Functions and secretion of the alimentary tract: part 1

Question 1

food ingestion is stimulated by

Answer 1

Hunger = intrinsic for food
appetite= preferential of food

Question 2

Mastication ( chewwing)

Answer 2

Teeth= designed for cutting (incisors) and grinding (molars) of food.
Muscles for chewing= controlled by nuclei in brain stem.

Question 3

Stimulation of specific reticular areas (brain stem taste centers)

Answer 3

causes rhythmic chewing action.

Question 4

what other stimulation causes chewing ?

Answer 4

hypothalamus
brain cerebral cortex
amygdala

Question 5

mastication reflex

Answer 5

takes place in response to presence of reflex inhibition of mastication muscles (at first)→ lower
jaw drops→ initiates stretch reflex of jaw muscles→ rebound contraction→ automatically raises jaw→
closes teeth + compresses bolus against mouth linings→ inhibits jaw muscles again→ jaw drops→
rebound contraction again= process repeated again and again

Question 6

mechanical digestion of all food

Answer 6

chewing

Question 7

chemical digestive

Answer 7

digestive enzymes

Question 8

initiation of the swallowing process.

Answer 8

voluntary stage

food bolus pushed and compressed by the tongue against the palate to the pharynx.

Question 9

initiation of the swallowing process.

Answer 9

voluntary stage

food bolus pushed and compressed by the tongue against the palate to the pharynx.

Question 10

pharyngeal stage( in the pharynx )

Answer 10

involuntary stage/ process

Bolus stimulates epithelial swallowing receptor areas in
the pharynx, and tonsillar pillars→ to send action potentials to the brain stem.
initiates a series of automatic pharyngeal muscular contractions.

Question 11

soft palate will elavate and closes the posterior nares

Answer 11

to prevent food reflex intp the nasal cavity

Question 12

palatopharyngeal folds

Answer 12

are pulled medially to form sagittal slit: selectively allow properly masticated food to pass.

Question 13

function of epiglosttis

Answer 13

closes the larynx

Question 14

elevation of the larynx ………………. and …………..

Answer 14

enlarges the oesophageal opening and upper oesophageal sphincter relaxes.

contration of the pharyngeal muscular wall= peristalsis propulsion of food into oesophagus.

Question 15

Pharyngeal Stage of Swallowing Momentarily Interrupts Respiration:

Answer 15

last for 6 seconds
Swallowing center inhibits respiratory center of the medulla during this
time (within the 6 secs period)

Question 16

Esophageal Stage of Swallowing involves 2 Types of Peristalsis:

Answer 16

primary and secondary perilstalisis.

Question 17

primary peristalsis.

Answer 17

begins in the pharynx and terminates in the stomach.
last about 8-10 seconds in an upright person.

last about 6-8 secs due to gravitational force.

Question 18

secondary peristalsis.

Answer 18

when primary peristalsis fails, secondary peristalsis wave results from distention of oesophagus by retained food.

Question 19

Secondary peristalsis initiated by:

Answer 19

a) Intrinsic neural circuits in myenteric nervous system
b) Pharyngeal reflexes transmitted upward through vagal afferent fibers to medulla and back to esophagus
through glossopharyngeal & vagal efferent nerve fibers.

Question 20

Pharyngeal wall & upper 3rd esophagus.

Answer 20

has striated/ skeletal muscles= controlled by skeletal nerve impulses of
glossopharyngeal & vagal efferent nerve fibers.

Question 21

while the lower 2/3 of the esophagus

Answer 21

strongly controlled by vagal nerves associated with myenteric
nervous system.

When vagus nerve is cut→ myenteric plexus of esophagus takes over & stimulate secondary peristalsis

Question 22

when the vagus nerve is cutted what is happens?

Answer 22

→ myenteric plexus of esophagus takes over & stimulate secondary peristalsis.

Question 23

Esophageal peristaltic waves approaching stomach→

Answer 23

relaxation of the stomach through the inhibitory neurons accouring

Question 24

Function of the Lower Esophageal Sphincter (LES) (Gastroesophageal Sphincter):

Answer 24

Peristaltic wave moving down esophagus→ receptive relaxation of lower esophageal sphincter occurs→ food
enters stomach.
Tonic constriction of the LES prevents reflux of stomach contents into esophagus

Question 25

Prevention of Esophageal Reflux by Valve-like Closure of the Distal End of Esophagus:

Answer 25

a valve-like mechanism of a short portion of the oesophagus extending slightly to the stomach is called cardia prevents high intra-abdominal pressure from forcing stomach contents into oesophagus.

Question 26

storage function of the stomach

Answer 26

Food enter stomach→ stomach stretches→ vagovagal reflex (from stomach—brain stem—back to stomach) reduce muscular tone→ stomach stretches more (with limit of 0.8L to 1.5L).

Question 27

mixing of the food in the stomach is controlled by

Answer 27

gut wall basic electrical rhythmical waves called constrictor waves.

Question 28

when food enters the stomach

Answer 28

Gastric glands secret gastric juices→ juices mix with food material→ mixing waves (constrictor waves) initiated by gut wall basic electrical rhythm (“slow waves”) (move from body to antrum)→ constrictor waves become more powerful→ food moves towards pylorus→ pyloric muscles contracts→ impedes emptying through pylorus→ food contents mixed (retropulsion mixing mechanism)→ chyme formed.

Question 29

stomach emptying

Answer 29

Caused by strong peristaltic contractions in stomach Pylorus controls the degree of chyme being emptied.

Question 30

Role of Pylorus in Controlling Stomach Emptying:

Answer 30

Pyloric circular muscles= pyloric sphincter pyloric sphincter remains tonically contracted normally. degree of pyloric contraction increases or decreases depending on the influence of nervous or hormonal signals.

Question 31

Gastric Factors Promoting Emptying:

Answer 31

Gastric Food Volume: increased food volume → promotes stomach emptying Stretching of stomach wall→ stimulate local myenteric reflexes→ increase pyloric pump activity.

Question 32

hormones stimulating emptying if the stomach?

Answer 32

Stretching of the stomach wall and presence of certain foods. G cells are stimulated to secrete gastrin then stimulate parietal cells to H ions --> Hcl to promote activity of pyloric pump

Question 33

Mixing Contractions (Segmentation Contractions):

Answer 33

Chyme in duodenum→ cause distention→ stretching intestinal wall→ elicit local concentric contractions= segmentation contractions→ cause mixing of chyme with small intestine secretions.

Question 34

propulsive movement of chyme in the intestine

Answer 34

Peristalsis in Small Intestines: chyme moves through small intestines by peristaltic contractions

Question 35

Control of Peristalsis by Nervous & Hormonal Signals:

Answer 35

peristaltic activity increase by the gastroenteric reflex initiated by stomach distention & conducted through to small intestines by myenteric plexus. Hormonal factors include gastrin, CCK, insulin, motilin, serotonin; all enhance small intestinal motility

Question 36

Hormones that inhibits motility

Answer 36

Glucagon and secretin

Question 37

The Ileocecal Valve Prevents Backflow From The Colon to The Small Intestine:

Answer 37

Ileocecal valve protrudes into cecum→ increased cecum pressure→ forcefully closes it= preventing backflow into ileum. Ileocecal sphincter→ remain mildly constricted→ allows slow emptying of ileal content into cecum

Question 38

main function of the colon.

Answer 38

absorption of water and electrolytes and storage of faecal matter until expelled.

Question 39

process of the large circular and longitudinal muscles contractions occurs in the large intestines. is called

Answer 39

Haustrations which will the result-slowly dug into & roll over faecal material→ faecal material exposed to mucosal surfaces→ absorption occurs

Question 40

After meals, mass movement facilitated by gastrocolic and duodenocolic reflexe due to

Answer 40

stretching of stomach and duodenum.

Question 41

peritoneointestinal reflex

Answer 41

Stimulated by irritation of the peritoneum→ Inhibits excitatory enteric nerves→ cause intestinal paralysis (patients with peritonitis

Question 42

Renoitestinal and vesicointestinal reflexes

Answer 42

stimulated by irritation the kiddney and gallbladde