Secretin

[Matthew]

No it's not a secret. I am going to tell you what it is.

Remember how we were talking about all the neat and cool hormones and enzymes released in the stomach? Well I saved this one for last.

It is special because this hormone, secretin is special for the duodenum, where it is secreted. Once released, it signals to the stomach to basically slow down. How? Well, gastrin was the starter hormone that was stimulating stomach, so secretin acts by preventing the release of gastrin. Another neat function of secretin, is that it causes the pancreas to make more bicarbonate.

When you see bicarbonate, think neutralizing acid.

Now let's say you went to a barbeque and had beef brisket and ham. I can only imagine that you are getting a lot of protein and a bit of fat (on the outer part of the brisket). CCK is short for Cholecystokinin which is also another hormone that signals to the pancreas to secret through its duct digestive enzymes, like lipase (fat digestion) and trypsin (protein digestion). The barbeque sauce also has sugar, too, so amylase as well.

Creating a picture about CCK and a barbeque will go long ways for memory on test date.

Bile also gets recycled at the end of the small intestine; ileum. The jejunum does most of the absorption most of the nutrients. So putting everything together, absorption mostly in the jejunum, digestion in the duodenum, and recycling bile and completing last of absorption in the ileum.

The involuntary muscle (smooth) of the esophagus move in a wave-like motion to move the bolus (gooey) food down to the stomach. Protein digestion begins in the stomach with pepsin. Carobxypeptidase and maltase are secreted in the jejunum. Maltase is an enzyme that breaks down maltose, an aldehyde sugar.

The moment we start chewing on a piece of bread, carbohydrate, i.e. starch for polysaccharide, through the help of not so potent salivary amylase, to maltose and dextrin. (Outside knowledge, but interesting).

[kazuma]

do you think knowing the actions of Intrinsic Factor are also relevant to the mcat? or is it overkill

[admin]

Interesting but definitely overkill for the MCAT. If you see IF as a question then the answer is in the passage.