Transcript Ch14-1 Digestive Pt2 Notes

Processes of the Digestive System
 Ingestion –
 Propulsion –
 Peristalsis –
 Segmentation –
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Processes of the Digestive System
 Mechanical digestion
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Processes of the Digestive System
 Chemical Digestion
 Each major food group uses different
enzymes
 Carbohydrates are broken to
 Proteins are broken to
 Fats are broken to
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Processes of the Digestive System
 Absorption
 End products of digestion are absorbed in
___________________________
 Food must enter mucosal cells and then into
___________________________________
 Defecation
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Control of Digestive Activity
 Mostly controlled by reflexes via the _____________
__________________________________________
 Chemical and mechanical receptors are located in organ
walls that trigger reflexes
 Stimuli include:
 Reflexes include:
 Activation or inhibition of glandular secretions
 Smooth muscle activity
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Digestive Activities of the Mouth
 Mechanical breakdown
 Chemical digestion
 Food is mixed with saliva
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Activities of the Pharynx and Esophagus
 These organs have no digestive function
 Serve as passageways to the stomach
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Deglutition (Swallowing)
 Buccal phase
 Occurs in the mouth
 Food is formed into a bolus
 The bolus is forced into the pharynx by the
tongue
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Deglutition (Swallowing)
 Pharyngeal-esophageal phase
 _____________________ transport of the bolus
 All passageways except to the stomach are blocked
 Peristalsis moves the bolus toward the stomach
 The _____________________________________
is opened when food presses against it
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Food Breakdown in the Stomach
 Gastric juice is regulated by neural and
hormonal factors
 Presence of food or falling pH causes the
release of
 __________________ causes stomach glands
to produce protein-digesting enzymes
 _______________________________ makes
the stomach contents very acidic
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Necessity of an Extremely Acid
Environment in the Stomach
 Activates ________________________ to
____________________ for protein digestion
 Provides a hostile environment for
microorganisms
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Digestion and Absorption in the Stomach
 Protein digestion enzymes
 Pepsin –
 Rennin –
 The only absorption that occurs in the
stomach is of
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Propulsion in the Stomach
 Food must first be well mixed
 Rippling peristalsis occurs in the lower
stomach
Figure 14.15
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Propulsion in the Stomach
 The pylorus meters out chyme into the small
intestine
 The stomach empties in _______________ hours
Figure 14.15
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Digestion in the Small Intestine
 Enzymes from the brush border
 Pancreatic enzymes play the major digestive
function
 Help complete digestion of
 Carry out about half of all
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Digestion in the Small Intestine
 Pancreatic enzymes play the major digestive
function (continued)
 Responsible for
 Digest nucleic acids
 Alkaline content neutralizes acidic chyme
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Stimulation of the Release of Pancreatic
Juice
 Vagus nerve
 Local hormones
Figure 14.16
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Absorption in the Small Intestine
 ____________________is absorbed along the
length of the small intestine
 End products of digestion
 Most substances are absorbed by _________
________________ through cell membranes
 Lipids are absorbed by
 Substances are transported to the liver by the
hepatic portal vein or lymph
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Propulsion in the Small Intestine
 Peristalsis is the major means of moving food
 Segmental movements
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Food Breakdown and Absorption in the
Large Intestine
 No digestive enzymes are produced
 Resident bacteria digest remaining nutrients
 Produce some
 Release
 ____________________________________
are absorbed
 Remaining materials are eliminated via
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Propulsion in the Large Intestine
 Sluggish peristalsis
 Mass movements
 Presence of feces in the rectum causes a defecation
reflex
 Internal anal sphincter is relaxed
 Defecation occurs with relaxation of the
voluntary (external) anal sphincter
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Developmental Aspects of the Digestive
System
 The alimentary canal is a continuous tube by
the _______________ week of development
 Digestive glands bud from the mucosa of the
alimentary tube
 The developing fetus receives all nutrients
through the placenta
 In newborns, feeding must be frequent,
peristalsis is inefficient, and vomiting is
common
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Developmental Aspects of the Digestive
System
 Teething begins around age
 Metabolism decreases with old age
 Middle age digestive problems
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Developmental Aspects of the Digestive
System
 Activity of digestive tract in old age
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