Lecture 19 Flashcards Preview

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Flashcards in Lecture 19 Deck (39):
1

Pharynx:

-Skeletal muscle lined by mucous membrane
-Deglutition or swallowing is facilitated by saliva and mucus

2

Deglutition or swallowing:

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

3

Esophagus:

-Collapsed muscular tube
-Pierces the diaphragm at hiatus

4

Histology of the Esophagus:

Mucosa
Submucosa
Muscularis
Adventitia

5

Mucosa =

stratified squamous

6

Submucosa =

large mucous glands

7

Muscularis =

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

8

Adventitia =

connective tissue blending with surrounding connective tissue--no peritoneum

9

Physiology of the Esophagus - Swallowing:

Voluntary phase
Involuntary phase

10

Voluntary phase---

tongue pushes food to back of oral cavity

11

Involuntary phase----

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

12

Swallowing:

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

13

Peristalsis in swallowing:

-circular fibers behind bolus
-longitudinal fibers in front of bolus

14

Swallowing Time:

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

15

If lower sphincter fails to open

distension of esophagus feels like chest pain or heart attack

16

If lower esophageal sphincter fails to close

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

Control the symptoms by avoiding

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

18

Stomach:

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

19

Mucosa & Gastric Glands:

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

20

Intrinsic factor of Mucosa & Gastric Glands:

absorption of vitamin B12 for RBC production

21

Gastrin hormone of Mucosa & Gastric Glands:

“get it out of here”:
-release more gastric juice
-increase gastric motility
-relax pyloric sphincter
-constrict esophageal sphincter preventing entry

22

Muscularis:

-Three layers of smooth muscle
-Permits greater churning & mixing of food with gastric juice

23

3 layers of muscularis:

outer longitudinal, circular & inner oblique

24

Physiology--Mechanical Digestion:

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

25

Gentle mixing waves

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

26

More vigorous waves

travel from body of stomach to pyloric region

27

Intense waves near the pylorus

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

28

Physiology--Chemical Digestion in Stomach:

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

29

Protein digestion begins

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

30

Fat digestion continues

gastric lipase splits the triglycerides in milk fat

31

Regulation of Gastric Secretion and Motility:

Cephalic phase
Gastric phase
Intestinal phase

32

Cephalic Phase =

“Preparation”
Cerebral cortex
Vagus nerve

33

Cerebral cortex =

sight, smell, taste & thought
parasympathetic

34

Vagus nerve=

increases stomach muscle and glandular activity

35

Gastric Phase =

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

36

Nervous control keeps stomach active:

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

37

Endocrine influences over stomach activity:

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

Intestinal Phase =

“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

Hormonal influences
of Intestinal Phase:

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