digestive system Flashcards
vitamins are considered
cofactors / prosthetic groups
another term for the GI tract is
alimentary canal
During what stage in development is the GI tract developed?
Gastrulation
The GI lumen is continuous with
the outside environment
Epithelial cells
- where are they located in the GI?
- are generally found where inside the body?
line the outer surface of the GI lumen
generally found when in areas that have contact with the outside environment (e.g. GI lumen, respiratory tract)
Epithelial cells are attached to what?
the basement membrane
Apical
faces lumen
Tight junctions
bands running around the sides of epithelial cells.
separates body fluids from extracellular environment
apical is separated from remainder of cell surface by tight junctions
Basolateral surface
sides & bottom of an epithelial cell that form the surface opposite of the lumen
Desmosomes
a generalized cell junction used primarily for adhesion
what 2 layers of smooth muscle line the gut?
- longitudinal
2. circular
GI motility is defined as
rhythmic contractions of GI smooth muscle
What factors influence GI motility
- Automaticity
- Functional syncytium
- Has its own NS4. Regulated by hormonal input5. Parasympathetic NS stimulates motility + causes sphincters to relax
GI motility has its own NS. What is it called?
Enteric NS
Does the Parasympathetic NS stimulate or inhibit GI motility
Parasympathetic NS stimulates motility[remember: Parasympathetic NS is rest or digest. GI motility promotes digestion]
Does the sympathetic NS stimulate or inhibit GI motility
sympathetic NS inhibits motility[remember: sympathetic NS is fight or flight. Inhibiting motility inhibits digestion. You have more resources dedicated towards fighting or fleeing this way.]
What is the purpose of GI motility?
- Mixing of food
2. Movement of food
Mixing
disordered contractions
Movement
Ordered form of contraction aka Peristalsis
Peristalsis utilizes which of the two smooth muscles in the gut?
peristalsis utilizes circular smooth muscle.
peristalsis contracts circular smooth muscle.
Prevents food from moving backward
Movement is also aided by longitudinal smooth muscle. What effect does the contraction of longitudinal smooth muscle have on the gut?
contraction of longitudinal smooth muscle results in shortening of the gut AND forward movement of food
What stimulates GI secretions
- Food in the gut
2. Parasympathetic NS
What inhibits GI secretions
sympathetic NS
Exocrine glands are made up of what?
specialized epithelial cells that are organized into sacs - Acini
Acinar cells secrete products that
pass into ducts –> GI lumen
GI Exocrine organs
liver, gallbladder, pancreas
While the liver, gallbladder and pancreas include most exocrine secretions, there are still some exocrine secretion is accounted for by what?
specialized individual epithelial cells
Where are the specialized individual epithelial cellsspecialized individual epithelial cells that perform exocrine secretions located?
in the wall of the gut itself
specialized individual epithelial cells release secretions _______
directly into the lumen
specialized individual epithelial cells examples
gastric glands - release acid + pepsinogengoblet cells - secrete mucus
What is the function of mucus
to protect and lubricate
Is water considered a secretion? where is it reabsorbed?
yes.
in the small intestine and than the colon
Endocrine secretions are picked up by
capillaries
if an organ has both endocrine and exocrine glands than ______
the functions are performed by different cells
The pancreas has both endocrine and exocrine glands. name the cells that are responsible for each
Endocrine - Islets of LangerhansExocrine - pancreatic acinar cells
What are the accessory organs of the GI tract?
liver, gallbladder, pancreas
what are the functions of saliva
lubrication & digestion
saliva contains
contains salivary amylasesmall amount of lingual lipaselysozyme
saliva lysozyme is made by
lytic phages
salivary amylase converts
ptyalin -starch –> disaccharide
mouth performs zero digestion of
protein
The pharynx is the _______.
It has ___ number of tubes.
The tubes are _____
The pharynx is the throatIt has 2 tubes.
The tubes are trachea and esophagus
The trachea is lined with
cartilage
The trachea is conveys
air
the trachea is commonly referred to as the
windpipe
Epiglottis is _____
cartilagious flap
the function of the epiglottis is to
exclude solids and liquids from the trachea
food follows the path
through the pharynx
over the epiglottis into the esophagus
peristaltic action of the esophagus conveys it to the stomach
lower esophagus sphincter is also referred to as the
cardiac sphincter
the function of the lower esophagus sphincter is to the location of the lower esophagus sphincter is
prevent refluxnear the heart
we have ____ esophagus sphincter(s)
2
upper esophagus sphincter lower esophagus sphincter
the gastric pH is
2
parietal cells secreteare located in
parietal cells secrete HClare located in gastric mucous
Chief cells secrete
pepsin
pepsin is secreted in what form
as a zymogen
pepsinogen is converted to pepsin by
gastric acidity
pepsinogen is activated by
acidic proteolysis
most zymogens are activated by
proteolysis
chyme is
food + gastric secretions
pyloric sphincter
prevents passage of food from the stomach to the duodenum
regulation of the pyloric sphincter:inhibited when
inhibition of opening of the pyloric sphincter occurs when the small intestine has a large load of chymeCCK
when the small intestine has a large load of chyme, what 2 things specifically inhibit further stomach emptying?
the pH of the small intestine inhibits further emptying
the stretching of the duodenum also prevents the opening of the pyloric sphincter by causing sphincter contraction
pyloric sphincter contraction is associated with
inhibition of stomach emptying
The regulation of the pyloric sphincter is mediated by
nerves connecting the duodenum, stomach and by hormones (CCK)
CCK is secreted by what type of cells?
epithelial cells
What stimuli cause the secretion of CCK?
fats in the duodenum
CCK causes
secretion of digestive enzymes by the pancreas
stimulates gallbladder contraction
decreases gastric motility
inhibits stomach emptying
Gastrin is secreted by
G cells
Gastrin stimulates
acid & pepsin secretion
gastric motility
histamine secretion
Gastrin is stimulated by
food in the stomachparasympathetic stimulation
The _____ stimuli cause the secretion of histamine
stomach stretching and gastrin
Histamine binds to
H+ receptors on parietal cells
Histamine stimulates
acid release by parietal cells
the 3 segments of the small intestine include
- Duodenum
- Jejunum
- Ileum
Digestion begins where?
the mouth
Digestion is completed where?
duodenum & jejunum (segments of the small intestine)
Absorption begins where?
and continues through?
the duodenum the small intestine
What key feature of the small intestine allows it to accomplish absorption?
its large surface area
the large surface area of the small intestine is attributed to its
lengthvillimicrovilli
villi are
macroscopicmulticellular projections in the wall of the small intestine
microvilli
microscopic foldings of the cell membrane of individual intestinal epithelial cells
Brush border is _____ surface
the lumenal surface of the small intestine
Intestinal villus are
a finger-like projection of the wall of the gut into the lumen
Important structures of intestinal villus are
- villus
- lymphatic vessels
- peyer patches
intestinal villus contains ________ that absorb monosaccharides & amino acids
capillaries.
Capillaries merge into veins.
Veins merge into the large heptatic portal vein
the large heptatic portal vein transports blood containing
amino acids and carbohydrates from the guit to the liver
peyer patches are part of the _______ system.
Define peyer patches
dotting the villi that monitor GI contents and thus confer immunity to gut pathogens and toxins
2 ducts empty into the duodenum
- pancreatic duct
2. common bile duct
pancreatic duct
delivers exocrine secretions of the pancreas (digestive enzymes and bicarbonate)
common bile duct
delivers bile contains bile acids
Bile acids are made from ______ in the ______.
They are essential for what?
cholesterol in the liver essential for fat digestion
sphincter of oddi
both ducts (pancreatic and common bile duct) empty into the duodenum from the same orifice which is the sphincter of oddi.
duodenal enzymes are secreted by what cells
epithelial cells secrete enzymes
are all duodenal enzymes secreted ?
no.
some are not secreted.
They can also work inside the surface of the brush border epithelial cells.
These are referred to as brush border enzymes
duodenal hormones are secreted by
epithelial cells
the list of duodenal enzymes includes:
- CCK
- Secretin
- Enterogastrone
CCK main point
it promotes fat digestion and inhibits further stomach emptying
CCK is secreted in response to
fat in the duodenum
CCK’s effect is
its effector is the pancreas
causes the pancreas to secrete digestive enzymes
stimulates gallbladder (effector) contraction –> Bile release
decreases gastric motility (slowing down of the stomach)
gallbladder contraction
causes the release of bile
Secretin main point
required for digestion to occur
its effector is the pancreas
Secretin is secreted in response to
acid in the duodenum
Secretin’s main effect is
pancreas (effector) releases high - pH aq.
Buffer HCO3- in water —> neutralization of HCl released by the stomach (the effect)
Enterogastrone main point is
decreases stomach emptying
If its not absorbed in the duodenum than it is absorbed in the
jejunum & ileum
digestion ends in the
jejunum
Absorption occurs in the
ileum
the lower small intestine performs
special absorptive processes
Vitamin B12 is only in the
ileum
Ileocecal valve
separates the ileum from the cecum, which is the first part of the large intestine
colon
muscular tube
part of large intestine
roles is to absorb water and minerals and to form and store feces until defecation
the cecum
first part of the colon
entrance of chyme into cecum is ileocecal valve
appendix
finger-like appendage of the cecum
composed primarily of lymphatic tissue
colon has a lot of
facultative / obligate anaerobes
trypsinogen is converted into its active form by
enterokinase
Conversion of trypsinogen occurs in the
brush border
trypsin activates what
chymotrypsinogen, procarboxypeptidase, procollagenase
the duodenum secretes
- CCK –> causes the pancreas to secrete enzymes
- secretin –> causes the pancreas to secrete water and HCO3-
- parasympathetic activation –> increased pancreatic secretion
the alpha cells
part of the endocrine pancreas
secrete glucagon
mobilize fuel by stimulating the liver and adipocytes to release glucose and fats into the bloodstream
the beta cells
part of the endocrine pancreas
secrete insulin
stimulated to secrete insulin when we have elevated blood sugar
insulin lowers blood sugar
the delta cells
part of the endocrine pancreas
secrete somatostatin
somatostatin inhibits digestive processes
only _______ can lower blood glucose
only insulin can lower blood glucose
excess glucose does what?
it destroys many physiological systems @ cellular level including neurons, blood vessels & the kidneys
increasing blood glucose is done by:
3 hormones
- Glucagon (peptide hormone)
- Ephinephrine (AA derivative)
- Cortisol (steroid)
liver exocrine function does what
secretes bile
bile’s principal ingredient is what?
- bile acids
- cholesterol
- bilirubin
bile’s function is what?
it emulsifies fat particles in the duodenum into smaller clusters –> micelles
micelles have ________ which make them easily digested by ________
micelles have __GREATER SURFACE AREA______ which make them easily digested by __HYDROPHILLIC LIPASES______
Bile also does what? (part of its function)
bile’s other function is to help fatty particles diffuse across the intestinal mucosal membrane
Bile is made in ______
bile is made in the ____liver_____
Bile from the liver goes two places which are
bile from the liver is 1) secreted directly into the duodenum 2) stored in the gallbladder
bile in the gallbladder is ________ & released _______
bile in the gallbladder is _CONCENTRATED_______ & released _AFTER A FATTY MEAL______
gallbladder has _______ activity
gallbladder has _NO SECRETORY______ activity
the constriction of the gallbladder walls is stimulated by
CCK & the parasympathetic nervous system stimulates the constriction of the gallbladder walls
release of bile is dictated by ______
release of bile is dictated by __hormones & the nervous system____
liver receives blood from two sources:
- Hepatic arteries - oxygenated blood
2. Hepatic portal vein - venous blood draining the stomach & the intestines
the hepatic arteries deliver
the hepatic arteries deliver __oxygenated blood___
Hepatic portal vein deliver
Hepatic portal vein deliver __venous blood draining the stomach & the intestines__
the function of hepatocytes are
the function of hepatocytes are:
- extract nutrients from the liver
- monitor blood
what two groups contain glycogen?
both contain glycogen
- the liver
- skeletal muscle
only the liver can
only the liver can ___release free glucose into the blood___
why can only the liver release free glucose?
because G6P must be dephosphorylated and only the liver contains G6P Phosphatase
protein waste products are regulated by the ______
protein waste products are regulated by the __liver____
How does the liver assist with lipid metabolism
chylomicron remanants are taken up by hepatocytes. they combine the remanants with proteins to form –> lipoproteins.
lipoproteins re-enter the blood
lipoproteins are the source of ______ for other tissues of the body
lipoproteins are the source of _cholesterol and triglycerides_____ for other tissues of the body
the liver makes important _____ secretes them
the liver makes important __plasma proteins___ secretes them
_____ major center for drug & toxin detox
__liver___ major center for drug & toxin detox
no _____ digestion occurs in the mouth
no _protein____ digestion occurs in the mouth
WHY is the liver the major center for drug & toxin detox?
the Smooth ER of Hepatocytes has an enzyme pathway that breaks down drugs & toxins –> less toxic excreteable products
monosaccharides must use _______ to be taken into intestinal epithelial cells
monosaccharides must use __secondary active transport_____ to be taken into intestinal epithelial cells
sugars dissolve in _______
sugars dissolve in __hepatic portal vein_____
when there is chyme in the duodenum
- duodenum to secrete CCK and Secretin
- the gallbladder to release concentrated bile
- pancreas to release a basic solution of HCO3- plus digestive zymogens
Amino acid absorption
a 2 Active transporter (symport) specific to each AA complex uptake with Na+
followed by uniport facilitates movement out of the intestinal epithelial cells into the interstitutium
pancreas sends enzymes into the gut via ________
pancreas sends enzymes into the gut via ___sphincter of Oddi_____
CCK stimulates gallbladder _________ which causes _______
CCK stimulates gallbladder ___contraction______ which causes __bile into the bile duct into the duodenum_____
Micelles are ______ by ____
Micelles are __hydrolyzed____ by __pancreatic lipases__
micelles are hydrolyzed into ___________
micelles are hydrolyzed into __triglycerides –> monoglycerides + free fatty acid_________
hydrolyzed triglyceride produces
monoglyceride
free fatty acids
monoglycerides and free fatty acid move into the intestinal epithelial via ______
monoglycerides and free fatty acid move into the intestinal epithelial via __diffusion____
inside the epithelial cells monoglycerides are converted back into _______ which are packaged into _________
inside the epithelial cells monoglycerides are converted back into __triglycerides_____ which are packaged into __chylomicrons_______
lacteals are
lymphatic capillaries
_______ and _______ tissues contain the enzyme lipoprotein lipase
__adipose_____ and __liver_____ tissues contain the enzyme lipoprotein lipase
free fatty acids diffuse into ______ and _______ cells where they are made into ______ and then ______
free fatty acids diffuse into __adipocytes____ and __liver___ cells where they are made into __triglycerides____ and then __stored____
Fat soluble vitamins require ______ for solubilization and absorption
Fat soluble vitamins require __bile acids____ for solubilization and absorption
excess fat soluble vitamins are stored in __________ tissue
excess fat soluble vitamins are stored in __adipose________ tissue
