Zoology round two digestive system

Question 1

What is one function of the G.I tract?

Answer 1

To absorb nutrients

Question 2

The G.I tract acts as a barrier against what?

Answer 2

Ingested Toxins

Question 3

Barrier and nutrient absorption are carried out by what kind of cells?

Answer 3

Epithelial cells

Question 4

Epithelium of the digestive system has large number of
stem cells

Answer 4

– Single cell-layer epithelium has a very high rate of replacement
* 2-6 days to replace the ENTIRE epithelial lining of the digestive tract
– Epithelial cells constantly getting damaged from food etc.,

Question 5

Unique Features
* G.I. tract has a resident mucosal immune system to aid in
barrier function,

Answer 5

– Contains almost 1/2 of the body’s immune cells,
* G.I. tract is under constant assault from ingested toxins.

Question 6

Cephalic phase

Answer 6

– Small amount of acid secretion to “prime” the
gastric lumen for ingested bolus
– Voluntary: can be triggered by thought
– Largely due to CNS influencing the enteric
nervous system

Question 7

Mastication (chewing)

Answer 7

• Break up bolus
• Mix with saliva
  – mucus provides
  lubrication
  – salivary amylase begins
  starch breakdown

Question 8

Swallowing

Answer 8

• Voluntarily force the bolus to the back of your
  mouth (pharynx) with back you your tongue
  – Remember the respiratory system? The pharynx is the
  upper region, from the nasal cavity - larynx
• Once in pharynx, enteric neural control becomes
  automatic (involuntary).
  – Pharynx contracts to push bolus into esophagus
  – Epiglottis flips down to close off trachea
  – Upper and lower esophageal sphincters open in unison.