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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
Neuronal & hormonal mechanisms regulate gastric activity in 3 phases
cephalic phase gastric phase intestinal phase
26
Gastric (stomach) activity includes _________
gastric secretions and gastric motility
27
cephalic phase
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
28
gastric phase
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
29
intestinal phase
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
30
______ includes propulsion and mechanical breakdown
Gastric motility
31
Filling of stomach:
relaxation mediated by vagus nerve and stress-relaxation response of smooth muscle
32
__________ (interstitial cells of Cajal) set a constant (~3/min) rate of stomach contraction
Stomach enteric pacemaker cells
33
Factors that enhance gastric secretions also enhance_______ (i.e. stretch of stomach wall and presence of food activate long and short reflexes & gastric secretions)
strength of contractions
34
Fatty, hypertonic, acidic chyme in duodenum ______ and slow emptying
decrease strength of contraction
35
Slow entry of chyme into small intestine is controlled by _______; prevents SI from being overwhelmed.
enterogastric reflex and GI hormones
36
propulsion =
Peristaltic waves move from the fundus toward the pylorus
37
grinding =
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
retropulsion =
the peristaltic wave closes the pyloric valve, forcing most of the contents of the pylorous backward into the stomach
39
The stomach delivers the chyme to the ____
small intestine
40
The _____ is where the most of digestion and absorption occurs
small intestine
41
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.
stomach
42
Most of the substances required for digestion come from accessory organs:
liver, gall bladder, pancreas
43
Liver =
Upper right quadrant 4 anatomical lobes Gall bladder attached to posterior inferior portion
44
Porta hepatis =
“Door” of the liver Important structures enter and leave the liver here
45
Liver Primary digestive function =
produces bile to emulsify fats
46
The liver processes nutrient-rich venous blood from digestive organs (via hepatic portal vein):
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
The liver cleans and Detoxifies blood:
converts ammonia to urea metabolizes alcohol, drugs, medications, hormones processes bilirubin secretes bile pigments
48
Liver lobule =
Structural and functional unit
49
Hepatocytes
(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
Portal triad : 3 structures
Branch of hepatic artery (oxygen-rich arterial blood) Branch of (hepatic) portal vein (oxygen-low, nutrient-rich blood) Bile duct
51
Sinusoids =
“leaky” capillaries between rows of hepatocytes; contain macrophages
52
_____ carries blood away from lobule toward inferior vena cava
Central vein
53
_________ bring blood to the liver
Portal vein and Hepatic artery
54
Blood from digestive organs of the abdominal cavity (especially intestines) drains into ______
portal venous system
55
Portal vein brings ______ to liver for processing by hepatocytes
nutrient-rich, (but low oxygen) venous blood
56
Blood leaving liver through hepatic vein joins ______ feeding toward heart
inferior vena cava
57
Hepatocyte activity
1) Arterial and portal blood in sinusoids 2) Hepatocytes extract nutrients
58
Arterial and portal blood in sinusoids =
Arterial blood brings oxygen Portal venous blood brings newly absorbed nutrients from intestines
59
Hepatocytes extract nutrients =
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
Bile is produced in the liver and stored in the ____
gallbladder
61
Bile produced by liver hepatocytes:
Green, alkaline solution Contains : Bile salts (derived from cholesterol) Bilirubin (waste product of heme breakdown from red blood cells) Phospholipids Cholesterol
62
Bile flows out of liver though ___
bile duct toward small intestine
63
Excess bile backs up in bile duct and through cystic duct into gall bladder =
Bile is released under influence of hormones from enteroendocrine cells in the small intestine
64
Gallbladder stores and _____
concentrates bile (removes water)
65
In small intestine, bile will be used to emulsify fats =
Aids in digestion and absorption of fats in small intestine
66
Digestive enzymes and bicarbonate are produced by the _____ portion of the pancreas
exocrine
67
Exocrine pancreas:
Pancreatic acini and ducts form exocrine portion of pancreas and secrete digestive enzymes and pancreatic juice
68
Endocrine pancreas:
Pancreatic islets secrete hormones (insulin & glucagon) that enter the blood and regulate blood glucose
69
The pancreas produces _____
pancreatic juice = digestive enzymes and bicarbonate
70
Acini
clusters of secretory acinar cells
71
Acini secretes digestive enzymes into ducts:
Proteases (digest proteins) Amylase (digest starch) Lipases (digest fats) Nucleases (digest nucleic acids)
72
Most digestive enzymes are released in their inactive forms _____ and will be activated in small intestine
(zymogens)
73
Ducts =
Provide transport for acinar cell secretions Duct cells secrete bicarbonate ion buffer and water to neutralize acidic chyme
74
Bile and Pancreatic juice empty into the ____ via a common duct system
duodenum
75
Control of ______, _______and ______ by CCK and secretin hormones released from small intestine enteroendocrine cells
gall bladder contraction digestive enzyme release hepatopancreatic sphincter
76
The small intestine secretes the digestive hormones _____
CCK & Secretin
77
Small intestine enteroendocrine cells secrete hormones into _____
portal blood
78
Cholecystokinin (CCK) =
release is stimulated by proteins and fats in chyme
79
Secretin =
release is stimulated by acidic chyme
80
CCK & Secretin effects on the Pancreas =
Cholecystokinin (CCK) causes acinar cells to secrete enzymes into pancreatic ducts Secretin causes pancreatic duct cells to secrete bicarbonate buffer into duct
81
CCK effects on the Gall Bladder =
Cholecystokinin (CCK) causes contraction of smooth muscle in gall bladder wall
82
Secretin =
is a weak stimulus for bile production and release from liver
83
Secretin effects on bile production by the Liver =
Recycled bile salts in the portal blood strongly stimulate bile production and secretion
84
CCK effects on the Hepatopancreatic sphincter =
causes relation of the smooth muscle in the sphincter, allowing bile and pancreatic juice to enter the small intestine
85
____ form from precipitates of bile solutes as the gallbladder concentrates bile
Gallstones
86
Gallstones symptoms:
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
Inactive pancreatic digestive enzymes (zymogens) are activated in the _____
small intestine
88
___ is an enzyme attached to the apical surface of small intestine epithelial cells (brush border enzyme)
Enteropeptidase
89
Enteropeptidase activates trypsinogen to form ____
trypsin Trypsin can then activate the other zymogens
90
Chyme mixes with bile, activated enzymes and buffer in the ____
duodenum

Anatomy Exam 3 (11 decks)

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