Lecture 19

Question 1

Pharynx:

Answer 1

• Skeletal muscle lined by mucous membrane

- Deglutition or swallowing is facilitated by saliva and mucus

Question 2

Deglutition or swallowing:

Answer 2

1. bolus is pushed into the oropharynx
2. sensory nerves send signals to deglutition center in brainstem
3. soft palate is lifted to close nasopharynx
4. larynx is lifted as epiglottis is bent to cover glottis

Question 3

Esophagus:

Answer 3

• Collapsed muscular tube

- Pierces the diaphragm at hiatus

Question 4

Histology of the Esophagus:

Answer 4

Mucosa
Submucosa
Muscularis
Adventitia

Question 5

Mucosa =

Answer 5

stratified squamous

Question 6

Submucosa =

Answer 6

large mucous glands

Question 7

Muscularis =

Answer 7

upper 1/3 is skeletal, middle is mixed, lower 1/3 is smooth

Question 8

Adventitia =

Answer 8

connective tissue blending with surrounding connective tissue–no peritoneum

Question 9

Physiology of the Esophagus - Swallowing:

Answer 9

Voluntary phase

Involuntary phase

Question 10

Voluntary phase—

Answer 10

tongue pushes food to back of oral cavity

Question 11

Involuntary phase—-

Answer 11

pharyngeal stage:

• breathing stops & airways are closed
• soft palate & uvula are lifted to close off nasopharynx
• vocal cords close
• epiglottis is bent over airway as larynx is lifted

Question 12

Swallowing:

Answer 12

1. Upper sphincter relaxes when larynx is lifted
2. Peristalsis pushes food down
3. Lower sphincter relaxes as food approaches

Question 13

Peristalsis in swallowing:

Answer 13

• circular fibers behind bolus

- longitudinal fibers in front of bolus

Question 14

Swallowing Time:

Answer 14

Travel time is 4-8 seconds for solids and 1 sec for liquids

Question 15

If lower sphincter fails to open

Answer 15

distension of esophagus feels like chest pain or heart attack

Question 16

If lower esophageal sphincter fails to close

Answer 16

1. stomach acids enter esophagus & cause heartburn (GERD)
2. for a weak sphincter—don’t eat a large meal and lay down in front of TV
3. smoking and alcohol make the sphincter relax worsening the situation

Question 17

Control the symptoms by avoiding

Answer 17

coffee, chocolate, tomatoes, fatty foods, onions & mint
take Tagamet HB or Pepcid AC 60 minutes before eating
neutralize existing stomach acids with Tums

Question 18

Stomach:

Answer 18

Empties as small squirts of chyme leave the stomach through the pyloric valve

Question 19

Mucosa & Gastric Glands:

Answer 19

-Hydrochloric acid converts pepsinogen from chief cell to pepsin
Gastrin hormone (g cell)

Question 20

Intrinsic factor of Mucosa & Gastric Glands:

Answer 20

absorption of vitamin B12 for RBC production

Question 21

Gastrin hormone of Mucosa & Gastric Glands:

Answer 21

“get it out of here”:

• release more gastric juice
• increase gastric motility
• relax pyloric sphincter
• constrict esophageal sphincter preventing entry

Question 22

Muscularis:

Answer 22

• Three layers of smooth muscle

- Permits greater churning & mixing of food with gastric juice

Question 23

3 layers of muscularis:

Answer 23

outer longitudinal, circular & inner oblique

Question 24

Physiology–Mechanical Digestion:

Answer 24

1. gentle mixing waves
2. more vigorous
3. intense waves near the pylorus

Question 25

Gentle mixing waves

Answer 25

- every 15 to 25 seconds | - mixes bolus with 2 quarts/day of gastric juice to turn it into chyme (a thin liquid)

Question 26

More vigorous waves

Answer 26

travel from body of stomach to pyloric region

Question 27

Intense waves near the pylorus

Answer 27

open it and squirt out 1-2 teaspoons full with each wave

Question 28

Physiology--Chemical Digestion in Stomach:

Answer 28

1. Protein digestion begins 2. fat digestion continues 3. HCl kills microbes in food 4. Mucous cells protect stomach walls

Question 29

Protein digestion begins

Answer 29

- HCl denatures (unfolds) protein molecules | - HCl transforms pepsinogen into pepsin that breaks peptides bonds between certain amino acids

Question 30

Fat digestion continues

Answer 30

gastric lipase splits the triglycerides in milk fat

Question 31

Regulation of Gastric Secretion and Motility:

Answer 31

Cephalic phase Gastric phase Intestinal phase

Question 32

Cephalic Phase =

Answer 32

“Preparation” Cerebral cortex Vagus nerve

Question 33

Cerebral cortex =

Answer 33

sight, smell, taste & thought | parasympathetic

Question 34

Vagus nerve=

Answer 34

increases stomach muscle and glandular activity

Question 35

Gastric Phase =

Answer 35

“Working” 1. Nervous control keeps stomach active 2. Endocrine influences over stomach activity

Question 36

Nervous control keeps stomach active:

Answer 36

1. stretch receptors & chemoreceptors provide information 2. vigorous peristalsis and glandular secretions 3. chyme is released

Question 37

Endocrine influences over stomach activity:

Answer 37

1. presence of caffeine or protein cause G cells secretion into bloodstream 2. gastrin hormone increases stomach glandular secretion and churning and sphincter relaxation

Question 38

Intestinal Phase =

Answer 38

“Emptying” 1. Stretch receptors in duodenum slow stomach activity & increase intestinal activity 2. Distension, fatty acids or sugar signals medulla (sympathetic) 3. Hormonal influences

Question 39

Hormonal influences | of Intestinal Phase:

Answer 39

1. secretin hormone decreases stomach secretions 2. cholecystokinin(CCK) decreases stomach emptying 3. gastric inhibitory peptide(GIP) decreases stomach secretions, motility & emptying