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PHGY 210 Digestion Exam Questions And Accurate Answers
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PHGY 210 Digestion Exam Questions AndAccurate Answers
Other names for digestive system - Answer - gastrointestinal tract (GI tract)
- alimentary canal
Accessory digestive organs - Answer - teeth
- tongue
- salivary glands
- liver
- gallbladder
- pancreas
What activity mediates secretion? What is its purpose? - Answer Glandular activity - for
chemical breakdown
What activity mediates motility? What is its purpose? - Answer Muscular activity - for
propulsion and physical breakdown
How does progesterone affect the LES? - Answer - decreases resistance across LES
- due to fetus pushing upward on abdominal contents, accounts for heartburn in late
pregnancy
Can gastrin and other GIT hormones relax the LES? - Answer - not at physiological levels
(would have to take enormous quantities)
What is a function of the stomach? - Answer - mixing chamber
- reservoir (temporary holding)
,What are the three major regions of the stomach? - Answer - fundus
- body
antrum
3 motor functions of the stomach - Answer - temporary storage (1-2 L of food)
physical disruption and mixing of contents (bolus turned into semi-liquid texture
referred to as chyme)
propulsion into duodenum of small intestine (controlled propulsion)
Where is food storage in the stomach? - Answer - within the proximal stomach (upper
portion)
this portion of the stomach is thin-walled
Where does mixing and propulsion occur in the stomach? -Answer- in the distal stomach
(lower portion)
- this part of the stomach is thick-walled
Layers of the stomach wall -Answer- same four basic layers as rest of GIT, with some
modifications:
- gastric mucosa: made up of folds, rugae (increase area in proximal stomach), contains
a variety of cells on pits and glands, all of the epithelium in origin
- muscularis externa: circular and longitudinal muscle. Has added layer of smooth
muscle, oblique necessary for mix
How does the stomach accommodate itself for a meal? -Answer Thru receptive
relaxation
Rises in volume w/o a significant rise in intraluminal pressure
- confined to the proximal stomach
- volume ranges from 50 mL at rest to 1.5L to accommodate entering food
- receptive relaxation is a deglutition reflex
,Innervation responsible for receptive relaxation - Answer - activation of pharyngeal
receptors stimulates the deglutition center
- vagal efferents release ACh onto inhibitory enteric neurons in proximal stomach
- inhibitory enteric neurons in turn release NANC on stomach musculature to relax it
- inhibitory enteric neurons can also stimulate vagal afferents via local distension
created by entering meal to provide information back to deglutition center long
vago-vagal reflex and sustain receptive relaxation NOT due to deglutition center
What if the vagi to the proximal stomach are cut? - Answer - receptive relaxation is
limited
- results in great increase in intragastric pressure
Steps of "appropriate" activity in the upper GIT - Answer 1. generation of pressure to
advance pharynx
2. reflexes which protect the airways
3. UES relaxation
4. contraction of pharyngeal constrictors
5. primary peristalsis propagated down esophagus
6. LES relaxation
7. accommodation of stomach by gastric receptive relaxation
In what part of the stomach does peristalsis occur? - Answer only the distal stomach
peristalsis initiates at center of stomach, terminates after sphincter contraction at the
end of the antrum. What initializes gastric peristalsis? - Answer local enteric reflexes to
local distension
The amplitude of stomach contraction depend on: - Answer the magnitude of the
stimulus as well as the interaction of neural and hormonal factors
, Upon what does the frequency, direction and velocity of stomach contraction depend?
-Answer the electrical characteristics of smooth muscle
Electrophysiological properties of stomach muscle -Answer- no peristalsis in upper
stomach (steady resting potential)
- in the lower stomach, there are rhythmic waves of partial depolarization (+10-15 mV,
last 1-4 seconds and recur at regular intervals—every 20 seconds, so stomach
contracts 3 times/min synchronously in the circumference of the stomach)
- these rhythmic waves are known as Slow Waves
Other names for Slow Waves - Answer - basic electrical rhythm (BER)
- electrical control activity (ECA)
Synchronous nature of the Slow Waves (BER) - Answer - depolarisations/repolarisations
are synchronous circumferentially
- depolarisations/repolarisations migrate along a longitudinal axis
Electrical Response Activity (ERA) - Answer - second electrical signal at the peak of
BER depolarisation
- spikes at the peak of the depolarisation
- associated with contraction
- only contributor to tension in stomach muscle (increases when there's spikes, no
change without spikes)
Upon what does the magnitude of stomach tension-amplitude of contraction-depend? -
Answer The number of spikes per burst in the ERA
- the maximal frequency of stomach contractions is determined by the frequency of the
BER
Characteristics of the BER (ECA) - Answer - always present-does not correlate with
contractions
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