Gastrointestinal

Question 1

Where do parasympathetic nerves to the GI tract have their first extracranial synapse? What are the neurotransmitters and receptors at this synapse?

Answer 1

In gangion surrounding the gut; Ach on nicotinic Ach receptors

Question 2

Where do sympathetic fibers to the GI tract first synapse?

Answer 2

In prevertebral ganglion

Question 3

What is the neurotransmitter at the postganglionic synapse for sympathetic innervation of the gut?

Answer 3

Norepinephrine

Question 4

Which layer of the GI tract contains the ganglia that hold the first synapses for parasympathetic fibers coming from the brain?

Answer 4

Auerbach’s plexuses in the muscularis externa

Question 5

Does the enteric nervous system have more or fewer neurons than the spinal cord?

Answer 5

Many more

Question 6

Which plexuses contain the cell bodies of the enteric nervous system?

Answer 6

Meissner’s plexuses (submucosal)

Question 7

What effect does nitric oxide have on the GI tract?

Answer 7

Sphincter relaxation

Question 8

For each of the following, do they act mostly as hormones or neuropeptides in the GI tract?– Gastrin– Secretin– Gastrin-releasing peptide (GRP)– GIP– Glucagon, GLP-1, GLP-2– VIP– Motilin

Answer 8

– Gastrin: hormone– Secretin: hormone– Gastrin-releasing peptide (GRP): neuropeptide– GIP: hormone– Glucagon, GLP-1, GLP-2: hormone– VIP: neuropeptide– Motilin: hormone

Question 9

For each of the following, do they act mostly as hormones or neuropeptides in the GI tract?– Substance P; tachykinins– Pancreatic polypeptide– Peptide YY– Ghrelin

Answer 9

– Substance P; tachykinins: neuropeptides– Pancreatic polypeptide: hormone– Peptide YY: hormone– Ghrelin: hormone

Question 10

Are G-cells in the proximal or distal part of the stomach?

Answer 10

Distal

Question 11

What receptor does gastrin bind to?

Answer 11

CCK receptor-B

Question 12

How is gastrin release inhibited? What cells release this modulator?

Answer 12

By somatostatin released from D cells

Question 13

What three regulators will stimulate acid production by the parietal cell?

Answer 13

Gastrin, histamine, and Ach

Question 14

What does the prefix cholecysto- refer to?

Answer 14

Gall bladder

Question 15

Cholecystokinin stimulates contaction of what organ, and secretion of what enzymes?

Answer 15

Gallbladder contraction; pancreatic enyme secretion

Question 16

Both secretin and CCK induce secretion of what ion?

Answer 16

Bicarbonate: HCO3-

Question 17

Both secretin and somatostatin inhibit release of what hormone that acts on the stomach?

Answer 17

Gastrin

Question 18

What are the major actions of vasoactive intestinal peptide (VIP)?

Answer 18

Epithelial cell secretion and smooth muscle relaxation (in the sphincter of Oddi)

Question 19

What are the three effects of the tachykinin Gastrin Releasing Peptide (GRP)?

Answer 19

Mediates of the vagal release of gastrin, stimulates pancreatic secretion, and increases GI motility

Question 20

What antibiotic is an agonist for motilin? What side effect does this cause?

Answer 20

Erythromycin; overactive gut

Question 21

Where is ghrelin made? What is its principle effect?

Answer 21

In the fundus of the stomach; it increases food intake

Question 22

What stimulates the release of somatostatin? What inhibits its release?

Answer 22

Gastric acid in the lumen; inhibited by high luminal pH

Question 23

What are ECL cells in the gut? What do they release to promote gastric acid release?

Answer 23

They are a type of neuroendocrine cell found in the gastric glands of the gastric mucosa beneath the epithelium in the vicinity of parietal cells. They release histamine in response to gastrin.

Question 24

Saliva contains what major ion? What is its principal function in the distal esophagus?

Answer 24

Bicarbonate; neutralizes gastric acid to protect distal esophagus

Question 25

What two digestive enzymes is saliva rich in?

Answer 25

Salivary amylase and lingual lipase (although this is only significantly active for infants)

Question 26

What is the difference in function between the proximal and distal stomach?

Answer 26

The proximal is primarily a secretion reservoir, while the distal is responsible for mixing and griding.

Question 27

When vagal activity of the stomach increases, what two cell types in the fundic glands are stimulated?

Answer 27

Parietal cells and chief cells

Question 28

Where are chief cells concentrated in the fundic gland?

Answer 28

Primarily toward the interior

Question 29

What enzyme do chief cells secrete?

Answer 29

Pepsinogen

Question 30

What are two classes of drugs that can be used to inhibit the function of parietal cells?

Answer 30

Proton pump inhibitors, acting on the H+/K+ATPase, and H2blockers acting on the histamine receptors

Question 31

What regulatory mechanism is used to activate and deactivate proton pumps in parietal cells?

Answer 31

Sequestering of the membrane-bound pumps into vesicles, and then fusion of these vesicles with the canaliculi on activation

Question 32

Does histamine released by ECL cells in the fundic gland activate chief cells, parietal cells, or both?

Answer 32

Both

Question 33

What hormone inhibits the action of G-cells in the antrum? Which cell type secretes it, and what do those cells secrete it in response to?

Answer 33

Somatostatin; D cells, in response to low pH

Question 34

What neurotransmitter influences ECL cells in the stomach? What other cell type does it affect?

Answer 34

Acetylcholine from vagal stimulation; Parietal cells

Question 35

Pancreatic juice is very alkaline, with lots of bicarbonate; what does this neutralize?

Answer 35

Gastric acid

Question 36

What channels face the luminal side of the pancreatic duct cell?

Answer 36

A Cl-/HCO3-exchanger and a CFTR that passes Cl-ions

Question 37

What hormone influences the activity of the luminal channels of the pancreatic duct cells, along with the HCO3-/Na+symporter?

Answer 37

Secretin

Question 38

Which intracellular messenger is used by secretin stimulation to induce fusion of zymogenic granules in the pancreatic acinar cell?

Answer 38

cAMP

Question 39

What amino acids are conjugated onto primary bile acids in order to get them into bile? Why are they necessary?

Answer 39

Glycine and taurine, which make the bile acid more hydrophilic (bile is watery)

Question 40

Where are primary bile acids reabsorbed?

Answer 40

The terminal ileum

Question 41

Bile acid is comparable to which household cleaning product?

Answer 41

Soap or detergent

Question 42

Bile acids surround fatty acids in spherical structures called…

Answer 42

Micelles

Question 43

Primary and secondary bile salts are mixed with what other components to make bile?

Answer 43

Phospholipids, cholesterol, and a little bit of protein, electrolytes and bilirubin.

Question 44

What hormone controls smooth muscle contraction of the gall bladder?

Answer 44

Cholecystikinin

Question 45

What innervation causes smooth muscle contraction in the bile duct, and what sphincter is relaxed by this innervation using which neurotransmitter?

Answer 45

Vagal innervation releasing Ach causes contraction; NO and VIP released to relax the sphincter of Oddi at the head of the bile tract

Question 46

Besides the muscle or the nerve, where else can the problem in a GI motility order manifest?

Answer 46

The brain-gut axis (signalling)

Question 47

What cells usually produce gas and distension of the bowel tract?

Answer 47

Bacteria

Question 48

There are slow waves of electrical activity in the GI tract; in which part are these waves most frequent?

Answer 48

The small intestine

Question 49

Besides slow waves, what other electrical activity can be propagated through the GI tract?

Answer 49

Spike activity, caused by reaching the threshold for an action potential

Question 50

What function do interstitial cells of Cajal serve in the GI tract?

Answer 50

Electrical pacemakers of slow wave activity

Question 51

What parts of the GI tract are tonically contracted (normally closed or constricted)?

Answer 51

storage organs like the gastric fundus and cecum, and sphincters

Question 52

What does the “intestinal housekeeper” do?

Answer 52

They are waves of peristalsis that flush out the GI tract between meals

Question 53

What is the kind of GI contraction that does not result in a proximal-to-distal gradient called? In which part of the GI tract is this the major contractile process?

Answer 53

Segmentation; the small and large intestine

Question 54

Does peristalsis require contraction, relaxation, or both?

Answer 54

Both

Question 55

Which neurotransmitters are important for peristalsis?

Answer 55

Serotonin (5-HT), acetylcholine, and nitric oxide

Question 56

Where do the retrograde contractions of vomiting begin?

Answer 56

In the duodenum

Question 57

Where is the vomiting reflex controlled?

Answer 57

In the central vomiting center of the medulla of the brain

Question 58

Can cortical input cause vomiting? Can input from the vestibular system (balance) cause vomiting?

Answer 58

Yes to both

Question 59

Is the lower esophageal sphincter a true sphincter?

Answer 59

No

Question 60

Which neurotransmitter relaxes GI sphincters?

Answer 60

Nitric oxide

Question 61

Which two GI sphincters are under voluntary contral?

Answer 61

The upper esophageal sphincter and the external anal sphincter

Question 62

Does vasoactive intestinal polypeptide (VIP) promote or inhibit the smooth muscle relaxation caused by nitric oxide?

Answer 62

Promote

Question 63

Do the laryngeal muscles contract after or before the nasopharynx closes during swallowing?

Answer 63

Generally, the larynx elevates after the nasopharynx closes

Question 64

Once the bolus gets into the esophagus during swallowing, what contracts to prevent food from refluxing into the pharynx?

Answer 64

The upper esophageal sphincter

Question 65

How long does it take food to reach the stomach from the pharynx during swallowing?

Answer 65

5-6 seconds

Question 66

When does the lower esophageal sphincter begin to relax during swallowing?

Answer 66

When the pharynx contracts, well before the bolus has reached it; this is vagally mediated

Question 67

What muscular structure surrounds the lower esophageal sphincter (that is not within the esophageal wall)?

Answer 67

The diaphragm

Question 68

What is the basal lower esophageal pressure at rest?

Answer 68

20mmHg

Question 69

What innervation mediates the antrum’s action of grinding and retropulsing food?

Answer 69

Vagal innervation

Question 70

What is the normal “rhythm” of the stomach?

Answer 70

3 cycles per minute

Question 71

What causes the housekeeping waves of the GI tract? What is the audible signal of its action? What happens to it during a meal?

Answer 71

The migrating motor complex; stomach rumbling noises; it is inhibited during meals

Question 72

A special stain was used to highlight the pacemaker cells of the GI tract. What are they called?

Answer 72

Interstitial cells of Cajal

Question 73

What is the storage area of the colon for liquids?

Answer 73

The cecum

Question 74

Does the colon perform more peristalsis or segmenting contractions?

Answer 74

Segmenting

Question 75

Which are more common in the colon: low amplitude contractions, or high amplitude contractions?

Answer 75

Low amplitude (>100/day)

Question 76

High amplitude contractions of the colon are concurrent with what GI process?

Answer 76

Defecation

Question 77

What is the gastrocolic reflex?

Answer 77

When the stomach is distended, we tend to want to have a bowel movement right away (to clear out the GI tract)

Question 78

What hormones are used in the efferent limb of the gastrocolic reflex?

Answer 78

Cholecystokinin (CCK) and gastrin

Question 79

Why do you need to squat (or at least sit) to defecate?

Answer 79

To straighten the anorectal angle

Question 80

What skeletal muscle wraps around the anal canal like a sling and creates the anorectal angle?

Answer 80

The puborectalis muscle

Question 81

What maintains more of the resting tone of the anal sphincter: the internal or the external sphincter?

Answer 81

The internal anal sphincter

Question 82

Why does watery stool potentially cause incontinence?

Answer 82

The volume of the stool and the sensation of this by the anal canal are part of the physiology of continence

Question 83

Secretion is most often associated with the […] of intestinal epithelia, while absorption is associated with […].

Answer 83

Secretion is most often associated with the crypts of intestinal epithelia, while absorption is associated with villi.

Question 84

About how much water is excreted as saliva, gastric, biliary, and pancreatic juices per day?

Answer 84

Saliva and biliary juice: 1L/d eachGastric and pancreatic juice: 2L/d each

Question 85

What fraction of the water content of the food passing through the small intestine is absorbed in the small intestine?

Answer 85

80%, from ~8L/d to ~1.5L/d presented to the proximal colon.

Question 86

How much water is normally excreted in the feces each day?

Answer 86

~100-200mL

Question 87

What is the typical maximum capacity of the colon to absorb water, in the course of a day?

Answer 87

About 5L

Question 88

What happens when colonic H2O absorption is maxed out?

Answer 88

Diarrhea

Question 89

Where does fluid being absorbed through an epithelium accumulate in the absorptive state?

Answer 89

Between the tight junctions and the basement membrane

Question 90

What solute is used to facilitate osmotic transport of water in the colon?

Answer 90

Na+

Question 91

What kind of pressure moves water from the absorptive spaces between epithelial cells into the capillaries?

Answer 91

Hydrostatic pressure

Question 92

Are tight junctions leakier (allowing larger molecules to diffuse through them) in the jejunum or the colon?

Answer 92

Leakier in the jejunum

Question 93

What are the three main methods by which sodium is transported in the intestines to drive fluid absorption?

Answer 93

1) solute-coupled sodium transport2) sodium hydrogen exchangers3) electrogenic sodium transport

Question 94

During nutrient-coupled sodium transport in the intestine, what drives Na+out of the basolateral membrane? What imports Na+via the apical membrane?

Answer 94

An Na+/K+ATPase expels Na+from the basolateral membrane.An Na+/glucose symporter, e.g. SGLT-1, imports Na+ on the apical membrane.

Question 95

What is oral rehydration therapy?

Answer 95

A solution of salts and sugars given by mouth that facilitates reabsorption of water by the intestines and decreasing diarrhea

Question 96

In sodium-hydrogen exchange, what transporter on the apical membrane is used to move Na+into the cell?

Answer 96

An Na+/H+exchanger

Question 97

In sodium-hydrogen exchange within the intestines, what transporter on the apical membrane is used to maintain acid/base balance?

Answer 97

A Cl-/HCO3-exchanger, which pumps out bicarbonate and Cl-into the cell.

Question 98

In electrogenic sodium absorption in the intestines, is the Na+transported across the apical membrane using an ATPase?

Answer 98

No, it uses a channel and follows an electric gradient created by a basolateral Na+/K+ATPase

Question 99

In which part of the small intestine does electrogenic Na+transport become more important?

Answer 99

The distal part (the ileum and some of the duodenum)

Question 100

Because of Na+transport, does the intestinal lumen have a net negative or positive charge? What ion can this draw into the lumen? Therefore, what ion imbalance can be caused by uncontrolled diarrhea?

Answer 100

A net negative charge due to the exit of positive ions; K+may be drawn into the lumen; hypokalemia can result from uncontrolled diarrhea

Question 101

Cl-is absorbed during absorption of Na+and water in the intestinal lumen. Does it typically drive fluid absorption?

Answer 101

No, it typically drives fluid secretion

Question 102

What Cl-channel in the apical membrane allows it to exit into the lumen during chloride secretion?

Answer 102

CFTR

Question 103

What is the second messenger for VIP, secretin, PGE1, and bradykinin?

Answer 103

cAMP

Question 104

What second messengers do many bacterial toxins use to promote intestinal secretions?

Answer 104

cAMP and cGMP

Question 105

What causes osmotic diarrhea?

Answer 105

A nonabsorbable solute in the bowel lumen causes water to enter the lumen (mostly in the small bowel) and the water load exceeds colonic absorptive capacity

Question 106

What carbohydrates can cause osmotic diarrhea?

Answer 106

Lactose (e.g. from a lactase deficiency), sorbitol and aspartame (chewing gum or diet sodas)

Question 107

What minerals can you use to cause osmotic diarrhea? When is this an appropriate treatment?

Answer 107

Sodium sulfate, magnesium citrate; typically used before an endoscopy to clear out the bowels

Question 108

With osmotic diarrhea, will stool volume decrease and symptoms improve with fasting?

Answer 108

Yes

Question 109

What things can cause secretory diarrhea?

Answer 109

Secretagogues that increase cAMP, cGMP, and Ca++: bacterial toxins, hormones, bile acids, drugs (caffeine, methylxanthines), or inflammatory mediators (histamine)

Question 110

Why is caffeine a natural laxative?

Answer 110

It increases levels of cAMP, stimulating secretory processes in the bowel.

Question 111

In secretory diarrhea, does fasting cause relief from the symptoms?

Answer 111

No

Question 112

What is the major symptom of people with cholera that causes them to die? What is the treatment?

Answer 112

Dehydration from secretory diarrhea; treated with IV fluids

Question 113

Why do changes in motility cause diarrhea?

Answer 113

The bowel needs time to absorb water, so moving contents too quickly (hypermotility) can inhibit water absorption

Question 114

How do most common antidiarrheals (e.g. Immodium) function to decrease diarrhea? What is the common side effect that can result?

Answer 114

They slow down movement of the bowel, allowing more time for water absorption; this can cause constipation

Question 115

Besides neural transmitters and endocrine signalling, what other two forms of cellular communication affect GI control?

Answer 115

Paracrine communication: release of chemicals into interstital spaceAutocrine communication: type of paracrine communication providing feedback inhibition

Question 116

Why are GI hormone-secreting cells called enterochromaffin cells? Where are they found?

Answer 116

Called enterochrommafin cells based on their histological staining properties; found in pancreatic islets and between mucosal cells of columnar cell epithelia

Question 117

What sensation in the gut is correlated with the release of the tachykinin Substance P?

Answer 117

Pain

Question 118

What effect does the hormone motilin have on the gut?

Answer 118

It binds to receptors on smooth muscle, increasing motility and phase III contractions of the migrating motor complex

Question 119

What endocrine hormone is the “global inhibitor” of the GI control system?

Answer 119

Somatostatin

Question 120

What receptors does distension of the stomach activate, leading to a reflex response that increases gastric acid production?

Answer 120

Stretch receptors

Question 121

Both pancreatic juice and salivary juice contain a higher concentration of what anion as their flow increases?

Answer 121

Bicarbonate: HCO3-

Question 122

Which receptor type is most important for the stimulated release of digestive enzymes from pancreatic acinar cells?

Answer 122

CCK-B receptors

Question 123

When physicians say “malabsorption” what other process besides absorption can they also mean to be broken?

Answer 123

Digestion

Question 124

Are the lingual lipases and gastric lipases significantly contributory toward breakdown of lipids in an adult?

Answer 124

No

Question 125

Which lipases in the GI tract are most significant in an adult?

Answer 125

Pancreatic lipases

Question 126

What does the suffix -ogen and the prefix pro- both signify with regard to enzyme naming?

Answer 126

It is an inactive form that is later activated (usually by cleavage)

Question 127

Which amylase is secreted by the pancreas?

Answer 127

α-amylase

Question 128

What class of molecules is not broken downby pancreatic digestive enzymes?

Answer 128

Disaccharides, which are digested in the small intestine

Question 129

Where are minerals (e.g., iron, magnesium) chiefly absorbed in the GI tract?

Answer 129

Duodenum

Question 130

When EtOH is ingested, which part of the GI tract is chiefly responsible for its absorption?

Answer 130

The stomach

Question 131

Which four vitamins are fat soluble and must be solubilized in lipids to be absorbed?

Answer 131

Vitamins A, D, E, and K

Question 132

Can disaccharides by absorbed by the intestinal epithelia?

Answer 132

No, only monosaccharides

Question 133

What enzyme is used to break down starch?Where is it secreted?What are the products of this cleavage?

Answer 133

Amylase;pancreas and saliva;the disaccharide maltose, trisaccharide maltotriose, and α-dextrins and oligosaccharides—short chains of glucose

Question 134

What converts the products of amylase breakdown (maltose and α-dextrins) into glucose? Where is it secreted?

Answer 134

Maltase; from the intestinal brush border membrane

Question 135

What enzyme breaks down sucrose and where is it secreted?

Answer 135

Sucrase-isomaltase, which is secreted from the intestinal brush border membrane

Question 136

Where is lactose broken down in the GI tract? Which enzyme is responsible for this?

Answer 136

The small intestine; lactase

Question 137

What two monosaccharides are known to be actively transported (either by an ATPase or via symport with an ion gradient) into the intestinal epithelium?

Answer 137

Glucose and galactose. (Fructose transport is thought to be facilitated diffusion but it is not yet clear.)

Question 138

What two monosaccharides form sucrose?

Answer 138

Glucose and fructose

Question 139

What two monosaccharides form lactose?

Answer 139

Glucose and galactose

Question 140

Can small oligopeptides be absorbed across the intestinal epithelium?

Answer 140

Yes

Question 141

Where does protein digestion begin? What enzyme initiates this?

Answer 141

Stomach; pepsin, assisted by gastric acid

Question 142

How are the pancreatic enzyme precursors activated in the duodenal lumen (and only there)?

Answer 142

Enterokinase, which lives on the brush-border of the duodenum, activates trypsinogen → trypsin, which then activates the other enzymes (chymotrypsin, elastase, and carboxypeptidase)

Question 143

If the parietal cells are not making acid, will pepsinogen be activated in the stomach?

Answer 143

No

Question 144

Do the pancreatic proteases cleave proteins indiscriminately or at specific sites?

Answer 144

At specific sites, dependent on the enzyme

Question 145

What do pancreatic lipase and co-lipase do to triglycerides?

Answer 145

Break them down into monoglycerides and free fatty acids

Question 146

What is the composition of a mixed micelle?

Answer 146

Monoglycerides and free fatty acids inside, bile salts on the outside

Question 147

What must FFAs be repackaged into by intestinal epithelia to leave the cells and enter the lymphatic system?

Answer 147

Chylomicrons and VLDLs

Question 148

What’s the definition of a medium chain fatty acid?

Answer 148

6-8 carbons in the chain

Question 149

What proteins are needed to form chylomicrons in intestinal epithelia?

Answer 149

Lipoproteins

Question 150

What is this metabolic disorder? What is it caused by?

Answer 150

Aβ-lipoproteinemia; there is an accumulation of fat in the intestinal epithelia because lipoprotein β cannot be synthesized to form chylomicrons for lipid export

Question 151

Which circulatory network is used to get bile salts back to the liver from the ileum?

Answer 151

The portal system

Question 152

Are vitamin B, vitamin C, and niacin fat solubule or water soluble?

Answer 152

Water soluble

Question 153

Before binding to [substance] in the duodenum, secreted from parietal cells in the stomach, vitamin B12 is bound to R-factors like haptocorrin found in saliva and gastric juice.

Answer 153

Before binding to intrinsic factor in the duodenum, secreted from parietal cells in the stomach, vitamin B12 is bound to R-factors like haptocorrin found in saliva and gastric juice.

Question 154

Before binding to intrinsic factor in the duodenum, secreted from [cell type] in the [organ], vitamin B12 is bound to R-factors like haptocorrin found in saliva and gastric juice.

Answer 154

Before binding to intrinsic factor in the duodenum, secreted from parietal cells in the stomach, vitamin B12 is bound to R-factors like haptocorrin found in saliva and gastric juice.

Question 155

Before binding to intrinsic factor in the duodenum, secreted from parietal cells in the stomach, vitamin B12 is bound to […] found in saliva and gastric juice.

Answer 155

Before binding to intrinsic factor in the duodenum, secreted from parietal cells in the stomach, vitamin B12 is bound to R-factors like haptocorrin found in saliva and gastric juice.

Question 156

Before binding to intrinsic factor in the duodenum, secreted from parietal cells in the stomach, vitamin B12 is bound to R-factors like haptocorrin found in [digestive juice types].

Answer 156

Before binding to intrinsic factor in the duodenum, secreted from parietal cells in the stomach, vitamin B12 is bound to R-factors like haptocorrin found in saliva and gastric juice.

Question 157

Does vitamin B12bind immediately to intrinsic factor in the stomach?

Answer 157

No, it only associates with it in the distal duodenum, after pancreatic proteases separate vitamin B12from R factors (haptocorrin)

Question 158

What is another name for vitamin B12?

Answer 158

Cobalamin

Question 159

What biochemically rare mineral is contained in vitamin B12?

Answer 159

Cobalt

Question 160

What tissue can be permanently damaged by hypocobalaminemia? What metabolic substance is deficient in this disease?

Answer 160

Neural tissue; vitamin B12(also called cobalamin)

Question 161

If you do not absorb sufficient protein, what is the typical clinical finding? Why?

Answer 161

Edema; water accumulates in the interstitial spaces because of hypoalbuminemia

Question 162

If you are malabsorptive for fat, what are the typical clinical findings?

Answer 162

Steatorrhea (fatty stool), and sometimes weight loss

Question 163

When you are malabsorptive for carbohydrates, what clinical findings result and why?

Answer 163

Diarrhea, bloating and gas because the microbes of the distal gut get more carbs then they usually do, and proliferate

Question 164

What clinical problems result from a vitamin K deficiency, and why?

Answer 164

Bruising, because vitamin K is needed for posttranslational modification of coagulation proteins

Question 165

Besides neuropathy, what is another clinical finding associated with vitamin B12deficiency, common with folate or iron malabsorption? What is the difference in the histological presentation of these anemias and why?

Answer 165

Anemia; however, iron-deficiency anemia is microcytic (a heme production issue), while vitamin B12and folate deficiencies are megaloblastic (indicating DNA synthesis problems).

Question 166

What effects does gastrin have on the GI tract? What cells are stimulated? What receptor does it bind to?

Answer 166

It stimulates secretion of gastric acid and pepsinogen, and hypertrophy of the gastric mucosa; the parietal cells and chief cells; the CCK-B receptor is used.