Structure + Anatomy
These are the four layers that make up the wall of the alimentary canal, from deep to superficial.
mucosa, submucosa, muscularis externa, serosa
This process involves alternating contraction and relaxation of smooth muscle layers to propel contents through the GI tract.
peristalsis
Inhibits gastric secretions in the cephalic phase.
no appetite/depression
What begins the breakdown of carbohydrates? Where does this occur?
salivary amylase, mouth (parotid glands)
What activates pepsinogen into pepsin? Why is this necessary?
HCl, pepsin denatures proteins (role in protein breakdown)
These three accessory organs connect to the duodenum and assist in digestion via secretions.
liver, gallbladder, and pancreas
This process occurs mostly in the small intestine and mixes chyme with digestive juices by moving it back and forth.
segmentation
gastrin
These enzymes, released by the pancreas, break proteins into peptides in the small intestine.
trypsin, chymotrypsin, carboxypeptidase
What are 2 structural modifications specific to the stomach?
rugae + oblique layer
Name the 3 types of cells of the stomach and what they each secrete.
mucous neck cells: thin acidic mucus
parietal cells: HCl, intrinsic factor
chief cells: pepsinogen, gastric lipase
In order, name the first four structures food passes through after leaving the stomach.
duodenum, jejunum, ileum, and cecum
Which 2 events stimulate an increase gastric secretions in the gastric phase?
2. peptides, caffeine, and an increase in pH
Enzyme that breaks down fats into monoglycerides and free fatty acids in the small intestine.
pancreatic lipase
Obstruction of the hepatopancreatic sphincter impairs digestion by reducing the availability of:
pancreatic juice and bile
This GI structure contains Peyer's patches, is the final part of the small intestine, and connects to the large intestine.
ileum
This muscular valve regulates the flow of chyme from the stomach into the small intestine, controlling the rate of gastric emptying.
pyloric sphincter
This intestinal hormone inhibits gastric activity when chyme enters the duodenum.
enterogastrones (secretin + CCK)
Describe the process of protein absorption.
amino acids enter the capillary blood of villi via facilitated diffusion and then enter liver via hepatic portal vein
breaks large fat globules into small droplets, increasing the surface area of the fats and making it easier for lipase enzymes to digest them
Function of lacteals.
responsible for the absorption of dietary fats and fat-soluble vitamins; transport monoglycerides to systemic capillaries
List the six essential digestive processes in order and identify the one that is responsible for breaking polymers into absorbable monomers using enzymes.
ingestion, propulsion, mechanical digestion, chemical digestion, absorption, and defecation
chemical digestion is the correct process
Name the 4 inhibitiory events of gastric secretions in the small intestine.
Stretching of duodenum
Acidic chyme
Fatty chyme
Hypertonic chyme
How does lipid absorption differ from carbohydrate and protein absorption?
monoglycerides and fatty acids travel through lacteals of villi to systemic circulation via lymph in thoracic duct
Describe the two phases of swallowing. Which is voluntary?
buccal phase: voluntary, tongue pushes bolus to oropharynx
pharyneal-esophageal phase: involuntary, swallowing reflex moves bolus through pharynx and esophagus