HRR: secretions and motility II Flashcards
What is the cephalic phase?
Readies the GI tract for a meal; happens before we even take in food.
What happens during the cephalic phase?
Saliva production, PSNS activation enhances secretions and gall bladder contraction.
Salivary glands are innervated by…
Maxillary, facial, and glossopharyngeal nerves.
What is the oral phase?
We had taken in food; breaks up food to increase surface area with digestive enzymes.
What are the main enzymes in saliva?
Salivary amylase and lingual lipase.
What muscles are used in chewing?
Masseter, temporalis, medial and lateral pterygoids.
What are the 3 big salivary glands?
Parotid, submandibular, sublingual.
Describe PSNS innervation of the parotid gland.
- Preganglionic fibers from cranial nerve 9 (glossopharyngeal nerve) synapse at the otic ganglion.
- The postganglionic fibers merge with the auriculotemporal branch of nerve 5 (trigeminal) to stimulate the parotid gland via ACh.
Describe the PSNS innervation of submandibular and sublingual glands.
- Preganglionic fibers from cranial nerve 7 (facial nerve) travel via chorda tympani to the submandibular ganglion.
- The postganglionic fibers merge with the lingual nerve from cranial nerve 5 (trigeminal) to stimulate the glands via ACh.
Describe sympathetic innervation of salivary glands.
- Preganglionic fibers from the spinal cord synapse in the superior cervical sympathetic ganglion
- postganglionic fibers travel via adjacent nerves and vessels to stimulate the glands via norepinephrine.
Which is responsible for protein/enzyme secretion and production: PSNS OR SNS?
SNS.
The parotid gland has ___ secretion.
Serous.
The submandibular gland has ___ secretion.
Serous/mucous.
The sublingual gland has ___ secretion.
Mucous.
What are acinar cells?
Cells that determine secretion type in salivary glands. They’re the ‘end pieces’ in the structure of glands and are stimulated by ACh and substance P.
Describe movement of salivary fluid starting at acini.
Acini, intercalated ducts, striated ducts, excretory ducts, single large duct taking saliva to the mouth.
Acinar cells make __ secretion.
Primary.
Ductal cells make ___ secretion.
Secondary (modified).
Describe the contents of saliva.
Water, potassium, bicarb, sodium, digestive enzymes. Generally hypotonic.
What is primary secretion?
The fluid produced by acinar cells that is high in amylase, mucin, potassium, bicarb, sodium, chloride, and water.
Describe how acinar cells secrete fluid.
- ACh binds to a receptor on the basolateral membrane, increasing intracellular calcium
- This drives the sodium potassium pump, removing sodium from the cell.
- The NCCK2 pump then brings in sodium, chloride, and potassium.
- The sodium, chloride, and bicarb will leave the cell on the luminal side, bringing water with them through leaky tight junctions.
What is secondary secretion?
Striated ducts reabsorb sodium and chloride and secrete more potassium and bicarb, increasing osmolarity to almost isotonic and alkalizing it.
Are tight junctions in acinar cells or striated ducts leakier?
Acinar cells.
The swallowing center involves which nerves?
Trigeminal, glossopharyngeal, vagus, hypoglossal.
The nucleus ambiguous is necessary in the…
Swallowing center.
What is inhibited as we swallow?
Respiration and vomiting.
Describe the process of swallowing.
- The tip of the tongue presses against the hard palate to move bolus up and back into the mouth.
- Bolus enters the pharynx, stimulating touch receptors to initiate swallowing reflex.
- Soft palate pulls upward, and nasopharynx is blocked via palatopharyngeal folds. This opens a passage to the pharynx.
- Vocal cords close, and larynx moves forward and up against the epiglottis to prevent aspiration and open upper esophageal sphincter
- UES relaxes to prepare upper esophagus.
- Pharyngeal constrictor muscles contract and propel bolus into the upper esophagus.
What are the 3 things preventing food from going through the airway?
Closing epiglottis, opening UES, inhibiting respiration.
What is the primary job of the esophagus?
Propel food bolus to the stomach via peristalsis.
Describe esophageal sphincters at rest.
They are contracted to prevent reflux or regurgitation via tonic contraction through ACh/substance P.
What stimulates relaxation of esophageal sphincters?
NO and VIP.
Describe the functions of the inner circular layer in the esophagus.
It contracts behind the bolus and relaxes ahead of the bolus to propel it forward.
Describe the functions of the outer longitudinal layer in the esophagus.
It relaxes behind and contracts ahead of the bolus to dilate the lumen so it can receive the bolus.
Much of peristalsis is regulated by…
The myenteric plexus.
What is secondary peristalsis?
Squeezing of the esophagus that does not happen due to ingestion of food but instead happens as a result of distension to clear the esophagus. This could be from retained bolus, refluxed contents, etc.
When is receptive relaxation?
The LES opens and the proximal stomach relaxes to accommodate incoming food.
What neural processes drive receptive relaxation?
Myenteric inhibitor neurons and vagal relaxation.
What is Sjogren’s syndrome?
Autoimmune condition that attacks salivary glands.
What is sialolithiasis?
Stone in a duct which causes obstruction, swelling, and pain.
How does cystic fibrosis impact saliva?
It will become thick and more mucousy.
What is zenker’s diverticulum?
Weakness in the wall of Killian’s triangle causing a diverticular outpouching of the upper esophagus.
What is achalasia?
LES struggles to relax in response to swallowing. Usually due to myenteric plexus degeneration, specifically inhibitor neurons, causing the tonic contraction to occur constantly.
What is the buzzword for achalasia?
Bird-beak appearance.
What structures act as a barrier to prevent reflux?
LES, diaphragmatic crura, gastroesophageal flip valve.
What is Barrett’s esophagus?
A change in the lining of the distal esophagus from stratified squamous to intestinal columnar epithelium via intestinal metaplasia. This happens in response to excessive acid exposure and is supposed to be protective, but predisposes the person to adenocarcinoma.
