Part 4.3: Digestion Flashcards
Cells in the gastric pits and secretions
parietal cells - HCl Chief cells - pepsinogen
pareital cells rely on the ____ reaction and a ___ shift to bring CO2 into the cells
bicarbonate reaction and a chloride shift.
3 factors that shut off gastric secretion
1) As levels of protein declines. - protein is a powerful driver of G cells.
2) falling pH -causes release of somatostatin
3) duodenal stimuli that inhibits gastric motility - fat -acidity -hypertonicity -distension.
purposes of barfing
1) getting rid of toxins 2) feeding offspring 3) undigestable bits for avian carnivores: they barf up bones and feathers and fur because they can’t digest those components of prey.
in mammals with simple stomachs, how does vomiting work? What portions of the body close during vomiting? What muscles are involved?
complete relaxation of stomach, esophagus and sphincters, while the glottis and nasal cavity closes. - deep inspiration, diapgrahm pushes down on the stomach, abdominals push on the stomach.
how do ruminants and some birds vomit?
reverse peristalsis. In owls, gastric motility increases AFTER digestion is complete. this packs up the indigestible pellet.
in the grass hopper, they have a ___ for storage and a ____ for a grinding organ. Do they have a stomach?
in the grass hopper, they don’t really have a stomach, instead, they have a CORP for storage and a PROVENTRICULUS for a grinding organ. they have a modified stomach which houses digestive glands.
do birds have stomachs? What alternative structures do they have? (3)
no stomach
1) crop; for storage
2) proventriculus: a glandular stomach
3) gizzard: a muscular stomach. the gizzard goes to the small intestine.
what cells are available in the avian proventrisuclus that allow it to act asa glandular stomach?
1) mucousal cells
2) oxynticopeptic cells (avian chief cells) - secretes both pepsinogen and Hcl
the avian proventriculus is ___ in herbivorous birds and ___ in sea birds.
the avian proventriculus is SMALL_ in herbivorous birds and LARGEin sea birds.
in birds, the proventriculus expels digesta into the ____.
gizzard
gizzard is lined with opposing ___ ___ layers.
smooth muscle
what are gizzard stones
birds literally eat rocks to macerate and help breakdown large pieces of food.
most digestion and absorption occurs in the __ ___
small intesttine
3 regions of small intestine
1) duodenum 2) jejunum 3) ileum
the pancreas and liver empty secretions into the ___ of the small intestine
duodenum
the pancreas exocrine function is comprised of clusters of ___ cells into sacs called ____>
ACINAR cells into sacs called ACINI (duct cells).
The endorine pancreas component and their products
islets of langerhans. secretes insulin and glucagon in response to blood sugar. (from beta and alpha cells respectively)
purpose of duct cells of the pancrease
exocrine function that releases alkaline substance to neutralize acidity from chyme. Connects to the acini cells, which secrete exocrine products like tripsinogen and stuff.
two cells of the exocrine portion of the pancreas and their function
1) duct cells: secretes aqueous NaHCO3 solution (aka centroacinar cells)
2) acinar cells: secretes digestive enzymes (3 types)
3 types (Classes) of digestive enzymes secreted by the acinar (type of exocrine cell) cells of the pancreas
1) proteolytic enzymes 2) pancreatic amylase (and chitinase in some vertebrates) 3) pancreatic lipase.
Trypsin is a ____ enzyme. What form is it secreted by the pancrease in? How does it get activated?
proteolytic enzyme. secreted in the form of trypsiongen, and then gets activated by enterokinases in the walls of the duodenum.
how does the pancreas prevent trypsinogen from being activated too early?
also produces trypsin inhibitor for further protection
T/F trypsin is autocatalytic
true. once a few molecules of trypsin are activated, they can activate themselves. Just like pepinogen in the stomach
two proteolytic enzymes that are activated by trypsin. purpose?
1) chymotrypsinogen
2) procarboxypepsinogen
- all 3 proteolytic enzymes (+Trypsinogen) target special amino acid bonds.
T/F the pancrease produces amylase
true. breaks carbs down way more than salivary amylase did.
why is pancreatic chitinase important?
good for arthropod and insect eaters. other insectivores use symbiotic bacteria
if an arthropod and insect eater doesn’t have pancreatic chitinase, what do they have to digest chitin?
they need to use symbiotic bacteria that eats chitin in the guts of the animal. ex/ bats have a chitin eating bacteria in their stomachs that allow them to eat bugs.
___ ___ is a principle enzyme of fat digestion
pancreatic lipase
what does pancreatic lipase do?
hydrolyses triglycerides into monoglycerides and free fatty acids.
___ ___ are the absorbable units of fat
fatty acids.
in the exocrine pancreas, acinar cells package all four types (pancreatic amylase, lipase, tripsin, chitinase) of enzymes together in the form of ____, which release their contents into lumens by exocytosis
GRANULES
T/F: the pancreas can modulate which enzymes are secreted
false. regardless of what you eat (ex/ salad vs burger), they release all enzymes, even lipases, which woudn’t really be needed for a salad.
the 3 phases of timing of the stomach
1) cephalic 2) gastric 3) intestinal phases.
for the most part, the pancrease isn’t stimluated during the __or ___ phases, but mostly during the ___ phase.
not stimulated during the cephalic or gastric stage, but mostly during the intestinal phase, when teh duodenum can influence gastric secretion
2 enterogastrones that are released to influence intestinal secretion (pancreatic secretion into duodenum) and motility
1) secretin: drives duct cell to secrete alkaline substance.
2) cholecystokinin CCK
secretin is stimulated by ___ in the duodenum. Mechanism of release.
ACID. duodenum releases secretin into blood, and secretin stimulates DUCTcells of pancreas to release sodium bicarbonate. NEGATIVE feedback flow.
CCK is stimulated by ___ and ___ in the duodenum. Mechanism of release?
fat and protein. duodenum secretes CCK into blood, and the CCK stimualtes ACINAR cells to release pancreatic enzymes by exocytosis.
secretin acts on ___ cells, while CCK acts on ____ cells of the panceas
secretin acts on DUCT cells, while CCK acts on ACINAR cells of the panceas
