GI Physiology

Question 1

What is the oral mucosa?

Answer 1

A thick stratified squamous epithelium that is resistant to abrasion

Question 2

What is the function of the oral mucosa?

Answer 2

Produced defensins to inhibit bacterial growth. There are many bacteria in the mouth and it’s necessary to control bacterial overgrowth. Defensins, proteins with antimicrobial properties are secreted for this purpose and you see lots of IgA in saliva. There is a need to control the oral microbiota and reduce the tendency of bacteria to stick to teeth.

Question 3

When do the deciduous teeth appear and when are they replaced?

Answer 3

Within the first 6-24 months of life, they are gradually replaced in childhood as the permanent teeth erupt usually around age 12.

Question 4

What does saliva contain?

Answer 4

Mostly water (90%)
Lingual lipases and alpha-amylase
Slightly acidic (pH 6.75-7) to provide reasonably optimal conditions for enzyme function
Mucoproteins (mucin) act as lubricants
Lysozyme
Immunoglobulins (esp IgA)
Electrolytes
Calcium and phosphate (dental repair)

Question 5

What glands release saliva?

Answer 5

Parotid, submandibular and sublingual.
- Open into the oral cavity
- The glands themselves can become inflamed.
Each produces saliva of a slightly different composition.

Question 6

How is saliva controlled?

Answer 6

By salivatory nuclei in the medulla and pons of the brainstem.

Mechanoreceptors and chemoreceptors in the mouth stimulate the production of saliva with a high water content.

Also, there is input from higher brain centers (thinking about food) and lower digestive tract (irritation) can also induce salivation

Question 7

What does contraction of the circular smooth muscle do?

Answer 7

Squeezes gut contents

Question 8

What does contraction of the longitudinal muscle do?

Answer 8

Shortens that portion of the gut

Question 9

How is the smooth muscle spontaneously active?

Answer 9

The interstitial cells of Cajal have ‘pacemaker’ activity
The enteric neurons or extrinsic neurons modulate this basic activity.

The loss of the cells of cajal can lead to gut motor dysfunction disorders

Question 10

What type of cell lines is the esophagus?

Answer 10

Stratified squamous epithelium to resist abrasion

Question 11

What is the muscularis layer of the oesophagus?

Answer 11

skeletal in first third (voluntary), smooth in last third (involuntary, mixed in the middle third

Question 12

What does the puter layer consist of?

Answer 12

Adventitia - fixed to structures by connective tissue

Question 13

What do the cells lining the gastro-oesophageal junction change from and to?

Answer 13

Lining changes from squamous to columnar epithelium (glandular)