GI - Mulroney Flashcards
Path/structures of the GI tract: Mouth - 2 glands are..... Esophagus - 2 structures are...... Stomach and Duodenum - \_\_\_\_\_\_ Sphincter - contributing organs = - duodenum length ~ \_\_in Intestinal tract = Anus - Anal sphincters =
Parotid and Salivary
Upper esophageal sphincter (UES) & Lower (LES)
Pyloric
Liver/Gallbladder, Pancreas
12in
Jejunum (~8ft), Ilium (~10ft), Ileocecal sphincter, Ascending colon, transverse colon, descending colon
Internal and External anal sphincters
The GI tract is composed of smooth muscle, except in ______, upper __________ and _______________.
mouth, esophagus, external anal sphincter
The diverse cell types in the small intestine allow ________, ________, ________ of motility and secretion.
digestion, protection, regulation
The splanchnic circulation encases the intestines; blood flows from the ________ through the _____ vein to the ____. This is the ____ ____ effect.
intestines, portal, liver
first pass
What are the functions of the GI tract? D E E P
M
A
S
S
- Digestion– Enzymes and HCl (*HCl does not actually digest, it makes chunks smaller, increasing surface area?)
- Endocrine– LOTS of hormones which act on GI tract and other tissues
- Elimination– rids body of undigested waste
- Protection– HCl, IgAs, opsonins, and other immune cells
- Motility– propels and mixes chyme
- Absorption– of almost everything you eat
- Secretion– buffers mucus, hormones (into blood), enzymes
- Storage– stomach and colon
Fluid intake is ~_ L/day
2
You may only ingest _ liters of fluid a day, but the GI tract SECRETES - LITERS. This means it has to absorb _-_LITERS of fluid each day!
2, 7-8, 9-10
The secretions help _______, ________, and _____ the chyme.
lubricate, digest (HCl, enzymes), and buffer (HCO3 buffers the acid)
The movement of fluids and gases in and out of the intestines can be heard sometimes. These sounds are called ___________.
borborygmi
Changes in __ through the tract are important to GI function.
Stomach acid ~
Chyme in jejunum ~
pH
1
7 (pH where enzymes can function)
Regulation of the GI tract:
▪ Enteric Nervous System
- _________ plexus (muscle/movement)
- _________ plexus (secretions)
▪ ____________ Nervous System (mainly vagal to transverse colon, then pelvic nerves to anus)
▪ ____________ Nervous System (post-ganglionic adrenergic fibers from celiac, superior and inferior mesenteric and hypogastric plexes)
▪ ___
▪ Lumenal ______-, ______- and ____receptors (act on the enteric NS)
▪ _________
myenteric submucosal Parasympathetic (pro) Sympathetic (slow)~running is good for motility by forcing GI to relax? CNS~anticipatory response for pro! chemo-, mechano- and osmo Hormones
What is the nervous system specific to the GI tract called?
What are the two nerve nets and what do they control?
Enteric Nervous System
myenteric plexus (muscle/movement) submucosal plexus (secretions)
The interdigestive state has a special type of motility:
The Migrating Myoelectric Complex, or MMC
The MMC:
•Begins about ___ hours after you finish eating •Housekeeping movement– sweeps undigested material and bacteria into ______
•Is active from mid-stomach through the terminal ileum •Has 4 phases, with the main propulsive movements occurring during phase III (phases I, II and IV have minor, disregulated contractions): an entire cycle lasts 75-120 min.
•Phase III contractions only last about __min each cycle, but the series of contractions sweep material lower in the tract. Phase III is stimulated by the hormone ______, secreted into blood from the M cells of the small intestine.
3-4 hours
colon
10 min, Motilin
*MMC when have not eaten for a period of time?
Moving down the GI tract–
Swallowing– begins as ________ action (remember the skeletal muscle in the upper esophagus/pharynx), and then is involuntary as the ________ and _________ nervous systems take over.
In the esophagus there are 2 types of propulsion, ______ and ________ esophageal peristalsis.
*Smooth muscle disorders in the GI tract can affect the enteric nerves…
voluntary
enteric (from mechanoreceptors) and autonomic
primary and secondary
Receptive relaxation concept =
SEE SLIDE 7 of Motility lecture
Principle of bariatric surgery is to reduce the ability of the stomach to _____________ food.
accommodate
Gastric emptying…..see slide 9
Motility lecture
How are contractions generated?
By electrical impulse.
Resting Membrane Potential = slow waves (stomach ~ 3min, small int ~ 10-12min).
RMP = Base Electrical Rhythm (BER)
Spike potential = > -40mV at peak of BER if there is a stimulus = Ca + Calmodulin.
*See slide 11 Motility lecture
Depolarization by:
Hyperpolarization by:
stretch, ACh/parasymp, gastrin, serotonin, subst. P (tachykinin)
NE, sympathetics, Vasointestinal Peptide, NO?
Peristalsis:
May be under more vagal/extrinsic control
*slide 12 motility helpful
Segmentation:
May be under more intrinsic (enteric nerve) control
*slide 13 motility helpful
Contraction of the gall bladder releases ____ into the _________, which facilitates ____ absorption. _____ stimulation relaxes the sphincter of Oddi (into the duodenum), and later in digestion (during the intestinal phase) the hormone ___(in addition to vagal stimulation) will stimulate gallbladder ___________.
bile, duodenum, lipid
Vagal, CCK, contraction
In the colon, the_________ contract to make sacs in the colon (_______). This is _________ propulsion. It is SLOW, and designed for storage and dehydration of _____ to feces.
taneia coli
haustrae
segmental (NOT segmentation)
chyme
Haustrae are formed by contraction of the __________.
taneia coli
Mass Movements:
• These are peristaltic contractions that are stimulated by GI __________ and the ______ nerve, in response to ______ in the upper GI tract. (this works great in babies!) The haustrae smooth out into a tube, and the mass movement contractions force the feces into the descending colon and rectum. This will typically stimulate the defecation reflex (or rectosphincteric reflex).
hormones, vagus
chyme
Clinical Significance of GI Motility:
- Constipation
- Diarrhea
- Inflammatory Bowel Disease
- Inflammatory Bowel Syndrome
- Congenital disorders (eg, Hirschsprung’s d.)
Rectosphincteric reflex =
transient involuntary relaxation of the internal anal sphincter in response to distention of the rectum.
Gastrocolic reflex =
an increase in motility of the colon consisting primarily of giant migrating contractions, or mass movements, in response to stretch in the stomach and byproducts of digestion in the small intestine. Thus, this reflex is responsible for the urge to defecate following a meal. The small intestine also shows a similar motility response. The gastrocolic reflex’s function in driving existing intestinal contents through the digestive system helps make way for ingested food.
Secretions through the GI tract:
Mouth =
Saliva
Lingual lipase
Salivary alpha-amylase
R-Proteins = Transcobalamin-1 (TC-1)
Esophagus =
Electrolytes
mucus
Stomach =
HCl, intrinsic factor pepsinogens gastric lipase mucus, gastrin somatostatin histamines
Pancreas:
Exocrine glands =
buffers and enzyme (tripson, chymotrypsin, procarboxypeptidase, lipase, colipase, proelastase, alpha-amylase) monitor peptides (trypsin inhibitor; stimulates CCK)
Pancreas:
Endocrine Glands =
insulin
glucagon
somatostatin
Liver and gallbladder =
bile and buffers (electrolyte)
Small intestine =
Buffers (mucus and electrolytes) enterokinase brush border disaccharidases brush border peptidases secretin gastrin CCK VIP GIP motilin 5HT somatostatin
Hormones secreted by the GI tract: Gastrin Site of secretion = Stimuli = Actions =
G-cells in antrum of stomach and in the duodenum
Stretch, peptides, amino acids, vagus (through GRP)
Stimulate gastric H+, increased lower GI motility, increased gastric mixing
Hormones secreted by the GI tract: Secretin Site of secretion = Stimuli = Actions =
S-cells of the duodenum
Acidic chyme
increased pancreatic, biliary and intestinal buffers, decreased gastric H+
Hormones secreted by the GI tract: Cholecystokinin (CCK) Site of secretion = Stimuli = Actions =
I-cells of the duodenum and jejunum
Small peptides, amino acids and fats
increased pancreatic enzyme secretion, contracts gallbladder, relaxes Sph. Of Oddi
Hormones secreted by the GI tract: Glucose Insulinotropic Peptide (gastric inhibitory peptide, GIP) Site of secretion = Stimuli = Actions =
Duodenum and jejunum
Fatty acids, glucose, amino acids
increased pancreatic insulin secretion, (decreased gastric H+)
** GIP really doesn’t have physiologic effect on acid, only pharmacologic
Hormones secreted by the GI tract: Motilin Site of secretion = Stimuli = Actions =
M-cells of the duodenum
Fasting
Stimulates Phase III MMC contractions
Hormones secreted by the GI tract: Glucagon-Like Peptide (GLP)-1 and Peptide YY Site of secretion = Stimuli = Actions =
Mainly jejunum/lower SI Jejunum/ileum
Chyme
Satiety (decreased hypothalamic NPY)
Hormones secreted by the GI tract: Ghrelin Site of secretion = Stimuli = Actions =
Oxnytic cells of stomach
Fasting
Hunger (increased hypothalamic NPY)
Hunger:
In the fasting state, _______ is secreted into blood from oxnytic cells in the stomach.
In the arcuate nucleus of the ______________ ghrelin stimulates ___, an orexigenic peptide (stimuates _______).
ghrelin, hypothalamus, NPY, hunger
Satiety:
When you eat, several peptides, including peptide __ and _____ are secreted into the circulation—they suppress ______________, decreasing appetite
YY, GLP-1 (glucagon-like peptide)
hypothalamic NPY
Satiety: Longer acting?
[In addition to gut peptides…. ______ is produced in adipose (and other) tissues and is considered the counterpart of ______– when you eat, glucose and insulin increase circulating ______ which decreases appetite by suppressing ___ in the arcuate nucleus. ]
Leptin
ghrelin
leptin
NPY
Daily Salivary Output:
Parotid Glands serous fluid (w/amylase)
Submandibular Glands mixed serous/mucous fluid
Sublingual Glands mucous fluid
<
>
Saliva is ALWAYS __________ to plasma
hypotonic
Saliva:
“Primary Secretion”
•Contains \_\_\_\_\_\_\_
•{Na, K+, Cl-, HCO3-]similar to \_\_\_\_\_\_\_
•Modification of \_\_\_\_ content
•Electrolyte concentration \_\_\_\_\_\_\_\_\_\_ proportional to flow of salivaamylase
plasma
ionic
directly
The PNS (through facial (\_\_\_\_\_\_\_ & \_\_\_\_\_\_\_\_ glands) and glossopharyngeal (\_\_\_\_\_\_ glands) nerves) controls salivary flow: See slide 6, secretions!!!
submax & sublingual
parotid
Regulation of Salivary Flow: the following Increases or Decreases flow? • Parasympathetics, Ach • CNS (cephalic phase) • Nausea • Esophageal distension • Chewy, flavorful foods • Dry, acidic, alkaline foods • Meats, sweets, bitter foods
Increases
Regulation of Salivary Flow: the following Increases or Decreases flow? • Sympathetics, NE • Hormones (ADH, Aldo) • Sleep • Dehydration • Drugs • aging
Decreases
What does saliva do?
- Taste - adds to it due to digestion of some nutrients
- Coagulation factors
- Antimicrobial action (decrease saliva = more cavities)
- Protection (cools hot food)
- Digestion
- Lubrication (mucus)
- Oral hygiene (no saliva at sleep = bad morning breath, swallowing flushes bacteria out)
Gastric Secretions: into lumen to make chyme
HCl = ________ cells (activated by vagal stimulation of food in stomach): starts a chemical rending of food to increase Stomach Acid (pH ___) before comes into the duodenum from the stomach. Not only under neural (vagus) control but also under intrinsic control via gastrin – a blood borne mediator and potent secretagogue.
Intrinsic factor (IF) = _______ Cells: second line of defense for ________________________. B12 attached to ____ (which prevents it _______ from being digested by pepsins in stomach). IF binds to Vit B12 at a site to protect from pancreatic proteases in the small intestine.
Pepsinogens = _____ Cells: Cleaved by HCl to pepsin (need an ______ environment to make pepsin. Pepsin breaks down proteins into smaller peptides). Start _______ digestion. _______ digestion starts in stomach. Rule of thumb ______% of digestion occurs preduodenal.
Gastrin = ____ Cells in antrum of stomach and duodenum: ONLY secreted into ______: hormonal aspect of HCl secretion. Stim by vagus nerve (PSNS) in response to food/stretch in stomach. _________ HCl secretion from parietal cells.
Lipase = _____ Cells: continues _____ digestion at ____ pH.
Mucus = _______ Cells: lubricates & sticks to cell to trap _______________
Other =
- Histamine (H1)– H1 receptors – ________ HCl
- Somatostatin (SS) – modulates/________ HCl
HCl = Parietal cells (activated by vagal stimulation of food in stomach): starts a chemical rending of food to increase SA (pH 1.5) comes into the duodenum from the stomach. Not only under neural (vagus) control but also under intrinsic control via gastrin – a blood borne mediator and potent secretagogue.
Intrinsic factor (IF) = Parietal Cells: second line of defense for vit B12 (B12 is essential and necessary for RBC maturation, no B12 = pernicious anemia). B12 attached to TC-1 (which prevents it from being digested by pepsins in stomach). IF binds toVit B12 at a site to protect from pancreatic proteases in the small intestine.
Pepsinogens = Chief Cells: Cleaved by HCl to pepsin (need an acidic environment to make pepsin. Pepsin breaks down proteins into smaller peptides). Start protein digestion. Protein digestion starts in stomach. Rule of thumb 20-30% of digestion occurs preduodenal.
Gastrin = G-Cells in antrum of stomach and duodenum: ONLY secreted into blood: hormonal aspect of HCl secretion. Stim by vagus nerve (PSNS) in response to food/stretch in stomach. Increases HCl secretion from parietal cells.
Lipase = Chief Cells: continues lipid digestion at low pH.
Mucus = Epithelial Cells: lubricates & sticks to cell to trap bicarbonate HCO3-
Other =
- Histamine (H1)– H1 receptors – increase HCl
- Somatostatin (SS) – modulates/decreases HCl
