GI 3 Flashcards
What is the total amount of daily secretions of mucous in the GI?
6.7 liters
mucous is secreted by what cells?
goblet cells
Which of the salivary glands only produce mucous?
buccal glands
Which of the salivary glands produce serous and mucous fluid? Why are they known as Extrinsic Glands?
- parotid gland
- submandibular gland
- sublingual gland
they only inc/dec saliva secretion in response to Autonomic Stimulation or Chemoreceptors –> they produce 80% of the saliva
salivary constituents include a high level of these 3 things.
- potassium
- bicarbonate
- amylase
What are the 3 functions of saliva?
- remove bacteria
- destroy/opsonize bacteria via IgA
- digest food particles
What can increase the secretion of saliva by 20x
sour taste
What are the 2 major secretions of parietal cells in the stomach?
- intrinsic factor
- HCI
What does chief cells secrete?
pepsinogen
What are the 3 stimuli of HCL formation?
- Ach
- Gastrin
- Histamine
Stomach cancer is associated with what infection?
H. pylori infection in the fundus
Intrinsic factor is important in the absorption of what vitamin?
Vitamin B12
What converts pepsinogen to pepsin?
presence of HCl
Where does the K+ come from for the H+/K+ antipoter?
saliva and leak channels
What is the major secretion of the pancreas?
sodium bicarbonate
bicarbonate is secreted by ductal cells in response to what?
secretin
trypsinogen is converted into trypsin by what
enterokinase enzyme in SI
What does the pancreas secrete to break down protein?
trypsin
carboxypolypeptidase
What does the pancreas secrete to break down carbs?
pancreatic amylase
What does the pancreas secrete to break down fats?
pancreatic lipase
what does pancreatic lipase do?
breakdown triglycerides into fatty acids and glycerol
what is the major secretion of the liver?
bile
what is the main function of bile?
emulsify fat
Why don’t we see unconjugated bilirubin in the urine?
it is bound to albumin
What causes gallstones?
cholesterol will precipitate if its concentration exceeds the ability of the bile salts to emulsify
what is the function of the Brunner’s glands?
secrete bicarbonate in small intestines
what is the function of the crypts of Lieberkuhn?
secretes mucous/electrolytes/water into the small intestine
what is the major and only secretion of the large intestines?
mucous
What are the major function of mucous in the GI tract?
- Protect against abrasions
- Lubrication
- Resistant to digestion
- Buffers acids/bases
What are the 2 major stimulations of secretions?
Mechanical Stimuli from food Nervous stimulation (distention, chemicals, autonomic)
What stimulates G Cells to secrete Gastrin and what is the physiologic response?
Negatively charged proteins enter stomach –> buffers acids –> pH increases –> stimulates gastrin release –> parietal cells release HCl –> pH decreases
D Cells secrete somatostatin in response to what pH change in the stomach?
pH decreases (increased acidity)
This inhibits gastrin –> decrease HCl secretion from parietal cells
How does the structure of the Oxyntic Tubular Gland impact pepsinogen function?
Tubular Glands are a “pit” –> Chief Cells are deep in pit –> secrete pepsinogen –> does not get activated until it moves UP the gland toward the lumen –> pH is low at the lumen –> acidity triggers pepsinogen conversion to pepsin –> prevents autodigestion of the stomach
What structures of the Parietal Cell allow us to use medications to decrease acid secretion?
H2 Receptor Antagonists (Ranitidine)
Proton Pump Inhibitors (Omeprazole)
Intrinsic Factor secreted from Parietal Cells helps absorption of Vitamin B12 in what way?
Intrinsic Factor binds to B12 and prevents it from being digested in the gut –> also allows it to be better absorbed in the Small Intestine
What triggers (2) Pepsinogen release from Chief Cells?
- Parasympathetic stimulation
2. Direct stimulation via chemoreceptors from stomach acid
Where in the stomach are Chief Cells located?
Body of Fundus
Where in the stomach are G Cells?
Antrum
What stimulates the pancreas to secrete bicarbonate?
Low pH chyme enters the duodenum –> S Cells –> secrete Secretin –> stimulates pancreas to release bicarbonate
Why does the pancreas not digest itself with the presence of trypsinogen?
Trypsinogen held under inhibition from Trypsin Inhibitor –> stops auto-activation
Trypsinogen gets converted to trypsin when and where?
Inhibited trypsin travels via the pancreatic duct to the duodenum –> encounters brush border enterokinases –> activate to trypsin
Pancreatic Amylase convers starch carbohydrates into di- and tri-saccharides. Name the 3 main disaccharides.
Maltose
Sucrose
Lactose
Where do the 3 disaccharides get converted to monosaccharides for absorption?
Brush border of small intestines
Name the components that make up the 3 Disaccharides: Maltose, Sucrose, Lactose
Maltose = glucose + glucose Sucrose = glucose + fructose Lactose = glucose + galactose
Explain the passage of bile from hepatocytes.
Hepatocytes –> Bile Canuliculi –> Terminal Bile Ducts –> Hepatic Duct –> Common Bile Duct –> Sphincter of Oddi (when open) –> Ampula of Vater —> directly into Duodenum
What hormone triggers the gallbladder to contract, to release bile, and to relax the Sphincter of Oddi?
CCK
What triggers I cells to release CCK?
fatty acids entering the duodenum
Where are Brunner’s Glands located?
In the Small Intestine between Pylorus and Ampulla of Vater
What causes the secretion of bicarb from Brunner’s Glands?
Acidic (low) pH chyme entering the duodenum
Mucous secretion of the large intestine has what main purpose?
prevent abrasion of GI wall from solid fecal material
