Gastric, Intestinal, and Pancreatic Function Flashcards
Three functions of the stomach
- Movement of food to the duodenum
- Secretion of digestive enzymes, intrinsic factor, and hydrochloric acid
- Partial digestion of proteins
Anatomical location of the stomach and names of three distinct zones
- Fundus
- Body
- Antrum
Specific cell types in each zone of the stomach
Fundus: surface epithelial cells, mucus cells
Body: surface epithelial cells, mucus cells, parietal cells
Antrum: Mucous cells, G-cells, chief cells
Specific secretion(s) of surface cell epithelial
Produce mucus and shed and proliferate rapidly (every 3 days)
Specific secretion(s) of mucus cells
Secrete mucus
Specific secretion(s) of parietal cells
Hydrochloric acid and Intrinsic Factor
Specific secretion(s) of chief cells
Pepsinogen (that is converted in an acidic environment to pepsin)
Specific secretion(s) of G-cells
gastrin (gastrin stimulates the parietal cells to produce HCL)
Five functions of gastric hydrochloric acid
- Converts pepsinogen to pepsin
- Activates rennin (a milk curdling enzyme)
- Combines with food proteins to form acid metaproteins which are more easily digested by pepsin
- Prevent bacterial multiplication in the stomach
- Prevents precipitation of ingested calcium so that soluble calcium may be absorbed
Four stimuli for gastrin release
- When proteins, amino acids and calcium enter stomach
- Vagus nerve is activated and releases acetylocholine
- Catecholamines are circulating
- Antrum is distended
Three phases of gastric secretion
- Cephalic phases
- Gastric phase
- Intestinal phase
Cephalic phase stimuli and specific secretion produced in each phase
Vagus nerve, stimulated by site and smell, stimulates parietal cells to produce HCL and G-cells to produce gastrin
Gastric phase stimuli and specific secretion produced in each phase
- In the stomach, gastrin release stimulates parietal cells to produce more HCL
- Local antral distension stimulates further production of gastrin and therefore HCL
- Chief cells respond to acidic environment; pepsinogen is produced that is rapidly converted to pepsin at pH 3
- Chyme is produced (mucus-containing solution)
Intestinal phase stimuli and specific secretion produced in each phase
- Ingested food helps neutralize HCL
- Secretin is released, inhibiting gastrin-stimulated acid production and gastric motility
- Gastric secretions cease
Three functions of gastric fluid
- Initiation of protein digestion
- Physical and chemical preparation of ingested food for absorption
- Secretion of intrinsic factor to promote Vit B12 absorption in the ileum
Four normal constituents of gastric secretions
- Hydrochloric acid
- Enzymes (pepsin (most important), salivary amylase, gastric lipase)
- Mucus
- Intrinsic factor
Three abnormal constituents of gastric fluid
- Blood
- Food
- Organic acids
Appearance of fresh blood in the stomach
red
Appearance of blood that has remained in the stomach for a period of time
old blood is converted to hematin by the acidic pH and has a “coffee grounds” appearance
Four indications for gastric analysis
- Aid in eval of patients with recurrent ulcer disease
- Aid in diagnosis of Zollinger-Ellison syndrome by demonstrating a hypersecretory state
- Determine if patient is able to secrete HCL at all (pernicious anemia)
- Determine the completeness of vagotomy after gastric surgery
Specific diagnostic use of Basal Acid Output (BAO) for gastric function assessment
No stimulation after you fast and you measure if outputting acid; determine baseline pH
Specific diagnostic use of Maximum Acid Output (MAO) for gastric function assessment
Important in determining if the patient has low acidity or anacidity
Specific diagnostic use of Serum gastrin for gastric function assessment
Useful in diagnosis of the Zollinger-Ellison syndrome
Specific diagnostic use of Schilling test for gastric function assessment
Useful in the diagnosis of pernicious anemia
Specific diagnostic use of Hollander test for gastric function assessment
Useful in determining the completeness of vagotomy in peptic ulcer treatment; should not be increased in vagotomy
Recognize five lab findings in stomach cancer
- Achlorhydria in gastric fluid
- Anacidity or hypoacidity of gastric fluid
- Blood (“coffee grounds” appearance) in gastric fluid
- Blood in feces
- Iron deficiency anemia due to blood loss
Recognize causes for gastric and peptic ulcers
- Helicobacter pylori
- Smoking
- Caffeine
- Alcohol
- Stress
- Physical stress
- Acid and pepsin
- Nonsteroidal anti-inflammatory drugs (NSAIDs)
List the specific cause for the Zollinger-Ellison
gastrinoma (a gastrin-secreting tumor of malignant cells in the duodenum or from a tumor in a non-beta islet cells of pancreas
List the four typical lab findings for Zollinger-Ellison syndrome
- BAO > 10 mEq/hour
- MAO usually less than 25% higher than BAO, ie, both are high all the time
- Increased volume of secretion (160-800 mL/hour)
- Serum gastrin levels two to twenty thousand times normal!!!
Cause of pernicious anemia
Gastric problems are caused by malfunctioning parietal cells, responsible for HCL production and secretion of intrinsic factor (IF)
Six typical lab findings in pernicious anemia
- Anacidity
- Decreased gastric secretion volume
- Gastric atrophy
- Increased serum gastrin (>200 pg/mL)
- Macro-ovalocytes
- Hypersegmented neutrophils
Functions of the duodenum
Has 6 major hormones to aid in digestion and protection of the intestinal lining; intraluminal hydrolysis of starch, proteins, and lipids
Functions of the illeum
- Absorption of Vitamin B12 and whatever products of digestion that were not absorbed by the jejunum
- Diffuse neuroendocrine system cells secrete gastrin, secretion, and cholecystokinin into the bloodstream
Functions of the large intestine
- Absorption of water from the remaining indigestible food matters
- Absorption of vitamins that are created by bacteria inhabiting the colon
- Fecal compaction until it can be eliminated
Source of Cholecystokinin-pancreozymin (CCK-PZ)
Secreted by I cells of duodenum when digested proteins/fats enter duodenum and causes the:
Stimulus for Cholecystokinin-pancreozymin (CCK-PZ)
Secreted by I cells when protein and fats enter the duodenum
Three physiological effects Cholecystokinin-pancreozymin (CCK-PZ)
- Pancreas to produce enzymes
- Gall bladder to contract and empty contents
- Sphincter of Oddi to relax to allow gall bladder and pancreatic contents to ender duodenum
Source of secretin
S cells both the duodenum and jejunum
Stimulus of secretin
released when acidified contents of stomach reach duodenum (pH < 5)
Two physiological effects of secretin
- Acts in synergy with CCK for release of pancreatic enzymes
- Simulates secretion of large amount of diluent pancreatic fluid rich in sodium bicarbonate
Physiological effects of gastric inhibitory peptide
stimulates insulin release and is responsible for rapid metabolism of an oral glucose load
Physiological effects of Vasoactive intestinal polypeptide
Causes relaxation of gut circular smooth muscle as well as smooth muscle in blood vessels, causing vasodilation. Also stimulates pancreatic secretion
Physiological effects of motilin
Stimulates the contraction of the smooth muscles of the GI tract and contracts the lower esophageal sphincter
Physiological effects of somatostatin
- Most potent inhibitor of endocrine secretions;
- inhibits release of GI and pancreatic hormones, as well as the release of GH and TSH;
- Inhibits actions of all these hormones on their target tissues
