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BMS150 - Post Test 2 > Small Intestine Anatomy & Physiology (Week 11) > Flashcards

Small Intestine Anatomy & Physiology (Week 11) Flashcards

1
Q

What are the three regions of the small intestine?

A

1) duodenum
2) jejunum
3) ileum

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2
Q

shortest and widest part of the small intestine, C-shaped, and closely associated with the head of the pancreas

A

duodenum

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3
Q

length of duodenum

A

~ 25cm

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4
Q

length of jejunum

A

~ 1m

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5
Q

length of ileum

A

~ 2m

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6
Q

True or False: The vast majority of the duodenum is retroperitoneal (behind the peritoneum)

A

True

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7
Q

The jejunum has larger circular folds called ______________

A

plicae circulares

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8
Q

The ileum has many large lymphoid nodules called ________________

A

Peyer’s patches

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9
Q

The first 2/3 of the duodenum is supplied by the ___________ artery off the celiac trunk

A

hepatic

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10
Q

The hepatic artery branches into the __________ and __________

A

gastroduodenal artery,

anterior superior pancreaticoduodenal artery

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11
Q

The superior mesenteric artery (SMA) branches into the _____________

A

inferior pancreaticoduodenal artery

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12
Q

The pancreas and duodenum receive arterial blood from both the ________ and _________

A

hepatic artery,

superor mesenteric artery (SMA)

Note: “from the top it’s from the hepatic artery and from the bottom it’s from the mesenteric artery”

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13
Q

The last 1/3 of the duodenum to the ileum + first part of the large intestine up until the transverse/descending colon receives arterial blood from the ________________

A

superior mesenteric artery

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14
Q

The superior mesenteric vein receives venous blood from?

A
  • small intestine
  • portions of the large intestine
  • stomach
  • pancreas
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15
Q

The splenic vein receives blood from?

A
  • stomach
  • spleen
  • pancreas
  • distal large intestine
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16
Q

The superior mesenteric vein and splenic vein join together to form the _____________, which drains almost all subdiaphragmatic fore-, mid-, and hindgut structures

A

hepatic portein vein

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17
Q

The hepatic portal vein drains into the __________

A

liver

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18
Q

Folds of mucosa and submucosa, characterized by permanent ridges about 10 mm tall that project into the lumen, encourages mixing, and enhances absorption by increasing surface area

A

plica circulares

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19
Q

Finger-like projections of mucosa that are 0.5-1mm long and vastly increase surface area of epithelium

A

villi

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20
Q

projections of apical membrane of absorptive cell that are 1 um long (super small), cylindrical, contain 20-30 actin filaments, and greatly increase surface area

A

microvilli

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21
Q

What type of cell of the small intestine can be characterized as simple columnar epithelium with microvilli and a short life span (~ a few days)?

A

surface absorptive cell/enterocytes

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22
Q

What type of cell of the small intestine can be characterized as:

  • scattered among the absorptive cells
  • specialized in mucus secretion
  • facilitates passage of material through bowel
A

goblet cell

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23
Q

What type of cell of the small intestine can be characterized as:

  • typical serous-secretory appearance, with basophilic basal cytoplasm and apical secretory vesicles
  • basal portion of the intestinal crypts, below the stem cells, release lyzosyme, phospholipase A2, and defensins (note: these are all immunoproteins)
  • regulate the microenvironment of the intestinal crypts and innate immune response
A

paneth cell

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24
Q

What type of cells in the small intestine secrete hormones?

A

1) enteroendocrine cells
2) mucosal cells

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25
Q

What do the following enteroendocrine cells in the small intestine secrete?

I cells:
S cells:
D cells:
K cells:
L cells:
Mo cells:

A

I cells: cholecystokinin
S cells: secretin
D cells: somatostatin
K cells: GIP
L cells: peptide YY, incretins
Mo cells: motilin

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26
Q

What do mucosal cells in the small intestine secrete

A

incretins (similar to L cells)

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27
Q

What is the main hormonal function of somatostatin?

Review: somatostatin is released by D cells

A

“turns down” the release of hormones from nearby cells

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28
Q

What is the main hormonal function of histamine?

A

If released from ECL –> stimulates acid secretion

If released from EC –> increased motility

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29
Q

What is the main hormonal function of gastrin?

Review: gastrin is secreted by G cells in the stomach (not small intestine)

A

increases secretion of stomach acid

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30
Q

What is the main hormonal function(s) of CCK (cholecystokinin)?

A
  • pancreatic enzyme secretion*
  • gallbladder contraction*
  • satiety
  • inhibits acid secretion
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31
Q

What is the main hormonal function of peptide YY?

A
  • inhibits gastric secretion
  • slows gastric emptying/motility
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32
Q

What is the main hormonal function of motilin?

A

migrating motor complex (stimulates contractions between meals)

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33
Q

What is the main hormonal function of secretin?

A
  • bicarbonate and water secretion from pancreas
  • inhibits gastric acid secretion
  • slow gastric emptying
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34
Q

Stretch from chyme against intestinal wall elicits ______________ (local reflex)

A

concentric contractions

note: this is NOT the same as peristalsis

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35
Q

Concentric contractions in the small intestine are spaced 1 to 5cm and cause ___________

A

segmentation

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36
Q

Chyme propelled through the small intestine by propulsive waves that move towards the ansu is known as ____________

A

peristalsis

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37
Q

a powerful wave of contractile activity that travels long distances down the small intestine and is caused by intense irritation or unusual distension

A

peristaltic rush

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38
Q

distension in the alimentary canal causes distal parts of the canal to relax and proximal parts to contract (circular muscle)

A

“law of the gut”

Note: peristaltic reflex/”law of the gut” is mediated by the enteric nervous system (ENS) and various hormones

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39
Q

The hormones that enhance peristalsis include:

A
  • gastrin
  • CCK
  • serotonin
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40
Q

The hormones that inhibit peristalsis include:

A
  • secretin
  • peptide YY
  • epinephrine
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41
Q

What are some requirements for chyme to enter the duodenum?

A
  • food particles must be very small (<2mm)
  • small volumes of low pH fluid (large volumes of low pH/acidic fluid = damaging)
  • gradual release (to allow absorption and chemical digestion)
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42
Q

The _____________ is the major organ that regulates rates of gastric emptying

A

duodenum

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43
Q

Both the sympathetic nervous system (@ spinal cord) and the enteric nervous system (submucosal and myenteric plexuses) will INHIBIT gastric emptying in response to what?

A
  • increased or decreased osmolarity in the duodenum
  • decreased pH (increased acidity) in the duodenum
  • distention or any chemical irritation of the duodenum
  • breakdown productions of proteins and fats (mostly proteins) in the duodenum
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44
Q

True or False: CCK is secreted in the small intestine, but mostly in the ileum

A

False

Mostly in the duodenum

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45
Q

What substances elicit CCK release?

A

FATS** > peptides > carbs

46
Q

True or False: Secretin is secreted throughout both the duodenum and jejunum

A

True

47
Q

What substances elicit secretin release?

A

low pH > fats, capsaicin, bile acids

48
Q

a major hormone that performs the role of the “ileal brake”, secreted by L cells in the distal small intestine (ileum)

A

peptide YY

49
Q

What substances elicit peptide YY release?

A

FATS > carbs, amino acids

50
Q

True or False: If undigested food reaches the distal small intestine (ileum), then peptide YY “slows everything down”

A

True

51
Q

What is an oleate meal?

A

A meal that is high in fat

52
Q

True or False: Compared to acidic and saline meals, oleate meals tend to increase the rate of gastric emptying.

A

False

Oleate (fatty) meals tend to slow gastric emptying, whereby there is more food remaining in the stomach after a period of time, compared to an acidic and saline meals.

53
Q

The _______________ valve forcefully closes when excess pressure builds up in the cecum

A

ileocecal

54
Q

True or False: The ileocecal sphincter usually remains mildy constricted

A

True

55
Q

Digestive juices (which includes large quantities of water and electrolytes) are secreted by _____________ at a rate of about _____________ mL/day

A

enterocytes,

1800mL/day (1.8L)

56
Q

True or False: intestinal juices have a pH of 7.5-8.0 and are a little more alkaline that ECF, due to the presence of more bicarbonate

A

True

57
Q

The ________________ are found proximal to the sphincter of Oddi and secrete alkaline mucous in response to:

  • tactile stimuli or irritating stimuli of the overlying mucosa
  • vagal stimulation
  • GI hormones (esp. secretin)
A

Brunner’s Glands

Note: vagal stimulation can both increase acidic secretion in the stomach and alkaline mucous in the small intestine

58
Q

What is the function of Brunner’s Glands?

A

protect duodenal wall from digestion by gastric juice

59
Q

Brunner’s Glands are inhibited by ______________ (parasympathetic/sympathetic) stimulation

A

sympathetic

60
Q

Chyme arrives in the duodenum via the ________ sphincter

A

pyloric

61
Q

function of bile

A

emulsification of lipids

62
Q

function of pancreatic enzymes

A

the hydrolysis of fats, proteins, and carbohydrates into smaller molecules

63
Q

bile is secreted by the liver by the right and left _______________

A

hepatic ducts

64
Q

the right and left hepatic ducts join to form the ___________________

A

common hepatic duct

65
Q

the common bile duct is formed at the junction of the ___________ and _____________

A

cystic duct and common hepatic duct

66
Q

the sphincter of Oddi regulates the release of bile into the _________ from the ampulla of Vater

A

duodenum

67
Q

If the sphincter of Oddi is closed, then the bile is stored in the _____________

A

gallbladder

68
Q

The main pancreatic duct meets the common bile duct at the __________

A

ampulla of Vater

69
Q

True or False: The sphincter of Oddi regulates biliary secretions but not pancreatic secretions into the duodenum

A

False

The sphincter of Oddi regulate both biliary and pancreatic secretions into the duodenum

70
Q

Enterokinase activates/cleaves trypsinogen to ____________

A

trypsin

71
Q

Trypsin activates/cleaves:

chymotrypsinogen –> ?

proelastase –> ?

procarboxypeptidase –> ?

A

chymotrypsinogen –> chymotrypsin

proelastase –> elastase

procarboxypeptidase –> carboxypeptidase

Note: these are all enzymes relevant to PROTEIN digestion

72
Q

What is the function of pancreatic amylase?

A

carbohydrate digestion (digests starch in particular)

73
Q

What enzymes are used for lipid digestion?

A
  • pancreatic lipase/co-lipase
  • phospholipase A2
74
Q

enzymes break macronutrients down into smaller and smaller particles through the process of hydrolysis

A

enzyme digestion

Note: all pancreatic, gastric, and brush border enzymes use hydrolysis as a means of breaking a macromolecule into smaller molecules

75
Q

Food is first mixed with saliva in the mouth, which contains the enzyme __________ secreted mainly by the parotid glands

A

ptyalin (alpha-amylase or salivary amylase)

76
Q

Pyalin hydrolyzes ___________ into the disaccharide maltose and other small polymers of glucose (3-9 glucose molecules, aka oligosaccharides)

A

starch

77
Q

What blocks the activity of ptyalin?

A

the acid of gastric secretions (pH <4)

we’re swallowing our saliva as we eat, so once it reaches the stomach, that’s when it stops working (because it’s too acidic in the stomach)

78
Q

What enzyme do we use for digestion of carbohydrates in the small intestine?

A

pancreatic amylase

Note: like salivary amylase, but “much much more powerful”… “the most important enzyme for digestion of starches”

79
Q

What are the three major enzymes that digest (hydrolyze) the major disaccharide sugars in our diet?

A

1) lactase
2) maltase (isomaltase)
3) sucrase

80
Q

glucose + galactose = ?

A

lactose

81
Q

glucose + glucose = ?

A

maltose

82
Q

fructose + glucose = ?

A

sucrose

83
Q

Pepsin is most active between pH _________

A

1.5-3.5

84
Q

True or False: In the mouth, there is only mechanical digestion of protein and no enzymatic digestion

A

True

85
Q

True or False: In the stomach, HCL denatures protein but is not involved in hydrolysis

A

True

Note: denaturation improves the “exposure” of peptide bonds to digestive enzymes

86
Q

Where does most protein digestion occur?

A

duodenum and upper jejunum

87
Q

Upon entering the small intestine, polypeptides (protein) are attacked by the following enzymes: trypsin, chymotrypsin, carboxypolypeptidases, and proelastase

Which of these four enzymes activates the others?

A

trypsin

88
Q

33% of protein is absorbed as ___________ and 67% is absorbed as ____________

A

free amino acids,

peptides

89
Q

Why is the digestion of fats challenging?

A

not very water soluble (therefore tends to accumulate in large droplets) –> reduces surface area –> poor water solubility –> impairs the process of chemical digestion and absorption

90
Q

How do we improve the digestion of fats?

A

emulsify the fat droplets into very small droplets that have an amphipathic molecule on the outside (formation of micelles)

Note: this increases surface area which improves interaction with water

91
Q

________ contains a variety of amphipathic molecules that help with the formation of micelles…

  • lecithins
  • bile salts
  • cholesterol
A

Bile

92
Q

Outside of the micelle is ____________ (hydrophobic/hydrophilic)

A

hydrophilic

93
Q

Inside the micelle is _____________ (hydrophobic/hydrophilic)

A

hydrophobic

94
Q

Once micelles have been formed, _____________ acts on the triglycerides inside the micelle

A

pancreatic lipase

95
Q

True or False: Pancreatic lipase works alone to digest lipids

A

False

Usually requires colipase to help it insert into the micelle and activate it

96
Q

What does pancreatic lipase break triglycerides into?

A

2 free fatty acids and 2-monoacyl glycerol

97
Q

When free fatty acids and 2-monoacyl glycerol diffuse across the brush border of the enterocyte, they reassemble into _______________

A

triglycerides

98
Q

Phospholipase works similar to pancreatic lipase, except it breaks down _____________ into fatty acids and other components

A

phospholipids

99
Q

After triglycerides are reassembled into the enterocyte, they are inserted into ________________

A

chylomicrons

100
Q

a spherical lipoprotein, with a phospholipid bilayer and proteins on the outside and that absorbs triglycerides and cholesterol in the inside

A

chylomicron

Note: chylomicrons are necessary for transporting triglycerides and cholesterol esters (big molecules) throughout our circulation

101
Q

Chylomicrons are secreted into the ____________ and eventually transported into the _____________, to join the venous blood

A

lymphatic vessels,

thoracic duct

102
Q

True or False: Carbohydrates, amino acids, and small free fatty acids can diffuse across the basement membrane of the enterocyte, into the capillary loops within the villus, but larger lipids need to be carried by chylomicrons, which enter via openings of the lacteals (lymphatic capillaries within the villi)

A

True

103
Q

When absorption at the small intestine is unsuccessful, nutreints remain int he lumen of the intestine, potentially leading to what?

A
  • diarrhea
  • micronutrient and macronutrient deficiencies
104
Q

What are four major malabsorption problems that can occur?

A

1) disturbances in intraluminal digestion
2) disturbances in terminal digestion
3) disturbances in transepithelial transport
4) disturbances in lymphatic transport

105
Q

when enzymes/bile secreted into the lumen are inadequate for the near-complete breakdown of proteins, carbs, or fats

A

disturbances in intraluminal digestion

106
Q

when the brush border enzymes cannot break down small peptides or disaccharides

A

disturbances in terminal digestion

107
Q

when nutrient, fluid, and/or electrolyte transport are disordered

A

disturbances in transepithelial transport

108
Q

when lipid transport is impaired

A

disturbances in lymphatic transport

109
Q

pathogenesis of celiac disease

A

damage to the villi and microvilli resulting in loss of surface area and overall absorptive enterocyte function

characterized by disturbances in:
- terminal digestion
- transepithelial transport

110
Q

pathogenesis of chronic pancreatitis

A

lack of major digestive enzymes from the pancreas leads to major impairment in absorption, diarrhea, and nutrient deficiencies

characterized by disturbances in:
- intraluminal digestion

111
Q

pathogenesis of disaccharidase deficiencies (e.g., lactose intolerance)

A

lack of disaccharide [digestion?] results in unabsorbed sugar in the lumen –> results in bacterial gas production and osmotic diarrhea

characterized by disturbances in:
- terminal digestion

112
Q

pathogenesis of gastroenteritis (e.g., bacterial, viral, parasitic)

A

damage to the brush border or dysregulation of electrolyte transport results in impaired ability to absorb nutrients

characterized by disturbances in:
- terminal digestion
- transepithelial transport

BMS150 - Post Test 2 (9 decks)

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