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WEEK 13 Flashcards

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1
Q

what is the main function of the small intestine

A

digestion and absorption of nutrients

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2
Q

Fill in.
Reduced expression or mistargeting of NHE3 protein
results in _______ in patients with a rare genetic
disorder

A

diarrhea

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3
Q

Fill in.
___________ ________ can inhibit NHE3 mediated Na-H+ exchange, that operates in parallel with Cl-HCO3- exchange, mediated by PAT1

A

Intestinal inflammation

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4
Q

Fill in.
NHE mechanisms mediate ________ _____ ______ in the small intestine

A

electroneutral NaCl absorption

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5
Q

true or false.
NHE expressed in the small intestine are also expressed in the colon.

A

True

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6
Q

fill in.
Electrogenic Na+ absorption is mediated by apical epithelial sodium channels called ______ _____ .

A

ENaC channels

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7
Q

ENaC channels are primarily found in the ______, and ______ but also observed in the ileum.

A

colon ; rectum

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8
Q

ENaC channels are expressed in the ______ _____ .

A

brush border

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9
Q

ENaC channels are strongly _______ by a ________, amiloride

A

inhibited; diuretic

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10
Q

ENaC channels are _________ by the mineralocorticoid hormone, ___________.

A

stimulated; aldosterone

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11
Q

What are three mechanisms utilized by chloride absorption?

A

1-2. electroneutral pathways: Na-H and Cl-HCO3- exchange. this is the main mechanism for chloride absorption

  1. paracellular absorption: passive ; absorbed between cells; This pathway predominates in the small
    intestine
    depends on the transmural potential difference
    and the chloride gradient.
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12
Q

fill in.
a. The products of lipid digestion- __________ and ______ _____ are dissolved in bile _______.

b. Lipid digestion in the _______ and duodenum yields monoglycerides and long chain fatty acids.
Other lipid products in the alimentary canal like phospholipids, cholesterol, and fat-soluble vitamins, along with the lipolysis products, form micelles with bile ______ .

c. Lipids are absorbed in the small intestine via _______

d. Fatty acids, monoglycerides leave micelles →
enter ________ cells → _________ formation → __________ formation → chylomicron enter ______ → ________

A

a. monoglycerides; fatty acids ; micelles

b. stomach ; salts

c. diffusion

d. epithelial ; triglyceride ; chylomicron ; lacteals ; lymphatics (enter blood vessel)

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13
Q

Fill in.
The three products of carbohydrate digestion are glucose, ________, and ________. The absorption of these sugars is a _____ – stage process

A

galactose; fructose; two

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14
Q

Fill in.
A. On the ______ membrane SGLT1 is a Na- dependent glucose and ______ transporter.

B. The transporter is expressed at the brush border of _________ in the small intestine. It transports sodium and glucose at a _:1 ratio. This transporter relies upon the Na-K ATPase to maintain the Na-gradient

C. Inhibition of the Na-K ATPase reduces glucose and
galactose absorption. Each cycle of the SGLT-1 transporter brings _____ _____ molecules with every molecule of glucose accounting for roughly ____ L of water absorption per day

D. This is the molecular basis of oral rehydration therapy used to treat ______ and other diarrheal diseases

E. GLUT5 is responsible for the apical absorption of ________ via _______ diffusion

F. Excess glucose, Fructose and galactose is transported out of the basolateral membrane using _______

A

A. Apical ; galactose ;

B. enterocytes; 2

C. 260 water ; 5

d. cholera

E. fructose ; facilitated

F. GLUT2

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15
Q

True of false.
The movement of glucose through this transporter will depend only on the relative concentrations of the sugar inside and outside the cell.

A

True.

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16
Q

True or false.
GLUT2, is a ________ sugar transporter.

A

facilitated

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17
Q

True of false.

The intestine is only capable of transporting single amino acids

A

False.
The intestine is capable of transporting not only
single amino acids, but also short oligomers,
encompassing di-, tri-, and perhaps even
tetrapeptides.

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18
Q

Fill in.
Amino acid transport utilizes Na+, ___ , ___, and ___ as it’s transport partners

A

K+, H+, Cl-

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19
Q

How do amino acid-Na+ coupled transporters differ

A
  • in their transport partners (Na+, K+, H+, Cl-)
  • whether they are electroneutral or electrogenic
  • In specificity for different classes of amino acids
  • Multiple brush border transport systems for amino acids depend on Na+ either directly or indirectly
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20
Q

true or false.
Dipeptides and tripeptides are inefficiently absorbed in the small intestine.

A

False. they are efficiently absorbed.

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21
Q

Fill in.
The transport of di- and tripeptides is ________ dependent on Na+ because:
1. Na+ is needed to drive the Na+/H+ exchanger (NHE3)
2. NHE3 generates a _______ gradient.
3. A proton gradient is needed for H+/peptide transport
4. In this way the absorption of Na+ is coupled to the absorption of another H+ important nutrient amino acids and ______.

PEPT1 ( peptide transporter-1) mediates proton-coupled uptake of a broad variety of peptides.
Its activity is coupled to the activity of the ______. It has an extremely ______ substrate specificity. It can transport peptides of various sizes (di-, tri-, tetra-peptides) and charges.

A

indirectly ; proton ; peptides ; NHE3 ; broad

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22
Q

True or false.
Cystolic digestion occurs during the transport of peptides

A

true.

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23
Q

Fill in.
Basolateral amino acid transport systems are organized into _______ transport systems based on amino acid characteristics.

A

six ;

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24
Q

The basolateral membrane can operate in both directions depending on what?

A
  1. the luminal amino acid concentration
  2. cellular demand
  3. electrogenic driving forces
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25
Fill in. Water soluble vitamins use a ___________ mechanism for absorption in the ______. This includes B vitamins, Vitamin ___, Folic acid , _______ acid, and ______ acid
Na-cotransport ; ileum; C ; Nicotinic ; Pantothenic
26
True or false. B12 is found in animal products
true.
27
Fill in. B12 is bound to _______ protein. ______ and the acidic pH liberate B12 from food proteins. In the stomach, B12 binds to a carrier protein _________ , which protects B12 from _______. In the small intestine, _______ degrades haptocorrin, releasing B12. Free B12 binds to ______ intrinsic factor protects B12 from degradation. Absorption into intestinal enterocytes is a ________ mediated process. B12-IF complex is internalized and sent to _________ where intrinsic factor is degraded. The released B12 is exported from the basolateral membrane by the _______ ________ _______ protein-1 (MRP1). B12 deficiency results in ________ anemia.
dietary; Pepsin ; haptocorrin ; degradation ; trypsin ; gastric ; receptor; lysosomes ; multi-drug resistant associated ; megaloblastic
28
Fill in. The small intestine extends from the _____ ______ to the ileocecal valve
pyloric sphincter
29
From proximal to distal, the small intestine is divided into which three regions?
- duodenum, jejunum and ileum
30
Small intestine is made of what kind of cells?
- Simple columnar epithelial cells, absorptive cells called enterocytes, and a small amount of goblet cells
31
What are the mucosa adaptations that expand the surface area of the small intestine?
- Plicae circulares are microscopic folds of the mucosa and submucosa, and they circle the intestine. They are more organized than Rugae - Villi are microscopic, fingerlike projections of the mucosa. They are covered in simple, columnar, epithelium, and extend up from the mucosa. - Micro villi are tiny cytoplasmic extensions on the apical surface of epithelial cells.
32
What are the invaginations surrounding and between villi in the small intestine?
- Crypts of lieberkuhn
33
Where do the stem cells that give rise to both crypt and villus epithelial cells reside?
- Toward the base of the Crypts
34
Defined the brush border.
- Found on the membrane of microvilli (small intestine) - Made of a dense glycocalyx - Protect the cells from digestive enzymes
35
What do brush border hydrolases do?
- Perform the final steps of digestion for specific nutrients
36
What type of cells do the crypts contain?
- Enterocytes which are simple columnar epithelial cells with microvilli that are specialized for absorption. - Goblet cells that secrete mucus - Enteroendocrine cells. They are different from stem cells and are specialized for secretion of hormones. This includes: - Enterochromaffin cells that secrete serotonin, - D cells found in the duodenum that secretes somatostatin, - I cells found in the duodenum, and jejunum that secrete cholecystokinin, - S- cells in the duodenum and jejunum that secrete secretin. - Paneth cells found at the base of the intestinal glands and have a highly granular appearance. These granules contain several anti-microbial compounds like defensins and lysozyme.
37
Where are Brunners glands typically found?
- In the submucosa of the proximal duodenum. This is where the duodenum is exposed to acid.
38
Brunners glands are unique to what type of animals?
- Placental mammals
39
Describe Breuners glands.
- The glands are made of mucin-secreting cuboidal to columnar cells, arranged on lobules - Secretion from Brunners glands contributes to a layer of mucus - The mucous layer protects delicate epithelial surface that first encounter gastric chyme and pancreatic juice. - Brunners Glands raise the ph luminal contents and provide an immunological defense.
40
What stimulates Brunner’s gland secretion?
- Tactile irritating stimuli of the duodenal mucosa - Vagal stimulation - Secretin
41
What decreases secretion from brunner’s glands?
- Sympathetic activity - Prolonged, sympathetic activity, makes mucosa vulnerable to acid chyme
42
In the small intestine, how is fluid absorbed?
- Fluid absorption is driven by coupled transport of nutrients - Between meals, for the reuptake is driven exclusively by the movement of electrolytes
43
In the small intestine, how was fluid secretion accomplished?
- Fluid secretion is driven by the active transport of chloride ions into the lumen through the CFTR channel
44
Describe the CFTR channel.
- Stands for cystic fibrosis transmembrane regulator protein - CFTR is a cAMP- regulated anion channel highly expressed in the small intestine mucosa - CFTR mediates secretion of chloride, bicarbonate and fluid - Chloride secretion establishes an electrical driving force that makes the lumen negative. This driving force is for trans-epithelial sodium secretion via the paracellular pathways. - The movement of sodium and chloride into Luminal compartment generates the osmotic driving force for water flow producing an isotonic secretory product.
45
What are the three molecular requirements for chloride secretion into the lumen of the small intestine? Where must they be located?
- Sodium potassium ATPase - Basolateral potassium channels - NKCC1 transporter - on the basolateral membrane of epithelial cells
46
What does a Basolateral potassium channel in the small intestine do?
- Set the membrane potential - Recycle the potassium brought in by the sodium potassium ATPase - Activate the same cAMP/Pk-A pathway that activate CFTR
47
What does the NKCC1 transporter do?
- Mediates the Basolateral influx of chloride - Import one sodium and potassium and 2 chlorides per cycle - The rate of chloride entry, through this transporter determines the overall rate of chloride secretion
48
True or false. the small intestine enterocytes produces digestive enzymes found at the brush border .
- True
49
What does isoMaltase do?
- It is an enzyme that breaks isomaltase down
50
What is the most important mechanism for regulating the secretions of the small intestine?
- Local enteric reflexes
51
What does intestinal lipase do?
- Breaks neutral fats into glycerol and fatty acids
52
The chemical digestion in the small intestine relies on what three accessory digestive organs?
- Liver - Gall bladder - Pancreas
53
What is the exocrine portion of the pancreas made of? what is the endocrine portion of the pancreas made of?
- exocrine pancreas: acinar and duct tissue - Endocrine pancreas: islets of langerhans
54
what does the liver do? What does the gallbladder do? What does the pancreas do?
- liver: produces bile - Gallbladder: stores, concentrates, and releases bile - Pancreas: produces pancreatic juice, which contains digestive enzymes, and bicarbonate ions
55
What do acinar cells do?
- Synthesize store and secrete digestive enzymes - They have a very high protein synthesis rate. Due to the highly developed ER combined with the mechanisms to modify and transport, newly synthesize proteins through the secretory pathway
56
What are digestive enzyme stored as in acinar cells?
- zymogen granules, inactive form
57
What is the ER in the acinar cells used for?
- Major storage of intracellular calcium - Calcium mediates secretion of stored digestive enzymes into the pancreatic ductal system.
58
How is how much in granules released from acinar cells when they are stimulated?
-Through exocytosis
59
What prevents leakage of digestive enzymes out of the ducts in small intestine?
- tight junctions between acinar cells
60
How are acinar cells coupled?
- Through gap junctions
61
What is needed to trigger exocytosis in acinar cells?
- An increase in intracellular calcium
62
Where is secretin made?
- s cells in duodenum, in the crypts of lieberkuhn
63
What effect does secretin have on duct epithelial cells?
- Causes the pancreas to secrete large quantities of fluid with a high bicarbonate concentration
64
What accounts for the majority of the total secretion of pancreatic digestive enzymes?
- CCK
65
Describe the absorb, nutrient phase in the pancreatic secretions?
- Directly stimulate pancreatic acinar cells - Activate hormonal in neural pathways
66
What is in a portal triad?
- Hepatic portal vein - Hepatic artery - Bile duct
67
What is a functional unit of the liver?
- Lobule
68
Describe what the liver does
- Important in digestion and metabolism - Stores, glycogen, fat-soluble vitamins, iron and copper - handles cholesterol homeostasis - Responsible for a plasma, proteins synthesis, which is important in maintaining plasma osmotic pressure - Involved in heme breakdown ( bilirubin) - Involved in detoxification of drugs
69
Describe blood flow in a lobule of the liver.
- Hepatic portal vein to hepatic artery to sinusoids to Central vein to hepatic vein to the inferior vena cava
70
What are the cells of the liver that produce bile?
- Hepatocytes
71
What is bile composed of?
-Water, electrolytes, bio salt, bile acids cholesterol, bio pigment, bilirubin, and phospholipids
72
Describe the flow of bile secretion.
- hepatocytes to bile canaliculi to smaller ducts to larger ducts to the duodenum or stored in the gallbladder
73
What does epithelial cells line the bile duct secrete?
- A Sodium bicarbonate solution. - This is stimulated by secretin
74
What are the roles bio has in digestion?
- emulsify fat - Facilitate fat and cholesterol absorption
75
What attaches the gallbladder to the rest of the extrahepatic biliary system?
- Cystic duct
76
The gallbladder is a part of what type of biliary system?
- extrahepatic
77
In regards to an acidic fatty containing chyme enters the duodenum. What does secretin,CCK and ACH do?
- secretin: stimulates the biliary duct to secreate a watery bicarbonate, rich fluid - CCK: the main stimulator. Stimulates the smooth muscle of the gallbladder to contract. and signal sphincter of Oddi to relax. - ACh: produces weak gallbladder contractions
78
What are the different regions the colon is divided into?
- Cecum - Colon: ascending colon, transverse colon, descending colon, sigmoid colon - Rectum and anal canal
79
How long is the large intestines and when does it begin?
- 5 feet long - Begins after the ileocecal valve
80
Fill in. The large intestine processes ________ material after most _______ are removed
- indigestible, nutrients
81
True or false. After a meal is ingested, MMC is immediately interrupted.
- True. The small intestine his enter the Fed pattern or state.
82
What happens when bile emulsifies lipids?
- Increases the surface area available for lipases to break down the lipid
83
Fill in. The ascending colon is the ______ site of _________ water, and any other nutrient.
- primary, absorption
84
What is the primary secretion of the large intestine?
- Mucus from goblet cells
85
Fill in. The descending colon stores _____ until they are emptied into the rectum .
- feces
86
What are the primary functions of the colon?
- Absorb water - Absorbed electrolytes - Produce and absorb vitamins - Form and propel feces forward into the rectum for elimination
87
The large intestine has three unique anatomical features. Name them and describe them.
- Teniae Coli : three longitudinal ribbons of smooth muscle; make up the entire longitudinal muscle layer of the muscularis of the large intestine - Haustra: balloon like pouches; singular = hostrum ; tonic contractions of the teniae coli cause a colon to bunch up into these - Epiploic appendages: attach to the teniae coli; small fat, filled sac to visceral peritoneum; unknown function
88
What is the mucosa in the large intestine made of ?
- Simple, columnar epithelium - Epithelial cells for absorption - Goblet cells
89
What is gut Flora?
- 100 trillion nonpathogenic bacteria found in the large intestine. - Gut flora, turns dietary fiber into short chain fatty acids that can be absorbed. Via fermentation. This is food for the bacteria in the gut - It is responsible for the synthesis of vitamin K - It competes with pathogenic strains of bacteria - It educates the host immune system
90
What are the two types of movement in the large intestine?
- haustral contractions - Mass movements. Aka high amplitude, propagating contraction.
91
What triggers haustral contractions?
- Chyme in the colon
92
Where do haustral contractions occur?
- primarily in the transverse and descending colons - But does also occur in the sigmoid colon to further concentrate fecal waste
93
How often do haustral contractions occur?
- about 30 minutes throughout the day - Last for 1 min
94
Fill in. Haustral contractions help in the absorption of _________
- water
95
True or false. Compared to haustral contractions, mass movements in the large intestine are slow.
- False. They are strong waves of contractions and quickly force contents forward
96
Where do mass movement begin in the large intestine?
- Midway through the transverse colon
97
What provokes gastrocolic reflex?
- Distention in the stomach and the breakdown products of digestion in the small intestine
98
Does mechanical digestion occur in the esophagus?
- no. Neither mechanical or chemical digestion occurs in the esophagus
99
True or false. Cellulose is digestible.
- False. It is not cellulose provides no nutritional benefit. It is an important dietary component in the form of fiber.
100
What do maltose, sucrose and lactose all have in common?
- They are all disaccharides, and they all contain glucose.
101
True or false. The average American diet is 50% carbohydrates.
- True
102
What is maltose broken down into?
- 2 glucose
103
What is sucrose broken down into?
- One glucose and one fructose
104
What is lactose broken down into?
- One glucose and one galactose
105
What breaks down starch, and glycogen in the oral cavity?
- Salivary amylase; into dextrins, maltose and maltotriose
106
True or false. the stomach breaks down carbohydrates
- False
107
What breaks down carbohydrates in the small intestine?
- pancreatic amylase; into disaccharides
108
Where do disaccharides get broken down into monosaccharides?
- The brush border of the small intestine. - A lot of glucose to absorb here
109
True or false. 15 to 20% of the average American diet is proteins with another 35 g coming from G.I. secretions .
- true
110
Where does protein digestion begin?
- In the stomach via HCl
111
What function does HCl serve in the stomach for digesting proteins?
- It’s denatures ingested proteins - Activates pepsin
112
What does pepsin do?
- It is an endonuclease - A Cleves internal peptide bonds of aromatic amino acids - Allows the polypeptides to pass into the small intestine to be further broken down
113
What breaks down large polypeptides in the small intestine?
- Trypsin, chymotrypsin, Carboxypeptidase
114
What does trypsin do? What does chymotrypsin do?
- trypsin: Cleves peptides at the carboxyl side of lysine and arginine - Chymotrypsin: Cleves, peptide bonds on the carboxyl side of tyrosine, phenylalanine, tryptophan, leucine
115
What breaks down, short polypeptides and amino acids into amino acids at the brush border?
- Carboxypeptidase- liberates individual amino acids - Amino peptidase- liberates individual amino acids - Dipeptidase- acts on short couplets of amino acids to break into individual amino acids
116
What does carboxypeptidase do?
- Release one amino acid at a time from the carboxyl terminal end of a protein
117
What lipases carryout lipid digestion?
- Lingual lipase - Gastric lipase - Pancreatic lipase
118
What breaks triglycerides down in the oral cavity?
- Lingual lipase
119
What breaks Diacylglycerol, fatty acid, and triglycerides down in the stomach?
- Gastric lipase
120
Fill in. Lingual and gastric lipases are considered ______ lipases
- acidic
121
True or false. Lingual lipase, swallowed with food remains active for a time in the stomach.
- true
122
True or false. both lingual and gastric lipases break individual fatty acids off, the ingested triglycerides.
- true
123
Fill in. Lingual and gastric lipases make minor contribution to lipid digestion in adults but I’m much more important in ______ .
- infants
124
How does bile aid, pancreatic lipase in the small intestine?
- Increases the available surface area available for pancreatic lipase to work
125
Describe pancreatic lipase.
- Eight digest triglycerides into their components - Such as monoglycerides, glycerol, fatty acids - Found in the lumen of the small intestine
126
Fill in. Plant and animal tissue we consume contains ________ _____.
- nucleic acids ( DNA and RNA)
127
Where does nucleic acid digestion begin?
- Lumen of the small intestines
128
What breaks DNA down into nucleotides in the small intestine?
- Pancreatic nucleuses: deoxyribonuclease, ribonuclease
129
What is a nucleotide?
- A phosphate, a sugar (ribose or deoxyribose), and a base
130
What breaks nucleotides down into nucleosides?
- Nucleotidases - Brush border of small intestine
131
What breaks nucleosides into nitrogenous bases, sugars, and phosphates?
- Nucleosidases and phosphatases
132
Where does carbohydrate and protein absorption take place specifically in the small intestine ?
- The jejunum
133
Where are bile salts and vitamin B 12 absorbed in the small intestine?
- The distal ileum
134
Where are the majority of electrolytes in water, absorbed in the alimentary canal?
- The small Intestine
135
What does the apical absorption of sodium depend on?
- Sodium- dependent nutrient transporters; like sugar or amino acid transporters - Sodium-proton exchangers; this mediates the electroneutral NaCl absorption - Na+ channels; this mediates colon-predominant electrogenic Na+ absorption
136
Disruptions in electrolyte concentration of the aluminal contents will lead to passive movement of water, which can cause what?
- Diarrhea or constipation
137
fill in. Studies suggests that _____ is primarily responsible for sodium and water absorption.
- NHE3
138
True or false. Three NHE I saw forms have been identified in enterocyte apical membranes
- true. They are NHE2 , NHE3 , NHE8
139
Fill in. Missense mutations in the gene encoding for NHE3 result in _____ ______ ______
- congenital sodium diarrhea

advanced human physiology (13 decks)

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