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BIOL-3603 > Part 4.2: Digestion > Flashcards

Part 4.2: Digestion Flashcards

1
Q

crop is a specialization of the ___

A

esophagus

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2
Q

Cool specialization about the crop (exaptations 2)

A

1) bird lactation “crop milk.” –> epithelial cells respond to prolactin in some birds. Crop cells thens syntheisze lipids and are then regurgitated with food for the chicks. 2) fermentation vat for cellulose digestion and detoxification of plant alkloids.

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3
Q

key functions of stomach (2)

A

1) storage and
2) digestion (beyond salivary contribution)

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4
Q

in addition to storage or digestive functions, the stomach acts as a ___ ___ for some insects

A

filter chamber (seen in aphids) aphid-farming ants eat the filtrate that comes from the aphids. Co evolutionary relationship that developed becasue the aphids can filter the water out of meals and create a sugary sap

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5
Q

there are specializations in the stomach seen in birds and ruminants, but humans have a stomach that is considered __-

A

monogastric. we do not have chambers like a cow

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6
Q

____ sphincter is between the esophagus and the stomach

A

gastroesophageal sphincter.

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7
Q

top of the stomach is _____ the bottom part of the stomach is the ___

A

top= fundus/cardiac pylorus = bottom (body= middle)

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8
Q

the sphincter between the pylorus (portion of the stomach) and the duodenum

A

pyloric sphincter

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9
Q

in the stomach, the mixing and pulverising of food into chyme occurs in the ___. How is it facilitated?

A

ANTRUM (lower portion). facilitated by layers of smooth muscle.

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10
Q

the wave of contraction that moves across the muscle of the stomach allows the stomach to move chyme into the duodenum

A

peristaltic contraction

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11
Q

emptying into he duodenum is controlled by:

A

1) the stomach itself 2) the duodenum ** go through table 14-2.

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12
Q

duodenal factors that inhibit emptying of the stomach. Explain. (4 factors)

A

1) fat--> strongest inhibiting stimulus, and can only be digested slowly. if the duodenum is detecting a lot of fat, then it sends negative signals to the stomach because its gonna take a long time to address this fat.
2) acidity; important for intitiating digestion in the stomach. as pH drops in the small intestine, signals tell the stomach to stop pushing things into the duodenum. this prevents damage to duodenal mucosa and the denaturation of digestive enzymes.
3) hypertonicity in the duodenum. Proteins and carbs are broken into AAs and glc. this increases OSMOLARITY. - when osmolarity rises, gastric emptying is inhibited until small molecules can be absorbed.
4) distention. Physical stretching of duodenum causes negative feedback.

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13
Q

2 mechanisms that allows for duodenum to exert negative feedback on gastric emptying

A

1) enterogastrones: released from the duodenal mucosa and travel in the blood to the stomach and stop peristaltic movement –> gastric inhibitory peptide
2) neural inhibition. autonomic nervous system for slow inhibition, enteric nervous system for fast inhibition.

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14
Q

____ are released fromthe duodenal mucosa and travel in the blood to the stomach to allow for a negative feedback loop

A

enterogastrones.

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15
Q

3 primary secretions that allows the stomach to conduct digestions

A

1) mucous for protection and lubrication 2) Hcl 3) digestive enzymes like PEPSIN

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16
Q

T/F Acid helps break apart nutrients into their macromolecules

A

FALSE. it provides antimicrobial properties and kills bacteria that was ingested.

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17
Q

purposes of HCl in the stomach (4)

A

1) starts denaturing proteins (easier for them to be digested and broken apart into AAs if it is unfolded)
2) kills microorganisms
3) aids in destruction of connective tissue.
4) activates pepsinogen into pepsin. there is no breaking down into macromolecules done by Hcl.

*** true digestion does not occur because of HCl

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18
Q

pepsin protein is found in the ____

A

stomach

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19
Q

pepsin is secreted by ____ cells. describe the process of activation and the different gastric cells involved

A

Chief cells in the gastric pits of the stomach in the form of PEPSINOGEN. with the help of Hcl secreted by parietal cells, the pepsinogen is cleaved into active pepsin.

20
Q

_____ secrete H+ and Cl- into the stomach lumen

A

parietal cells. creates an acidic ph as low as 2.

21
Q

how can H+ be concentrated in the stomach?

A

via active transport on behalf of the parietal cells. there are 3-4 million times more H+ there is a bicarbonate reaction occuring in pareital cells that converts CO2 into the bicarbonate ions.

22
Q

CO2 sources that allow parietal cells to pump H+ into lumen

A

1) plasma 2) metabolism

23
Q

the ____ tranporter on the membrane of the parietal cell between the plasma fluid ACTIVELY exchanges bicarbonate into Cl-, so that Cl- can move into the gastric lumen.

Draw the method of HCl concentration on behalf of the parietal cell into the gastric lumen

A

HCO3-/Cl- transporter. See image of parietal cell transporters in the slide.

24
Q

two distinct regions of the gastric mucosa stomach involved in gland secretions. The gastric mucosa is lined with ____ ____

A

1) oxynitic region: 2) pyloric gland area: .

the gastric mucosa is lined with GASTRIC PITS

25
Q

the gastric pits in the stomach are found in the ___, where as the peristaltic movements originate in the ____

A

the gastric pits in the stomach are found in the MUCOSA, where as the peristaltic movements originate in the SUBMUCOSA ( and muscularis externa)

26
Q

exocrine secreteory cells in the oxynitic region of the stomach contain ___ cells and ___ cells and ____ cells and ____ (at the bottom)

A

mucous cells and chief cells, and pareital cells and enterochromaffin like cells. (pepsinogen)

27
Q

a bunch of secretory cells in one place

A

gland.

28
Q

pareital cells are located on the ___ portion of the gastric gland, whereas the mucous neck cells are located at the ____

A

pareital cells are located on the BASAL portion of the gastric gland, whereas the mucous neck cells are located at the ISTHMUS/UPPER PORTION

29
Q

what are the paracrine secretory cells inthe oxynitic mucosa? Function? How are they activated?

A

enterochromaffin-like cells. sensitive to hormone gastrin and Ach. SECRETES HISTAMINE to stimulate parietal cells to secrete more HCl.

30
Q

what is paracrine signalling

A

signals given off by cells to affect the cells beside them

31
Q

gastric gland cells in the pyloric gland area

A

D cells and G cells.

32
Q

both D cells and G cells cells found in the pyloric gland area of the stomach have ___ function

A

endocrine and paracrine secretory cells.

33
Q

purpose of G cells. How are they stimulated? What do they secrete?

A

part of positive feedback loop. secretes GASTRIN to stimulate parietal, chief, and ECls cells (to secrete more histamine to activate parietal cells even further). Stimulated by Ach and protein products

34
Q

purpose of D cells. What do they secrete and how are they stimulated. Where are they douns?

A

involved in negative feedback. secretes somatostatin. stimulated by acid to apply the brakes of parietal cell activation, G cell activation, or ECL cell activation

found in the pyloric gland area.

35
Q

** LOOK AT table 14-3!!

A

know the product secreted, stimuli for secretion ,and functions of secretory product.

36
Q

gastric secretion is modulated by the autonomic nervous system by ____. What occurs?

A

Ach. stimulates parietal, chief, G (stimulates parietal and ECL cells)and ECL cells (which further stimulate parietal cells). Allows for POSITIVE FEEDBACK.

37
Q

chemicals that regulate gastric secretion (4)

A

1) ach: stimulates chief, parietal and ECL cells.
2) gastrin : stimulates parietal and ECL cells. ( to stimulate the parietal cells even further)
3) histamine: secreted by the ECL cells to enhance parietal cell secretion. 4) somatostatin: inhibits all other cells to slow down HCl secretion and slow down digestion

38
Q

what is the cephalic phase of stomach regulation

A

stomach activates before food reaches the stomach. causes stomach rumbling. even just thinking about food can increase secretion.

39
Q

what is the gastric phase of stomach regulation

A

more secretion occurs when food is in the stomach

40
Q

T/F you can bypass the cephalic phase in order to get digestion going

A

true. you don’t need to be primed by your thoughts in otder to start digestion. ex/ you don’t need to watch the cooking show to get your digestion going before you even start eating.

41
Q

phases that time stomach secretion/gastric regulation

A

1) cephalic phase 2) gastric phase. 3) intestinal phase.

42
Q

what is the intestinal phase of stomach regulation. How can this phase be inhibited?

A

the intestinal phase of gastric secretion involves factors originating in the small intestine that influence gastric secretion, as with gastric emptying. Even if the stomach is completely isolated from the intestinal tract, placement of food into the upper part of the duode- num can still induce acid secretion in the stomach.

intestinal gastrin (from G cells) is secreted into the blood because of the presence of protein products in the duodenum, and stimulates the stomach to get going even more. –> EXCITATORY COMPONENT

INHIBITORY EFFECT: this phase gets inhibited if the duodenum exerts negative feedback effects. fat, acid, hypertonicity, or distension in the duodenum brought about by stomach emptying.

  • The enterogastric reflex and the enterogastrones suppress the gastric secretory cells, while they simultaneously reduce the excitability of the gastric smooth muscle cells. when the pH of the intestine becomes too low, enteroglucagon (an enterogastrone) is re- leased into the circulation and “shuts off” the flow of gastric juices.
43
Q

Functions (7) of the saliva

A

1) moistening
2) digestion (salivary amylase)
3) Defense (lysozymes, siGa)
4) taste
5) neutralization: often rich in bicarbonate buffers
6) thermoregulation (aids in panting and evaporative cooling)
7) poisons; hemotoxic, neurotoxic
8) anticoagulations
9) silk
10) pheromones

44
Q

two primary plexuses that create the enteric nervous system

A

the intrinsic nerve plexuses: two major networks of nerve fibers—

1) the myenteric plexus
2) submucous plexus—located entirely within the digestive tract wall and running its entire length

45
Q

look at the outline of stimulation of gastric secretion (14-3)

A
46
Q

3 methods of shutting off gastric secretion

A

1) reduction in presence of protein (that usually drive G cells) aka stomach emptying
2) falling pH *causes release of somatostatin to prevent addition Hcl release)
3) duodenal stimuli that inhibits gastric motility also inhibits gastric secretion–> recall: fat, acidity, hypertonicity, distension.

BIOL-3603 (13 decks)

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