Ducts of Pancreas

• No striated ducts• Intercalated ducts = intralobular ducts• Intercalated ducts drain directly into

interlobular ducts – simple squamous or low columnar epithelium

• Main pancreatic ducts (Wirsung and Santorini) – simple columnar epithelium

Pancreatic Juice Secretion

• Secretin – Secreted in response to HCl– Produces HCO3-rich secretion to neutralize acidic

chyme (pancreatic enzymes function at optimal neutral pH)

• Cholecystokinin (CCK)– In response to the entry of proteins and fats– Enzyme-rich fluid which act mainly on extrusion of

zymogen granules

Gallbladder

• Hollow, pear-shaped organ attached to the lower surface of the liver

• Lies in gallbladder fossa

• Can store 30-50 mL of bile

Gallbladder

• Fundus• Body • Neck• Cystic duct

Gallbladder

• Main functions:– Stores bile– Concentrates bile (water absorption) – Releases bile when necessary into the digestive

tract

• Bile – fat emulsifier

Gallbladder Wall

• Mucosa:– Have anastomosing folds, no villus– Simple columnar epithelium without goblet cells– Lamina propria

• Smooth muscle layer – stimulated by CCK• Perimuscular connective tissue layer • Serosa

Extrahepatic Bile Passages

• Hepatic ducts• Common hepatic duct• Cystic duct• Common bile duct

• Simple columnar epithelium

Important Structures

• Ampulla of Vater (hepatopancreatic ampulla)– Formed by union of pancreatic duct and CBD

• Sphincter of Oddi – Muscular valve that controls the flow of digestive

juices (bile and pancreatic juice) through the ampulla of Vater

• Major and minor duodenal papilla– Openings into the duodenum

Liver

• Largest gland of body (approx. 1.5 kg)

• Right upper quadrant, under diaphragm

Liver

• Functions:– Produces bile: hepatic ducts → gallbladder– Synthesis: plasma proteins, hormones– Carbohydrate storage: glycogen– Detoxification and excretion of endogenous and

exogenous toxic substances

Liver

• Functions:– Eliminates particulate materials from blood

(phagocytosis)– Processes dietary amino acids, carbohydrates, lipids

and vitamins before they are released into general circulation

Glisson’s Capsule

• Thin fibroelastic capsule enclosing liver

• Covered with mesothelium

Blood Vessels

• Portal vein– Nutrient-rich blood from GIT → liver

• Hepatic artery– Supplies liver pareynchyma with arterial blood

• Enter through porta hepatis

Portal Triad

• Distinctive arrangement in a hepatic lobule• Consists of:– Hepatic artery– Hepatic portal vein– Bile duct

Portal Area

• Interlobular connective tissue + structures found in it (portal triad, lymphatic vessels, nerves)

Liver Architecture

Shape Model

Hepatic (classical) lobule

Polygonal Anatomical

Portal lobule Triangular (centered around portal triad)

Exocrine fxn (bile secretion)

Hepatic acinus Elliptical or diamond-shaped

Zone I (periportal)Zone II (transition zone)Zone III (centrilobular)

Blood flow and metabolic

Liver Cells

• Hepatocytes• Kupffer Cells

Hepatocytes

• 80 % of cell population of liber• Perform practically all metabolic and

secretory functions• Polygonal cells arranged in layer (hepatic

plates) which anastomose with each other or with sinusoids

• Nuclei: 1 or 2, round, prominent nucleoli• Cytoplasm: grainy, eosinophilic with many

organelles

Kupffer Cells

• Fixed macrophages• Remove old red blood cells from circulation

and recycle their iron content• Stellate shape (protoplasmic processes)• Form the wall of hepatic sinusoids along with

endothelial cells• Nuclei: pale, vesicular