Chapter 17: The Digestive System Flashcards
What are tonic contractions ?
maintain contraction over a long period of time
- “told to relax”
- stimulated by the Interstitial Cells of Cajal (ICC)
- Ex.) sphincters, stomach, anal
What are phasic contractions ?
contract on demand
- “told to contract”
- stimulated by the Nervous System
- Ex.) esophagus, intestines
What causes the phasic contractions to vary ?
- more Ca+ means a stronger muscle contraction
- the AP frequency
- duration of stimulus
What is peristalsis movement ?
oral to aboral movement in one direction
- meant to move the food through the GI tract
- in the esophagus, stomach, and intestines
- short distances
What is segmentation movement ?
back and forth churning movement
- contraction behind and in front of blous means to mix the food with the secretions
What is mass movement ?
forceful, peristalsis-like movements that move the waste in the colon
- 2-3x per day
What is migrating myoelectric complex ?
long overlapping peristalsis waves that ensure your food moves along and doesn’t stay put
- stomach through large intestine
- oral to aboral
Where is the deglutition(swallowing) center in the brain ?
medulla
What do the G cells secrete and why ?
gastrin
- stimulated to secrete by the stretching of the stomach, ACh, peptide, and amino acids
What do the Enterochromaffin (ECL) cells secrete and why ?
histamine
- simulated to secrete by ACh and gastrin
What do the parietal cells secrete and why ?
HCl (gastric acid) and Intrinsic Factor
- stimulated to secrete by ACh, gastrin, and histamine
What does the duodenum secrete and why ?
Cholecystokinin (CCK) and Secretin
- CCK stimulated to secrete by the presence of fats and proteins in the stomach
- Secretin stimulated to secrete by acids in the duodenum (low pH)
What do the D cells secrete and why ?
somatostatin
- stimulated to secrete because of acid in the stomach
What do the chief/principal cells secrete and why ?
pepsinogen and gastric lipase
- stimulated to secrete when exposed to acidic conditions
- ACh or acid secretion
What do the salivary glands secrete and why ?
salivary amylase
- stimulated to secrete because of sour tastes (low pH), sight or smell of food, or tactile stimulation of the oral cavity
What is the function of CCK ?
stimulates the production and secretion of bile, and of pancreatic enzymes
What is the function of secretin ?
stimulates HCO3- (bicarbonate) release from the liver
What is the function of HCO3- ?
to buffer the gastric acid to prevent damage
What is the function of pepsinogen and gastric lipase ?
- protein digestion
- digest lipids (fats)
What is the function of gastrin ?
activate gastric acid secretion
What is the function of histamine ?
stimulate gastric acid secretion
What is the function of somatostatin ?
to inhibit gastrin and histamine secretion
What is the function of HCl ?
activates the pepsin and kills bacteria
What is the function of intrinsic factor ?
to absorb vitamin B12 needed for RBCs
Where is the emesis center ?
medulla
What is gastroparesis ?
slowing down of the stomach so it’s not emptying as efficiently as it should
- associated with gastric pacemakers of motility
What is gastric dumping syndrome ?
emptying of the stomach that is so quick to the point where you overwhelm your duodenum
- causes you to not have efficient digestion or even absorption
What is emesis ?
vomitting
What is chyme ?
food and any digestive secretions in it
Where does digestion start ?
in the duodenum
What do Goblet Cells produce ?
mucus
What do Granular Cells produce ?
immune function
What do Enteroendocrine cells produce ?
hormone
What are the enterocolic and duodenocolic reflexes for ?
stretch receptors in the stomach and duodenum that initiate mass movement
What initiates the defecation reflex ?
distension of stretch receptors in the rectum
What neural system controls the internal anal sphincter ?
parasympathetic
What neural system controls the external anal sphincter ?
somatic
During the resting state is the internal anal sphincter contracted or relaxed ?
contracted
During the Micturition (peeing) state is the external anal sphincter contracted or relaxed ?
relaxed
What is the process of the defecation reflex ?
- the internal anal sphincter relaxes
- there is continued contraction of the external sphincter
- continued peristalsis and increased pressure in the rectum
- the external anal sphincter relaxes
What is the Enterohepatic Circulation ?
the bile salts are absorbed from the ileum –> where the hepatic portal veins transports it back to the liver
- can be recycled 2-5 times per meal`
When is glucagon released ?
when the blood glucose levels are low
- tonic release
- alpha cells
When is insulin released ?
when blood glucose levels are high
-beta cells
Which NS is a long reflex ?
central nervous system
Which NS is a short reflex ?
enteric nervous system
What is dysphagia ?
difficulty swallowing
What is Gastroesophageal Reflux Disorder (GERD) ?
the lower esophageal sphincter isn’t closed as tightly and the acid goes up to the tissue of the esophagus
- not heartburn
- happens frequently
- can be caused by increased gastric pressure and excess acid secretion
What stimulates the cephalic phase ?
sight, smell, taste, chewing
What stimulates the gastric phase ?
stretch, amino acids, and peptides in the stomach
What stimulates the intestinal phase ?
stretch, acidity, osmolarity, and digestive products
What do the capillary beds in the small intestine absorb ?
carbohydrates and amino acids
What do the lacteals in the small intestine absorb ?
lipids (fats)
Where does the digestion of Carbohydrates start ?
oral cavity with the salivary amylase
Where is amylase produced ?
oral cavity and pancreas
What do the Carbohydrates digest into ?
Starch into glucose
What do the Proteins digest into ?
amino acids
What do Lipids digest into ?
triglycerides (glycerol and 3 fatty acids)
What is Celiac disease ?
immune reaction to having gluten in the intestines
- causes loss of absorptive surface, and poor tissue repair
What is Crohn’s disease ?
an inappropriate inflammatory response at mucosal layer of gut
- an inflammatory bowel disease
- causes loss of absorptive surface, and poor tissue repair
What is Ulcerative Colitis ?
an inappropriate inflammatory and ulceration response to the colon (at mucosal layer of the gut)
- an inflammatory bowel disease
- causes loss of absorptive surface, and poor tissue repair
What is Pernicious Anemia ?
parietal cells lack intrinsic factor
- lack of absorption of vitamin B12
In what part of the small intestine are there more ICC waves/min ?
duodenum
- because there is more segmetation here
What stimulates the parietal cells to release HCl ?
Ach (parasympathetic), gastrin, and histamine
What inhibits the parietal cells ?
Somatostatin and Prostaglandin E2 (PGE2)
What cause the alkaline tide ?
HCO3-/Cl- Pumps
- HCO3 absorption (into the bloodstream), and Cl- gets secreted (into the lumen) which creates the tide and raised blood pH
What hormone or paracrine agents gets added to the ICC cell’s to stimulate it to make the AP stronger ?
gastrin
What structure of the colon gives us the strong mass movements ?
teniae coli
What causes the reversal of the alkaline tide ?
2° active transport
- Na+/H+ antiport
- H+ is being pumped out into the bloodstream which neutralizes the tide
