Part 4.3: Digestion

Question 1

Cells in the gastric pits and secretions

Answer 1

parietal cells - HCl Chief cells - pepsinogen

Question 2

pareital cells rely on the ____ reaction and a ___ shift to bring CO2 into the cells

Answer 2

bicarbonate reaction and a chloride shift.

Question 3

3 factors that shut off gastric secretion

Answer 3

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.

Question 4

purposes of barfing

Answer 4

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.

Question 5

in mammals with simple stomachs, how does vomiting work? What portions of the body close during vomiting? What muscles are involved?

Answer 5

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.

Question 6

how do ruminants and some birds vomit?

Answer 6

reverse peristalsis. In owls, gastric motility increases AFTER digestion is complete. this packs up the indigestible pellet.

Question 7

in the grass hopper, they have a ___ for storage and a ____ for a grinding organ. Do they have a stomach?

Answer 7

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.

Question 8

do birds have stomachs? What alternative structures do they have? (3)

Answer 8

no stomach

1) crop; for storage
2) proventriculus: a glandular stomach
3) gizzard: a muscular stomach. the gizzard goes to the small intestine.

Question 9

what cells are available in the avian proventrisuclus that allow it to act asa glandular stomach?

Answer 9

1) mucousal cells
2) oxynticopeptic cells (avian chief cells) - secretes both pepsinogen and Hcl

Question 10

the avian proventriculus is ___ in herbivorous birds and ___ in sea birds.

Answer 10

the avian proventriculus is SMALL_ in herbivorous birds and LARGEin sea birds.

Question 11

in birds, the proventriculus expels digesta into the ____.

Answer 11

gizzard

Question 12

gizzard is lined with opposing ___ ___ layers.

Answer 12

smooth muscle

Question 13

what are gizzard stones

Answer 13

birds literally eat rocks to macerate and help breakdown large pieces of food.

Question 14

most digestion and absorption occurs in the __ ___

Answer 14

small intesttine

Question 15

3 regions of small intestine

Answer 15

1) duodenum 2) jejunum 3) ileum

Question 16

the pancreas and liver empty secretions into the ___ of the small intestine

Answer 16

duodenum

Question 17

the pancreas exocrine function is comprised of clusters of ___ cells into sacs called ____>

Answer 17

ACINAR cells into sacs called ACINI (duct cells).

Question 18

The endorine pancreas component and their products

Answer 18

islets of langerhans. secretes insulin and glucagon in response to blood sugar. (from beta and alpha cells respectively)

Question 19

purpose of duct cells of the pancrease

Answer 19

exocrine function that releases alkaline substance to neutralize acidity from chyme. Connects to the acini cells, which secrete exocrine products like tripsinogen and stuff.

Question 20

two cells of the exocrine portion of the pancreas and their function

Answer 20

1) duct cells: secretes aqueous NaHCO3 solution (aka centroacinar cells)
2) acinar cells: secretes digestive enzymes (3 types)

Question 21

3 types (Classes) of digestive enzymes secreted by the acinar (type of exocrine cell) cells of the pancreas

Answer 21

1) proteolytic enzymes 2) pancreatic amylase (and chitinase in some vertebrates) 3) pancreatic lipase.

Question 22

Trypsin is a ____ enzyme. What form is it secreted by the pancrease in? How does it get activated?

Answer 22

proteolytic enzyme. secreted in the form of trypsiongen, and then gets activated by enterokinases in the walls of the duodenum.

Question 23

how does the pancreas prevent trypsinogen from being activated too early?

Answer 23

also produces trypsin inhibitor for further protection

Question 24

T/F trypsin is autocatalytic

Answer 24

true. once a few molecules of trypsin are activated, they can activate themselves. Just like pepinogen in the stomach

Question 25

two proteolytic enzymes that are activated by trypsin. purpose?

Answer 25

1) chymotrypsinogen
2) procarboxypepsinogen
- all 3 proteolytic enzymes (+Trypsinogen) target special amino acid bonds.

Question 26

T/F the pancrease produces amylase

Answer 26

true. breaks carbs down way more than salivary amylase did.

Question 27

why is pancreatic chitinase important?

Answer 27

good for arthropod and insect eaters. other insectivores use symbiotic bacteria

Question 28

if an arthropod and insect eater doesn’t have pancreatic chitinase, what do they have to digest chitin?

Answer 28

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.

Question 29

___ ___ is a principle enzyme of fat digestion

Answer 29

pancreatic lipase

Question 30

what does pancreatic lipase do?

Answer 30

hydrolyses triglycerides into monoglycerides and free fatty acids.

Question 31

___ ___ are the absorbable units of fat

Answer 31

fatty acids.

Question 32

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

Answer 32

GRANULES

Question 33

T/F: the pancreas can modulate which enzymes are secreted

Answer 33

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.

Question 34

the 3 phases of timing of the stomach

Answer 34

1) cephalic 2) gastric 3) intestinal phases.

Question 35

for the most part, the pancrease isn’t stimluated during the __or ___ phases, but mostly during the ___ phase.

Answer 35

not stimulated during the cephalic or gastric stage, but mostly during the intestinal phase, when teh duodenum can influence gastric secretion

Question 36

2 enterogastrones that are released to influence intestinal secretion (pancreatic secretion into duodenum) and motility

Answer 36

1) secretin: drives duct cell to secrete alkaline substance.
2) cholecystokinin CCK

Question 37

secretin is stimulated by ___ in the duodenum. Mechanism of release.

Answer 37

ACID. duodenum releases secretin into blood, and secretin stimulates DUCTcells of pancreas to release sodium bicarbonate. NEGATIVE feedback flow.

Question 38

CCK is stimulated by ___ and ___ in the duodenum. Mechanism of release?

Answer 38

fat and protein. duodenum secretes CCK into blood, and the CCK stimualtes ACINAR cells to release pancreatic enzymes by exocytosis.

Question 39

secretin acts on ___ cells, while CCK acts on ____ cells of the panceas

Answer 39

secretin acts on DUCT cells, while CCK acts on ACINAR cells of the panceas