Download Chapter 6 Digestion and absorption 问答题 1. Depicting composition

Chapter 6
Digestion and absorption
问答题
1. Depicting composition and function of gastric juice
1) HCl
a. activates pepsinogen b. kills bacteria
c. promotes pancreatic secretion and intestinal secretion
d. promotes Fe2+ and Ca2+ absorption in the initial part of small intestine
2) pepsinogen,Secreted in the form of zymogen
Pepsinogen---HCl------pepsin-----decompose protein
3) intrinsic factor: forming complex combined with B12 activate the receptor in ileum to promote
B12 absorption
4) Mucus: lubrication, protection, mucus HCO3- barrier
2. How do parietal cell secrete HCl
H+ in HCl is originated from H¬2O in parietal cells. H2O can be hydrolyzed into H+ and OH-.
H+ is transported into small tubes with the help of H+ pump that need to consume energy. OHneutralizes with H2CO3, which is the combination of H2O and CO2 catalyzed by a type of
enzyme Carbonic Anhydrase. H2CO3 is quickly divided into H+ and HCO3-. H+ and OH- are
combined into H2O, while HCO3- that can be absorbed into the blood is combined with Na+ and
then changed into NaHCO3 that can raise the pH value in the blood.
3. Explain gastric emptying
Gastric emptying(stomach emptying) is promoted by the intense peristaltic contractions in the
stomach antrum.At the same time ,emptying is opposed by varying degrees of resistance to the
passage of chyme at the pylorus.
The gastric activity reinforces after chyme enters into stomach. pylorus opening is the prerequisite
of gastric emptying ,while the rising of pressure in the stomach is its essential momentum. Among
the three types of nutrient, sugar, protein and fat, sugar is the fastest while fat is the slowest as to
the velocity of gastric emptying.
4. Describe physiological action of gastrointestinal hormones
1) Regulate the secretion of digestive glands and the activity of digestive.
2） Regulate secretion of other hormoines.
3） trophic action 4. work on immunosystem