Chewing-swallowing-esophageal Motility

Question 1

Saliva general information

Answer 1

Produces on average 1000 mL

Average pH = 6.0 -7.0

• high levels of bicarbonate ions and potassium ions
• is a hypotonic solution in the mouth

Increased secretion = parasympathetics

Factors that decrease saliva

• dehydration
• atropine
• sleep

Question 2

What enzymes are in saliva?

Answer 2

1) (a)-amylase (ptyalin)
- initiates digestion of carbohydrates by hydrolysis (a)-1,4 bonds to form disaccharides
- inactivated by low pH of the stomach

2) lingual lipase
- initiates digestion of lipids
- breaks down triglycerides into FA’s and monoglycerides
- is NOT inactivated by stomach acid

lingual lipase can cleave FAs from all three positions on a triglyceride (compared to pancreatic lipase)

Question 3

What are the antibacterial actions of saliva

Answer 3

Lysozyme = attacks bacteria and helps digestion

Lactoferrin = attacks pathogens as well as binds iron ions (preventing iron from being used as fuel source)
- also hydrolysis RNA genome of pathogens

Thiocyanate ions = requires lactoferrin, defending or lysozyme to pierce the bacteria, but then rush inside and are bactericidal

IgA = antibody in the saliva

Defensins = pokes holes and binds to receptors of pathogens

Question 4

Swallowing mechanism

Answer 4

1) amylase breaks down carbohydrates
2) teeth crush the food into a bolus
3) the bolus is swallowed (deglutition) down the pharyngitis to the esophagus

Question 5

Swallowing phases

Answer 5

1) oral phase
- VOLUNTARY
- tongue pushes bolus to the oropharynx

2) pharyngeal phase
- INVOLUNTARY
- mechanoreceptors, thermoreceptors and taste receptors in the pharynx/upper esophagus detect food presence
- these receptors then send afferents to the swallowing center in the medulla
- medulla sends efferents via vagus and glossopharyngeal which causes pharynx and esophagus muscles to contract
- also, causes soft palate/uvula to close path to nasopharynx and epiglottis to cover the trachea. The UES is also relaxed allow bolus to move through it

3) esophageal phase
- UES closes and the swallowing center signals to the vagus nerve to contract esophageal muscles causing peristalsis of the bolus down to the stomach
- LES relaxes as well and the bolus enters the stomach

Question 6

How is the muscles of the esophagus broken down?

Answer 6

Upper 1/3 = striated muscles
- are voluntary

Lower 2/3 = smooth muscles
- are involuntary

Question 7

What are the main neurotransmitters used in LES relaxation?

Answer 7

VIP and nitric oxide

- released via vagal efferents and myenteric plexus

Question 8

GERD

Answer 8

Caused by any of the following

• inappropriate relaxation of the LES
• increased intrabdominal pressure (being obese)
• hiatal hernia presence

Results in stomach acid getting reflexes through the LES. This results in “Barrett esophagus” where stratified squamous tissues begin metaplasia into columnar cells

• increases risks of cancer
• is painful like heartburn

Question 9

Achalasia

Answer 9

A disorder in which peristalsis of the lower 2/3 of the esophagus fails and the LES fails to relax and allow the bolus through
- is believed to be due to damage to the myenteric plexus

Esophageal pressure charts will show upper/middle and lower esophagus all contract at the same time (bad) and the the LES will tonically tighten up after swallowing has initiated (usually remains relaxed)
- pressures in LES is around 60-80 (normal is 0-10)

imaging will show “birds beak” esophagus

Question 10

What is the intrathoracic, intraesophageal and intraabdominal pressure like?

Answer 10

Intrathroacic = intraesophageal&raquo_space; intrabdominal
- this is why food travels down the esophagus (also gravity)

• this is also why GERD can form in pregnancy or obesity patients*