small inetstine part 1

7/31/2019 Small Inetstine Part 1

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THESMALL

INTESTINE


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longest segment of the GI tract( about 2.5 7 m or 8 18 ft)it is a muscular tube extending from

pyloric sphincter to the ileocecalvalve.it is the bodys major digestive org

an

is where most chemical digestiontakes place

Fx: for digestion and absorption

Small Intestine


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1. Duodenum - is the first portion of thesmall Intestine, and receivesthe contents of the stomach.

2.Jejunum middle section and where themajority of the absorption ofnutrients takes place

3. Ileum distal section- where the majority of th

eabsorption of nutrients takes place

3 SUBDIVISIONS


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FUNCTIONS OFTHE SMALL

INTESTINEDigestionAbsorption


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DIGESTION


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The small intestine is where most chemical

digestion takes place.Most of the digestive enzymes that act in the

small intestine are secreted by the pancreasand enter the small intestine via thepancreatic duct.

The enzymes enter the small intestine inresponse to the hormone cholecystokinin,which is produced in the small intestine inresponse to the presence of nutrients.

The hormone secretin also causesbicarbonate to be released into the small

intestine from the pancreas in order toneutralize the potentially harmful acid

DIGESTION


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ABSORPTION


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Microvilli Are tiny projections of the plasma membrane of

the mucosa cells that give the cell surface a fuzzyappearance, sometimes referred as the BRUSH

BORDERVilli

Are fingerlike projections of the mucosa that giveit a velvety appearance and feel.

Circular folds Also called PLICAE CIRCULARES Are deep folds of the mucosa and submucosa

layers

3 Structures that increasethe absorptive surface


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The transport of digested end products fromthe lumen of the GI tract to the blood orlymph.

For absorption to occur, the digested foodsmust first enter the mucosal cells by activeor passive transport processes.

The small intestine is the major absorptivesite.

ABSORPTION

ABSORPTION OF


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CHON(amino acids)

ABSORPTION OFFOODSTUFFS

( Active Transport)CHO

(monosaccharide glucose, galactose,fructose)

LIVER

CAPILLARY BLOOD IN THEVILL

viaHepaticportal vein

ABSORPTION OF


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Monoglycerides

ABSORPTION OFFOODSTUFFS

( Diffusion)Fatty Acids

SYSTEMICCIRCULATION

LACTEALS OF THE VILL

viaLymph in the

thoracic duct


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Nutrients are absorbed atspecific locationsthroughout the smallintestine and duodenum

CHO, CHON, fats, sodiumand chloride area absorbedinjejunum.

Vit. B12 and bile salts areabsorbed in the ileum.

Magnesium, phosphate, and

SITE OF ABSORPTION


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1. Segmentation contraction- produce mixing waves that move more

the intestinal contents back and forth ina churning motion

2. Intestinal peristalsis-propels the contents of the small

intestine toward the colon

BOTH MOVEMENTS ARE STIMULATED BYTHE PRESENCE OF CHYME!

CONTRACTIONS OCCUR INTHE SMALL INTESTINE

small inetstine part 1

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