GI Control Systems of the Gut Flashcards
One of the most common problems in small animals
Canine gastritis
Equine gastric ulcer
Over 75% of the cases (especially race track)
Because they’re competitive and want to run
Margo plicatis
Separation between the glandular and nonglandular sides of the stomach
Left displacement of the Abomasum (LDA)
The abomasum is normally seen on the right of ruminants stomach, but you can see it on the left side
Right Abomasum displacement
Abomasum seen on the top of the stomach
Gastrointestinal Physiology
Normal function, not in clinics
Gastroenterology
Clinical physiology (seen in clinics)
What does general GI Physiology include?
Includes: definition, divisions of the gut, histology of the gut and control systems
Special GI Physiology
Includes: motility, secretion, digestion/ absorption, fermentation
GI tract definition
A tube-like structure that extends from the mouth to the anus and supplies the body, including itself, with nutrients, water and electrolytes by performing 4 functions, digestions, absorption, secretion and motility
Division of the gut
Mouth
Esophagus
Stomach
Small intestine (duodenum, jejunum, ileum)
Large Intestine (cecum, colon and rectum)
What are the 4 parts of the gut?
- Mucosa
- Submucosa
- Muscularis
- Serosa
Clinical considerations if the serosa
It’s apart of the peritoneum
If the tissue is dry —> adhesions —> peritonitis
So during surgery you want to keep it wet and clean
What makes up the muscularis of the gut?
Inner circular muscle (thick, toward lumen)
Myenteric muscle
Outer longitudinal muscle (thin, away from lumen)
Submucosa
Strong, holding layer
If you don’t suture it’ll lead to intestinal rupture
Includes the submucosal plexus
Mucosa
Muscularis mucosa
Lamina propria
Epithelium (secretion of gut from endocrine cells)
What is the foundation of the mucosa level?
Lamina propria
What do you do to relieve Esophageal Achalasia?
Myotomy/ Myectomy where you cut the muscle to relieve pressure
But in this case don’t cut the submucosa!
What are the systems located within the wall of the GI tract referred to?
Intrinsic systems
What are the systems located outside the wall of the GI tract referred to?
Extrinsic systems
What is within the intrinsic system?
Nerves- Enteric nervous system
Endocrine Secretions -Secretin, Gastrin, CCK, GIP and Motilin
What is within the extrinsic system?
Nerves- Vagus and splanchic nerves
Endocrine Secretions -Aldosterone
What are the 2 plexes within the enteric nervous system?
Myenteric and Submucosa
Myenteric nerves plexus
Auerbach (discoverer)
Between the 2 muscle layers of the GI tract
F: motility
Submucosa nerve plexus
Meissner
Lies under or over the submucosa depending on orientation
F: control of blood flow and secretions
How many neurons are within the ENS?
Over 100 million
What is the difference between the enteric and other nerve cells?
Regular neurons fire the neurotransmitter from the end of the axon terminal, while enteric nerve cells neurotransmitter is fired from the whole length of the neuron
Within the enteric system, where are the neurotransmitters secreted from?
Varicosities
What will make the AP in regular nerves?
When Na+ enters the cell
What will make AP in smooth muscle cells?
When Na+ and Ca+ enter the cell
Why are channels of enteric neurons slow to open and close?
For the longer duration of AP in the enteric nerves
How do you classify enteric nerves?
Morphology (shape)
Electrophysiology (properties/ activity)
Chemical coding (neurotransmitters present)
How is morphology of the enteric system classified?
Dogiel type 1 (small cell body, short multiple dendrites)
Dogiel type 2 (large cell body, long terminal 1)
Afterhyperpolarization type enteric nerve
Continuous
Goes from the stomach to the rectum
S type enteric nerve
Synaptic (quick)
Within the anal sphincter
What neurotransmitters are present in enteric neurons? (chemical coding)
Aborad Direction (inhibitory motor neurons) with vasoactive intestinal peptide and nitric oxide
Orad direction (excitatory motor neurons) with substance P and ACh
Interstitial cells of Cajal (ICCs)
Triangular cell body with multiple dendrites
Generates electrical activity on its own without stimulation
When does contraction occur?
When AP (from enteric nerve) meets the plateau phase (Phase 3 of slow waves, ICCS)
Slow wave
Resting (0)
Rising (1, depolarization and rising ca++)
Plateau (3, where contraction takes place)
Falling (4, repolarization, falling phase, k+ out)
Resting (0)
What allows Na++ to enter the smooth muscle cell?
Slows waves from ICCs
How does the stomach contract ?
Doesn’t need an AP from and enteric neuron, only the plateau phase (slow wave)
What does loss of ICCs lead to?
Loss of contraction
Intestinal obstruction
Motility problems
What will an enterectomy do to ICCs
Killing ICCs at the incision point
ICCs only affected in recovery time
Afterwards the ICCs will regenerate and re-wire
What causes intestinal obstruction?
Plasticity (when older animals have trouble contracting gut)
Age (because regeneration takes place when young)
What are the motility problems?
Chronic intestinal Pseudo-obstruction
Stromal Tumors (making ICCs non-functional)
Sphincter
Area with continuous contraction unless you need quick relaxation for a short time
Ex: bile from duodenum or gall bladder
What are the nerves of the extrinic control system?
Vagus and pelvic nerves (parasympathetic)- stimulates gut motility
Splanchnic nerve (sympathetic)- inhibits gut motility
What are the GI hormones?
Gastrin
Cholecystokinin
Secretin
Gastric Inhibitory Peptide
Motilin
Where are all the GI hormones secreted from ?
The duodenum (small intestine)
What is the only secretion from the stomach?
Gastrin
What is the function of gastrin?
Increase gastric secretion
Cholecytokinin function
Contract the gall bladder, releases bile into the duodenum, and exocrine pancreatic secretion
What is the function of Gastric inhibitory peptide?
Inhibits acid secretion
Stimulates insulin secretion
What is the function of motilin?
Increased motility
What is the stimuli of gastrin?
Protein (meat)
What is the stimuli of CCK?
Fat and protein
What is the stimuli of secretin
Nature’s antacid, depending on what foods will increase acids
What is the stimuli of motilin?
Fasting (no food)
Which hormones stimulates the gut?
Gastrin, CCK and motilin
What inhibits the gut?
Secretin
What are the two mechanisms for gastrin secretion?
Acid from the parietal cells by the vagus nerve or Ach/ gastrin stimulation
What increases gastric secretion?
G cells
What does the increase of gastric acid cause?
Gastric duodenum ulcers
What is gastrin important in diagnosing?
Zollinger-ellison syndrome or gastrinoma (duodenum tumor)
Non-beta cell pancreatic cancer
Duodenal cancer
Hypergastrinemia/ Diarrhea/ Hypokalemia/ Steatorrhea (fatty stool)
What are the little and big gastrin?
Antrum (G17) and Duodenum (G34)
How do you stop gastrin?
- H2 blocks (histamine receptors)
- Branch vagotomy (cutting certain vagus nerve branch)
Obesity in vet med
Overweight- 56%
Obesity- 25%
Giving gut hormones will help with weight
What does CCK inhibit?
Gastric emptying and food intake (possible anti-obesity medicine
What is the term called at the end of the first meal and before the second meal (not eating)?
Intermeal interval
Surgical treatments for obesity
Roux-en-Y Gastric Bypass
Vertical Sleeve Gastrectomy
Roux-en-Y Gastric Bypass
Surgery changing the structure of GI so food can pass quickly for minimal digestion
Connects the intestine to the jejunum
Vertical Sleeve Gastrectomy
Suturing the stomach so it looks like a sleeve
Decreasing the size of the stomach
Intra-arterial Catheterization
Placing a catheter to the GI tract as closely as you can
1. Aorta
2. Cranial bicentric artery
3. Celiac (artery supplying stomach
Giving CCK meds after
Reduction of body weight by CCK-8
Loose 1/3 of your weight
For heavy people
What does secretin inhibit?
Gatric secretion (nature’s anti-acid)
What does secretin stimulate?
Gastrin secretion during gastrinoma (tumor)
Pancreatic Bicarbonate
Pancreatic Water
Pepsinogen Secretion
Migrating Motor Complex (MMC)
Peristaltic movement
Phases: 1= silent, 2 and 3= activity front
Generated by motilin
What activates a parietal cell?
Gastrin and vagus
(ECL then parietal)
