digestive - phyanalec Flashcards by J G

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

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

serous

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– enzyme that has a weak antibacterial action

found in saliva

lysozyme

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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

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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

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have a sweet taste

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

Maltose & Isomaltose

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Food spends how much time in the mouth

very little

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

mucin

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salivary gland secretion is regulated by primarily

parasympathetic NS

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

SALIVARY GLAND SECRETION

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-sympathetic stimulation increases

mucous content of saliva (dry mouth with thick mucus)

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

MASTICATION

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

MASTICATION

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

voluntary

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

esophageal

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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

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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

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

relaxation

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Wave ofof circular muscles propels bolus through esophagus

strong contraction

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

Gravity

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

stomach

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– semifluid mixture of food and stomach secretions; acidic

chyme

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

HCl

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

pepsin

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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

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

intrinisc factor

neural mechanisms in digestive tract

* CNS in medulla oblongata | * Enteric plexus in digestive wall

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

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

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

TYPES OF STOMACH MOVEMENT – cause relatively weak contractions -thoroughly mix ingested food with stomach secretions to form chime -more fluid part of chyme is pushed toward pyloric sphincter -more solid part of chime is pushed toward body of stomach

mixng waves

TYPES OF STOMACH MOVEMENT cause stronger contractions -force chyme toward and through pyloric sphincter -pyloric sphincter usually remains closed because of mild tonic contraction -each peristaltic contraction is sufficiently strong to cause partial relaxation of pyloric sphincter -↑motility, ↑emptying

peristaltic waves

– major inhibitor of motility and emptying | -stomach emptying is slower after a fatty meal due to the release of

cholecystokinin

major stimulus of gastric motility and emptying

Distension of stomach wall –

uncomfortable sensation resulting from low blood glucose levels -begin 12 – 24 hours after the previous meal

HUNGER PANG –

ENZYMES OF SMALL INTESTINE: | break peptide bonds In proteins to form amino acids

Peptidases –

ENZYMES OF SMALL INTESTINE: | – break down disaccharides (like maltose) into monosaccharides (glucose)

disaccharidases

ENZYMES OF SMALL INTESTINE: produced by duodenal glands and goblet cells -dispersed throughout the epithelial lining of small intestine

mucus

type of contraction | – proceed along the length of the intestine for variable distances and cause chyme to move along small intestine

peristaltic

propagated for only short distances and mix intestinal contents

SEGMENTAL CONTRACTIONS –

most absorption occurs in

duodenum and jejunum, some in ileum

contains no digestive enzymes -dilutes and neutralizes stomach acid - dramatically increases efficiency of fat digestion and absorption - contains excretory products (cholesterol, fats, bile pigments like bilirubin)

bile

– major function of small intestine

ABSORPTION IN SMALL INTESTINE

– bile pigment that results from hemoglobin breakdown

bilirubin

- emulsify fats, breaking the fat globules into smaller droplets (digestive enzymes cannot act efficiently on large fat globules) - most are reabsorbed in the ileum

BILE SALTS

BILE SECRETION | -stimulated by (3)

parasympathetic stimulation through vagus nerve by secretin cholecystokinin

stimulates gallbladder to contract and release bile into duodenum)

cholecystokinin

EXOCRINE SECRETIONS of pancreas neutralize acidic chyme that enters small intestine from stomach -increased ph resulting from HCO3 secretion stops pepsin digestion but provides proper environment for the function of pancreatic enzymes

bicarbonate ions

EXOCRINE SECRETIONS of pancreas major proteolytic enzymes -continue protein digestion that started in the stomach

2. TRYPSIN, CHYMOTRYPSIN, CARBOXYPEPTIDAS

EXOCRINE SECRETIONS of pancreas | continues polysaccharide digestion that began in oral cavity

3. PANCREATIC AMYLASE –

EXOCRINE SECRETIONS of pancreas | lipid-digesting enzyme

. LIPASE

EXOCRINE SECRETIONS of pancreas | enzymes that degrade DNA and RNA to their component nucleotides

5. NUCLEASES

initiates release of watery pancreatic solution that contains large amount of HCO3 -stimulus of secretin release: presence of acidic chyme in duodenum

SECRETIN –

– stimulates pancreas to release an enzyme-rich solution | -primary stimulus: presence of fatty acids and amino acids

CHOLECYSTOKININ –

KIND OF STIMULATIONSTIMULATION – stimulates secretion of pancreatic juices

PARASYM

inhibits secretion of pancreatic juices

SYM

time required for material to pass through large intestine

18 – 24 hrs –

time required for chyme to pass through small intestine

3 – 5 hrs –

chyme in the colon (converted to feces in colon)

FECES

– elimination of feces

Defecation

stores feces until defecation | -inhabited by many bacteria

COLON

– strong contractions undergone by large parts of colon every 8-12 hours - propel the colon contents toward anus - very common following some meals, especially breakfast

MASS MOVEMENTS

digestive - phyanalec Flashcards

(62 cards)