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Anatomy Exam 3 > Lecture 8 : Gastrointestinal System II : Stomach, Liver and Digestive Enzymes > Flashcards

Lecture 8 : Gastrointestinal System II : Stomach, Liver and Digestive Enzymes Flashcards

1
Q

The stomach is located in the :

A

upper left quadrant of the abdominopelvic cavity

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2
Q

Greater omentum =

A

sheet of mesentery suspended from inferior border of stomach

Immune function

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3
Q

Lesser omentum =

A

sheet of mesentery between liver and stomach

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4
Q

The stomach is a J-shaped temporary “storage tank” that aids in ___________

A

chemical and mechanical digestion, propulsion of food

Can hold around 1 gallon of food

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5
Q

Rugae

A

longitudinal folds in wall that allow for expansion

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6
Q

Stomach anatomy

A

Thick muscularis externa with 3 layers

Rugae

Pyloric sphincter

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7
Q

Pyloric sphincter =

A

controls entry of chyme into small intestine

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8
Q

the stomach converts the bolus of food to ____ by mechanical (churning) and chemical (acid and enzymes) breakdown

A

chyme

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9
Q

4 Layered Wall:
(of stomach)

A

Mucosa = contains simple columnar epithelium (mucus cells) with gastric pits & gastric glands

Submucosa = contains submucosal plexus in connective tissue

Muscularis externa contains (3) smooth muscle layers:
oblique, circular, longitudinal

Serosa = covered by visceral peritoneum

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10
Q

4 Cell Types Contribute to Gastric Juice:

(found in the surface epithelium and “neck” of gastric gland)

A

Mucous cells
Parietal cells
Chief cells
Enteroendocrine cells

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11
Q

Mucous cells

A

Secretion of mucous & Bicarbonate (HCO3-)

protective barrier

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12
Q

Parietal cells

A

Secretion of intrinsic factor
> Allows Vitamin B12 absorption in small intestine (required for erythropoiesis)

Produce hydrochloric acid (HCl): secrete H+ and Cl- to create acidic environment: pH ~2
>Denatures proteins, breaks down cell walls of plant foods
> Kill bacteria & microorganisms
> Activation of pepsinogen to pepsin

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13
Q

Chief cells

A

Major function: Secrete pepsinogen – inactive form of protease pepsin (digests proteins)

Minor function: Secrete gastric lipase (digest fats)

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14
Q

Enteroendocrine cells

A

(“gut endocrine”) secrete hormones into blood

Sense food in the lumen

Secrete chemical messengers into interstitial fluid where they can act as paracrine (short distance) or hormone signals

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15
Q

G cells secrete ____ into bloodstream; stimulate HCl production and motility

Others secrete ______

A

gastrin

histamine, serotonin

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16
Q

Parietal cells secrete________ions separately, which combine in the lumen to form hydrochloric acid

A

H+ and Cl-

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17
Q

____ and ____ stimulate parietal cells to produce and release acid

A

Gastrin

histamine

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18
Q

The Mucous-Bicarbonate Barrier protects the stomach from ___

A

itself

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19
Q

_______ secrete mucus & bicarbonate (HCO3-)

A

Mucous cells

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20
Q

Three (3) Factors that create the barrier:

A

Thick coating of bicarbonate rich mucous from the mucous cells

Epithelial cells joined by tight junctions

High turnover of epithelial (mucous) cells

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21
Q

________ can disrupt mucosal barrier and be absorbed in stomach

A

Alcohol and aspirin

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22
Q

Disruption of the mucous barrier leads to ______

A

gastric ulcers

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23
Q

Gastric ulcer

A

can damage organ wall and lead to perforation, peritonitis, hemorrhage

exacerbated by acidic conditions & stress, NSAIDs

most ulcers caused by H. pylori bacteria

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24
Q

Helicobacter pylori

A

~ 50% of us have it, but causes ulcers in only ~10-20% of people who have it

drill into mucus layer

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25
Q

Neuronal & hormonal mechanisms regulate gastric activity in 3 phases

A

cephalic phase

gastric phase

intestinal phase

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26
Q

Gastric (stomach) activity includes _________

A

gastric secretions and gastric motility

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27
Q

cephalic phase

A

1a) sight and thought of food
1b) stimulation of taste and smell receptors

takes place in cerebral cortex -> hypothalamus and medulla oblongata -> vagus nerve -> stomach

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28
Q

gastric phase

A

2a) stomach distention activates stretch receptors -> long and short reflexes -> stomach

2b) food chemicals and rising pH activate chemoreceptors -> G cells -> Gastrin release to blood -> stomach

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29
Q

intestinal phase

A

3a) presence of partially digested foods in duodenum or distension of the the duodenum when stomach begins to empty -> intestinal gastrin release to blood -> brief effect -> stomach

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30
Q

______ includes propulsion and mechanical breakdown

A

Gastric motility

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31
Q

Filling of stomach:

A

relaxation mediated by vagus nerve and stress-relaxation response of smooth muscle

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32
Q

__________ (interstitial cells of Cajal) set a constant (~3/min) rate of stomach contraction

A

Stomach enteric pacemaker cells

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33
Q

Factors that enhance gastric secretions also enhance_______ (i.e. stretch of stomach wall and presence of food activate long and short reflexes & gastric secretions)

A

strength of contractions

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34
Q

Fatty, hypertonic, acidic chyme in duodenum ______ and slow emptying

A

decrease strength of contraction

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35
Q

Slow entry of chyme into small intestine is controlled by _______; prevents SI from being overwhelmed.

A

enterogastric reflex and GI hormones

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36
Q

propulsion =

A

Peristaltic waves move from the fundus toward the pylorus

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37
Q

grinding =

A

the most vigorous peristalsis and mixing action occur close to the pylorus

the pyloric end of the stomach acts as a pump that delivers small amounts of chyme into the duodenum

38
Q

retropulsion =

A

the peristaltic wave closes the pyloric valve, forcing most of the contents of the pylorous backward into the stomach

39
Q

The stomach delivers the chyme to the ____

A

small intestine

40
Q

The _____ is where the most of digestion and absorption occurs

A

small intestine

41
Q

Some digestion of proteins & breakdown of the food occurs in the ____, but the majority of digestion continues in the first part of the small intestine.

A

stomach

42
Q

Most of the substances required for digestion come from accessory organs:

A

liver, gall bladder, pancreas

43
Q

Liver =

A

Upper right quadrant

4 anatomical lobes

Gall bladder attached to posterior inferior portion

44
Q

Porta hepatis =

A

“Door” of the liver

Important structures enter and leave the liver here

45
Q

Liver
Primary digestive function =

A

produces bile to emulsify fats

46
Q

The liver processes nutrient-rich venous blood from digestive organs (via hepatic portal vein):

A

helps maintain blood glucose homeostasis

involved in fat metabolism, storage and transport of lipids

synthesizes cholesterol and lipoproteins

stores some vitamins

produces plasma proteins

47
Q

The liver cleans and Detoxifies blood:

A

converts ammonia to urea

metabolizes alcohol, drugs, medications, hormones

processes bilirubin

secretes bile pigments

48
Q

Liver lobule =

A

Structural and functional unit

49
Q

Hepatocytes

A

(liver cells)

Produce and secrete bile

Process nutrients (store glucose, use amino acids to make plasma proteins)

Store fat soluble vitamins

Detoxification of blood

50
Q

Portal triad : 3 structures

A

Branch of hepatic artery (oxygen-rich arterial blood)

Branch of (hepatic) portal vein (oxygen-low, nutrient-rich blood)

Bile duct

51
Q

Sinusoids =

A

“leaky” capillaries between rows of hepatocytes; contain macrophages

52
Q

_____ carries blood away from lobule toward inferior vena cava

A

Central vein

53
Q

_________ bring blood to the liver

A

Portal vein and Hepatic artery

54
Q

Blood from digestive organs of the abdominal cavity (especially intestines) drains into ______

A

portal venous system

55
Q

Portal vein brings ______ to liver for processing by hepatocytes

A

nutrient-rich, (but low oxygen) venous blood

56
Q

Blood leaving liver through hepatic vein joins ______ feeding toward heart

A

inferior vena cava

57
Q

Hepatocyte activity

A

1) Arterial and portal blood in sinusoids

2) Hepatocytes extract nutrients

58
Q

Arterial and portal blood in sinusoids =

A

Arterial blood brings oxygen

Portal venous blood brings newly absorbed nutrients from intestines

59
Q

Hepatocytes extract nutrients =

A

Store glucose as glycogen

Build amino acids into proteins and add back into sinusoids

Produce bile and secrete into bile canaliculi which flows into bile duct

60
Q

Bile is produced in the liver and stored in the ____

A

gallbladder

61
Q

Bile produced by liver hepatocytes:

A

Green, alkaline solution

Contains :
Bile salts (derived from cholesterol)

Bilirubin (waste product of heme breakdown from red blood cells)

Phospholipids

Cholesterol

62
Q

Bile flows out of liver though ___

A

bile duct toward small intestine

63
Q

Excess bile backs up in bile duct and through cystic duct into gall bladder =

A

Bile is released under influence of hormones from enteroendocrine cells in the small intestine

64
Q

Gallbladder stores and _____

A

concentrates bile (removes water)

65
Q

In small intestine, bile will be used to emulsify fats =

A

Aids in digestion and absorption of fats in small intestine

66
Q

Digestive enzymes and bicarbonate are produced by the _____ portion of the pancreas

A

exocrine

67
Q

Exocrine pancreas:

A

Pancreatic acini and ducts form exocrine portion of pancreas and secrete digestive enzymes and pancreatic juice

68
Q

Endocrine pancreas:

A

Pancreatic islets secrete hormones (insulin & glucagon) that enter the blood and regulate blood glucose

69
Q

The pancreas produces _____

A

pancreatic juice
= digestive enzymes and bicarbonate

70
Q

Acini

A

clusters of secretory acinar cells

71
Q

Acini secretes digestive enzymes into ducts:

A

Proteases (digest proteins)
Amylase (digest starch)
Lipases (digest fats)
Nucleases (digest nucleic acids)

72
Q

Most digestive enzymes are released in their inactive forms _____ and will be activated in small intestine

A

(zymogens)

73
Q

Ducts =

A

Provide transport for acinar cell secretions

Duct cells secrete bicarbonate ion buffer and water to neutralize acidic chyme

74
Q

Bile and Pancreatic juice empty into the ____ via a common duct system

A

duodenum

75
Q

Control of ______, _______and ______ by CCK and secretin hormones released from small intestine enteroendocrine cells

A

gall bladder contraction

digestive enzyme release

hepatopancreatic sphincter

76
Q

The small intestine secretes the digestive hormones _____

A

CCK & Secretin

77
Q

Small intestine enteroendocrine cells secrete hormones into _____

A

portal blood

78
Q

Cholecystokinin (CCK)=

A

release is stimulated byproteins and fats in chyme

79
Q

Secretin =

A

release isstimulated by acidic chyme

80
Q

CCK & Secretin effects on the Pancreas =

A

Cholecystokinin (CCK) causes acinar cells to secrete enzymes into pancreatic ducts

Secretin causes pancreatic duct cells to secrete bicarbonate buffer into duct

81
Q

CCK effects on the Gall Bladder =

A

Cholecystokinin (CCK) causes contraction of smooth muscle in gall bladder wall

82
Q

Secretin =

A

is a weak stimulus for bile production and release from liver

83
Q

Secretin effects on bile production by the Liver =

A

Recycled bile salts in the portal blood strongly stimulate bile production and secretion

84
Q

CCK effects on the Hepatopancreatic sphincter =

A

causes relation of the smooth muscle in the sphincter, allowing bile and pancreatic juice to enter the small intestine

85
Q

____ form from precipitates of bile solutes as the gallbladder concentrates bile

A

Gallstones

86
Q

Gallstones symptoms:

A

pain in upper right or epigastric quadrants, or referred to shoulder

Problematic when caught in cystic duct or common bile duct = can block opening of pancreatic duct and cause pancreatitis

87
Q

Inactive pancreatic digestive enzymes (zymogens) are activated in the _____

A

small intestine

88
Q

___ is an enzyme attached to the apical surface of small intestine epithelial cells (brush border enzyme)

A

Enteropeptidase

89
Q

Enteropeptidase activates trypsinogen to form ____

A

trypsin

Trypsin can then activate the other zymogens

90
Q

Chyme mixes with bile, activated enzymes and buffer in the ____

A

duodenum

Anatomy Exam 3 (11 decks)

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