Gastrointestinal Ii

Front 1

Layers of stomach from outside to inside:

Back 1

Serosa (connective tissue)

Muscularis (Circular and longitudinal)

Intramural plexus (myenteric and submucosal)

Submucosal layer (mucus)

Mucosa layer

Front 2

Zones of the stomach from proximal to distal?

Back 2

Cardiac

Fundic

Body (rugae)

Pyloric zone

Front 3

What two parts of the stomach have the majority of gastric juices?

Back 3

Body

Fundus

Front 4

Where does regulation of gastric secretions come from?

Back 4

Endocrine (Gastrin)

Paracrine (Somatostatin)

Neural (Vagus-Ach/gastrin releasing peptide)

Front 5

Where is gastrin located?

Back 5

Stomach and intestine

***HORMONE***

Front 6

What cell produces the enzymes of gastric juice?

Back 6

Chief cells

Front 7

What cell produces stomach acid? (HCL)

Back 7

Parietal cell

Front 8

What are the cell types of the gastric glands at the bottom of gastric pits?

Back 8

Surface mucous cells

Mucous neck cells

Parietal cells

Chief cells

Endocrine cells

Endochromaffin like cells (ECL)

Ghrelin

Front 9

What are some characteristics of surface mucous cells?

Back 9

Lifespan 3-5 days

Protection

Secrete mucus (contains mucin)

Lubrication

Front 10

What do mucous neck cells do?

Back 10

Protect and replace cells in lumen after desquamation

Front 11

What do parietal cells do?

Back 11

HCL source

Intrinsic factor

R proteins

Front 12

What comprises chief cells?

Back 12

Pepsinogen (Acitvated by HCL to pepsin)

Gastric lipase (fat digestion)

Front 13

What comprises endocrine cells?

Back 13

Somatostatin (inhibit HCL and gastrin)

Gastrin

Front 14

What do ECL (enterochromaffin like cells) do?

Back 14

Release histamine which stimulates HCL secretion

Front 15

What does ghrelin do?

Back 15

Hormone during fasting

Acts on hypothalamus to stimulate hunger

Opposes satiety effects of leptin and peptide YY

Front 16

What is intrinsic factor responsible for?

Back 16

(parietal cells)

Only indispensable gastric secretion

Required for Vit B12 absorption

Binds to Vit B12 in duodenum

Front 17

What are R-proteins responsible for?

Back 17

(parietal cells)

Protects Vit B12 from degradation

High affinity for B12 in acidic environ

Cleaved by trypsin in duodenum....intrinsic takes over here

Front 18

What is activated by HCL?

Back 18

Pepsinogen to pepsin

Front 19

What is released by D cells?

Back 19

Somatostatin (endocrine cells)

Inhibits HCL/gastrin secretion

Front 20

What is released by G cells?

Back 20

Gastrin (endocrine cells)

Stimulates gastric motility/increased HCL secretion

Decreased gastric emptying (pyloric sph contract)

Front 21

What can endocrine cells both stimulate and inhibit?

Back 21

HCL secretion

Front 22

What chemical reaction works to increase HCL on the lumen-side of the stomach?

Back 22

H20 + C20 (CA)=H2C03=HC03 + H+ (acid)

Front 23

Where does the HC03 pass through to keep the "neutrality" of the system?

Back 23

HC03/Cl exchanger

Front 24

Where does the Cl go?

Back 24

Follows its concentration gradient toward lumen (apical)

Front 25

The remaining H+ remaining goes where, and through what exchanger?

Back 25

Apical side

H+/K+ ATPase exchanger

The K+ is exchanged and transported AGAINST its gradient back INTO the cell

Front 26

What is important to know about the Na+/K+ ATPase pump located on the basolateral (blood) side?

Back 26

This keeps the drive of K+ moving all the way across from blood---> cell---> lumen

*also moves Na+ against its gradient out of the cell into the blood

Front 27

Regulation of HCL/gastric secretions? (3)

Back 27

Neural

Paracrine (DO NOT DUMP INTO BLOOD)

Endocrine (DUMPS IN BLOOD)

Front 28

What are the neural regulators of HCL secretion?

Back 28

PSNS-parietal cells releasing ACh (stimulates)

Vagal ACh-D cells (somatostatin), parietal, mast c.

Vagal-GRP (gastrin-releasing peptide)

Front 29

What are the endocrine regulators of HCL?

Back 29

G cells--->gastrin into blood-->parietal-->HCl release--->direct

Gastrin and GIP ---> parietal cells--->direct

Secretin and peptide YY-->indirect

Gastrin-->activate ECL-->hist.release-->indirect

Front 30

What are the paracrine regulators of HCL?

Back 30

PSNS can act INDIRECTLY by activating ECL cells which release histamine-->parietal cells

DIRECTLY-ECL can release histamine itself (serotonin too)

Front 31

What type of cells secrete 90% of the body's serotonin? (5HT)

Back 31

Gut ECL cells

Front 32

What are 5HT cells (serotonin) useful as?

Back 32

Anti-emetics

Front 33

How does serotonin affect peristalsis in the intestines?

Back 33

Vasoactive neuropeptide with vasoconstricting actions

Front 34

What type of cells also secrete histamine?

Back 34

Mast cells

Front 35

Stimulators of gastric acid secretion? (HCL) (3)

Back 35

Parasympathetic (vagal)---> ACh

Gastrin (hormone)

Histamine (paracrine)

Front 36

Inhibitors of HCL secretion? (5)

Back 36

1.Secretin???-->G cells-->inhibit gastrin-->inhibit parietal cell

2. Somatostatin---> inhibits G cells--> inhibits parietal cells

3. GIP-->inhibits parietal cells

4. Peptid YY-->indirect

5. Prostaglandins-->inhibits G cell and ECL cells

Front 37

What stimulates the chief cells to produce pepsinogen?

Back 37

Vagus

Gastrin

Histamine

Secretin

CCK

Front 38

What two things does H. pylori release that makes it damaging to the stomach lining?

Back 38

Urease-breaks off the NH3, which creates a buffer in the acidic environment, creating a forcefield-like protection around the H. pylori

Mucinase-disrupts the mucus/HC03 barrier, allows more bacteria to colonize, damage to the surface mucus cells from surrounding acidic environment (mucin cells damaged)

Front 39

What are the 3 phases of gastric secretion?

Back 39

Cephalic phase

Gastric phase

Intestinal phase

Front 40

Cephalic phase:

Back 40

"Anticipation"

1.Prepares GI for food

2.Chemo/mechanoreceptors on tongue, buccal canal, nasal mucosa

3. Vagal effects-->gastrin-->acid-->enzymes

Front 41

Gastric phase:

Back 41

1. Food in stomach-->vagal effects-->gastrin-->pH changes

2. Communication in stomach

3. Acidic chyme enters duodenum (important for feedback of HCL secretion)

4. Decreasing gastric emptying by pyloric sphincter (allows more time for mixing)

Front 42

Intestinal phase:

Back 42

1. More in ileum and colon

2. Lots of intestinal mucosal secretions

3. Accessory organs release secretions (pancreas, liver, GB (indirectly)--->hepatic duct-->sphincter of Oddi-->duodenum

Front 43

An acidic environment is important for the activation of what enzyme?

Back 43

Pepsinogen to pepsin

Front 44

In response to a meal, what is released?

Back 44

HCL-->decreases pH

Front 45

As soon as chyme enters the duodenum, what hormone is secreted into the blood that will act on G cells to decrease the HCL production?

Back 45

Secretin (affects stomach, duodenum, pancreas)

**releases electrolytes to buffer acid)

Front 46

What is the reason buffers (HC03) are released into the small intestine?

Back 46

To protect the mucosa by increasing the pH to allow pancreatic enzymes to work effectively

Front 47

Does the large intestine have villi?

Back 47

No

Front 48

What do the villi on top of the pits in the small intestine do?

Back 48

Increase surface area for digestion/absorption

Front 49

What are the layers of the small intestinal mucosa?

Back 49

Villi (surface area)

Epithelium

Enterocytes (absorption) TOP

Goblet cells (mucus releasing)

Endocrine cells

Crypt cells (pit) BOTTOM

Cells of Paneth (immune effect)

Lacteal layer (capillaries surround-fat absorb)

Front 50

What do the crypt cells contain?

Back 50

Cystic Fibrosis transporter-CFTR (Cl- channel)

Secretes Cl- into gut (apical-lumen)

Na+ and H20 follow (secretin stimulates)

Na+ tries to balance out charge and H20 follows

Front 51

Paneth cells

Back 51

Host defense

Secrete zinc and lysozymes

Front 52

Goblet cells

Back 52

Mucus

Front 53

Endocrine cells (toward pits)

Back 53

Secrete gastrin, CCK, secretin, GIP, motilin (Phase III of MMC), serotonin

Front 54

Brunner's glands (toward pits and intestinal gland)

Back 54

First part of duodenum before sphincter of Oddi

Secrete thick mucus and proteases

Stimulated by secretin and vagus

Inhibited by SNS

Front 55

Where is the source for final activation of enzymes?

Back 55

Duodenum (enterokinase)

Front 56

What stimulates different hormones with its composition?******

Back 56

CHYME!!!!!

Front 57

Match the hormone with its general action:

Gastrin

Back 57

Stimulate gastric H+

Front 58

Match the hormone with its general action:

Secretin

Back 58

Increase pancreatic buffer (HC03)

Front 59

Match the hormone with its general action:

Cholecystokinin (CCK)

Back 59

Increase pancreatic enzyme secretion

Contract GB

Relax sphincter of Oddi

Front 60

Match the hormone with its general action:

GIP (gastric inhibitory peptide/glucose insulinotropic peptide)

Back 60

Decrease gastric H+ secretion

Increase pancreatic insulin secretion

Front 61

Match the hormone with its general action:

Motilin

Back 61

Stimulates phase III contractions of MMC

Front 62

Match the hormone with its general action:

Peptide YY

Back 62

Decrease HCL

Front 63

What are the primary enzyme secretions of the pancreas?

Back 63

CCK

Insulin

Front 64

Electrolyte secretions of the pancreas?

Back 64

Secretin

Vagovagal reflexes

Front 65

Where does activation of pancreatic proteases (enzymes) occur?

Back 65

Duodenum

Front 66

What kind of cells are at the end of the pancreas what dump contents into the pancreatic duct for adjustment of electrolytes?

Back 66

Acini cells

Front 67

Where do the pancreatic enzymes and bile (from liver, and GB) all pass through in order to get to the duodenum?

Back 67

Sphincter of Oddi

Front 68

What is termed a "fire extinguisher" inside the pancreatic duct?

Back 68

Trypsin inhibitor (prevents the release of trypsin, which is an enzyme that breaks down protein)

Front 69

What is bile primarily utilized for?

Back 69

Lipid metabolism

Front 70

Where do the acini cells orginate from? (2)

Back 70

Endocrine gland (insulin, glucagon, somatostatin)

Exocrine gland (enzyme, electrolyte secretions)

Front 71

What cells of the pancreas are primarily involved in structure, function, and primary secretory actions?

Back 71

Acinar (outside--->enzymes)

Centroacinar (inner--> electrolytes, HC03)

Front 72

Secretions travel out of the pancreas from the acinar and centroacinar cells via what two ducts?

Back 72

Extralobular duct (further absorption/secretion)

Main duct (NO titrating done here)

*go into duodenum from here*

Front 73

What is a zymogen?

Back 73

Inactivated form of an enzyme

Front 74

What enzyme converts trypsinogen to activated trypsin?

Back 74

Enterokinase (enteropeptidase in duodenum)

Front 75

Trypsin converts:

Chymotrypsinogen--->

Procarboxypeptidase--->

Procolipase--->

Prophospholipase--->

Back 75

Chymotrypsin

Carboxypeptidase

Colipase

Phospholipase

Front 76

Pancreatic lipase + procolipase=?

Back 76

Hydrolyzation of lipids

Front 77

Pancreatic amylase--->

Back 77

Starch digestion

Front 78

When would pancreatic secretions stop being released?

Back 78

When chyme reaches the ileum (distal portion of small intestines)

Front 79

What are 3 things secreted into the lumen of the colon?

Back 79

H+

HC03

K+

Front 80

What does the ileum secrete?

Back 80

(always in play)

H+

HC03

(HC03, H20, K+ in play here)

Can also reabsorb NaCl from the lumen to blood

Front 81

What is in the enterocytes of the ileum and colon that allows HC30 to be released as a buffer?

Back 81

Carbonic anhydrase

(HC03 secreted in exchange for a Cl)

Front 82

Which sections of the GI tract do not have manipulation of secretions?

Back 82

Ileum

Colon

Front 83

What is secreted into the colon?

Back 83

H+

K+

HC03

Front 84

What are some colonic secretions?

Back 84

-CFTR (cystic fibrosis transfer enzyme)

Secretes Cl into lumen

-K+ going with concentration gradient out of cell

-Na/H exchanger

-HC03/Cl exchanger

-mucus goblet cells

Front 85

The generation of what electrolyte from luminal bacterial action will acidify chyme?

Back 85

H+

Front 86

Like the ileum, colonic cells also produce?

Back 86

Carbonic anhydrase, and secretes H+ into lumen

HC03 helps buffer acid-prone chyme

Front 87

If a short chain fatty acid (SCFA) didn't get absorbed earlier, where will they try to be absorbed?

Back 87

Distal colon

Front 88

If the chyme needs to be acidified, what type of exchanger is used in the distal colon?

Back 88

H+/K+ ATP pump exchanger

Front 89

Micro villi of the small intestines increases the surface area to what?

Back 89

250m2

Increases contact time and ability to secrete gastric juices

Front 90

Where is absorption and secretion done in the microvilli?

Back 90

Absorption done top

Secretion from bottom

Front 91

What is the target of an enzyme?

Back 91

Substrate

Front 92

What is the only type of 'saccharide' we can absorb?

Back 92

Monosaccharide

Front 93

What are the disaccharides?

Back 93

Maltose

Isomaltose

Lactose

Sucrose

Front 94

Where does the breakdown of starch begin?

Back 94

Mouth (salivary alpha amylase)

Front 95

Break down of starch in the small intestines:

Back 95

Pancreatic amylase

-All polysaccharides (many sugars) digested within 10-20 min by the time the chyme reaches upper jejunum

Front 96

What are not absorbed in the small intestine that require help from brush border enzymes?

Back 96

Disaccharides

Small glucose polymers

Front 97

What sugars (monosaccharides) can we absorb?

Back 97

Glucose & Galactose

Glucose & Glucose

Glucose & Fructose

Front 98

Disaccharides?

Back 98

Lactose---> Glucose + Galactose

Maltose---> Glucose (2)

Sucrose---> Glucose + Fructose

Broken down by brush border saccharidases

Front 99

How are glucose and Na+ transported into the cell?

Back 99

Joint carrier

Front 100

What enzyme breaks up sucrose?

Back 100

Sucrase

(Into Fructose and Glucose)

Front 101

How does fructose enter the apical side?

Back 101

GLUT5 transporter

Front 102

How does glucose and/or galactose enter the cell?

Back 102

Piggybacks on Na+/glucose transporter (SGLT1)

Uses concentration Na+ gradient

Front 103

What is SGLT1 dependent on for movement of molecules?

Back 103

Na+ concentration

Front 104

Once on the basolateral side, what do glucose, galactose, and fructose use to travel to the liver?

Back 104

GLUT2 transporter

Front 105

Effects of unabsorbed carbs results in?

Back 105

Osmotic effects

Gas

*hydrophilic-moves easily through water

*highly efficient

Front 106

Stomach:

HCL stimulates the secretion of pepsinogen to cleave pepsin to break down what?

Back 106

Protein

Front 107

What are pepsins inactivated by?

Back 107

Higher pH

Front 108

Pancreas:

Provides protection against excessive enzymatic "chewing" up along the way by secreting?

Back 108

Trypsin inhibitor

*also secretes nucleases which break down nucleic acids into purine and pyrimidine bases

Front 109

Where are triglycerides cleaved and transformed into fatty acids and diglycerides initially?

Back 109

Mouth-->lingual lipase

Stomach-->gastric lipase

Front 110

The entry of fats and peptides into the small intestine will cause this to be released, which in turn causes GB constriction--->release of bile?

Back 110

CCK

Front 111

What needs to combine with bile salts in order to activate lipase?

Back 111

co-lipase--->chews up triglycerides

Front 112

Phospholipase A2 is activated by this and cleaves phospholipids (lethicin) into lysolecithin?

Back 112

Trypsin

Front 113

What cells transport lipids across the unstirred (aqueous layer/hydrophilic) H20 layer to the enterocytes?

Back 113

Micelles

Front 114

Once the protected fatty acids and sugars reach the cytoplasm via the broken down micelle, what do they combine to form?

Back 114

Chylomicrons

Front 115

What do chylomicrons do?

Back 115

Transport the fatty acids and sugars to the liver by entering the lymph lacteals

Front 116

Where are the micelles reassembled?

Back 116

Smooth endoplasmic reticulum

Front 117

How much bile is lost with each passage or cycle?

Back 117

10%

*bile acids will make their way back to liver

Front 118

Where does most bile absorption occur?

Back 118

Terminal ileum via secondary active transport with Na+

Front 119

What % of bile is recycled?

Back 119

90%

Front 120

Where does water absorption primarily occur?

Back 120

Jejunum

Ileum

Front 121

How much water does the colon absorb while dehydrating chyme to feces?

Back 121

0.5L

Trying to make inhospitable for bacteria

Making more acidic

Front 122

What is the purpose of haustrations and where are they found?

Back 122

Found in colon

Facilitates absorption in absence of villi

Constricting teniae coli=concentrates chyme

Front 123

What is the "colonic" salvage?

Back 123

Final absorption by colon of Na+ and H20-aldosterone effect

Front 124

Where does fecal absorption begin?

Back 124

Late transverse colon

Front 125

What are the main electrolytes in feces? (2)

Back 125

K+

HC03

Front 126

Would more or less motility cause diarrhea?

Back 126

Less, this gives less time for absorption, so more water is present=loose feces

Front 127

Feces is primarily composed of what?

Back 127

75% water

25% solids