chapter 23 part 2 Flashcards
4 major regions of the stomach
cardia
fundus
body
pyloric portion
cardia
portion of the stomach leading immediately from the esophagus
fundus
dome-shaped portion
body
midportion of stomach
pyloric portion
inferior funnel-shaped portion of the stomach
leads into small intestine
pyloric sphincter
Thickening of tissue that controls the release of food from the stomach into the intestine
controls how much food enters the small intestine to prevent overfilling
omenta
mesenteries extending from the greater/lesser curvature of the stomach
lesser omentum
runs from liver to stomach
greater omentum
runs from the stomach to the intestines
functions: attaches and anchors stomach to other digestive organs
parasympathetic fibers via
vagus nerve
when parasympathetic division activated: stomach activity increases
sympathetic fibers via
thoracic splanchnic nerves
sympathetic division activated: stomach less active
stomach has 3 layers of muscle
circular, longitudinal, and oblique
oblique muscle layer in stomach
provides extra muscle layer to generate force
what happens to the stomach when the oblique muscle contracts
twisting like ringing out washcloth
increase mixing function
surface epithelia of stomach
simple columnar cells that secrete large amounts of mucus
gastric pits
indentation of mucosa
lead into gastric glands: gastric juices produced here
types of gastric gland cells
- mucous neck cell
- parietal cell
- cheif cells
- enteroendocrine cells
mucous neck cell
produces acidic, thin mucus
parietal cell
secrete HCI and intrinsic factor
HCI
makes stomach extremely acidic: pH 1.5-3.5 is normal
functions of HCI
Activates protein-digesting enzyme: pepsin, denatures proteins breaks down plant cell walls, and kills of many bacteria
intrinsic factor
needed for survival
necessary for vitamin B12 absorption in small intestine
chief cells
produce pepsinogen
pepsinogen converted to pepsin: begins protein digestion
enteroendocrine cells
release hormones
1. histamine
2. serotonin
3. somatostatin
4. gastrin
histamine
stimulates parietal cells to release HCI
serotonin
stimulates contraction of muscle in stomach wall
somatostatin
plays several inhibitory roles in the stomach and other organs
three mechanisms of protection for stomach from gastric juices
- thick coating of alkaline mucus on the internal surface of the stomach wall
- epithelial cells joined by tight junctions
- damaged epithelial cells shed and quickly replaced
gastrin
increases HCI secretion, stimulates contraction of intestinal muscles, releases ileocecal valve, stimulated mass movement of materials
chyme
mixture of gastric juices and partially digested food
retropulsion
as food is mixed/churned in the pylorus, a small amount of liquid/ small food particles can pass through pyloric valve
rate of contraction of stomach is established by
enteric pacemaker cells
rate of emptying stomach depends on
- whats in the stomach (solid or liquid)
- how distended the stomach is
- contents of first part of small intestine
the liver
accessory organ to the small intestine
4 lobes of the liver
right, left, caudate and quadrate
falciform ligament
divides left from right, suspends liver from diaphragms
holds liver in place
round ligament
remnant of the umbilical vein
liver products drain from lobes via
common hepatic ducts
hepatocytes
liver cells
each liver lobule is packed with
liver cells (hepatocytes)
liver composed of tightly packed hexagon shaped
liver lobules
hepatocyte functions
bile secretion,
process bloodborne nutrients, store fat-soluble vitamins
detoxifies blood
each corner of lobule contains a portal triad
hepatic artery branch
hepatic portal branch
bile duct
liver sinusoids
drain blood from the portal triad, emptying into central vein
where does blood cleansing occur
liver sinusoids : surrounded by hepatocytes
bile canaliculi
drain bile secreted by hepatocytes which enter bile duct of portal triad
central vein
run through center of each liver lobule
bile
yellow green alkaline solution produced by the hepatocytes
components of bile
bile salts
bilirubin
bile salts
component of bile aiding in digestion and absorption of fats
constantly recycles
bilirubin
bile pigment formed by heme breakdown
gallbladder
accessory organ to the liver/small intestine: storage site for highly concentrated bile
sits at the inferior surface of the liver
very green in color when filled
how does the gallbladder empty
via a cystic duct into the common bile duct
the pancreas
accessory organ to the small intestine
function of the pancreas
secretes substances that help digest a wide variety of foodstuff
exocrine part of pancreas secretes
pancreatic juice: responsible for digestion
2 parts of exocrine pancreas
acini: synthesize, stores and secretes digestive enzymes
in pancreases digestive enxymes are inactive: pancreas would digest itself
ducts: transports secretions of acini
endocrine part of pancreas
contains pancreatic islets
alpha cells: secrete glucagon (hyperglycemic)
beta cells: secrete insulin (hypoglycemic)
composition of pancreatic juice
water, enzymes and electrolytes
alkaline in nature: important to small intestine bc mixes w low pH chyme to make more basic
digestive enzymes
amylase (starches)
proteases(proteins)
lipases(fats)
nucleases(nucleic acids)
