Gastro Physiology Flashcards
During the intestinal phase of digestion, the typical fluid load to the jejunum is ______ L per day. Consisting of dietary water, saliva, gastric juice, pancreatic juice, intestinal secretion, and about 0.5 L of _____
7-10
Bile
Specializations of the GI tract to accomplish it’s functions
- Stomach acid and other digestive fluids
- The villi and microvilli of the small intestine
- The enteric nervous system
- The splanchnic circulation
- The colonic microbiome
What cells are responsible for ingesting foreign bodies entering the blood via the gastrointestinal tract?
Kupffer cells
In this type of swallowing the nasopharynx is closed by the soft palate, deflection of the food bolus by the epiglottis (away from the larynx), and relaxation of the upper esophageal sphincter
Involuntary
Endocrine functions of the pancreas
secrete the hormones insulin and glucagon
What 3 things work together to stimulate gastric acid formation
Gastrin, histamine, and acetylcholine
What type of highly phagocytic cells, located in the liver, are exposed to the portal blood flow and serve as a sentinel for antigens/bacteria arising from the intestine?
Kupffer cells
What is secreted in the pyloric gland area of the stomach?
Endocrine secretions:
Gastrin, Somatostatin, Histamine
The colon contains a longitudinal layer of smooth muscle called
Teniae coli
What keeps the stomach from digesting itself?
A mucus-bicarbonate barrier at the mucosal surface
In what condition do patients lack a functional Cl- channel in the luminal membrane of the pancreatic duct cells ultimately causing malabsorption?
Cystic Fibrosis
What must relax to allow the food bolus into the stomach?
Lower esophageal sphincter, controlled by autonomic nerves
GI circulation is also known as ______ circulation, and is most effected by the SNS
Splanchnic
Extraintestinal diseases that have been shown to be affected by the gut microbiome include:
- weight control (obesity)
- inflammatory bowel disease
- the general immune response (autoimmune diseases)
- resistance to infectious disease
What is the functional unit of the intestines?
Villus
Functions of the colon during the intestinal phase of digestion
Absorption of fluid
Transport of electrolytes
Storage and elimination of fecal waste
Most common cause of pancreatitis in women?
gallstones
Functions of bile
- emulsifies fats
- allows for excretion of hydrophobic molecules
- helps neutralize gastric acid (it’s alkaline)
What are the Motor functions of the stomach?
Reservoir for ingested food, mixing of ingested food, regulates the delivery of food to the small intestines at appropriate rate and consistency
About ____ liters of fluid is delivered to the colon per day, and approximately _____ liters are absorbed.
The maximum reabsorption capacity of the colon is ____ liters. If the total fluid load exceeds this, _______ occurs.
2
1.9
5
Diarrhea
Parts of the GI tract
mouth, esophagus, stomach, duodenum, jejunum, ileum, cecum, colon, rectum, anus
How do proton pump inhibitors work?
They bind and inhibit the H+/K+ -ATPase pump on the luminal surface of parietal cells
Major functions of the organs in the GI tract
- Nutrient intake and processing for absorption
- Water balance
- Protection from invasive organisms and toxins
- Endocrine functions mostly involving the regulation of nutrients (eg glucose and lipid metabolism, protein synthesis)
How is the food bolus moved through the esophagus?
smooth muscle peristalsis, coordinated by the enteric nervous system
In what ways do non-pathogenic bacteria benefit the GI system?
- provide beneficial metabolic functions
- provides increased resistance to pathogens/allergens
What stimulates the feedback loop to shut off secretion of gastric acid
Somatostatin
If bacterial antigens survive the acid in the stomach and bind to the luminal surface of the distal small bowel, they stimulate this type of lymphocytic cell to circulate and populate all of the musical tissues of the body?
IgA-secreting plasma cells
Sympathetic noradrenergic activity in the enteric nervous system has what effect in the GI tract
decreases intestinal smooth muscle activity and causes sphincters to contract
In Splanchnic circulation, all the blood from the GI tract drains to the liver via
hepatic portal vein
What stimulates and releases Gastrin in the stomach?
Stimulated by stomach stretch, released by Gastrin-releasing peptides (GRP) by enteric nervous system
Contraction of the gallbladder occurs during what phase of digestion?
intestinal
in response to a meal
What phase of gastrointestinal response involves gastrin, histamine, and acetylcholine that bind to parietal cells to stimulate gastric acid production?
Gastric phase
What is involved in cobalamin absorption?
Intrinsic factor
The major network of nerve fibers involved with secretions in the gastrointestinal tract
Submucous plexus (Meissner)
What must relax to allow food into the esophagus?
Upper esophageal sphincter, controlled but the extrinsic nerves
What is involved in the Exocrine functions of the stomach?
Water- dissolve & dilute ingested food
Acid (HCl)- denature dietary proteins and sterilize the meal
Enzymes (pepsin & gastric lipase)- protein & fat digestion
Intrinsic factor- a glycoprotein that is necessary for B12 absorption
Mucus-bicarbonate barrier- protects against corrosive properties of the gastric juices
Components that STIMULATE gastric acid production
Gastrin
Histamine
Acetylcholine
Bile is composed of what 4 things?
Bile acids
Bile salts
Micelles of bile salts
Bile pigments (bilirubin)
This phase is characterized by the anticipation and sight, smell and taste of food. There is vagal outflow from the brain that stimulates release of GRP and acetylcholine, and encourages secretory function in the salivary glands and stomach
Cephalic phase
Contractions in the colon form bulges known as
Haustra
What part of the stomach contains the antrum and the pylorus (20%)
Pyloric gland area
This is composed of enterocytes, mucous-secreting goblet cells, and endocrine cells
Villus epithelium
Endocrine cells in the duodenal wall produce…
cholecystokinin (CCK) and secretin
Endocrine secretions in the pylorus
Gastrin, Somatostatin, Histamine
This feature of the anus is skeletal muscle around the anal canal controlled by the extrinsic nerves
External anal sphincter
How is the surface area in the small intestine amplified for greater absorption?
Transverse folds in mucosa (place circulares), arrangement of mucosa into villi, microvilli on the enterocytes that line the small intestine
This phase of the gastrointestinal response involves the movement of chyme into the intestines, a feedback inhibition of gastric acid production via the release of enterogastrones (Secretin) from the small intestines, with further digestion, absorption of nutrients and water, motility, and eventually elimination
Intestinal phase
Other functions of the liver
- carb, lipid, & cholesterol metabolism
- amino acid & protein synthesis
- storage of vitamins A, D, E, K, B12, iron and copper
- detox & biotransfomation
Functions of saliva
- lubricates food
- solvent for food molecules that stimulate taste buds
- adds digestive enzymes to help break down food
- antibacterial activity in the oral cavity
Functions of the rectum
- electrolytes and water continue to be absorbed
- indigestible luminal contents are further broken down by anaerobic bacteria
- stool is thickened and mixed with mucous
What does the normal flora of the intestinal tract do?
- Help with digestion and nutrient acquisition
- Create a protective host defense mechanism in numbers
- Play a role in extraintestinal disease in the body
What are involved in the Endocrine functions of the stomach?
Ghrelin- regulation of hunger and satiety
Gastrin- stimulates parietal cells
Somatostatin- deactivates G cell secretion of gastrin
Salivation is stimulated by…
thought, smell or taste of food by conditioned reflexes, and by nausea.
Test to assess swallowing and esophageal function
Esophageal manometry
What components INHIBIT gastric acid production?
Somatostatin
Prostaglandin E2
G cells- directly inhibited when pH in stomach is at or below 3
What part of the stomach contains the cardia, fungus, and body (80% of stomach)
Parietal Gland area
Another name for digested food bolus
Chyme
3 classes of functions of the stomach
Motor, endocrine, exocrine
The major network of nerve fibers involved with motility in the gastrointestinal tract
Myenteric plexus (Auerbach)
Rectal distension initiates the
rectosphincteric reflex
- Internal sphincter relaxes and initiates the urge to defecate.
- Voluntary contraction of the external sphincter can override this reflex.
What inhibits breathing during swallowing?
Reticular formation in the brainstem. A stroke in this area may cause pt to have difficulty with swallowing
The process of bile acid secreted by hepatocytes, delivered to GI tract via biliary tract, absorbed by the small intestine, and then returned to the liver via the portal venous system is called?
enterohepatic circulation of bile acids
Important process because the bile acid pool is not large enough to assimilate the lipid contents of a typical meal.
@95% of bile salts are reabsorbed
The acinar cells of the pancreas create these enzymes…
Acetylcholine (vagus)
Cholecystokinin (small intestine)
They are stimulated by secretagogues
Digestive enzyme that breaks down fats
Lipase
In this type of swallowing the food bolus is pushed to the back of the tongue and pushed in to the pharynx
Voluntary
Hepatocytes secrete…
canalicular bile w/ bile salts, cholesterol, phospholipids, and bile pigments
It takes about ____ seconds for food to reach the stomach from the mouth
10
This feature of the anus is smooth muscle controlled by the autonomic nerves.
Internal anal sphincter
Absorption of iron and calcium occurs in the…
duodenum
3 salivary glands
Sublingual, submandibular, parotid
What hormone stimulates gallbladder contraction and mediates the relaxation of the sphincter of Oddi, allowing billiard and pancreatic secretions to enter the duodenum?
CCK
What are the 3 phase of gastrointestinal response?
1- cephalic phase
2- gastric phase
3- intestinal phase
During the intestinal phase in the Jejunum and Ileum, what is absorbed?
Carbs, protein, fat, salts, and water.
bile acids and B12 are absorbed in the distal ileum.
Main digestive function of the pancreas
secrete enzymes that break down the macromolecules in food to produce smaller nutrient molecules for intestinal absorption
What is secreted in the parietal gland area of the stomach?
Parietal cells secrete hydrochloric acid (HCl) & intrinsic factor.
+Peptic (Chief) cells secrete pepsinogen
What are the 2 major networks of nerve fibers intrinsic to the gastrointestinal tract?
Myenteric plexus (Auerbach plexus)- between outer longitudinal and middle circular muscle layers
Submucous plexus (Meissner plexus), between the middle circular layer and the mucosa.
Fancy name for swallowing
deglutition
30% of cardiac output is pumped to the GI system via these 3 arteries
celiac a.
superior mesenteric a.
interior mesenteric a.
Salivation is inhibited by…
sleep, dehydration, fatigue, fear
What is involved in the prevention of pancreatic autodigestion?
Acinar cells produce zymogens in vesicles. Trypsin is activated in small intestines and required to activate other zymogens. Pancreas produces a trypsin inhibitor
parasympathetic cholinergic activity in the enteric nervous system has what effect in the GI tract
increases the activity of intestinal smooth muscle
What is the major location of commensal bacterial in the body? And what percentage of the feces consist of mostly anaerobic bacteria?
Colon
20%
Giant colonic peristaltic contractions triggered by the entry of food into the stomach and duodenum.
Gastrocolic reflex
Digestive enzyme that breaks down carbs
Amylase
_____ L of saliva is secreted daily
1.5 liters
Major accessory glands of the GI tract
Salivary glands, gastric mucosal glandular structures, intestinal mucosal glandular structures, pancreas, liver, gallbladder
The Sphincter of Oddi and the Brunner’s glands (that secrete mucous) are in what part?
duodenum
Bile is produced in the _____ and secreted via the _____
liver
biliary tract
Most common cause of gallstones in men?
alcohol use
This phase of digestion includes mixing chyme with digestive secretions and enzymes, propulsion of luminal contents away from the mouth via segmentation and peristalsis
Intestinal phase in Jejunum and Ileum
What are the two types of gallstones?
Cholesterol and Pigment (calcium bilirubinate)
