Gastrointestinal Patho (pptx 1) Flashcards
List 4 primary function of GI tract
1) Ingestion
2) Digestion
3) Absorption
4) Elimination
List 5 things assessment of GI tract should look at
1) Swallowing
2) Eructation
3) Thrush
4) Abdominal pain
5) Emesis
Describe the esophagus
Tube-like structure that lies behind the trachea in thorax & extends from the pharynx to the stomach (~ 10 in)
List 3 things the esophagus consists of
1) Smooth muscle layers
2) Mucosal & submucosal glands secrete mucus
3) Sphincter at either end of the esophagus
Esophagus:
What are the mucosal & submucosal glands that secrete mucus important for?
Surface protection & lubrication
What are the 2 sphincters at either end of the esophagus?
1) Upper (Pharyngoesophageal)
2) Lower (Gastroesophageal)
Upper (Pharyngoesophageal) sphincter
Striated muscle, prevents air entering esophagus during breathing
Lower (gastroesophageal) sphincter Hint: 2
1) Circular muscle, passes thru opening in diaphragm (hiatus)
2) Reflux prevention
How does food move through the esophagus?
Through peristalsis
List the 3 parts of the stomach
1) Fundus (upper portion)
2) Body
3) Pylorus
List 3 phases of the digestive process
1) Cephalic phase
2) Gastric phase
3) Intestinal phase
List 2 functions of gastric secretions
1) Chemical breakdown
2) Disinfect ingested food
List 4 types of cells found in the stomach
1) Gastric goblet cells
2) Parietal cells
3) Chief cells
4) G cells
What do the parietal cells of the stomach secrete?
HCL & intrinsic factor
What do the chief cells of the stomach produce?
Pepsinogen → which converts to pepsin; then breaksdown proteins
What do G cells of the stomach release/ secrete?
Gastrin
What do parietal cells utilize & contain? Hint: 2
1) Utilize proton pump
2) Contain histamine receptors (i.e. H2 receptors)
Where do we see high concentrations of prostaglandins?
In the gastric mucosa & secretions
List 2 functions of prostaglandins in gastric acid secretion
1) Inhibit acid secretion
2) Stimulate mucus & bicarb secretion
Function of stomach cells (Table):
Goblet cells
Secretes mucus
Function of stomach cells (Table):
Parietal cells Hint: 3
1) Secrete HCL – sterilizes & breaks down food (mainly PRO & CHO)
2) Secretes IF – needed to absorb vit B12 in SI
3) Acid synthesis controlled by proton pump
List 3 proton pump triggers (Table)
1) Acetylcholine
2) Histamine
3) Gastrin
Function of stomach cells (Table):
Chief cells
secrete pepsinogen
→ converts to pepsin (enzyme for protein digestion)
Function of stomach cells (Table):
Gastric mucosal cells Hint: 2
Prostaglandin E2 (PGE2)
1) Protective
2) Stimulates gastric mucus production & pancreatic bicarb secretion
Function of stomach cells (Table):
G cells Hint: 4
Gastrin
1) PRO digestion
2) ↑ gastric motility
3) Stimulate secretions from parietal & chief cells
4) Triggers release of bile from gallbladder & enzymes from pancreas
List 3 steps of gastric emptying
1) Peristalic contraction originates in upper fundus & sweeps down toward pyloric sphincter
2) Contraction becomes more vigorous as it reaches thick-muscled antrum
3) Strong antral peristalic contraction propels the chyme forward
List 3 steps of gastric mixing
1) When peristalic contraction reaches pyloric sphincter, the sphincter is tightly closed & no further emptying takes place
2) When chyme that was being propelled forward hits the closed sphincter, it is tossed back into antrum
3) Mixing of chyme is accomplished as chyme is propelled forward & tossed back into antrum
Approx. how long is the small intestine
20 feet
List the 3 parts of the SI & what they are responsible for
1) Duodenum → digestion
2) Jejunum → absorption
3) Ileum → reabsorption
What does the duodenum of the SI contain?
Contains opening for common bile duct & main pancreatic duct
What does the jejunum of SI contain? Hint: 5
1) Amino Acids
2) Glucose
3) Fe (iron)
4) Ca (calcium)
5) Fat-soluble vitamins (A, D, E, K)
What kind of circulation takes place in the ileum of SI?
Enterohepatic circulation → primary func. reabsorption of vit. B12 & return of bile acids to liver
Where do the SI and LI join together?
At the ileocecal valve
What is the mucosal lining of the SI made up of?
Villi → finger-like projections
List 3 things each villi has
1) Artery
2) Vein
3) Lymph vessel
List the functions of the enterocytes on the villi
1) Secrete brush border enzymes
→ aid in digestion of carbs & proteins
2) Molecules diffuse thru membrane OR actively transported across mucosal surface
When enterocytes of the villus diffuse thru the membrane/ transport across surface where do they enter?
Enter blood OR fatty acids (thru lacteal) → then goes thru portal vein or lymphatics into systemic circulation
List 3 major function of microflora
1) Metabolic activities that salvage energy & absorbable nutrients
2) Trophic effects on intestinal epithelial cells
3) Protection from pathogenic organisms
List the 3 metabolic activities of the microflora
1) Fermentation of nondigestible carbs → provides major source of energy for the colon
2) Vitamin synthesis (K2 (Menaquinone); B12)
3) Absorption of Ca, Mg, & Fe
Approx how long is the LI?
4.5 - 5 feet in length
List 7 things the LI is composed of
1) Cecum
2) Ascending colon
3) Transverse colon
4) Descending colon
5) Sigmoid colon → waste products (feces)
6) Rectum
7) Anal canal
What is the role of the LI?
To absorb water & salt & to store feces until defecation
List the 4-layered tube of the GI wall
1) First (inner mucosal) layer
2) Second (submucosal) layer
3) Third (muscularis externa) layer
4) Fourth (serosal) layer
What is the first (inner mucosal) layer of the GI wall made up of?
A lining of epithelial tissue known as lamina propria, & the muscularis mucosae
List 4 functions of the first (inner mucosal) layer of the GI wall
1) Production of mucus
2) Secretion of digestive enzymes
3) Absorption of breakdown products of digestion
4) Maintenance of a barrier; immune defence
What does the second (submucosal) layer of the GI wall contain? Hint: 3
1) Blood vessels
2) Nerves
3) Structures responsible for secreting digestive enzymes
List the 2 layers of smooth muscle in the third (muscularis externa) layer of the GI wall that facilitate movement
1) Inner layer → smooth muscle cells in circular pattern
2) Outer layer → smooth muscle cells longitudinally arranged
What is the fourth (serosal) layer of the GI wall made up of?
Serous membrane consisting of the mesothelium
1) Outer layer → visceral peritoneum
2) Inner layer → parietal peritoneum
Describe the mesenteries of the abdominal cavity
Double-folded connective tissue that attached the intestines to the posterior abdominal wall
How many sections do the mesenteries of the abdominal cavity consist of?
3 sections
List 2 functions of the mesenteries of the abdominal cavity
1) Helps in supplying BV, lymphatics, & nerves to the intestines
2) Helps in storing fat
List the 2 types of intestinal motility movement
1) Segmental mixing/ kneading movements (Haustrations)
2) Propulsions or propulsive mass movements
How do the segmental mixing/ kneading movements of intestinal motility work?
Shuffles contents back & forth among haustra
Increases contact time w mucosa for absorption of water & electrolytes)
What is the primary type of intestinal motility movement?
Segmental mixing/ kneading movements (haustrations)
What is segmental mixing/ kneading movements initiated by?
Autonomic nerves within smooth muscle cells
When do propulsions/ propulsive mass movements occur & what happens?
Usually after a meal
Lg segment contract & moves contents forward into sigmoid colon & rectum → stimulates defecation
What do smooth muscle cells function as for the GI tract?
The pacemaker
Slow waves → 3-12 per min
What does the regulatory control of intestinal motility result from?
An interplay between the enteric, ANS, & intestinal smooth muscle cells
List 2 things that make up the enteric nervous system
1) Myenteric (Auerbach) plexus
2) Submucosal (meissner) plexus
Myenteric (Auerbach) plexus Hint: 2
1) Located btwn circular & longitudinal muscle layers
2) Gut motility
Submucosal (Meissner) plexus Hint: 2
1) Btwn mucosal & muscle layers
2) Controls secretions, absorption, contraction of segments in intestinal tract
What is activity in the enteric nervous system regulated by?
Local influences (mechanoreceptors/ chemoreceptors), ANS, & info btwn plexuses
Parasympathetic innervation of ANS Hint: 2
1) Supplied by vagus nerve
2) Stimulation → ↑ motility & secretions
Sympathetic innervation of ANS Hint: 2
1) Stimulation is inhibitory
2) ↓ motility & secretory activity
Swallowing & esophageal motility Hint: 2
1) Mastication begins the digestive process
2) Propulsion of food from mouth to stomach
List the 3 phases of swallowing
1) Oral
2) Pharyngeal
3) Esophageal
Describe primary peristalsis
Controlled by the swallowing center & begins when food enters the stomach
Describe secondary peristalsis
Partially mediated by smooth muscle fibers in esophagus
→ esophageal sphincter
→ parasympathetic stimulation
→ gastrin
List 4 things associated with gastric motility
1) Stomach serves as a food storage reservoir
2) Chyme: food broken down into creamy mixture
3) results in mixing of solid food & emptying gastric contents into duodenum (2-3 contractions/ min)
4) Role of the antrum
Gastric motility:
What does the pyloric sphincter prevent?
The backflow of gastric contents & allows them to flow into the duodenum
What is the site of absorption & digestion of food?
Small intestine
List 2 types of SI movement
1) Segmentation
2) Propulsive
List 2 types of colonic motility & defecation
1) Segmentation mixing movement (Haustration)
2) Propulsive mass movement
What is normal colonic transit time?
24-48 hrs
What does normal stool consist of?
75% water and 25% solid matter
What is defecation controlled by?
Internal & anal sphincters
LIst 6 GI hormones
1) Cholecystokinin
2) Gastrin
3) Ghrelin
4) Glucagon-like peptide 1
5) Glucose-dependent insulinotropic polypeptide
6) Secretin
List 5 GI secretions
1) Salivary
2) Gastric
3) Pancreatic
4) Biliary
5) Intestinal
Approx how much fluid is secreted from GI tract each day?
~ 7,000 mL
What is digestion?
Process of dismantling foods into their constituent parts
List 3 things digestion requires
1) Hydrolysis
2) Enzyme cleavage
3) Fat emulsification
What is hydrolysis?
Breakdown of a compound; involves a chemical reaction with water
What is fat emulsification?
Breakdown of fats into free fatty acids & monoglycerides
What is absorption?
Process of moving nutrients & other materials
List 2 things absorption occurs through
1) Active transport
2) Diffusion
