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Flashcards in digestive - phyanalec Deck (62)
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1

- helps keep the oral cavity moist
-contains enzymes that begin the process of digestion
-secreted at rate of 1L per day
-prevents bacterial infection in the mouth by washing the oral cavity
-contains lysozyme

saliva

2

part of saliva that dissolves molecules, which must be in solution to stimulate taste receptors

serous

3

– enzyme that has a weak antibacterial action
found in saliva

lysozyme

4

acts as buffer to neutralize the acids produced by oral bacteria
-reduces the harmful effects of bacterial acids on tooth enamel

Bicarbonate ions in saliva

5

a digestive enzyme in the serous part of saliva
-breaks covalent bonds between glucose molecules in starch and other polysaccharides to produce disaccharides maltose and isomaltose

salivary amylase

6

have a sweet taste
-digestion of polysaccharides by salivary amylase enhances the sweet taste of food

Maltose & Isomaltose

7

Food spends how much time in the mouth

very little

8

– a proteoglycan that gives a lubricating quality to the secretions of the salivary glands
-contained in the secretions of submandibular and sublingual glands

mucin

9

salivary gland secretion is regulated by primarily

parasympathetic NS

10

-increase in response to tactile stimulation and sour tastes, thought of food, odors, sensation of hunger

SALIVARY GLAND SECRETION

11

-sympathetic stimulation increases

mucous content of saliva (dry mouth with thick mucus)

12

-breaks large food particles into many small ones, which have a larger total surface area

MASTICATION

13

-increases efficiency of digestion because digestive enzymes act on molecules only at the surface of food particles

MASTICATION

14

phase of swallowing
bolus is formed in the mouth
-bolus pushed by the tongue against hard palate
-bolus goes into the oropharynx

voluntary

15

phase of swallowing
– moving food from pharynx to stomach
-muscular contractions of esophagus occur in peristaltic waves

esophageal

16

phase of swallowing
reflex initiated when a bolus of food stimulates receptors in oropharynx
-begins with elevation of the soft palate (closes the passage between oropharynx and nasopharynx)
-pharynx elevates to receive bolus of food from mouth
-pharyngeal constrictor muscles contract in succession, forcing food through pharynx
-upper esophageal sphincter relaxes, food goes to esophagus

pharyngeal

17

-sufficiently forceful to allow a person to swallow even while doing a headstand or floating in the zero-gravity environment
-causes relaxation of the lower esophageal sphincter in esophagus as peristaltic waves approach stomach

peristaltic waves

18

• Wave of of esophageal muscles precedes the bolus of food down the esophagus

relaxation

19

Wave ofof circular muscles propels bolus through esophagus

strong contraction

20

assists movement of the material, especially liquids, through the esophagus

Gravity

21

-function primarily as storage and mixing chamber for ingested food
-some digestion occurs, but it’s not its principal function

stomach

22

– semifluid mixture of food and stomach secretions; acidic

chyme

23

stomach secretion
– produces a ph of 2.0 in the stomach
-kills microorganisms and activates pepsin (active) from pepsinogen (inactive)

HCl

24

stomach secretion
breaks covalent bonds of proteins to form smaller peptide chains
-exhibits optimum activity at a ph of about 2.0

pepsin

25

stomach secretion
– lubricates and protects the epithelial cells of stomach wall from damaging effect of acidic chime and pepsin
-irritation of stomach mucosa stimulates secretion of greater volume of mucus

mucus

26

stomach secretion
binds with Vit B12 and makes it more readily absorbed in small intestine
-important in DNA synthesis and RBC production

intrinisc factor

27

neural mechanisms in digestive tract

• CNS in medulla oblongata
• Enteric plexus in digestive wall

28

PHASES OF THE STOMACH REGULATIONS
– different sensations stimulate centers in medulla oblongata
-AP are sent along parasympathetic axons within vagus nerve
-in stomach wall, preganglionic stimulate postganglionic in enteric plexus
-postganglionic stimulate secretory activity in cells of stomach mucosa, causing release of different secretions (HCl, pepsin, etc)
-neurons stimulate release of gastrin and histamine from endocrine cells

cephalic

29

PHASES OF THE STOMACH REGULATIONS
– period of greatest gastric volume secretion
-activated by presence of food in stomach
-food in stomach is mixed with gastric secretions (chyme formation)
-stomach distention stimulates stretch receptors
-stretch receptors generate AP to activate CNS and local reflexes
-result is increased secretion
-peptides ~ gastrin ~ additional HCl

gastric

30

PHASES OF THE STOMACH REGULATIONS
– inhibits gastric secretion
-controlled by the entrance of acidic chime into duodenum, which initiates both neural and hormonal mechanism
-when chime ph in duodenum is 2.0 or below, the inhibitory influence of IP is greatest
-secretin is released in response to low ph
-cholecystokinin is released in response to fatty acids and peptides, inhibits gastric secretions
-acidic chime inhibits CNS stimulation, initiates local reflexes that inhibit gastric secretion

intestinal

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