GI Lecture 46 & 47 Flashcards
Cephalic phase
- activation of the GI tract in readiness for the meal
- thinking about food
- 10% stimulation
Preparation to receive/digest food
- increased salivary secretion
- increased gastric secretion
- increased pancreatic secretion
- Gall bladder Contractoin
- Relaxation of Oddi’s sphincter
Oral phase
- Same responses as cephalic phase
- Additional activation of GI from sensory of taste buds and mechanical receptors in mouth and upper pharynx
Chewing
- digestion begins here
- no absorption in mouth
Xerostomia
- dry mouth
- impaired salivary secretion
- lower pH as a result
- tooth decay, esophageal erosions, difficulty swallowing
Chewing Muscles
- Temporalis
- Masseters
- Lateral Pterygoids
- Medial Pterygoids
What innervates the chewing muscles?
Mandibular division (branch 3) of Trigeminal Nerve
Secretions from the GI tract are from? (3)
- glands associated with tract (salivary glands, pancreas, liver)
- glands formed by gut wall
- intestinal mucosa itself
Secretaogogues
any substance that stimulates secretion
What are the major salivary glands? (3)
- Parotid
- Submandibular
- Sublingual
What type of secretions are from the parotid glands?
Serous (water, electrolytes, enzymes)
What type of secretions are from sublingual glands?
Mucous (mucin glycoprotein)
What type of secretions are from submandibular glands?
Mixed (both)
Acini
units of secretion via salivary gland
Path of Saliva
Acinar cells produce initial saliva, which passes through intercalated duct, then striated duct
-out through the excretory duct and finally into the main collecting duct
Myoepithelial cells
- contract to expel saliva in forward direction (contain actin & myosin fibers)
- present in the acini and intercalated ducts
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Adenoma?
Functions of Saliva
- Lubrication of ingested food with mucus
- Protection via dilution/buffering of ingested food, neutralization during vomiting, and contains lysozyme to maintain health oral tissue
- initial digestion
Major Components of Saliva
Na, K, Ca, Mg, and Cl
-sometimes Fluoride too
Major Organic Constituents of Saliva
- Salivary amylase (initiates starch digestion)
- Lingual Lipase (lipid digestion)
- Glycoprotein (mucin upon hydration)
- Lysozyme (attacks material wall)
- Kallikrein (converts plasma protein into bradykinin vasodilate
How is human saliva hypotonic?
higher K & HCO3
lower Na & Cl
Three types of transporters
- Na-H exchanger
- Cl-HCO3 exchanger
- H-K exchanger
How is salivary secretion controlled?
- Neural
- primarily parasympathetic (IP3, Ca)
Pharyngeal phase
- soft palate pulled upward
- palatopharyngeal fold moves inward
- epiglottis covers larynx
- UES relaxes to receive food bolus
- pharynx contracts
Esophageal phase
- propels food & sphincters protect airway from swallowed material
- primary peristaltic comtraction propels food
- followed by secondary peristaltic waves to clear esophagus
- LES opens and stomach relaxes (receptive relaxation)
What is the mucosa covered by?
- stratified squamous epithelium
- only in esophagus and anal sphincters
What is metaplasia?
- squamous cells transitioning to columnar epithelium
- due to GERD
What is Barret’s disease?
squamous transitioning to intestinal cells
GERD acronym stand for?
Gastroesophageal reflux disease
What is a hiatal hernia?
- Upper portion of stomach protruding into the chest cavity through esophageal hiatus
- same symptoms as GERD
What is Achalasia?
- Smooth muscle of esophagus does not have normal peristalsis and LES does not relax normally
- damage to nerve plexus
- common symptoms include: dysphagia, regurgitation, and chest pain
Vomiting
- reverse peristalsis of small intestine
- relaxed pyloric sphincter
- forced inspiration against a closed glottis
- decrease intra-thoracic pressure and increase intra-abdominal pressure
- retching
- salivation increases
