Introduction to GI Physiology Flashcards
Essentially all of the digestive absorption occurs in the _______.
Small intestine
What is the largest gland associated with the oral cavity?
Parotid gland
The pharynx is considered a sphincter. What causes it to open?
Once food is pushed to the roof of the mouth and back, vagal afferents are sent to the swallowing center of the medulla and the vagal efferents go back to the pharynx causing it to relax and allows food to move to the esophageal region
What are the proximal and distal parts of the stomach responsible for respectively?
Proximal- Storage
Distal- Mixing and dumping into the duodenum
What are the two important functions of the ileum?
- Reabsorption of B12
- Reabsorption of bile salts that move into portal circulation back to the liver and start the bile secretion cycle all over again
Where in the abdomen is polyps disease most common?
Ascending colon
NOTE: Diverticulosa is common interns of the sigmoid colon
Which of the schincters is the abdomen is not tonically constricted?
Ileocecal sphinter.
What are the constiuents of salivia? What is the function of each?
-
Mucins
- Lubrication
-
Amylase
- Digestion of starch
-
Lipase (lingual)
- Digestion of fat
-
Lysozyme
- Antibacterial
-
IgA
- Immune protection
- Nerve growth factor
- Epidermal growth factor
Mechanism of salivary secretion
Stage 1
- Acinar cell secrete a NaCl-rich fluid called primary saliva, which isotonic__
Stage 2
- The primary saliva is modified and passed along the ductal tree
- NaCl is reabsorbed
- KHCO3 is secreted
- Ductal epithelium is poorly permeable to H2O
- Final saliva is hypotonic
How is salivary amylase activity maintained in the stomach?
By buffers and substrate protection
An ____________ is superficial to a muscularis mucosa, while a __________ extends through the muscularis mucosa.
Erosion; ulcer
Direction of slow wave propogation in colon
What are the 4 main amino acids in gastrin? How does this compare to cholecystokinin?
Gastrin- Trp-Met-Asp-Phe
Cholecystokinin- Gly-Trp-Met- Asp-Phe
What is the basic glandular structure of salivary, gastric and pancreatic cells?
A blind end surrounded by acinar cells
NOTE: They produce secretory polps into the blind ends of the duct. This initial solution moves down to be elaborated in the lume of the organ
Stimulated salivary secretio is _________- dependent.
Flow
NOTE: As you increae the flow rate, you will raise the pH. This is mostly determined by the increase in bicarbonate.
What is the main purpose of the villi found in the mucosal layer?
Increase the absorptive area of the small intestine
What are the three parts of the lining of the mucosal layer? What is the function of each?
-
Mucosal membrane
- Detects changes of contents of the lumen
-
Lamina propria
- Connective tissue layer that has an immunological function
- Muscularis mucosa
Characteristics of the vomit and stool of a person with an ulcer.
Vomit often has bright red blood and stool will be a tar color; this is indicative of an internal bleed
What are the tw components of the muscularis externa?
- Inner circular layer
- Outer longitundinal layer
NOTE: The principal movement of peristalsis down the GI tract is by contraction and interplay between the layers of the muscularis externa
The _______ is the final layer of the the GI tract made up of connective tissue coating that eventually gives way to the mesentery.
Serosa
NOTE: If you have an ulcer that breaks through the submucosa and gets into the peritoneal cavity, you have a problem and this needs to be surgically repaired, otherwise it can cause peritonitis.
What are the two nerve plexuses of the GI wall? What are the characteristics of each?
Myenteric plexus
- Between the inner circular and outer longitudinal layer
- Involved in motor function
Submucosal plexus
- Inner wall of the circular layer and projecting into the submucosa
- Involved in sensory function
NOTE: The submucosal plexus sends out axons that connect to the epithelial cells that line the villi and give rise to the changes in the lumen of the intestinal tract
Why is the sigmoid colon susceptible to diverticulitis?
Because of it’s relationship to hydrostatic pressure
Why is the slow wave in the direction of the ascending colon?
Becuase it is the last stop for reabsorption of water and electrolytes
What is the significance of the right hepatic flexure?
it is important because the colon is mostly static until appropriately stimulated and when this happens there will be mass movements at this flexure. This will push stored material across the transverse colon.
Where is amylin localized? What us it’s function?
Localization: Pancreatic beta cells
Function: Satiety factor
Where is ghrelin localized? What is it’s function?
Localization: CNS, stomach, intestine
Function: Released by fasting
What is the function of pancreatic PP?
- Decreses postprandial exocrine
- Pancreatic secretion via vagal-dependent pathway
Where is gastrin localized and what is it’s function?
Localization: Antrial G cells
Function: Reguation of gastric H+
Where is cholecystokinin localized and what is it’s function?
Localization: Instestinal I cells
Function: Regulation of pancreatic enzyme secretion
Where is somatostatin localized and what is it’s function?
Locatlization: Gastric D cells
Function: Pancreatic regulator of H+ and gastrin
Where is gastrin-releasing peptide localized and what is it’s function?
Localization: GI nerves
Function: Gastrin release and acid secretion
Where is gastric inhibitory peptide localized and what is it’s function?
Localization: Intestinal K cells
Function: Regulation of insulin release/ inhibitor of H+
Where is motilin localized and what is it’s function?
Localization: M cells
Function: Interdigestive intestinal motility
Where is calcitonin gene-related peptide localized and what is it’s function?
Localization: Primary afferents and myenteric neurons
Function: Neural mediator of primary afferents
Where is pancreatic polypeptide-related localized and what is it’s function?
Localization: Enteropancreatic endocrine cells, sympathetic neurons
Function: Neural modulation of sympathetic transmission, inhibitor of pancreas
Where is vasoactive interstinal polypeptide localized and what is it’s function?
Localization: Myenteric inhibitory motoneurons/submucosal neurons
Function: Neural inhibitor of motility/ stimulant of fluid secretion
Where is histamine localized and what is it’s function?
Localization: ECL-cells
Function: Stimulus of gastric acid secretion
Where is norepinephrine localized and what is it’s function?
Localization: Extrinsic digestive nerves
Location: Vascular regulation
Where is serotonin localized and what is it’s function?
Localization: EC cell of digestive tract
Function: Stimulus of peristalsis
Where is substance P localized and what is it’s function?
Localization: Digestive nerves
Function: Neurotransmitter
Which 4 amino acids are essential for the activity of gastrin?
Tryptophan, methionine, asparagine, and phenylalanine
What are the essential amino acids?
Tryptophan, methionine, asparagine, and phenylalanine
Tyrosine, Methionine, and glycine
Gastrin
Stimulus for Secretion
Areas of Distribution
Signifiant Physiological Actions
Stimulus for Secretion
- Distention
Areas of Distribution
- A,DJ
Significant Physiological Actions
- Gastric acid and pepsin secretion
- Growth of stomach and intestine mucosa
- Gastric motility
- Closure of lower esophogeal sphincter
CCK (Cholecystokinin)
Stimulus for Secretion
Areas of Distribution
Signifiant Physiological Actions
Stimulus for Secretion
- Fat
Areas of Distribution
- D,J,I
Signifiant Physiological Actions
- Gallbladder contraction
- Relaxation sphincter of Oddi
- Pancreatic enzyme release
- Gastric emptying
- Pancreatic aqueous secretion
- Inhibition of gastric acid and pepsin secretion
Secretin
Stimulus for Secretion
Areas of Distribution
Signifiant Physiological Actions
Stimulus for Secretion
- Acid
Areas of Distribution
- D,J,I
Signifiant Physiological Actions
- Pancreatic aqueous secretion
- Pancreatic enzyme secretion
- Inhibits gastric acid and pepsin secretion
- Inhibits gastric emptying
GIP
Stimulus for Secretion
Areas of Distribution
Signifiant Physiological Actions
Stimulus for Secretion
- Fat, glucose
Areas of Distribution
- D,J,I
Signifiant Physiological Actions
- Inhibits gastric acid and pepsin secretion
- Inhibits gastric emptying
- Stimultes insulin secretion
Somatostatin
Stimulus for Secretion
Areas of Distribution
Signifiant Physiological Actions
Stimulus for Secretion
- Acid in lumen
Areas of Distribution
- F,A,D,J,I,C
Signifiant Physiological Actions
- Inhibits gastrin, secretin, VIP, GIP, motilin
- Inhibits gastric acid secretion
- Inhibits pancreatic exocrine secretion
- Inhibits gastric motility
Histamine
Stimulus for Secretion
Areas of Distribution
Signifiant Physiological Actions
Stimulus for Secretion
- Injury (vagus post ganglionic)
Areas of Distribution
- Mast cells (ECL)
Signifiant Physiological Actions
- Stimulates gastric secretion of HCl and pepsin
Motilin
Stimulus for Secretion
Areas of Distribution
Signifiant Physiological Actions
Stimulus for Secretion
- Fasting
Areas of Distribution
- D,J,I
Signifiant Physiological Actions
- Stimulates contraction of intestinal smooth muscle
Peptide YY
Stimulus for Secretion
Areas of Distribution
Signifiant Physiological Actions
Stimulus for Secretion
- Fats, CHO in lumen
Areas of Distribution
- I,C
Signifiant Physiological Actions
- Inhibits gastric emptying
- Inhibits interstinal transit
- Inhibits gastric and pancreatic secretions
Pancreatic polypeptide
Stimulus for Secretion
Areas of Distribution
Signifiant Physiological Actions
Stimulus for Secretion
- Vagus
Areas of Distribution
- PP cells of Islets of Langerhan
Signifiant Physiological Actions
- Stimulates small intestine absorption
- inhibits pancreatic exocrine secreton
- Inhibits pancreatic endocrine secretion
