GI Physiology (1-4)

What does 'orad' mean in gastrointestinal anatomy?

Toward the mouth or oral region.

What does 'aborad' mean in gastrointestinal anatomy?

Away from the mouth or oral region.

What does 'proximal' mean in gastrointestinal anatomy?

Toward the oral cavity.

What does 'distal' mean in gastrointestinal anatomy?

Away from the oral cavity.

What are the major anatomical structures of the gastrointestinal tract?

Mouth, esophagus, stomach, small intestine, large intestine, rectum/anus.

How does the gastrointestinal tract anatomy differ between monogastric animals and ruminants?

Monogastric animals have a single chambered stomach; ruminants have a complex stomach with multiple chambers.

What is the function of the rumen in ruminants?

Site of fermentation in the forestomach before final digestion.

Where does fermentation occur in hind-gut fermenters?

In the large intestine.

What are the physiological functions of the stomach?

Digestion (acidic, enzymatic, and mechanical).

What is the primary function of the small intestine?

Enzymatic digestion, absorption, and immune function.

What is the role of the large intestine?

Fermentation and absorption of water.

What is the function of the cecum?

Fermentation.

What are the layers of the tubular GI tract?

Mucosa, submucosa, muscularis, serosa.

What is the primary function of the mucosa in the GI tract?

Lines the lumen of the GI tract.

What does the muscularis layer do?

Produces wave-like contractions (peristalsis).

What is peristalsis?

Progression of coordinated contractions and relaxations of the smooth muscles of the GI tract to propel food.

What is the function of the enteric nervous system (ENS)?

Controls nearly all aspects of GI function including motility, secretions, and blood flow.

What are the two components of the enteric nervous system?

Myenteric (Auerbach) plexus and submucosal (Meissner) plexus.

What is the role of the autonomic nervous system (ANS) in GI motility?

Regulates GI function through parasympathetic and sympathetic innervation.

What is the function of the lower esophageal sphincter (LES)?

Prevents stomach acid reflux and keeps stomach contents from entering the esophagus.

What does the pyloric sphincter control?

Passage between the stomach and duodenum.

What is the role of the ileocecal valve?

Prevents bacterial overgrowth between the ileum and colon.

What is the function of goblet cells in the intestinal epithelium?

Secretes mucus for protection and lubrication.

What is the role of Paneth cells?

Secretes antimicrobial peptides and growth factors.

How often do epithelial cells in the intestine regenerate?

Every 3-5 days.

What is the significance of epithelial regeneration in the intestine?

Critical for barrier maintenance and integrity of the intestinal lining.

What are tight junctions in the intestinal barrier?

Protein networks that seal the space between adjacent epithelial cells and regulate transport.

What is the last line of defense in the intestinal barrier?

The adaptive immune system located in the lamina propria.

What is colitis?

Inflammation of the small intestine.

What can deep injury in the GI tract result in?

Loss of intestinal lining and damage to stem cells.

How does inflammation affect the GI tract?

It can disrupt the regeneration process.

What role does GI microbiota play in mucosal physiology?

It competes with pathogens to prevent infections and influences GI motility.

What is the relationship between microbiota and gut health?

Microbiota-derived signals are crucial for immune response and maintaining gut health balance.

What is microbiota?

Organisms in a defined environment.

What is a microbiome?

Organisms and their output, including proteins and metabolites.

What is a metagenome?

All of the genes present in a microbiota.

What does GALT stand for?

Gut-associated lymphoid tissue.

What is the function of GALT?

It differentiates between nutrients and potentially harmful substances.

What is the largest immune organ in the body?

GALT.

How does diet affect microbiota function?

Diet plays a key role in supporting microbiota function.

What is the importance of maintaining microbiota diversity?

It is crucial for a healthy gut.

What does the immune system do in relation to the GI tract?

It helps differentiate between nutrients and harmful substances.

What is the role of regulatory T-cells in the GI tract?

They support immune response and prevent excessive immune reactions.

What are lymphoid follicles?

Clusters of immune cells, usually B lymphocytes, in the mucosa of the intestine.

What are Peyer's patches?

Immune system tissues found in the small intestine, specifically the ileum, that monitor digestive tract contents for pathogens.

What is the function of the GI microbiota?

It includes microorganisms that live in the GI tract, compete with pathogens, and influence GI motility by producing neurotransmitters.

What is peritoneal fluid?

Abdominal fluid used to lubricate the peritoneum, normally clear and low in cell count and protein.

What are some diagnostic tests for evaluating bacteria in the GI tract?

Culture, PCR, toxin ELISA, dysbiosis index.

What is the prehension phase of swallowing?

The grasping of food with lips or teeth.

Which cranial nerves are involved in the prehension phase?

CN V (jaw), CN VII (lips), CN XII (tongue).

What occurs during the mastication phase?

Breakdown of food into a bolus to aid in swallowing.

What muscles are involved in mastication?

Masseter, temporalis, pterygoids, and digastrics.

What is the pharyngeal phase of swallowing?

An involuntary phase where the bolus is pushed to the oropharynx.

What is the role of the medulla oblongata in swallowing?

It coordinates the involuntary nervous system to prevent aspiration.

What are the esophageal sphincters?

The upper esophageal sphincter (UES) and lower esophageal sphincter (LES) prevent reflux.

What is the significance of swallowing apnea?

Breathing is momentarily interrupted during the pharyngeal phase to prevent aspiration.

What are species-specific differences in prehensile organs?

Canine: tongue and teeth; Bovine: tongue; Equine: lips.

What is the saliva composition in bovines?

Bovines produce a large amount of saliva which contains bicarbonate and phosphate

What is quidding in equines?

Dropping feed due to difficulty in making a food bolus.

What is the length of the equine esophagus?

120-150 cm.

What type of muscle is present in the esophagus of dogs and ruminants?

Entirely striated muscle.

What is Myasthenia Gravis?

An autoimmune disease causing fluctuating weakness in voluntary muscles.

How does Myasthenia Gravis affect dogs?

It can cause severe megaesophagus due to entirely striated esophageal muscle.

What is choke in equines?

Esophageal obstruction occurring at the junction of striated and smooth muscle.

What can cause choke in equines?

Food not being lubricated, motility disorder, or low-quality feed.

What is the role of regulatory T-cells (Tregs) in the immune response?

They maintain tolerance and respond to pathogens.

What are the specialized cells involved in antigen sampling in the GI tract?

Paneth cells and M-cells (peyers patches and lymphoid folliciles) /dendritic cells.

What is the appearance of normal peritoneal fluid?

Clear, yellow/straw colored, with low cell count and low protein.

What is the function of the esophageal muscles?

To facilitate the movement of the bolus through peristaltic waves.

What is the role of the cough reflex during swallowing?

To expel food if it mistakenly enters the airway.

What is the dysbiosis index?

A PCR test for different pathogens in the GI tract.

What is the role of saliva in canines?

Used for cooling, evaporation, and wound licking.

What is the significance of the transition zone in the esophagus?

It marks the change from striated to smooth muscle.

What is the role of the UES during swallowing?

It relaxes to allow the bolus of food to enter the esophagus.

What is the effect of Buscopan in equines?

It prevents peristalsis by acting as a muscarinic receptor antagonist.