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
