Lecture 30 Digestive Flashcards Preview

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Flashcards in Lecture 30 Digestive Deck (44)
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1

GI Tract

mouth -stratified squamous epithelium
pharynx
esophagus
stomach -simple columnar epithelium
small intestine
large intestine

2

Accessory Organs

salivary glands
liver
pancreas
gallbladder

3

Functions of the Digestive System

digestion
absorption
secretion
motility

4

digestion

chemical breakdown of food molecules by hydrolysis

5

absorption

of nutrients, electrolytes and H2O

6

secretion

mucus, digestive enzymes, acid, bicarbonate, electrolytes

7

motility

muscular movements of GI tract to mix and propel food
peristalsis - moves material forward
segmental contractions - mix contents

8

regional specialization (“assembly line”)

ingestion → mechanical breakdown → chemical digestion → absorption → waste processing

9

GI tract structure: 4-layered tube

mucosa
submucosa
muscularis (externa)
serosa

10

mucosa

mucosa - epithelium + lamina propria (areolar CT) + muscularis mucosae

11

submucosa

submucosa - connective tissue, vascular

12

muscularis (externa)

muscularis (externa) - smooth muscle

13

serosa

- thin covering membrane (visceral peritoneum)

14

Mouth, Pharynx and Esophagus
functions:

ingestion, mastication (chewing), deglutition (swallowing)

15

salivary glands

secrete saliva: H2O, ions, mucus, enzymes: amylase, lipase

16

amylase

begins chemical digestion of starch → disaccharides

17

esophagus

swallowing (upper portion), peristalsis (lower portion)
lower esophageal sphincter controls entry into the stomach

18

Stomach
functions

storage
mechanical breakdown of food → chyme
sterilization
chemical digestion: acid (HCl) and enzymes (pepsin)

19

stomach structure

mucosa: simple columnar epithelium, gastric glands
- secrete acidic gastric juice (pH 1-2), 1-3 L/day
- mucous cells secrete alkaline mucus to protect stomach epithelium
muscularis: 3 layers thick
- pyloric sphincter controls passage of chyme from stomach to duodenum

20

acid secretion

parietal cells secrete hydrochloric acid (HCl)
CO2 + H2O  H2CO3  H+ + HCO3-
H+ is active transported into the lumen, Cl- follows via diffusion through channels
HCO3- is transported back into ECF (countertransport with Cl-)

21

chief cells

enzyme secretion
chief cells secrete pepsinogen (inactive), activated at low pH to form pepsin
pepsin digests proteins into smaller peptides

22

Small Intestine, Liver and Pancreas Functions and SI regions

Small Intestine, Liver and Pancreas
functions: chemical digestion and absorption
SI regions: duodenum, jejunum, ileum

23

Digestion

duodenum receives chyme from stomach, secretions from liver and pancreas

24

Liver

processes absorbed nutrients (delivered via hepatic portal vein)
secretes bile, stored in gallbladder
bile salts

25

bile salts

derived from cholesterol, function to emulsify fats → micelles

26

bile pigments

(bilirubin, biliverdin) - waste products from hemoglobin breakdown

27

Pancreas

acinar cells secrete digestive enzymes:
trypsin, chymotrypsin, carboxypeptidase, amylase, lipase
many enzymes are secreted in inactive form (zymogens), activated by trypsin in lumen

28

duct cells

secrete bicarbonate (NaHCO3) to neutralize acid (pH → 8)

29

SI (brush border)

enzymes complete digestion
complete digestion of starch

30

exopeptidase

digests terminal peptide bonds to release amino acids