DIGESTIVE SYSTEM

drg. ANIS A. MAKKY, MKes

ORAL BIOLOGY DEPARTEMENT

AIRLANGGA UNIVERSITY

SURABAYA, APRIL 16, 2007

SMALL INTESTINE

major organ of both : digestion and absorption

this convoluted tube extends : from the pyloric sphincter to the ileocecal valve

20 feet long ? 3 regions:

duodenum, jejunum, and ileum.

10" long

much of it is retroperitoneal

the common bile duct :

delivering bile from the liver and gallbladder

main pancreatic duct :

delivering pancreatic juice from the

pancreas

DUODENUM

it’s extends from the jejunum to

the ileocecal valve

it’s about 12' long.

JEJUNUM

it’s about 8' long

extends between the duodenum

and the ileum

ILEUM

mucosa has intestinal glands (cavities) :

for secretion of intestinal juice

mucosa also has circular folds, villi &

microvilli :

for increased surface area

“brush border” has many enzymes

HISTOLOGY

“brush border” has many enzymes

(embedded in plasma membranes) :

    1. several carbohydrate-digesting enzymes

    2. peptidases

    3. nucleosidases

    4. enterokinase

epithelial cell “shedding”

    important enzyme activator.

PLICAE CIRCULARES

large deep

permanent folds of the mucosa and

submucosa

they slow the movement of chyme

(more time for digestion/absorption)

they increase the surface

VILLI

fingerlike projections of the mucosa

they also increase the surface area

within the core of each villus is a capillary bed

and a lacteal :

for transport of the absorbed nutrients.

• between the villi exist pits : intestinal glands or ‘crypts of Lieberkuhn’• the cells lining these pits secrete : intestinal juice (mucus, enzymes, etc.), lysozyme-secreting cells, and stem cells.

in the proximal duodenum :

the submucosa houses Brunner's glands secrete an alkaline mucus to help neutralize the acidic

chyme (coming from the stomach)

INTESTINAL PHASE OFREGULATING DIGESTION

1. chyme enters duodenum

2. three hormones secreted from SI mucosa

3. receptors in SI mucosa sense food

or chemical presence in duodenum

4. neuronal activation of sympathetic NS

or inhibiton of parasympathetic NS

REGULATING of ABSORPTION

C L P, Ca2+, Fe2+ :

duodenum & jejunum

bile salt, vit.B12,H2O,electrolite : ileum

monosacharide & amino acid :

secreted into cappilar

lipid :

secreted into central lacteal

absorption of H2O : passive (osmotic gradient)

mucosa epithelial cell of intestine :

collect to form tubulus is like kidney :

* functions as Na+/K+ pump within basolateral

membrane

* can stimulates absorption of NaCl & H2O

within ileum

3 HORMONES from SMALL INTESTINE    

1. gastric inhibitory peptide (GIP) :

    * fatty acids in chyme : induce GIP secretion

    * inhibits gastric secretion

    * inhibits gastric “churning”

    * activates insulin secretion

2. secretin :

    inhibits gastric secretion

3. cholecystokinin (CCK) :

    * fatty acids in chyme : induce CCK secretion

    * CCK slows gastric emptying

   

LARGE INTESTINE

function :

* absorb water

* then eliminate them as feces

compared to the small intestine :

diameter is bigger but its length is far shorter

(only about 5')

their tone causes the LI wall to pucker into

pocketlike sacs called ‘haustra’

LI : significant numbers of bacterial colonies

they enter via both the anal canal and the oral

cavity and colonize the LI

in the LI, they metabolize and ferment

indigestible carbohydrates

they also synthesize B vitamins as well as

vitamin K.

haustral contractions move material from

one haustrum to another and aid in mixing

mass movements : slow waves of peristalsis

one stimulus of colonic mass movements

is the presence of food within the stomach

this is known as the gastrocolic reflex.

feces enter and stretch the rectal wall :

initiate the defecation reflex

this results in :

* the contr. of the sigmoid colon and rectum

muscularis

* the relaxation of the internal anal sphincter

* contr. diafragma

higher input determines whether the external

sphincter remains :

contracted or relaxes.

prolonged diarrhea may result in :

* dehydration

* acidosis

* and other electrolyte imbalances

if water absorption >> than normal :

due to waste moving too slowly through the

colon constipation !!!

fats are not digested until the small intestine

there they are first emulsified by bile

and then acted upon by pancreatic lipase

most ingested fats are broken down into glycerol,

monoglycerides, and fatty acids

fatty acids & monoglycerides :

passively enter intestinal epithelial cells

they're combined with cholesterol & proteins

form chylomicrons

BREAK DOWN OF LIPID

protein digestion begins in the stomach : pepsin

in the SI, protein digestion continues with trypsin

and many other proteases

the end result : free amino acids

amino acids enter the intestinal epithelial cells

via cotransport with sodium

BREAK DOWN OF PROTEIN

after absorption of electrolite & H2O : colon

forming of feces : in the colon

feces in the rectum :

pressure of rectum reflex of defecation

problems : constipation (absorption >>) diarrhea (absorption <<)

DEFECATION

pressure of rectum

contraction of m.longitudinal of rectal

support by parasimpathetic stimulation (n. pelvic)

feces enter canal anal

sphincter anal internal & external relaxation

feces exit from anal

DEFECATION MECHANISM

DIARE

fast movement of fecal matter through

colon

excretion of excess fluid together feces

etio : enteritis, psychogenic, colitis

ulcerative

Tx : change fluid & electrolite that lost

(saline iv & glucose)

1. cholera :

* enterotoxin released by bacteria of cholera

* enterotoxin stimulates active transport of

NaCl followed by H2O into lumen

* iritation of mucosa

* secretion , motility * electrolite & fluid secretion from crypts

Lieberkuhn 10-12 L/hr

* reabsorp colon 6-8 L/hr

2. celiac sprue :

* intestinal mucosa rupture

* disturb of absorption by consumption

of gluten

3. lactose intolerance

COLITIS ULCERATIVE

etiology : idiophatic, alergy

destructive immune

secretion

motility

colon wall : inflamation & ulcer

MORNING SICKNESS

• nausea , vomitus • prevalence : * 51.4 % : nausea; 9.2 % : vomitus

*1: 500 gravid hiperemesis gravidarum• prolonged :12-22 weeks• etio : * HCG

* estrogen * deficiency B6 * gastric emptying : time >>

NAUSEA – VOMITING MECHANISM

• stimulasi pusat muntah di medula, yang mengendalikan zona pemicu kemoreseptor (Chemoreceptor Trigger Zone – CTZ)

di otak

• Peristaltik lambung menurun

• Tonus duodenum & jejunum meningkat

• Reflux lambung

• Kontraksi lambung, kontraksi diafragma, kontraksi otot abdomen

• Isi lambung keluar

PENATALAKSANAAN

• Kasus yang berat :

– Obat-obatan :

• Sedatif : fenobarbital

• Vitamin : B1 dan B6

• Antiemetik (bila diperlukan)

– Terapi psikologik dan isolasi

– Cairan parenteral

– Penghentian kehamilan

otak (korteks)

Saluran lambung-usus,Jantung, testis

Pusat muntah

MetoklopramidDomperidone

Chemoreceptor Trigger Zone(CTZ)

neuroleptikaAnti histamin

organkeseimbangan

Pusat muntah (batang otak)

Aferen

Eferen

GIT/vestibular, korteks serebri,

CTZ (chemoreceptor Trigger Zone)

impuls ke diafragma, otot abdomen,

lambung serta esofagus.

LIVER

THANK YOU