Swallowing

Question 1

what is the inner circular layer used for

Answer 1

peristalsis

Question 2

what is the outer longitudinal layer used for

Answer 2

bowel shortening

Question 3

nerve fibers what nerve innervate the upper tract?

lower tract?

Answer 3

upper = vagus

lower = pelvic

Question 4

skeletal muscles in esophagus receive what kind of fibers…and signals

Answer 4

post-ganglionic fibers which release Ach for contraction and inhibit Ach release for relaxation

Question 5

Auerbach’s plexus

Answer 5

preganglionic fibers end on the enteric nerves within this plexus

located between the ICM and OLM

initiate contraction by releasing Ach and relaxation by releasing NO

Question 6

upper esophagus sphincter (UES)

Answer 6

between oropharynx and esophagus

Question 7

lower esophagus sphincter (LES)

Answer 7

between esophagus and stomach

Question 8

pyloric sphincter

Answer 8

between pyloric stomach and duodenum

Question 9

ileocecal valve

Answer 9

between ileum and cecum (start of colon)

Question 10

time in esophagus

Answer 10

7 seconds

Question 11

time in stomach

Answer 11

2-3 hours

Question 12

time in small bowel

Answer 12

2-3 hours

Question 13

time in large bowel

Answer 13

2-3 days

Question 14

3 phases of swallowing

Answer 14

1. oral (voluntary) = mastication and decision to swallow
2. pharyngeal (involuntary)
3. esophageal (involuntary)

Question 15

oral phase of swallowing

Answer 15

under control of cranial nerves and consists of mastication and the decision to swallow …

with the latter initiating the pharyngeal and esophageal phases by transmission of neural signals to the

medullary swallowing center

Question 16

pharyngeal phase of swallowing

Answer 16

4 coordinated actions designed so that the food bolus is pushed from oral cavity across a relaxed UES into the esophagus

the soft palate and epiglottic simultaneously act to occlude the nasopharynx and larynx respectively

to ensure the food doesn’t go into the airway

Question 17

epiglottic closure

Answer 17

actuated by contraction of laryngeal muscles which elevate the larynx and lowers the epiglottis

Question 18

1st step of pharyngeal phase of swallowing

Answer 18

soft palate elevates to occlude the nasopharynx

Question 19

2nd step of pharyngeal phase of swallowing

Answer 19

laryngeal muscles contract to enable epiglottis to close the trachea

Question 20

3rd step of pharyngeal phase of swallowing

Answer 20

UES relaxes to enable bolus to enter esophagus

Question 21

4th step of pharyngeal phase of swallowing

Answer 21

pharyngeal muscles contract to initiate peristalsis to push bolus through relaxes UES into esophagus

Question 22

esophageal phase of swallowing

Answer 22

coordinated by medullary swallowing center

sends efferent signals to organ via the Vagus Nerve

result in segments of the body of the esophagus contracting sequentially so that the luminal bolus is propulsed in a caudal direction (peristalsis)

at the same time…efferent signals from vagus results in relaxation of UES and LES areas

Question 23

conditions that result in LES relaxation

Answer 23

1. primary peristalsis
2. secondary peristalsis
3. transient LES relaxation
4. belch reflex
5. deglutitive inhibition

Question 24

pressure rising in a given area of the esophagus precedes….

Answer 24

bolus movement through that area

Question 25

once bolus enters stomach...pressure in LES

Answer 25

returns to pre-swallow levels to act as a barrier to reflux

Question 26

primary peristalsis

Answer 26

initiated by a swallow

Question 27

secondary peristalsis

Answer 27

initiated by esophageal distention by a bolus that has failed to be moved into stomach by primary peristalsis

Question 28

transient LES relaxation and belch reflex

Answer 28

each initiated by gastric fundic distention by either food, liquid, or air

Question 29

deglutitive inhibition

Answer 29

initiated by rapid voluntary swallowing

Question 30

3 nuclei that form the major components of the medullary swallowing center

Answer 30

1. nucleus tractus solitarius --> recepient of all sensory signals to the center 2. nucleus ambiguous --> motor to skeletal muscle 3. dorsal motor nucleus (DMN) --> motor to smooth muscle

Question 31

function of fundus of stomach

Answer 31

storage function - has receptive relaxation (NO)

Question 32

body of stomach

Answer 32

acid-pepsin secretion where pacemaker region is located (3 contractions/min) --> strength of contraction determined by stretch-induced release of Ach from vagus nerve and release of gastrin from antral G cells from distension, elevated pH

Question 33

antrum of stomach

Answer 33

gastrin secretion (G cells in response to distension and elevated pH)

Question 34

pylorus of stomach

Answer 34

controls gastric emptying into duodenum

Question 35

gastric pacemaker

Answer 35

specialized muscle in the upper body of the stomach cells of cajal spontaneously depolarize and repolarize when depolarized enough to elicit an AP (from Ach and gastrin) --> contraction

Question 36

why is it important to only let small amounts of chyme into duodenum at a time?

Answer 36

1. sample the contents 2. accelerate the process of digestion by mixing contents with digestive enzymes secreted by the pancreas and bile salts delivered to duodenum from gallbladder 3. begin absorption of nutrients and water from luminal contents

Question 37

duodenal sampling

Answer 37

designed to reduce the rate of gastric emptying whenever the material in chyme suboptimal for digestion and absorption

Question 38

pH of duodenal sample

Answer 38

if too low...stimulates secretion of secretin from duodenal cells which (+) release of pancreatic basic juices and biliary juices for acid neutralization while also reducing gastic contractility

Question 39

osmolality of duodenal sampling

Answer 39

if too hyperosmolar --> stimulate vagus nerve (vasovagal) reflex that reduces vagal release of Ach in the vicinity of gastric musculature for reduction in gastric contractility

Question 40

fat content of duodenal sampling

Answer 40

if too fatty stimulate CCK release from duodenal epithelial cells for contraction of the gallbladder and release of pancreatic enzymes lipases that enhance fat absoprtion while also reuding gatric contracting

Question 41

general conditions that reduce gastric contraction

Answer 41

low pH, hyperosmolality, high fat in duodenum content