Digestive SystemDigestive System

Week 13Week 13

Dr. Walid DaoudDr. Walid Daoud

A. ProfessorA. Professor

The PancreasThe Pancreas

Pancreas is a soft oblong gland. It lies Pancreas is a soft oblong gland. It lies posterior to the greater curvature of the posterior to the greater curvature of the stomach and is connected by pancreatic stomach and is connected by pancreatic duct to the duodenumduct to the duodenum..Pancreas has a head, body and tailPancreas has a head, body and tail..Pancreatic juicePancreatic juice::

1-21-2 L / day. Alkaline pH (7.1- 8.2)L / day. Alkaline pH (7.1- 8.2)..Water and enzymes 98.5%Water and enzymes 98.5% . .

Sodium bicarbonate 1.5%Sodium bicarbonate 1.5%

ssssssss

Functions of Pancreatic JuiceFunctions of Pancreatic Juice

1 -Sod. bicarbonate:

Neutralizes acidity in duodenum.

2 -Pancreatic amylase:

Digests starch into maltose.

3 -Proteolytic enzymes:

Trypsin, chemotrypsin, carboxypeptidase.

4 -Pancreatic lipase:

Digests fat into glycerol and fatty acids.

The BileThe Bile

Hepatic cells secrete 1-2 L of bile daily. Hepatic cells secrete 1-2 L of bile daily. Alkaline pH (7.6-8.6) due to sod. bicarbonate Alkaline pH (7.6-8.6) due to sod. bicarbonate which is absorbed during storage of bile in which is absorbed during storage of bile in the gall bladder and bile becomes acidicthe gall bladder and bile becomes acidic..

Composition of bileComposition of bile::

11 - -Bile saltsBile salts..

22 - -CholesterolCholesterol..

33 - -Bile pigments: bilirubin and biliverdinBile pigments: bilirubin and biliverdin..

Steps of Bile Pigment FormationSteps of Bile Pigment Formation

11 - -Old red blood cells are broken releasing Old red blood cells are broken releasing iron + globin + bilirubin iron + globin + bilirubin..

22 - -bilirubin binds to plasma proteins forming bilirubin binds to plasma proteins forming hemobilirubin which is taken by the liver hemobilirubin which is taken by the liver . .

33 - -Bilirubin conjugates with glucoronic acid Bilirubin conjugates with glucoronic acid or SO4 forming cholebilirubin excreted by or SO4 forming cholebilirubin excreted by hepatic cells with bile hepatic cells with bile..

44 - -In the intestine cholebilirubin is reduced by In the intestine cholebilirubin is reduced by intestinal bacteria to stercobilinogen intestinal bacteria to stercobilinogen . .

Fate of StercobilinogenFate of Stercobilinogen

A- 2/3 lost in fecesA- 2/3 lost in feces..B- 1/3 absorbed in the portal bloodB- 1/3 absorbed in the portal blood to the to the liver cells and oxidized again into liver cells and oxidized again into bilirubin or excreted in bile (enterohepatic bilirubin or excreted in bile (enterohepatic circulation of stercobilinogen) circulation of stercobilinogen)..

C- Small amount passes in circulation andC- Small amount passes in circulation and excreted in urine as urobilinogen which is excreted in urine as urobilinogen which is

oxidized by air into urobilin oxidized by air into urobilin....

Functions of Gall BladderFunctions of Gall Bladder

11 - -Storage of bileStorage of bile..

22 - -Concentration of bileConcentration of bile..

33 - -Secretion of mucus (white bile)Secretion of mucus (white bile)..

44 - -Acidification of liver bileAcidification of liver bile..

55 - -Biliary pressure bufferBiliary pressure buffer..

66 - -Emptying of its contentsEmptying of its contents..

Small IntestineSmall IntestineSmall intestine (21 feet in length) is divided Small intestine (21 feet in length) is divided into 3 segmentsinto 3 segments::

11 - -Duodenum 2- Jejunum 3- IleumDuodenum 2- Jejunum 3- Ileum..

FunctionsFunctions::

11 - -Digestion mainly in upper halfDigestion mainly in upper half..

22 - -Absorption mainly in lower halfAbsorption mainly in lower half..

33 - -Movement of chyme into the colonMovement of chyme into the colon..

44 - -Secretion of hormones regulating digestionSecretion of hormones regulating digestion

Succus EntericusSuccus EntericusDigestive juice of small intestine, 2-3 L /day, Digestive juice of small intestine, 2-3 L /day,

alkaline pH 7.6, contains sod. bicarbonatealkaline pH 7.6, contains sod. bicarbonate& &

EnzymesEnzymes::

11 - -Peptidases groupPeptidases group..

22 - -Disaccharidases groupDisaccharidases group..

33 - -Intestinal lipaseIntestinal lipase..

44 - -NucleasesNucleases..

55 - -EnterokinaseEnterokinase..

Mechanism of Intestinal SecretionMechanism of Intestinal Secretion

11 - -Local axon reflexLocal axon reflex..

22 - -Hormonal mechanismHormonal mechanism..

33 - -Extrinsic nervesExtrinsic nerves..

Movements of Small IntestineMovements of Small Intestine

11 - -Peristaltic movementPeristaltic movement::

A wave of contraction preceded by a wave A wave of contraction preceded by a wave of relaxation of relaxation..

22 - -Mass peristalsisMass peristalsis::

A rapid wave of peristalsis along the whole A rapid wave of peristalsis along the whole length of intestine in less than 1 minute length of intestine in less than 1 minute..

33 - -AntiperistalsisAntiperistalsis..

44 - -Segmenting movementsSegmenting movements..

AbsorptionAbsorptionIt is the passage of digested nutrients It is the passage of digested nutrients (glucose, amino acids and fatty acids) from (glucose, amino acids and fatty acids) from alimentary canal into blood or lymphalimentary canal into blood or lymph..

90%90% of absorption occurs through the of absorption occurs through the villi villi in in small intestine and depends onsmall intestine and depends on::

11 - -DiffusionDiffusion..

22 - -Facilitated diffusionFacilitated diffusion..

33 - -OsmosisOsmosis..

44 - -Active transportActive transport..

Large IntestineLarge IntestineIt extends from the end of ileum to anusIt extends from the end of ileum to anus..

44 regions: cecum, colon, rectum & anal canalregions: cecum, colon, rectum & anal canal

Functional AnatomyFunctional Anatomy::

11 - -Proximal colon:Proximal colon: for absorption for absorption..

From cecum to middle of transverse colonFrom cecum to middle of transverse colon..

22 - -Distal colon:Distal colon: for storage for storage..

From middle of transverse colon to the From middle of transverse colon to the junction of pelvic colon with rectum junction of pelvic colon with rectum..

33 - -Rectum and anal canal:Rectum and anal canal: for defecation for defecation . .

ssssss

Functions of Large IntestineFunctions of Large Intestine

11 - -DigestionDigestion:: No digestion in human but in animalsNo digestion in human but in animals..

22 - -AbsorptionAbsorption..33 - -ExcretionExcretion..

44 - -Secretion of mucinSecretion of mucin..55 - -Storage of fecesStorage of feces . .

66 - -Synthesis of vitamin K and B complexSynthesis of vitamin K and B complex..77 - -DefecationDefecation..

- -Defecation ReflexDefecation Reflex

- -Gastrocolic ReflexGastrocolic Reflex