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Anatomy and physiology 2 > Digestive part B > Flashcards

Digestive part B Flashcards

1
Q

what is the function of laryngopharynx

A

– 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

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2
Q

what is the esophagus and its function?

A
  • Flat muscular tube that runs from laryngopharynx to stomach
    – Is collapsed when not involved in food propulsion
  • Pierces diaphragm at esophageal hiatus
  • Joins stomach at cardial orifice
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3
Q

what is gastroesophageal (cardiac) sphincter?

A

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

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4
Q

what layers does the esophagus has?

A

– Esophageal mucosa contains stratified squamous epithelium
 Changes to simple columnar at stomach
– Esophageal glands in submucosa secrete mucus to aid in bolus movement
– Muscularis externa: skeletal muscle superiorly; mixed in middle; smooth muscle inferiorly
– Has adventitia instead of serosa

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5
Q

what causes heartburn?

A

– Caused by stomach acid regurgitating into esophagus
– First symptom of gastroesophageal reflux disease (G E R D)
– Can be caused by excess food/drink, extreme obesity, pregnancy, running
– Also can be caused by hiatal hernia: structural abnormality where part of stomach protrudes above diaphragm
 Can lead to esophagitis, esophageal ulcers, or even esophageal cancer

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6
Q

what are the digestive processes of the mouth?

A
  • Pharynx and esophagus are conduits to pass food from mouth to stomach
  • Major function of both organs is propulsion that starts with deglutition (swallowing)
  • Deglutition involves 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
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7
Q

what is the function of the stomach?

A
  • Stomach is a temporary storage tank that starts chemical breakdown of protein digestion
    – Converts bolus of food to paste-like chyme
    – Empty stomach has ~50 m l volume but can expand to 4 L
    – When empty, stomach mucosa forms many folds called rugae
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8
Q

what are the major regions of the stomach?

A

– 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)

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9
Q

what is greater curvature?

A

convex lateral surface of stomach

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10
Q

what is lesser curvature?

A

concave medial surface of stomach

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11
Q

what is lesser omentum?

A

 Runs from lesser curvature to liver

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12
Q

what is greater omentum?

A
  • drapes inferiorly from greater curvature over intestine, spleen, and transverse colon
     Blends with mesocolon, mesentery that anchors the large intestine to abdominal wall
     Contains fat deposits and lymph nodes
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13
Q

what does ANS supplies the stomach?

A

– Sympathetic fibers from thoracic splanchnic nerves are relayed through celiac plexus
– Parasympathetic fibers are supplied by vagus nerve
* Blood supply
– Celiac trunk (gastric and splenic branches)
– Veins of hepatic portal system

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14
Q

what is the mucosa layer?

A

– Consists of simple columnar epithelium entirely composed of mucous cells
 Secrete two-layer coat of alkaline mucus
– Surface layer traps bicarbonate-rich fluid layer that is beneath it
– Dotted with gastric pits, which lead into gastric glands
 Gastric glands produce gastric juice

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15
Q

what are the types of gland cells?

A

– Glands in fundus and body produce most gastric juice
– Glands include secretory cells
 Mucous neck cells
 Parietal cells
 Chief cells
 Enteroendocrine cells

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16
Q

what is mucous neck cells?

A

 Secrete thin, acidic mucus of unknown function

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17
Q

what is parietal cells?

A

 Secretions include:
– Hydrochloric acid (H C l)
* 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 the small intestine

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18
Q

what is chief cells?

A

 Secretions include:
– Pepsinogen: inactive enzyme that is activated to pepsin by H C l and by pepsin itself (a positive feedback mechanism)
– Lipases
* Digests ~15% of lipids

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19
Q

what is enteroendocrine cells?

A

 Secrete chemical messengers into lamina propria
– Act as paracrines
* Serotonin and histamine
– Hormones
* Somatostatin (also acts as paracrine) and gastrin

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20
Q

what is a mucosal barrier?

A

– Harsh digestive conditions require stomach to be protected
– Mucosal barrier protects stomach and is created by three factors
 Thick layer of bicarbonate-rich mucus
 Tight junctions between epithelial cells
– Prevent juice seeping underneath tissue
 Damaged epithelial cells are quickly replaced by division of stem cells
– Surface cells replaced every 3–6 days

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21
Q

what is gastritis?

A

– Inflammation caused by anything that breaches stomach’s mucosal barrier

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22
Q

what is peptic and gastric ulcers function?

A

– 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 (N S A I Ds), such as aspirin

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23
Q

what is the digestive processes in the stomach?

A

– Carries out breakdown of food
– Serves as holding area for food
– Delivers chyme to the small intestine
– Denatures proteins by H C l
– Pepsin carries out enzymatic digestion of proteins
 Milk protein (casein) is broken down by rennin in infants
– Results in curdy substance
– Lipid-soluble alcohol and aspirin are absorbed into blood
– Only stomach function essential to life is secretion of intrinsic factor for vitamin B12 absorption
– B12 needed for red blood cells to mature
– Lack of intrinsic factor causes pernicious anemia
– Treated with B12 injections

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24
Q

how much does gastric mucosa secrete?

A
  • Gastric mucosa secretes >3 L of gastric juice/day and is regulated by:
    – Neural mechanisms
     Vagus nerve stimulation increases secretion
     Sympathetic stimulation decreases secretion
    – Hormonal mechanisms
     Gastrin stimulates H C l secretion by stomach and gastrin antagonist hormones by the small intestine
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25
Q

what are the 3 phases of gastric secretion?

A

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

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26
Q

what is the cephalic (reflex) phase?

A

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

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27
Q

how long does the gastric phase last?

A

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

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28
Q

what is the stimulation of gastric phase?

A

 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

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29
Q

what is the inhibition of the gastric phase?

A

 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

30
Q

what is the intestinal phase?

A

– Begins with a brief stimulatory component followed by inhibition

31
Q

what is the stimulation of intestinal phase?

A

 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

32
Q

what is the inhibition of intestinal phase?

A

 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

33
Q

what is Enterogastric reflex?

A

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

34
Q

what is enterogastrones?

A

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

35
Q

what is the mechanism of HCI formation?

A
  • 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
36
Q

what is the response of the stomach filling?

A

– 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

37
Q

what is gastric contractile activity?

A

– 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

38
Q

what is the regulation of gastric emptying?

A

– 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

39
Q

what is vomiting (emesis) caused by?

A

– 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)

40
Q

what are the accessory organs associated with small intestine?

A
  • Liver, gallbladder, and pancreas
41
Q

what is the liver function?

A

digestive function is production of bile
– Bile: fat emulsifier

42
Q

what is the gallbladder function?

A

chief function is storage of bile

43
Q

what is the pancreas’ function?

A

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

44
Q

what is the structure of the liver?

A

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

45
Q

what is a falciform ligament?

A

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

46
Q

what is a round ligament?

A

 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

47
Q

what does the common hepatic duct do?

A

leaves liver

48
Q

what does cystic duct do?

A

connects to gallbladder

49
Q

what does the bile duct do?

A

formed by union of common hepatic and cystic ducts

50
Q

what is the liver lobule and it functions?

A

 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

51
Q

what is portal triad function?

A

 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

52
Q

what is liver sinusoids?

A

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

53
Q

what is stellate macrophages (hepatic macrophages) function?

A

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

54
Q

what is bile?

A
  • 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
55
Q

what is enterohepatic circulation?

A

 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

56
Q

what is hepatitis?

A

 Usually viral infection, drug toxicity, wild mushroom poisoning

57
Q

what is cirrhosis?

A

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

58
Q

what is the gallbladder structure?

A
  • 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
59
Q

what causes gallstones (Hillary calculi)?

A

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

60
Q

where is the pancreas located?

A

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

61
Q

what is exocrine function?

A

produce pancreatic juice

62
Q

what is acini?

A

clusters of secretory cells that produce zymogen granules containing proenzymes

63
Q

what is ducts?

A

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

64
Q

what is endocrine function?

A

secretion of insulin and glucagon by pancreatic islet cells

65
Q

what is the composition of pancreatic juice?

A

– 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)

66
Q

what is the composition of pancreatic juice? part 2

A

– 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

67
Q

where does the bile duct and pancreatic duct unite?

A

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

68
Q

what opens major duodenal papilla via volcano shaped?

A
  • Ampulla
69
Q

what is the function of hepatopancreatic sphincter?

A

controls entry of bile and pancreatic juice into duodenum

70
Q

what is accessory pancreatic duct?

A

smaller duct that empties directly into duodenum

71
Q

what is the regulation of bile and pancreatic secretions?

A

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

72
Q

what is the regulation of bile and pancreatic secretions? part 2

A

– 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

Anatomy and physiology 2 (3 decks)

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