Physio - Pernuske Flashcards
What constitutes the upper and lower GI tract?
Upper: Oral Cavity, Pharynx, Esophagus, Stomach, Small intestine Lower: Large Intestine
What are the accessory organs to the GI tract?
- Salivary glands (parotid, submandibular, sublingual) - Exocrine Pancreas - Liver- Hepatic system - Gallbladder- Biliary system
Which sphincters are voluntary? What controls involuntary vs voluntary?
Upper esophageal and external anal Voluntary sphincters are supplied by somatic nerves. Involuntary sphincters are stimulated by autonomic nerves.
Name these layers
Serosa
Longitudinal muscle
Circular muscle
Submucosae
Muscularis mucosae
Lamina propia
Epithelium
In what layer are major blood vessels and lymphatics found in the GI system?
The submocosa layer
The interface between body and environment secretion, absorption, barrier, and immunologic protection specialized folds increase surface area is called what?
Mucosa
Which cells have villi and crypts, and where are they located?
Enterocytes in the small intestine
Explain the renewal of GI epithelial cells.
Stem cells at the base of the crypts divide, differentiate and migrate to the tips of the villi:
- Apoptosis occurs every 3-6 days after which the cell is shed into the lumen.
- Prevent the accumulation of mutations due to toxin exposure
Define:
Diverticulum-
Diverticulosis-
Diverticulitis-
Diverticulum- single pouch protruding from alimentary tract. Usually false not true.
Diverticulosis- multiple diverticula
Diverticulitis- impacted with feces, inflamed, painful,
if blood vessel is eroded hemorrhage
(True diverticula contain all layers of bowel wall. False do not.)
How is mucin organized? Are enterocytes coated with this?
Protein monomers combined into complexes by disulfide links,
2 layers in the stomach and colon, 1 layer in small intestine
- Glycosylation protects the protein core from proteases and carbohydrate side chains attract water forming a gel
- Enterocytes are coated with transmembrane mucins
What are they broken down into, by what enzyme, and where are they sent?
Protein
Carbohydrates
Triglycerides
Protein –> Peptides, AA –> Capillaries
by Protease (in duodenum/jejunum)
Carbohydrates –> monosaccharides, disaccharidases –> Capillaries (by Amylase)
Triglycerides –> Fatty acid, monoglycerides –> Lymphatics
(Lipases)
Amino acids and monosaccharides are absorbed where and by what mechanism?
Amino acids and monosaccharides are absorbed in duodenum and jejunum through secondary active transport
What is absorbed in the duodenum?
Amino acids
Disaccarhides are formed, but not absorbed
Iron
What is absorbed in the jejunum and ileum?
Monosaccharides
Calcium
Folate
Fat-soluble vitamins (ADEK)
Ileum
B12, Intrinsic Factor, Bile Acids
Water and Na
CO2, H+, K+, adenosine are all what?
Vasodilators –> increase blood flow
What are some causes and effects of mesenteric ischemia?
Causes:
- Occlusive mechanisms including thrombi (mesenteric infarction)
- Non-occlusive mechanisms including prolonged reflex vasoconstriction (due to hypovolemia, heart failure) or abnormal levels of circulating vasoconstrictors (e.g, epinephrine, angiotensin II)
Effects
- Postprandial Pain, Sitophobia
- Necrosis of the tips of the villi
- Loss of barrier function of the wall of the gut and uptake of vasodilator toxins (endotoxin) from the gut resulting in Septic Shock
Average Transit time?
Esophagus
Stomach
Small Intestine
Large Intestine
Average Transit time
Esophagus – 10s
Stomach – 3-5hrs
Small Intestine – 2.5-3hrs
Large Intestine – 30-40hrs
Most of the GI tract is covered by what type of muscle?
Non-striated Smooth Muscle
- exception is striated muscle in upper third of esophagus, pharynx, external anal sphincter
(T/F) Basal resting tension or “tone” is maintained without elevation in intracellular Ca++ and without energy expenditure.
True
What is the migrating motor complex and what hormone is at play?
Migrating Motor Complex: relaxation of sphincters and contractions in stomach and small intestine occurring during fasting(interdigestive) controlled by hormone motilin
This is your “clearing house” Sweeps everything out of compartment.
Where is the Submucosal nerve plexus and Myenteric nerve plexus located? Can they operate autonomously from the CNS?
- Submucosal nerve plexus within small and large intestine, sensory and blood flow, Meissner’s
- Myenteric nerve plexus between circular and longitudinal muscle layer from esophagus to internal anus (aka Auerbach’s)
- Can operate autonomously to mediate short reflexes independent of input from the CNS
Target cell and effect?
Gastrin
Cholecystokinin (CCK)
Secretin
Gastric Inhibitory Peptide or Glucose-Dependent Insulinotropic Peptide (GIP)
Motilin
- Gastrin – G cells in antrum of stomach detect amino acids leading to pepsinogen and H+ release by parietal cells.
- Cholecystokinin (CCK) - I cells in D/J detect fat and amino acids, secretion of pancreatic enzymes and bile salts involved in fat uptake
- Secretin - S cells primarily in D/J detect acid stimulates secretion of pancreatic juice including bicarbonate and inhibits gastric motility.
- Gastric Inhibitory Peptide or Glucose-Dependent Insulinotropic Peptide (GIP)- K cells in D/J detect carbohydrates and fat to inhibit gastric acid secretion and stimulate insulin release from pancreas.
- Motilin – secreted by endocrine cells; released cyclically during fasting state to initiate Migrating Motor Complex
