ANSWERS GRADED A+
✔✔What is the role of intrinsic factor and where is it eventually absorbed? - ✔✔Intrinsic
factor binds to vitamin b12, which cannot be absorbed unless it is bound. Vitamin b12
and other vitamins are absorbed in the small intestine, in particular, the ileum.
✔✔In which two physiologic phases of gastric secretion is HCl secretion stimulated? -
✔✔Cephalic and Gastric phases
✔✔Which of the GI hormones are secreted from the mucosa cells of the small
intestine? What is the overall effect of these hormones? - ✔✔Cholescytokinin (CCK):
-Stimulates gall bladder secretion
-Stimulates secretion of bicarbonate rich pancreatic fluid and zymogen-rich pancreatic
fluid
-inhibits gastric emptying
-contracts the pyloric sphincter
-exerts a trophic effect on the pancreas
-increases small intestinal motility
Gastrin:
-Stimulates secretion of bicarbonate rich pancreatic fluid and zymogen-rich pancreatic
fluid
-inhibits stomach emptying
-increases the tone of the lower esophageal sphincter
-stimulates HCl secretion
Secretin:
-Stimulates secretion of bicarbonate rich pancreatic juice, and to a lesser extent the
zymogen rich component
-inhibits HCl secretion
Gastrointeingal peptide IP:
-inhibits HCl secretion
Overall effect is to complete digestion via pancreatic enzyme release and provide an
optimal pH for enzyme activity.
✔✔Why is important to have a controlled release of partially digested chyme into the
small intestine? What are the factors that inhibit gastric emptying? - ✔✔There is a need
to decrease the amount of HCL that is in the chyme since it can be erosive to the
intestine. As the food is moving from the stomach to the intestine their is secretion of
pancreatic rich liquid, which is very basic in addition to bicarbonate to help alkali the
content.
, -Receptive relaxation: tone that exists within the GI tract
-Peristalsis
-Enterogastric reflex: inhibits gastric emptying and is stimulated when too much acid,
too much fat, hypertonic fluids (brought on by CCK and secretin)
✔✔How might accumulation of undigested substances in the small intestinal lead to a
decrease in plasma volume, decreased absorption and diarrhea? - ✔✔An accumulation
of undigested food will create a hypertonic fluid in the intestional tract. Rapid emptying
of the gastric contents into the small intestine causes a change in the osmolality of the
fluid. Typically, the osmolality is relatively equal to that of the plasma, leading to a
balance of water. Increased osmolality due to the presence of ions (such as Na+) or
food particles will cause an increased amount of water to be brought into the intestine,
causing diarrhea.
✔✔The pancreas secretes zymogens and an alkaline fluid. Describe the enzymes,
delineating the primary substrate for each enzyme. - ✔✔zymogens = inactive enzyme
Trypsinogen -> Trypsin: Activates other zymogens (controlled/regulated by: CCK/Taste
of food/distention of stomach)
Chymotrypsinogen -> Chymotrypsin: Breaks a peptide bonds forming peptide fragments
Procarboxypeptidase -> Carboxypeptidase: splits the terminal amino acid from the
carboxy end of the protein
->Lipase: removes fatty acids from triglycerides forming free fatty acids and
monoglycerides
->Amylase: splits the polysaccarides into monosaccharides
✔✔Define the role of enterokinase and tryspin inhibitor. - ✔✔Trypsin Inhibitor: within the
pancreatic fluid and prevents premature activation of zymogens
Enterokinase: secreted from mucosal cells of the duodenum and stimulates trypsinogen
into trypsin.
Premature activation within the pancreas could cause pancreatitis.
✔✔Describe which type of transport mechanisms are responsible for transport of
monoglycerides
and amino acids into the small intestinal (SI) epithelial cell. - ✔✔There are single or di
amino acid transport proteins. If a protein is larger than this, than a membrane bound
protein will break the large chain protein apart first. Then and only then can the protein
be transported through the single or di amino acid transporter.