Download digestion

Digestion ,Absorption ,& metabolism
- body food component travel together ,through GIT into the cell.
*basic principles of digestion:
-digestion:
• prepares the food for the body use ,under
effect of muscular &chemical reaction.
• -muscular layer of the elementary system
(serosa,submucosa,&mucosa),&fiber layer
longitudinal or circular layer, help in the
movement of food &push it forward ,this
movement called peristalsis.
• -chyme:fluid secreted by GIT to help in
digestion .
• -the action of food is under control of
nervous system at GIT wall called intramural nervous plexus extend from
esophagus to anus responsible for
regulation of the rate &intensity of muscle
contraction with coordination in various
movement.
*definition of digestion:
• -the process of break down food to
release its nutrients for absorption &
transport to the cell for use in the
body .
• *peristalsis:
• Wave like progression of contraction
& relaxation .
**types of GIT secretion:
• -1-Enzymes: chemical action e.g. lipase
,amylase .
• -2-hydro-choloric acid & buffer ions :
necessary ph .
• -3-mucous:protect the inside wall tissue of
GIT,lubricate &facilitate food mass
passage .
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• -4-water & electrolyte.
Mouth& esophagus:
preparation &delivery:
• -1*mastication:
• -chewing break-down food into smaller particles
by teeth & jaw muscle with tongue.
• -2*swallowing:
• -occur at mouth & pharynx.
• -rapid less than one second .
• -coordination &swallowing comes from(swallowing
centre area) in the brain stem.
• -gravity &muscle at the base of the tongue ,help
in the movement of the food down to esophagus
,in the up-right position .
• -in the stomach food enter by opening of the
sphincter to prevent reflux ,&occurrence of heart
burn .
• ** chemical or secretary digestion : 3 pairs of
salivary glands ,parotid ,sub-maxillary , sub-lingual
,secrete salivary amylase this enzyme is specific
for starch digestion
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• *factors affect salivary secretion :• 1-sight . 2-smell. 3-taste. 4-touch. 5thought of like & dis-like of food.
• -normal range of daily saliva
secretion between 800-1500ML,pH
neutral 6.0 7.4
-stomach : storage & initial digestive
process
.
• -as the food enter the stomach ,the muscle of the stomach
mix the food ,storage ,&control emptying .
• -when the food mixed with chyme ,the pyloric sphincter
constrict & relax for control of emptying at duodenum.
• **types of stomach secretion :
• a-acid : HCL hydro chloric acid .
• b-mucous : protect the wall of lining stomach & lubricant .
• c- enzymes: pepsin ,break down of protein (pepsinogen
converted to pepsin under HCL secretion ),gastric lipase for
fat , rennin in child-hood aid in co-agulation of milk ,but
absent in adult .
‫الخضار‬
• -control process of gastric secretion
under effect of :
• 1-nervous stimulus in response to sense
,ingested food & emotions ,e.g. anger &
hostility increase secretion , while fear &
depression ,decrease secretion .
• 2-hormonal stimulus in response to
entrance of food into stomach ,e.g. gastric
enterogastrone
-small intestine: major
digestion & absorption
• -under control of nervous plexuses
or hormonal stimulation ,the wall
stretch from pressure of food .
• -small intestine is chemical digestion
by secrete large number of enzymes
& assistance of pancreatic enzyme .
** types of secretion :
• a- enzymes .
• b-mucous from glands near the duodenum
to protect the mucosa of intestine .
• c-hormones that stimulate pancreas to
secrete alkaline juice .
• d-bile secreted from liver &store by gall
bladder to dissolve fat .
Absorption
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-end product of digestion .
-CHO (glucose, fructose, galactose ).
-fat (fatty acid ,glycerides).
-protein (amino-acid ).
-villi: finger like projection seen
under microscope help in absorption
*Routes of absorption :
• -proteins &CHO become water soluble ,enter to
blood stream ,go to liver ,&other tissue ,while fat
is not water soluble ,bile secreted in intestine
,help in digestion of fat .
• Large intestine : final absorption & waste
elimination .
• Water absorption take side at colon .
• As much as 25% of meal may remain in rectum up
to 7 hrs
‫الفواكه‬
Mineral absorption :
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Essential minerals as Na & K go to blood stream .
Bacteria in the colon syntheses vit K .
-intestinal bacteria affect color & odor of the stool .
Brown stool comes from bile pigment .
Intestinal gas or flatus produced by bacteria .
Fiber does not digested so it contribute to form bulk of the
stool .
• Normal feces contain 75% water, 25% solids .
• Solids ( fiber ,bacteria ,minerals ,small amount of fat ,
mucous).
Metabolism
• 1-CHO metabolism :
• Source of blood glucose *CHO &non
CHO substances *
• *CHO sources:
• -dietary starch & sugars .
• -glycogen from liver & muscle tissue ,
by hydrolysis glycogen to glucose .
*non CHO sources:
• -from protein & fat .
• -indirect source of glucose .
• *in case of protein glycogenic amino-acid could be
used in energy , if insufficient CHO .
• *in case of fat broken to fatty acid &glycerol
,glycerol converted to glycogen in the liver .
• -the process of production of glucose from
protein or fat is called gluconeogenesis.
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-normal blood glucose level 70-120mg \dl.
1- energy production .
2-energy storage :
Glucose converted to glycogen , stored in liver 7
muscle tissue .
• Excess glucose converted to fat & stored in
adipose tissue (fat tissue ).
• 3- glucose product :
• Glucose enter in DNA &RNA building .
‫الحمضيات‬
**hormonal controls
• -blood sugar lowering hormones
• a- insulin decrease blood sugar ,produced by beta cells in
the pancreas.
• -convert glucose in the liver to glycogen by process called
glycogen sis .
• -convert glucose to fat & storage in adipose tissue .
• b-blood sugar raising hormones :
• *1-glycogen -produced from alpha cells of pancreas,
opposite action of insulin .
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*2-somatostatin:
-delta cells of pancreas .
-anti insulin effect
*3-steroid hormones :
-secreted from adrenal gland .
-anti insulin effect
*4-Epinephrine :
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-secreted from adrenal medulla .
-break down glycogen in the liver to glucose .
*5-grouth hormone :
-secreted from anterior pituitary gland .
-anti insulin effect .
*6-thyroxine :
-increase glucose absorption from intestine