anatomy and physiology of digestive system (1)
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ANATOMY AND PHYSIOLOGY
OF DIGESTIVE SYSTEM
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Digestive System
FunctionAcquires nutrients from environmentAnabolism
Uses raw materials to synthesize essential
compounds
Catabolism
Decomposes substances to provide energy
cells need to function
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Actions of Digestive (!" #ract
!ngestion$ccurs when material
enters via the mouth
%echanical&rocessingCrushing ' Shearing
ma)es material easierto move through thetract
DigestionChemical brea)down
of food into smallorganic compounds forabsorption
Secretion*elease of water acids+
bu,ers+ enzymes -salts by epithelium of! tract and glandularorgans
Absorption%ovement of organic
substrates+ electrolytes+vitamins - water acrossdigestive epithelium
./cretion*emoval of waste
products from body0uids
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%outhSoft &alate&osterior *oof
Uvula
&ro1ection of softpalate
2ingiuinal FrenulumAttaches tongue to
mouth 0oor3ard &alateAnterior roof
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&haryn/&assageway for food and air
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.sophagus
#ube carries food to stomach
&eristalsis
%uscle contractions that move the food
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StomachCardioesophageal
Sphincter$pening at top of stomach
astric 4uiceStomach acid
ChymeSubstance left after
stomach digestion
&yloric Sphincter$pening at bottom of
stomach leads tointestines
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Salivary lands
&arotid glands5 nearears in mouth
Submandibular andsublingual glands&roduce saliva under
tongue
Saliva%oistens food
3elps start startchdigestion
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#eethDeciduous teeth6aby teeth
!ncisors5 cut food
Canines5 tear andpierce food
%olars5 grinding
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2iver and all 6ladder
&roduces bile
6ile enters smallintestine
3elps brea)downlipids
all bladder stores
bile
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&ancreas&roduces enzymesthat brea) food down
.mpties into small
intestine7eutralizes gastric
acid
&roduces insulin andglucagon
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2arge !ntestine!s horseshoe shaped
./tends from end of ileum to anus
2ies inferior to stomach and liver
Frames the small intestine
Also called large bowel
!s about 89: meters (;9< ft" long and =9:
cm (> in9" wide
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2arge !ntestine Functions*eabsorption of
waterCompaction of
intestinal contentsinto fecesAbsorption of
important vitamins
produced bybacteriaStorage of fecal
material prior todefecation
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&arts of 2arge !ntestine #he Cecum!s an e/panded pouch*eceives material arriving
from the ileum
Stores materials andbegins compaction
Appendix
Also called vermiform
appendi/
!s a slender+ hollow
appendage about < cm (>9?
in9" long
!s dominated by lymphoid
nodules (a lymphoid organ"
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&arts of 2arge !ntestine #he Colon3as a larger diameter and thinner wall than
small intestine
#he wall of the colon Forms a series of pouches (haustra"
3austra permit e/pansion and elongation ofcolon
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&arts of ColonAscending Colon6egins at superior border of cecum
Ascends along right lateral and posterior wall of
peritoneal cavity to inferior surface of the liver and bends
at right colic exure (hepatic 0e/ure"Transverse Colon
Crosses abdomen from right to left@ turns at left colic
exure (splenic 0e/ure"
!s supported by transverse mesocolon!s separated from anterior abdominal wall by greater
omentum
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&arts of ColonThe Descending Colon&roceeds inferiorly along left side to the iliac fossa
(inner surface of left ilium"
!s retroperitoneal+ rmly attached to abdominal wallThe Sigmoid Colon!s an S5shaped segment+ about 8: cm (? in9" long
Starts at sigmoid exure
2ies posterior to urinary bladder!s suspended from sigmoid mesocolon
.mpties into rectum
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&arts of Colon
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&arts of 2arge !ntestine #he *ectum
Forms last 8: cm (? in9" ofdigestive tract
!s an e/pandable organ fortemporary storage of feces
%ovement of fecal materialinto rectum triggers urge todefecate
#he anal canal is the lastportion of the rectum Contains small longitudinal folds
called anal columns
Anus Also called anal orice !s e/it of the anal canal 3as )eratinized epidermis
li)e s)in
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&hysiology of the 2arge !ntestine
Absorption in the 2arge !ntestine
*eabsorption of water
*eabsorption of bile salts !n the cecum
#ransported in blood to liver
Absorption of vitamins produced by bacteria
Absorption of organic wastes
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&hysiology of the 2arge !ntestine
#hree Bitamins &roduced in the 2arge !ntestine
89 Bitamin (fat soluble"
*equired by liver for synthesizing four clotting factors+
including prothrombin
E9 6iotin (water soluble"
!mportant in glucose metabolism
>9 &antothenic acid 6: (water soluble" *equired in manufacture of steroid hormones and
some neurotransmitters
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&hysiology of the 2arge !ntestine
$rganic astes
6acteria convert bilirubin to urobilinogens
and stercobilinogens6acteria brea) down peptides in feces and
generate
Ammonia+ !ndole - s)atole+ hydrogen sulde6acteria feed on indigestible carbohydrates
(comple/ polysaccharides"&roduce atus+ or intestinal gas+ in large intestine
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%ovements of the 2arge !ntestine
astroileal - gastroenteric
re0e/es
%ove materials into cecum while
you eat
%ovement from cecum to
transverse colon is very slow+
allowing hours for water
absorption
&eristaltic waves move material
along length of colon
Segmentation movements(haustral churning" mi/
contents of ad1acent haustra
%ovements from transversecolon through rest of large
intestine results from powerful
peristaltic contractions (mass
movements"
Stimulus is distension ofstomach and duodenum@
relayed over intestinal nerve
ple/uses
Distension of the rectal wall
triggers defecation re0e/
#wo positive feedbac) loops
6oth loops triggered by stretch
receptors in rectum
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Small intestine!s part of the ! tract between the stomach
and the large intestine
!t is where digestion and absorption ta)esplace
!s about ? meters long
Compost of three parts duodenum+ 1e1unum+
and the ileum
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> parts of the small
intestine 4e1unum5 midsection of thesmall intestine+
5 connects the
duodenum and the ileum 5 contains the
plicae circulares+ and villithat increase its surfacearea9
5 it is whereproducts of digestion suchas amino acids+ sugars+ andfatty acids are absorbedinto the bloodstream here
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Duodenum5 #he digestiveenzymes brea) down
proteins and bile andemulsify fats into micelles
5 !t receivesgastric chyme from thestomach+ together withdigestive 1uices from thepancreas (digestiveenzymes" and the liver(bile"9
5 contains6runnerGs glands+ whichproduce a mucus5richal)aline secretioncontaining bicarbonate9
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!leum5 is the nalsection of the smallintestine
5 1oins to thececum of the largeintestine at theileocecal 1unction9
5 containsalso villi similar tothe 1e1unum
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Functions of the small intestineDigestion
Absorption
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Digestionit is where mostchemical digestionta)es place
!t is where nutrientsundergo digestion suchas proteins+ lipids+ andcarbohydrates
!t is where digestiveenzymes act secretedby the pancreas andthe liver
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Absorptionmost of the nutrients
from ingested foodare absorbed
%ost absorptions ofthe occurs in the
1e1unum andduodenum