Lecture 19 Flashcards

1
Q

Pharynx:

A
  • Skeletal muscle lined by mucous membrane

- Deglutition or swallowing is facilitated by saliva and mucus

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2
Q

Deglutition or swallowing:

A
  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
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3
Q

Esophagus:

A
  • Collapsed muscular tube

- Pierces the diaphragm at hiatus

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4
Q

Histology of the Esophagus:

A

Mucosa
Submucosa
Muscularis
Adventitia

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5
Q

Mucosa =

A

stratified squamous

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6
Q

Submucosa =

A

large mucous glands

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7
Q

Muscularis =

A

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

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8
Q

Adventitia =

A

connective tissue blending with surrounding connective tissue–no peritoneum

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9
Q

Physiology of the Esophagus - Swallowing:

A

Voluntary phase

Involuntary phase

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10
Q

Voluntary phase—

A

tongue pushes food to back of oral cavity

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11
Q

Involuntary phase—-

A

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
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12
Q

Swallowing:

A
  1. Upper sphincter relaxes when larynx is lifted
  2. Peristalsis pushes food down
  3. Lower sphincter relaxes as food approaches
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13
Q

Peristalsis in swallowing:

A
  • circular fibers behind bolus

- longitudinal fibers in front of bolus

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14
Q

Swallowing Time:

A

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

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15
Q

If lower sphincter fails to open

A

distension of esophagus feels like chest pain or heart attack

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16
Q

If lower esophageal sphincter fails to close

A
  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
17
Q

Control the symptoms by avoiding

A

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

18
Q

Stomach:

A

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

19
Q

Mucosa & Gastric Glands:

A
-Hydrochloric acid converts pepsinogen from chief cell to pepsin
Gastrin hormone (g cell)
20
Q

Intrinsic factor of Mucosa & Gastric Glands:

A

absorption of vitamin B12 for RBC production

21
Q

Gastrin hormone of Mucosa & Gastric Glands:

A

“get it out of here”:

  • release more gastric juice
  • increase gastric motility
  • relax pyloric sphincter
  • constrict esophageal sphincter preventing entry
22
Q

Muscularis:

A
  • Three layers of smooth muscle

- Permits greater churning & mixing of food with gastric juice

23
Q

3 layers of muscularis:

A

outer longitudinal, circular & inner oblique

24
Q

Physiology–Mechanical Digestion:

A
  1. gentle mixing waves
  2. more vigorous
  3. intense waves near the pylorus
25
Q

Gentle mixing waves

A
  • every 15 to 25 seconds

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

26
Q

More vigorous waves

A

travel from body of stomach to pyloric region

27
Q

Intense waves near the pylorus

A

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

28
Q

Physiology–Chemical Digestion in Stomach:

A
  1. Protein digestion begins
  2. fat digestion continues
  3. HCl kills microbes in food
  4. Mucous cells protect stomach walls
29
Q

Protein digestion begins

A
  • HCl denatures (unfolds) protein molecules

- HCl transforms pepsinogen into pepsin that breaks peptides bonds between certain amino acids

30
Q

Fat digestion continues

A

gastric lipase splits the triglycerides in milk fat

31
Q

Regulation of Gastric Secretion and Motility:

A

Cephalic phase
Gastric phase
Intestinal phase

32
Q

Cephalic Phase =

A

“Preparation”
Cerebral cortex
Vagus nerve

33
Q

Cerebral cortex =

A

sight, smell, taste & thought

parasympathetic

34
Q

Vagus nerve=

A

increases stomach muscle and glandular activity

35
Q

Gastric Phase =

A

“Working”

  1. Nervous control keeps stomach active
  2. Endocrine influences over stomach activity
36
Q

Nervous control keeps stomach active:

A
  1. stretch receptors & chemoreceptors provide information
  2. vigorous peristalsis and glandular secretions
  3. chyme is released
37
Q

Endocrine influences over stomach activity:

A
  1. presence of caffeine or protein cause G cells secretion into bloodstream
  2. gastrin hormone increases stomach glandular secretion and churning and sphincter relaxation
38
Q

Intestinal Phase =

A

“Emptying”

  1. Stretch receptors in duodenum slow stomach activity & increase intestinal activity
  2. Distension, fatty acids or sugar signals medulla (sympathetic)
  3. Hormonal influences
39
Q

Hormonal influences

of Intestinal Phase:

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