Cephalic, Oral and Esophageal Phases Flashcards Preview

FHB Block 3 > Cephalic, Oral and Esophageal Phases > Flashcards

Flashcards in Cephalic, Oral and Esophageal Phases Deck (32):
1

What is the cephalic phase?

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

2

What activates the cephalic phase?

Idea of food, olfaction, visual stimuli, auditory stimuli

3

What nerve regulates increased salivary secretion during the cephalic phase?

9th cranial nerve

4

How is the oral phase different from the cephalic phase?

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

5

Name two enzymes that begin to digest food in oral phase

Salivary amylase and lingual lipase

6

What is the salivary mucin for?

lubrications- helps with chewing and swallowing

7

Are nutrients absorbed in the mouth?

No- with the exception of alcohol and some drugs

8

What is xerostomia and why is it a problem?

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

9

Secretions in the mouth are under what type of regulation?

Regulation of salivary secretions are 100% neural

10

What are the 3 major pairs of salivary glands?

Parotid, submandibular and sublingual

11

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

Serous- made up of water, electrolytes and enzymes

12

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

Mucous- made up of mucin glycoprotein

13

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

Mixed

14

Describe the general structure of a secretory gland

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)

15

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

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

16

What is the osmolality of initial saliva?

Isotonic

17

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

Net absorption of NaCl and secretion of KHCO3.

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

18

How does the composition of saliva change with flow rate?

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

19

What is the dominant regulation of saliva production/secretion?

Parasympathetic innervation

There is also sympathetic, but parasympathetic dominates

20

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

CN VII and IX

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

21

Where does sympathetic innervation of salivary glands originate?

T1-T3

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

22

Describe the swallowing reflex

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

23

What is the pharyngeal phase of swallowing?

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

24

What two things regulate the esophageal phase of swallowing?

Swallowing reflex and enteric nervous system

25

Describe the events of the Esophageal phase of swallowing

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



26

What hormones mediated relaxation of the LES?

VIP and NO

27

What is receptive relaxation?

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

28

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

Because increased abdominal pressure pushes gastric juices through the LES

GERD

29

How is GERD treated?

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

30

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

The LES no longer works properly

31

What is achalasia?

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

32

How is achalasia treated?

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