Digestive System Flashcards
What acronym can you use to remember the sequence of duodenum → jejunum →** ileum** in the small intenstine?
Dow Jones Industrial
What are the objectives of the small intestine?
- neutralizing the highly acidic chyme from the stomach
- continuing chemical digestion
- vitamin & nutrient absorption
This enzyme produced in the stomach is reponsible for the breakdown of fats
gastic lipase
When you think of stomach enzymes, think of pepsin and gastric lipase
What prevents pepsin from immediately doing proteolytic activity when it isn’t necessary
Chief cells secrete its inactive form pepsinogen, which is cleaved under highly acidic conditions to become its active form, pepsin
Enzymes secreted by the SI from its microvilli to digest fats and/or proteins
brush border enzymes
recall that disaccarides are a common form in which carbs are consumed
List the functions of the pancreas wrt the digestive system
- helps duodenum digestion by secreting alkaline fluid containing digestive enzymes that can break down all major biomolecule classes
- lipases (fat)
- proteases (protein)
- amylases (sugars)
What does bile consist of?
Bilurubin, bile salts, and some fats
bile emulsifies lipids and converts them to micelles
How is highly acidic chyme from the stomach neutralized via other digestive system organs?
- pancreas secretes alkaline fluid rich with bicarbonate
- liver’s bile is slightly alkaline
- duodenum secretes bicarbonate buffer via Brunner’s glands
Qhat region(s) of the small intestine are involved in nutrient absorption?
jejunum & ileum
Cells of the intestinal lining, characterized by microvilli
enterocytes
Name the regions of the large intestine in order (excluding the appendix)
- cecum
- ascending colon
- transverse colon
- descending colon
- sigmoid colon
- rectum
What is the pouch connected with the ileum through the ileocecal valve?
the cecum
Where is the largest community of bacteria in the human body located?
The gut microbiota is located in the large intestine
What is the role of bile?
To emulsify lipids so that digestive enzymes can do their work
Name the two hormones that regulate hunger
ghrelin & leptin
think “grrr” (I’m hungry!) for ghrehlin , and leptin is the opposite, it lets you know that you are full
What hormone is released by the stomach and pancreas when the stomach is empty?
ghrehlin
ghrehlin promotes appetite
Which hormone is secreted by adiptocytes and promotes feelings of satiety?
leptin
What is this hormone?
G-cells in the stomach secrete a hormone that promotes digestion by stimulating parietal cells to secrete gastric acid (HCl)
gastrin
Acidic chyme in the duodenum triggers the release of which hormone from S cells? What does this hormone do?
**secretin **triggers the secretion and release of bicarbonate rich mucus from the pancreas
think: pH regulator!
this is to neutralize the acidic chyme and promote the optimal functioning of the digestive enzymes that do their work in the small intestine
This hormone is secreted by the small intestine and stimulates the release and secretion of digestive enzymes from the pancreas, and the release of bile from the gallbladder
cholecystokinin (CCK)
think: digestion helper!
Which hormone produced from the GI system & hypothalamus helps slow down digestion by inhibiting the release of other hormones, and slowing the rate at which the stomach empties?
somatostatin
think: pumping the brakes on digestion
somatostatin also inhibits the release of growth hormone when released from the hypothalamus. This makes sense because GH is released from the hypothalamus
it’s released from the GI tract, pancreas, CNS, and hypothalamus!
Part of the autonomic nervous system that regulates the digestive functions of the gastrointestinal tract
enteric nervous sytem
think: part of ANS involved in digestion
Describe the general steps for carbohydrate absorption
include what they get broken down into, the cell transport used to get them across the membrane
- Carbs → monosaccharides
2.a 2º active transport coupled to Na+ gets glucose & galactose into epithelial cells
2.b Facilitated diffusion used for fructose - Monosaccharides enter circulatory system via facilitated diffusion
- Facilitated diffusion pushes monosaccharides in bloodstream
Describe how lipids are absorbed
include what they get broken down into, the cell transport used to get them across the membrane
- Lipids → micelles w/ aid of bile salts
- Lipid molecules break away for epithelial cell absorption
- Fats & cholesterol can diffuse through plasma membrane
- Fats & fat soluable vitamins are combined into chylomicrons
- Chylomicrons are released into interstitial space
- Fat is transported from interstitial space → lacteals
- Lipids pass through lymphatic system
- Lipids eventually drain into venous system
chylomicrons = fat droplets
Small intestine epithelial cells combine fatty acids + monoglycerides = triglycerides to avoid the concentrations of fats to equalize, which would cause absorption to stop
Fill in the blank
the hepatic portal vein runs from the capillaries of the ____ to the liver
** small intestine **
small intestine capillaries → hepatic portal vein → liver → hepatic portal system
What is the benefit of the hepatic portal system? That is, blood from small intestine being processed by the liver before entering the circulatory system?
The liver can:
* detoxify compounds
* metabolize medications/drugs
* store excess carbs as glycogen
* store exess fatty acids as triglycerides
* mobilize lipids into circulation as lipoproteins
* breaking down glycogen to release glucose (if necessary)
fill in the blanks
Proteins are broken down in the stomach by ____, and in the small intestine by ____ (name three)
pepsin in stomach;
trypsin and chymotrypsin, and carboxypeptidase in small intestine
____ is an enzyme that cleaves proteins on the carboxyl end of lysine or arginine (execept when followed by proline)
Trypsin
released in small intestine
____ are a class of enzymes that break down proteins from the amino end
aminopeptidases
it tells you what it does in the name…. amino peptidase , telling you it breaks down proteins at the amino end
Describe the path of proteins as they go from your mouth to a state where they can be used in the body
- Pepsin breaks down proteins in stomach
- Small intestine uses trypsin and aminopeptidases for more breakdown
- Single amino acid residues enter epithelial cells lining lumen of small intestine
- Amino acids enter circulatory system
Describe the path of carbohydrates as they go from your mouth to a state where they can be used in the body
- Salivary amylase breaks downs starches → dissachharides
- Small intestine breaks starches into monosaccharides via pancreatic amylase (one of many enzymes)
- Monosaccharides enter epithelial cells of SI
- Monosaccharides enter circulatory system
- Cellulose and undigested starch → large intestine
- “…” broken down or digested by gut flora → short-chain fatty acids