Digestion Flashcards
Extracellular digestion
digestion outside of the cell’s border
alimentary canal
- site of digestion in human/mammals.
- space is outside cell borders
Digestion
breakdown of food into its organic molecules.
mechanical digestion
physical breakdown of large food particles but does not involve the breakage of chemical bonds
Chemical digestions
Enzymatic cleavage of chemical bonds
Absorption
transport of products of digestions into circulatory system for distribution
Digestive tract
Oral Cavity –> Pharynx –> esophagus –> stomach–>Small intestine –> Large Intestine.
Also includes salivary glands and accessory organs such as pancreas, liver, gallbladder.
epithelial cells
cells that serve as a first border and primary protection against outside world.
cover exterior and interior surfaces.
mucous membranes
epithelia is most of our body cavities is known as that.
Basement membrane
a connective tissue layer in which epithelium is bound to.
ways of classifying epithelia
- Number of layers
- shape of cells
simple
1 layer
stratified
multiple layers
pseudostratified
1 layer but looks like several
cuboidal
sugar cube shape
columnar
columns shape
squamous
scale like shape
Oral Cavity
starting point of Digestive system
mastication
break down of food with teeth, lips, tongue
saliva
secreted by salivary glands
contains amylase
amylase
enzymes for breakdown of food. consists of ptyalin and lipase.
bolus
formed by tongue from the food and is forced back into the pharynx to be swallowed.
epiglottis
a fold that covers the trachea during swallowing.
in parynx area.
Pharynx
cavity that leads from mouth and nose to esophagus
esophagus
muscle tube: starts with striated muscle then transitions to smooth in thorax.
-majority of movement is involuntary (ANS)
peristalis
wave contraction in esophagus to push food.
Lower esophageal sphincter/ cardiac sphincter
First sphincter at the end of esophagus and before stomach.
Stomach
Major site of digestions
mucosa here is thick due to acid
Two stomach mucosa
Gastric glands
Pyloric Glands
Gastric glands
respond to signals from the brain
-3 cell types: mucous, chief, parietal
mucous cells
produce mucus to protect wall from harsh acidic environment
cheif cells
secrete pepsinogen/ pepsin (to digest protein)
parietal cells
secrete HCl,, which activates zymogens for pepsin-which is most active at pH level of 2
Pyloric glands
secrete hormon gastrin
produces chyme.
Gastrin
hormone that induces the secretion of HCl to mix content of stomach
Chyme
acidic,semifluid mix
Gastric Juice
Combo of secretions from chief and parietal cells.
Small intestine
Bulk of chemical digestion and most of absorption occurs here.
3 sections: dueodenum, jejunum and Ileum.
Villi/microvilli
specialized structure of small intestine which increases the surface area causing an increase in absoption.
Bacteria
help with digestion and absorption
Duodenum
most of digestive functions occur here.
once chyme enters, a release of hormones occurs.
Pancreatic Juice
Complex of enzymes in bicarbonate solution (basic solution)
helps neutralize acidic chyme.
-has pancreatic amylase, peptidase, and lipase
Bile
- complex of bile salts & pigments and cholesterol.
- produced by liver and gallbladder
- released in response to hormone CCK.
Bile salts
- important in mechanical digestion of fats
- have hydrophobic and hydrophilic regions allowing fats to emulsify and mix with chyme
Disaccharidases
maltase lactose, sucrose– carb digestion
peptidases
protein digestion
enterokinases
?
secretin
hormone to release pancreatic juice
CCK
hormone to stimulate release of bile and pancreatic juice.
enterogastrone
hormone to slow the movement of chyme to allow for greater time to digest.
Jejunum and Ileum
absorptive functions occur here.
Simple sugar absorption method
- active transport and facilitated diffusion into epethelial lining of gut
- then moved to intestinal capillaries, where concentration gradient exists between blood and epithelial cells.
- absorbed molecules go to the liver thru the hepatic portal circulation
Fat absorption method
- can easily go through cellular membrane
- they move into intestinal cells and reform into triglycerides
- they are then packed into insoluble chylomicrons and enter the lymphatic circulation thru lacteals instead of bloodstream.
Chylomicron processing
if directly into bloodstream they become LDL “bad cholesterol”.
LDL can be taken by the liver and repackaged into HDL “good cholesterol”
Vitamins abroption
Only 4 vitamins are fat soluble: A, D, E, K.
the rest are water soluble.
Large Intestine
for water absorption
3 sections: cecum, colon, rectum.
cecum
connects small and large intestine.
-appendix is found here
colon
absorbs water and salts (recycling system)
rectum
storage site for feces.
anus
opening of where waste is eliminated
has two sphincters: internal and external
internal/external sphincter
-internal is involuntary while external is voluntary.
pyloric sphincter
allows food to go from stomach to small intestine
