Gi Secretions

Front 1

What compounds can be found in saliva?

Back 1

1. alpha-amylase: startch digestion; secreted from salivary duct
2. Lingual lipase: lipid digestion (more important in nursing infants b/c of high lipid content in breast milk); secreted from tongue
3. R-binders: protect vitamin B12 from gastric proteases; secreted from the tongue; helps to prevent pernicious anemia

Front 2

What are the three paired salivary glands located in the mouth?

Back 2

1. Parotid glands (serous fluid w/ amylase)
2. Submaxillary glands (mixed serous/mucous fluid)
3. Sublingual glands (mucus fluid)

Front 3

Chronic Vomiting

Back 3

Loss in both potassium (hypokalemia) and H+ (alkalemia); a decrease in potassium could effect cardiac contractility

Front 4

What regulates salivary flow?

Back 4

PNS controls salivary flow, specifically the glossopharyngeal and facial nerves (NOT the vagus)
An increase in PNS outflow will stimulate an increase in salivary output
SNS only causes a slight increase in flow- blip in beginning due to contraction of myoepithelial cells, which spit out contents, then have very little secretion

Front 5

What increases salivary flow?

Back 5

Parasympathetic, Ach
CNS (cephalic process)
Nausea
Esophageal distention
Chewy, flavorful foods; dry, acidic, alkaline foods; meat, sweets, bitter food

Front 6

What decreases salivary flow?

Back 6

Sympathetic, NE
Hormone (ADH, Aldo)
Sleep
Dehydration
Drugs (antihistamine, chemotherapeutic)
Aging

Front 7

Functions of saliva

Back 7

"COLD TAP"
Coagulation factors, Oral hygiene, Lubrication, Digestion, Taste, Antimicrobial action, Protection

Front 8

Esophageal secretions

Back 8

Minor glands that secrete mucins to lubricate and help flow down

Front 9

Gastric Secretions

Back 9

HIPGLOM

Front 10

HCl

Back 10

Secreted by the parietal cells; chemical gross "digestion" of large particles; stimulated by the vagus nerve in cephalic phase (before food enters stomach- sight, smell, etc)

Front 11

Intrinsic factor

Back 11

Secreted by parietal cells; binding and protection of vitamin B12 from pancreatic proteases in the small intestine

Front 12

Pepsinogen

Back 12

Secreted by the chief cells; cleaved into pepsin by acidic environment for protein digestion

Front 13

Gastrin

Back 13

Secreted by G cells in the antrum; stimulation of HCl for continued secretion

Front 14

Lipase

Back 14

Secreted by the chief cells; lipid digestion

Front 15

Somatostatin

Back 15

Adjacent to the parietal cells; regulator to decrease HCl

Front 16

Histamine

Back 16

Adjacent to parietal cells; regulator to increase HCl

Front 17

Mucus

Back 17

Secreted from mucosal cells; protect gastric epithelial cells by trapping bicarb and forming a protective layer between epithelium and acidic contents of the stomach

Front 18

Factors that increase HCl secretion?

Back 18

Parasympathetic
Ach
Gastrin
Histamine

Front 19

Factors that decrease HCl secretion?

Back 19

Peptide YY
GIP
Secretin
Somatostatin
Prostaglandins

Front 20

What is the rate-limiting step for acid production?

Back 20

H+ transport via the H+ pump; For example, PPIs are effective in decreasing acid content of the stomach by blocking and reducing the number of H+ channels

Front 21

Helicobacter pylori

Back 21

Fecal-oral bacteria with a natural resistance to our gastric acid
Able to neutralize surrounding gastric acid by secreting urease
Destroy the mucus-bicarbonate barrier--> stomach acid and digestive enzymes from our gastric fluid layer are able to get to the epithelial cells-->inflammation leading to mucosal damage and ulcer formation

Front 22

Phases of Gastric Secretion

Back 22

1. Cephalic: presence of food in mouth triggers anticipatory reaction, initiating Ach release at the parietal cells- increased gastric acid secretion
2. Gastric: initiated when food in the stomach causes stretch and gastrin release; together with the vagus, increases gastric acid secretion
3. Intestinal: Occurs when chyme enters the duodenum a. Vagal reflex b. Enterogastric reflex 3. Hormonal feedback (CCK, Secretin)-- Decrease in gastric acid secretion

Front 23

Secretin

Back 23

Duodenal secretion; stimulated by acidic chyme to increase intestinal and pancreatic buffers

Front 24

Gastrin

Back 24

Duodenal secretion; stimulated by stretch, vagal stimulation to increase gastric acid

Front 25

CCK

Back 25

Duodenal secretion; stimulated by fats and glucose in chyme to increase the pancreatic enzymes

Front 26

GIP

Back 26

Duodenal secretion; stimulated by fatty acids, amino acids, glucose to increase insulin secretion (to prepare for incoming glucose)

Front 27

What stimulates the release of pancreatic enzymes?

Back 27

the duodenal hormone, CCK

Front 28

Pancreatic Proteases

Back 28

Secreted from the pancreas as inactive zymogens to protect the pancreas from auto-digestion
In the duodenum, enterokinase activates trypsinogen to trypsin
Trypsin is able to activate chymotrypsinogen and pro-carboxypeptidase for protein digestion

Front 29

Pancreatic lipase & co-lipase

Back 29

pancreatic lipase hydrolyzes lipids into small monoglycerides and free fatty acids; however, it needs co-lipase (activated by trypsin) to bind bile and make lipid accessible to the pancreatic lipase

Front 30

Pancreatic amylase

Back 30

activated by Cl-, so that it can digest starch molecules

Front 31

What happens at the end of a meal?

Back 31

As chyme empties out of the stomach, there is nothing left to stimulate the vagus. Without this stimulation, pancreatic secretions stop. As chyme moves toward lower portions of the GI tract, elevations in somatostatin, pancreatic polypeptide, and peptide YY all contribute to a decline in pancreatic secretions

Front 32

Jejunum and Ileum

Back 32

absorb Na, Cl, K, and nutrients
excrete H+, Bicarb

Front 33

Colon

Back 33

Absorbs all remaining NaCl and water
excretes K+ and bicarb

Front 34

**CC: Chronic Diarrhea

Back 34

Lose lots of bicarb, become acidotic