphoid tissue (MALT) protects intestine against microorganisms Individual lymphoid follicles Peyer’s patches (aggregated lymphoid nodules) In the lamina propria More in distal part of small intestine Why? where bacterial numbers increase Lamina propria also contains large numbers of plasma cells that secrete IgA Submucosa consists of areolar tissue Duodenal glands In the duodenum Secrete alkaline mucus to neutralize acidic chyme

Answer 54

1–2 L secreted daily Secreted in response to distension or irritation of mucosa Major stimulus for production is hypertonic or acidic chyme Slightly alkaline and isotonic with blood plasma Mostly water but also contains mucus Mucus is secreted by duodenal glands and goblet cells of mucosa

Answer 55

``` Starting with chyme From stomach Carbohydrates and proteins partially digested Fats undigested Takes 3–6 hours in small intestine to absorb all nutrients and most water Enzymes for digestion come from: Liver and pancreas bile, bicarbonate, digestive enzymes not brush border enzymes Brush border enzymes bound to plasma membrane Responsible for final digestion of chyme ```

Answer 56

Regulating chyme entry Chyme entering duodenum is usually hypertonic has to be slow to prevent osmotic loss of water from blood Low pH of chyme has to be adjusted upward Chyme has to be mixed with bile and pancreatic juice to continue digestion Enterogastric reflex and enterogastrones control movement of food into duodenum to prevent it from being overwhelmed

Answer 57

After a meal Segmentation is most common motion of small intestine Initiated by intrinsic pacemaker cells Mixes/moves contents toward ileocecal valve Intensity is altered by long and short reflexes and hormones Parasympathetic increases motility; sympathetic decreases it

Answer 58

Between meals Peristalsis increases initiated by rise in hormone motilin in late intestinal phase (every 90–120 minutes) Meal remnants, bacteria, and debris are moved toward large intestine Complete trip from duodenum to ileum takes ~2 hours

Answer 59

Ileocecal valve control Ileocecal sphincter relaxes and admits chyme into large intestine when: Gastroileal reflex enhances force of segmentation in ileum Gastrin increases motility of ileum Ileocecal valve flaps close when chyme exerts backward pressure Prevents regurgitation into ileum

Answer 60

Large intestine Three unique features Teniae coli: three bands of longitudinal smooth muscle in muscularis Haustra: pocketlike sacs caused by tone of teniae coli Epiploic appendages: fat-filled pouches of visceral peritoneum

Answer 61

Subdivisions of large intestine Cecum: first part of large intestine Appendix: masses of lymphoid tissue Part of MALT of immune system Bacterial storehouse capable of recolonizing gut when necessary Twisted shape of appendix makes it susceptible to blockages Colon: has several regions, most which are retroperitoneal (except for transverse and sigmoid regions) Ascending colon: travels up right side of abdominal cavity to level of right kidney Ends in right-angle turn called right colic (hepatic) flexure Transverse colon: travels across abdominal cavity Ends in another right-angle turn, left colic (splenic) flexureDescending colon: travels down left side of abdominal cavity Sigmoid colon: S-shaped portion that travels through pelvis ``` Subdivisions of large intestine (cont.) Rectum: three rectal valves stop feces from being passed with gas (flatus) Anal canal last segment of large intestine that opens to body exterior at anus Has two sphincters Internal anal sphincter smooth muscle External anal sphincter skeletal muscle ```

Answer 62

``` Retroperitoneal Cecum, appendix, and rectum Colon (except transverse and sigmoid) Intraperitoneal regions anchored to posterior abdominal wall by mesentery sheets called mesocolons ```

Answer 63

Appendicitis Acute inflammation of appendix Usually results from a blockage by feces that traps infectious bacteria Most common in adolescence when entrance to appendix is at widest Venous drainage can be impaired Ruptured appendix can cause peritonitis Symptoms Pain in umbilical region, moving to lower right abdominal quadrant Loss of appetite, nausea, and vomiting Treatment Surgical removal (appendectomy), or in some cases, with antibiotics.

Answer 64

Mucosa Thicker than other areas Simple columnar epithelium Except in anal canal Stratified squamous epithelium to withstand abrasion No circular folds, villi, or digestive secretions Lots of deep crypts goblet cells Remember goblet cells? What do they make?

Answer 65

Mucosa of anal canal Anal columns long ridges or folds Anal recesses between anal columns secrete mucus to aid in emptying Pectinate line horizontal line that parallels anal sinuses Visceral sensory nerves innervate area superior to this line Region insensitive to pain Somatic nerves innervate inferior to this line Region sensitive to pain Superficial hemorrhoidal veins in the anal canal form hemorrhoids if inflamed

Answer 66

Bacterial flora: consist of 1000+ different types of bacteria Wowza! Outnumber our own cells 10 to 1 Enter from small intestine or anus to colonize colon Metabolic functions Fermentation Ferment indigestible carbohydrates and mucin Release irritating acids and gases (~500 ml/day) Vitamin synthesis Synthesize B complex and some vitamin K needed by liver to produce clotting factors Keeping pathogenic bacteria in check Beneficial bacteria outnumber and suppress pathogenic bacteria Immune system destroys any bacteria that try to breach mucosal barrier How? Epithelial cells recruit dendritic cells to mucosa to sample microbial antigens and present to T cells of MALT, triggering production of IgA that restricts microbes

Answer 67

Gut bacteria and health Kinds and proportions of gut bacteria may influence: Body weight Susceptibility to various diseases including diabetes, atherosclerosis, fatty liver disease Our moods Manipulating gut bacteria may become a routine health-care strategy in future!

Answer 68

Antibiotic-associated diarrhea accounts for 14,000 deaths per year Clostridium difficile Most common cause of antibiotic-associated diarrhea Anaerobic bacterium often found in the large intestine Usually controlled by “good” bacteria If other bacteria are killed by antibiotics C. difficile takes over Can cause pseudomembranous colitis (inflammation of colon) May lead to bowel perforation and sepsis Are resistant to many antibiotics and difficult to treat New treatment fecal transplants to replace healthy bacteria to suppress C. difficile

Answer 69

12–24 hours No food breakdown occurs except by bacteria Absorption of Vitamins (made by bacterial flora), water, and electrolytes (especially Na+ and Cl−) Major function of large intestine is propulsion of feces to anus and defecation NOTE: Large intestine is not essential for life

Answer 70

``` Motility of the large intestine Haustral contractions most contractions of colon haustra sequentially contract in response to distension Slow segmenting movements Mostly in ascending and transverse colon Gastrocolic reflex initiated by food in stomach Results in mass movements slow, strong peristaltic waves activated three to four times per day Descending colon and sigmoid colon are pretty much for storage ```

Answer 71

``` Diverticula Herniations of mucosa Cause: Low-fiber diet Diverticulosis Presence of diverticula Common in sigmoid colon Affects half of people > 70 years Diverticulitis Inflamed diverticula May rupture and leak into peritoneal cavity May be life threatening ```

Answer 72

Irritable bowel syndrome Recurring abdominal pain, stool changes, bloating, flatulence, nausea, depression Stress is a common precipitating factor Stress management is important in treatment

Answer 73

Defecation Mass movements force feces toward rectum Defecation reflex A spinal reflex triggered by distension Parasympathetic signals Stimulate contraction of sigmoid colon and rectum Relax internal anal sphincter Conscious control allows relaxation of external anal sphincter Muscles of rectum contract to expel feces Valsalva’s maneuver Closing of glottis, contraction of diaphragm and abdominal wall muscles cause increased intra-abdominal pressure Levator ani muscle contracts, causing anal canal to be lifted superiorly and allowing feces to leave body

Answer 74

Diarrhea Watery stools Large intestine does not have enough time to absorb remaining water Causes irritation of colon by bacteria or jostling of digestive viscera (occurs in marathon runners) Prolonged diarrhea may lead to: dehydration and electrolyte imbalance (acidosis and loss of potassium)

Answer 75

``` Constipation Food remains in colon for too long Too much water is absorbed Stool becomes hard and difficult to pass Causes Insufficient fiber or fluid in the diet Improper bowel habits Lack of exercise Laxative abuse ```

Answer 76

Digestion breaks down ingested foods into their chemical building blocks Only these molecules are small enough to be absorbed across wall of small intestine Digestion Catabolic Breaks macromolecules down into monomers small enough for absorption Intrinsic and accessory gland enzymes are involved in digestion Enzymes carry out hydrolysis Water is added to break chemical bonds

Answer 77

Absorption process of moving substances from lumen of gut into body Lumen? What is it? Molecules pass through epithelial cells rather than between Due to tight junctions Enter cell through apical membrane (lumen side) Exit through basolateral membrane (blood side) Remember epithelial tissue structure? Lipid molecules can be absorbed passively through membrane Why? Polar molecules are absorbed by active transport Why? Most nutrients are absorbed before chyme reaches ileum -So most are absorbed in the duodenum and jejunum

Answer 78

Only monosaccharides can be absorbed Polysaccharides (starch) and disaccharides are broken down Begins in mouth with salivary amylase Then broken down into lactose, maltose, and sucrose Final breakdown into monosaccarides (glucose, fructose, galactose) Starch digestion in the small intestine Pancreatic amylase Breaks down starch to oligosaccharides and disaccharides Brush border enzymes dextrinase, lactase, glucoamylase, maltase, and sucrase Break oligosaccharides and disaccharides into lactose, maltose, and sucrose; and then into monosaccharides (glucose, fructose, galactose)

Answer 79

Monosaccharides enter the cell Co-transported across apical membrane Mostly by secondary active transport with Na+ Monosaccharides exit the cell exit across the basolateral membrane by facilitated diffusion

Answer 80

Lactase deficiency cannot consume lactose Lactose remains undigested creates an osmotic gradient in intestine that prevents water from being absorbed So-diarrhea Can even pull water from interstitial space into intestinal lumen Bacterial metabolism of lactose causes produces large amounts of gas results in bloating, flatulence, and cramping pain Treatment add lactase enzyme “drops” to milk or take a lactase tablet before consuming milk products

Answer 81

Source of protein Dietary digestive enzymes and proteins from breakdown of mucosal cells Proteins break: Large polypeptides then Small polypeptides and small peptides Finally into amino acid monomers, with some dipeptides and tripeptides Digestion begins in stomach Remember: pepsinogen is converted to pepsin at pH 1.5–2.5 Becomes inactive in high pH of duodenum

Answer 82

Steps of protein digestion in intestine Pancreatic proteases trypsin and chymotrypsin cleave protein into smaller peptides carboxypeptidase takes off one amino acid at a time from the end Brush border enzymes aminopeptidases, carboxypeptidases, and dipeptidases break oligopeptides and dipeptides into amino acids Amino acids cotransported across apical membrane of epithelial cell via secondary active transport carriers (Na+ or H+) Amino acids exit across basolateral membrane via facilitated diffusion

Answer 83

Emulsification Remember: triglycerides and their breakdown products are insoluble in water Bile salts break large fat globules into smaller ones

Answer 84

Digestion | pancreatic lipases break down fat into monoglyceride plus two free fatty acids

Answer 85

Micelle formation | products from digestion become coated with bile salts and lecithin

Answer 86

Diffusion | lipid products leave micelles and cross epithelial membrane via diffusion

Answer 87

Chylomicron formation lipid products are converted back into triglycerides and packaged with lecithin and lipoproteins (together called chylomicron) Chylomicron transport Chylomicrons are put out of the cell using exocytosis On basolateral side then go into the lymphatic lacteal Eventually emptied into venous blood at thoracic duct

Answer 88

Once in blood, chylomicrons are broken into free fatty acids and glycerol by lipoprotein lipase so they can be used by cells Short-chain fatty acids can diffuse directly into blood

Answer 89

Ingested food has DNA and RNA because our food is made of cells! Pancreatic nucleases hydrolyze nucleic acid to nucleotide monomers Phosphate, sugar and a nitrogen containing base Brush border enzymes, nucleosidases and phosphatases break nucleotides down nitrogenous bases, pentose sugars, and phosphate ions Breakdown products are actively transported by special carriers in epithelium of villi

Answer 90

``` Vitamin absorption In small intestine Fat-soluble vitamins (A, D, E, and K) carried by micelles diffuse into absorptive cells Water-soluble vitamins (C and B) absorbed by diffusion or by passive or active transporters Vitamin B12 (large, charged molecule) binds with intrinsic factor absorbed by endocytosis In large intestine vitamin K and B vitamins from bacterial metabolism are absorbed ```

Answer 91

Absorption of electrolytes What is an electrolyte? Most ions are actively transported Along length of small intestine Iron and calcium are absorbed in duodenum Na+ absorption is coupled with active absorption of glucose and amino acids Cl− is actively transported K+ diffuses in response to osmotic gradients lost if water absorption is poor Iron and calcium absorption is related to need Ionic iron is stored in mucosal cells with ferritin When needed, transported in blood by transferrin Ca2+ absorption I regulated by vitamin D and parathyroid hormone (PTH)

Answer 92

Absorption of water 9 L water enter small intestine daily Most from GI tract secretions 95% is absorbed in the small intestine by osmosis Most of rest is absorbed in large intestine Net osmosis occurs if concentration gradient is established by active transport of solutes Water uptake is coupled with solute uptake

Answer 93

Malabsorption Caused by anything that interferes with delivery of bile or pancreatic juice Or damaged intestinal mucosa For Example: from bacterial infection or some antibiotics Gluten-sensitive enteropathy (celiac disease) common malabsorption disease Immune reaction to gluten Gluten causes immune cell damage to intestinal villi and brush border Treatment: eliminate gluten from diet

chp 23 exam 4 Flashcards

(117 cards)