Wold 3 Flashcards
But, there are only 2
stomach**
2 glandular regions in the stomach.
There are 3 sections of the
stomach.
Pepsinogen is a
zymogen (i.e., it is a proenzyme that needs to be cleaved to become active)
Parietal cells produce
intrinsic factor
pancreas is an
exocrine gland
pancreas
Exocrine
bicarbonate ions digestive enzymes (many, many, many digestive enzymes)
CCK Secretion is potentiated by
*Pancreas
secretin
Pancreatic Bicarbonate secretion is essentially the same
as HCl secretion in reverse.
Regulation of Pancreatic Bicarbonate Secretion:
Hormone regulation by
secretin
Regulation of Pancreatic Bicarbonate Secretion
Feedback regulation by
acidity
CCK strongly potentiates the effects of
secretin
Liver:
Secretes bile into small ducts called
bile canaliculi
Liver
Canaliculi converge and drain into
larger bile ducts.
Small Intestine types of muscle contractions:
Peristalsis: progressive contractions of successive sections of
circular smooth muscle
Small Intestine types of muscle contractions
Segmentation: closely spaced contractions of
circular muscle layer. When this is rhythmic (i.e., sites of the circular contractions alternate between contraction and relaxation), chyme/bolus is mixed and slowly moved downward.
Bacteria can ferment some of these undigested substances, which will then be absorbed in the
large intestine, but this comes at a price…
motility in large intestine occurs as slow
“segmentation” contracts
large intestine; peristaltic-like contractions occur
3 – 4 times per day
How do we digest a meal?
Mouth
Chewing, salivation, amylase, lipase
How do we digest a meal?
Stomach
HCl, pepsinogen, lipase, gastrin
How do we digest a meal?
Small Intestine
Hormones—Secretin, Cholecystokinin
How do we digest a meal?
Accessory Organs
Pancreas—proteases, lipase, amylase, HCO3-
Liver—bile
How do we digest a meal?
Small Intestine
Absorption—carbohydrates, proteins, fats, vitamins, minerals
How do we digest a meal?
Large Intestine
Absorption—Na+, Cl-, water
Chyme has to ——- in order for us to digest a meal
keep moving
Stomach churning
Rate is determined by
pacemaker cells,
Stomach churning
magnitude determined by
excitatory stimuli
Stomach
Peristalsis from
body to pyloric sphincter
Small Intestine
Segmentation and Peristaltic contractions
Peristalsis controlled by
migrating myoelectric complex (initiated by motilin)
Primary purpose of the large intestine is to actively transport
Na+ from lumen to blood.
Large intestine
Also, bicarbonate secretion is coupled to
Cl- ion absorption.
Bacterial fermentation of some of the food bolus contents maximizes the absorption of nutrients from food in the
large intestine