Transcript digestion

Digestion ,Absorption ,& metabolism
Digestion in mouth
-digestion
 - body food component travel together ,through GIT into the
cell.
 *basic principles of 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 intra-mural 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 .
 *factors affect salivary secretion : 1-sight . 2-smell. 3-taste. 4-touch. 5-thought 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 .
 -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 .
 -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 .
Problems related to food
digestion
Incomplete
digestion
Lack of digestive
enzymes
Gallstones
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
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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
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Water absorption take side at colon .
As much as 25% of meal may remain in rectum up
to 7 hrs.
Mineral absorption :
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).
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Villus
epithelium
epithelial cells
Capillary network
lacteal
Villi – plural of villus
 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.
 -normal
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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 .
 **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 .
 *2-somatostatin:
 -delta cells of pancreas .
 -anti insulin effect
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 *3-steroid hormones :
 -secreted from adrenal gland .
 -anti insulin effect .
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*4-Epinephrine :
-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
 -2-lipid metabolism :
 *liver &muscle responsible for fat production& fat
breakdown .
 *lipo-protein comes from absorption of protein &fat
from intestine .
 *GH, ACTH, TSH increase release of fatty acid /
 *cortisone & hydro-cortisone increase fatty acid
production .
 *Epinephrine ,non epinephrine ,thyroxin ,insulin *
decrease cholesterol secretion .
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 3-protein metabolism
 : -responsible about tissue building ,&tissue break
down .
 -GH,gonadotrophine hormone ,thyroxin participate
in tissue anabolism tissue catabolism .
 -break down of protein give amino acid .
 -amino acid divided to :
 *1 nitrogen ,end product is ammonia passed in
urine & stool .
 *2non nitrogen residue (ketoacid).
 *3control agent (co-enzymes),enter in metabolic
process .