GI Flashcards
What are the major functions of the GI system
Transport food
Digestion
Absorption of nutrients
After mastication, what is the motility of the different GI segments?
Deglutition
What are the functions of the GI tract movements?
Move ingesta
Retain ingesta at a given site for digestion/absorption/storage
Break up and mix food
Circulate ingesta to come in contact with all absorptive surfaces
What is the voluntary phases of deglutition?
Food is molded into bolus and pushed back into the pharynx -> activation of sensory nerve endings -> initiate involuntary portion of deglutition
What occurs during the involuntary phase of deglutition?
In pharynx and esophagus
Breathing stops momentarily -> soft palate is elevated (close off nasopharynx) -> tongue depressed against the hard palate (close oral opening) -> bend epiglottis to block laryngeal opening -> muscular constriction to move bolus into esophagus
How is food moved through the esophagus during deglutition?
Food reaches esophagus -> upper esophageal sphincter relaxes to accept the bolus
-> thoracal part of esophagus contracts while lower spinsters relax
Peristaltic movements
A condition in which food particles/fluids or stomach contents reach the upper airways
Aspiration
What is disphagia ?
Difficulty swallowing
Orapharyngeal or esophageal
What is the regulatory center for energy homeostasis?
Hypothalamus
What neuropeptide of the hypothalamus stimulates hunger?
Neuropeptide Y (NPY) and orexin
What neuropeptide of the hypothalamus inhibits hunger?
Melanocyte-stimulating hormone
What non-hypothalamic hormone stimulates hunger?
Ghrelin
What non-hypothalamic hormone inhibits hunger?
Cholecystokinin (CCK)
Peptide YY (PYY)
Lectin (fat cells-> inhibits NPY release and stimulate MSH action)
Insulin
What are the primary functions of saliva?
Protect buccal mucosa and teeth
Facilitate deglutition
Enzymatic carbohydrate digestion
PH regulation (HCO3-)
Secondary functions:
Immunologic -IgA
Thermoregulation (evaporation)
Defense in some species
What is primary saliva ?
Cl-, Na+, H2O (basolateral transporters)
What is secondary saliva?
K+ and HCO3- (apical transporters)
How is saliva secretion regulated by the PSNS and SNS?
PSNS -> M3-receptors -> contraction of myoepithelial cells
SNS -> a1-receptors -> secretion of small volumes of mucous saliva
(Innate or conditioned response)
What are the two types of salivary glands of ruminants?
Isotonic and hypotonic to plasma
What are the four different routes by which secretions of GI tissue can reach their target cells?
Endocrine
Paracrine
Autocrine
Neurocrine
What are the characterisitics of a GI hormone?
Secreted by one cell to affect another
Transported in the blood
Stimulated by food and its action must be mimicked by a synthetic analog molecule ?
What hormone is synthesized in the antrum and duodenum?
Gastrin
Where are GIP and Motilin synthesized?
Duodenum and jejunum
Where is CCK synthesized?
Duodenum, jejunum, and ileum
Secretin stimulates ___________ secretion and inhibits _________ secretion
Bicarbonate ; acid
Gastrin stimulates __________ secretions
Acid
Gastric inhibitory polypeptide inhibits__________________ secretion and stimulates ______ secretion
Gastric; insulin
What is the action of motilin?
Induction of intestinal motility during fasting
What are the three glandular zones of the stomach?
Cardias
Fundus
Pylorus
What are the 5 cell types found in the stomach?
Surface mucous cells Parietal cells Mucous neck cells Enterochromaffine cell Chief cells
Parietal cells produce?
HCl
What do chief cells produce?
Pepsinogen ->pepsin
Prochymosine -> chymosine (calves and lambs)
Enteroendocrine cells produce?
hormones
G cells -> gastrin
D cells -> somatostatin
I cells -> CCK
What cells types of the stomach produce mucus?
Mucous producing cells
What is the function of mucus in the stomach?
Glycoproteins with many cystine residues -> form disulfide bridges -> protect and lubricate the mucosa
What three hormones induce production of HCl?
Gastrin
Histamin
ACh
What stimulates Gastrin release from G cells?
Gastrin releasing hormone
Food
What inhibits gastrin secretion by G cells
Somatostatin (from D cells)
How does ACh, histamin, and gastrin induce HCl secretion
ACh -> M3 receptors on parietal cells -> DAG and IP3 activation -> release of Ca from ER and phosphorylation of protein
- > transporters inserted into membrane
- > stimulation of H+, K+, and ATPase
Gastric acid is regulated by low PH inducing _________ from D cells which inhibits ____________
Somatostatin; gastrin secretion from G cells
Enzymatic secretion by chief cells is regulated by ?
ACh
CCK
Secretin
-> DAG and IP3 -> release of Ca2+ from ER and phosphorylation of protein -> increased exocytosis from vesicles
NSAIDs can produce ulcers by inhibiting __________
COX enzymes
Epithelial damage to the mucosa of the stomach is called a __________
Gastric ulcer
Gastric ulcers can be caused by?
Bacteria eg. H.pylori
NSAID
