Fisiologi Sistem Pencernaan

Hati dan pankreas

Learning Objective

1. Explain the functions of liver.

2. Explain the functions of gallblader.

3. Explain the functions of pancreas.

Liver

• Largest internal organ

• Receives major blood supply from hepatic portal vein• Brings venous blood rich in nutrients from digestive tract

• Hepatocytes• Livers cells

• Capable of regeneration

Liver

Liver

• Functions

1. Metabolic regulation

1. Carbohydrate metabolism

2. Lipid metabolism

3. Amino acid metabolism

4. removal of waste products

5. Vitamin storage

6. Mineral storage

7. Drug inactivation

Liver

• Functions

2. Hematological regulation

1. Phagocytosis and antigen presentation

2. synthesis of plasma proteins

3. removal of circulating hormones

4. removal of antibodies

5. removal or storage of toxins

6. synthesis and secretion of bile

Liver

• Functions

3. Circulatory regulation

4. Growth regulation

Typical albumin distribution in a healthy 70 kg adult

• total body albumin pool about 3.5–5.0 g/kgBW (250–300 g for a healthy 70 kg adult).

• ↑Synthesis:• Insulin

• GH

• Feeding

J. P. Nicholson et al. Br. J. Anaesth. 2000;85:599-610

42% 58%

lymphatic drainage

Hidrostatic P,Fenestrae, trans endotel

Skin 41%Muscle 40%Gut 7%Liver 3%Subcutaneous, etc. 9%

Gallbladder

• Attached to surface of the liver

• Bile pouch that stores bile

• Ducts• Hepatic Duct

• Cystic Duct

• Common Bile Duct

Gallbladder

Function: Bile storage Bile modification Bicarbonate secretion

Bile compasition Water Bilirubin Ion Cholesterol Bile salt

Bile Secretion

• Necessary for digestion and absorption of lipids in small intestine

• Mixture of bile salts, bile pigments, and cholesterol

• Bile salts emulsify lipids to prepare them for digestion

• Solubilize products of lipid digestion in packets called micelles

Bile Secretion and Recycling

1. Produced and secreted by liver

2. Stored in gallbladder

3. Ejected into small intestine when gallbladder contracts

4. After lipids absorbed, bile salts are recirculated to liver via enterohepatic circulation• Absorption of bile salts from ileum into portal circulation

• Delivery back to liver

5. Extraction of bile salts from the portal blood by hepatocytes

Bile Secretion and Recycling

Pancreas

• Exocrine and Endocrine Gland

1. Exocrine—Acinar Cells• Secretes essential digestive enzymes through pancreatic duct into

duodenum

2. Endocrine—Islets of Langerhans• Secretes insulin and glucagon into blood stream

Pancreas

Pancreas

Pancreatic Secretion

• Exocrine pancreas secretes ~1 L/day into duodenum• Fluid consists of HCO3

- and enzymes• HCO3

- neutralizes H+ delivered to duodenum from stomach• Enzymatic portion digests carbohydrates, proteins, and lipids into

absorbable molecules

• Structure of Pancreatic Exocrine Glands • Comprises ~90% of pancreas

• Rest of pancreatic tissue is endocrine pancreas and blood vessels

• Acinar Cells• Line blind end of branching duct system• Secrete enzymatic portion

• Ductal Cells• Line the ducts• Secrete aqueous HCO3

- component

HCO3- Secretion

• Apical membrane of ductal cells contains a Cl--HCO3-

exchanger

• Basolateral membrane contains Na+-K+ ATPase and a Na+-H+ exchanger

1. CO2 and H2O combine in cells to form H+ and HCO3-

2. HCO3- is secreted into pancreatic juice by Cl--HCO3

- exchanger

3. H+ is transported into blood by Na+-H+ exchanger• Absorption of H+ causes acidification of pancreatic venous blood

Regulation of Pancreatic Secretion

• Acinar cells (enzymatic secretion)• Receptors for CCK and muscarinic receptors for ACh

• CCK is most important stimulant• I cells secrete CCK in presence of amino acids and fatty acids in intestinal

lumen

• ACh also stimulates enzyme secretion

• Ductal cells (aqueous secretion of HCO3-)

• Receptors for CCK, ACh, and secretin

• Secretin (from S cells of duodenum) is major stimulant• Secreted in response to H+ in intestine

• Effects of secretin are potentiated by both CCK and ACh

Pancreatic Endocrine

Alpha cells produce glucagon Beta cells produce insulin Delta cells produce somatostatin Gamma cells produce Pancreatic polypeptide

Somatostatin

• Kadar somatostatin plasma meningkat dari 11±2 mjd 18±2 pmol/l setelah makan