Anatomy and Physiology of Digestive System (1)

8/18/2019 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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#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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$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

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Anatomy and Physiology of Digestive System (1)