Cephalic, Oral and Esophageal Phases

Question 1

What is the cephalic phase?

Answer 1

Activation of the GI tract in readiness for the meal – stimuli triggers responses in the GI system in the absence of food ingestion

Question 2

What activates the cephalic phase?

Answer 2

Idea of food, olfaction, visual stimuli, auditory stimuli

Question 3

What nerve regulates increased salivary secretion during the cephalic phase?

Answer 3

9th cranial nerve

Question 4

How is the oral phase different from the cephalic phase?

Answer 4

Food is introduced – leads to sensory inputs from taste buds and mechanical receptors in the mouth and upper pharynx

Question 5

Name two enzymes that begin to digest food in oral phase

Answer 5

Salivary amylase and lingual lipase

Question 6

What is the salivary mucin for?

Answer 6

lubrications- helps with chewing and swallowing

Question 7

Are nutrients absorbed in the mouth?

Answer 7

No- with the exception of alcohol and some drugs

Question 8

What is xerostomia and why is it a problem?

Answer 8

Dry mouth- leads to decrease in pH in the oral cavity which causes tooth decay, esophageal erosions and difficulty swallowing

Question 9

Secretions in the mouth are under what type of regulation?

Answer 9

Regulation of salivary secretions are 100% neural

Question 10

What are the 3 major pairs of salivary glands?

Answer 10

Parotid, submandibular and sublingual

Question 11

Classify the secretions of the parotid glands (serous, mucous or mixed)

Answer 11

Serous- made up of water, electrolytes and enzymes

Question 12

Classify the secretions of the sublingual glands (serous, mucous or mixed)

Answer 12

Mucous- made up of mucin glycoprotein

Question 13

Classify the secretions of the submandibular glands (serous, mucous or mixed)

Answer 13

Mixed

Question 14

Describe the general structure of a secretory gland

Answer 14

Blind ended acini secrete initial saliva that drains into a network of collecting ducts responsible for the modification of the saliva (through altering the electrolyte concentration)

Question 15

What is the role of myoepithelial cells in the secretory glands of the GI tract?

Answer 15

They contain actin and myosin fibers which allow them to contract following neural stimulation. This expels saliva from the acinar cells into the duct system

Question 16

What is the osmolality of initial saliva?

Answer 16

Isotonic

Question 17

What is the net result of the salivary ductal cells on the composition of saliva?

Answer 17

Net absorption of NaCl and secretion of KHCO3.

There is a net absorption of solute such that final saliva is hypotonic

Question 18

How does the composition of saliva change with flow rate?

Answer 18

The faster the flow rate, the less time saliva has to be modified by the ductal cells, and the more similar to plasma it is

Exception: as parasympathetic stimulation increases flow rate, secretion of HCO3- is selectively stimulated

Question 19

What is the dominant regulation of saliva production/secretion?

Answer 19

Parasympathetic innervation

There is also sympathetic, but parasympathetic dominates

Question 20

What CN’s provide parasympathetic innervation of the salivary glands?

Answer 20

CN VII and IX

ACh is released, binds to muscarinic receptors and IP3 signalling increases intracellular Ca2+ –> increased salivary secretion (

Question 21

Where does sympathetic innervation of salivary glands originate?

Answer 21

T1-T3

NE interacts with Beta adrenergic receptors and production of cAMP increases saliva secretion

Question 22

Describe the swallowing reflex

Answer 22

Propels food down the GI tract, meanwhile inhibiting respiration and food entrance into the trachea while swallowing

Begins when food reaches touch receptors near the opening of the pharynx

Question 23

What is the pharyngeal phase of swallowing?

Answer 23

Soft palate is pulled upwards and food moves into the pharynx

The UES relaxes to receive food bolus, and peristalsis is initiated

The swallowing reflex closes the UES after food crosses through to prevent reflux

Question 24

What two things regulate the esophageal phase of swallowing?

Answer 24

Swallowing reflex and enteric nervous system

Question 25

Describe the events of the Esophageal phase of swallowing

Answer 25

Primary peristaltic contraction pushes food down the esophagus. If primary is not enough, enteric nervous system initiates a secondary peristalsis to clear the esophagus of the bolus

LES relaxes to allow food to move through

Question 26

What hormones mediated relaxation of the LES?

Answer 26

VIP and NO

Question 27

What is receptive relaxation?

Answer 27

The orad of the stomach relaxes in response to the LES relaxing to make room for the food bolus

Question 28

Why do pregnant or obese people have increased rates of gastroesophageal reflux?

Answer 28

Because increased abdominal pressure pushes gastric juices through the LES

GERD

Question 29

How is GERD treated?

Answer 29

H2 receptor antagonists (block histamine effects) or omepraxole (proton pump inhibitors) – both blocks the secretion of HCl

Question 30

What is the major problem leading to gastric reflux with a hernia?

Answer 30

The LES no longer works properly

Question 31

What is achalasia?

Answer 31

Motility disorder of the esophagus– smooth muscle layer does not have normal peristalsis, and LES does not relax normally in response to swallowing

Question 32

How is achalasia treated?

Answer 32

Ca2+ channel blockers or BOTOX injection into the LES to prevent constriction and allow LES To relax