Liver, Pancreas, Gallbladder (MT3)

Liver

Parietal peritoneum creates double fold (coronary ligament) at back + front dividing it into 2 functionally independent lobes

1 lobe can be removed and the other can still function

Stroma

CT parts of an organ

Parenchyma of the liver

Hepatocytes

Lobes

Macroscopic view of the liver

Lobules

Microscopic level of the liver

Run entire length of the liver

Classical/Anatomical lobule

Hexagonal shape

Portal triads at each corner, central veins in center

For blood flow

Blood flow in the liver

Comes in from periphery of classical lobule toward the central vein

Portal lobule

3 central veins in a triangle (visualized), center is a portal triad

Describes bile flow

Functional lobule

2 portal triads and 2 central veins in a rhombus (visualized)

Describes how pathology progresses

Celiac artery

First artery to come off of the abdominal aorta

Splenic artery comes off to supply the spleen

R/L hepatic comes off to supply the liver

Liver blood flow

Mixes venous (from portal vein) and arterial blood (from hepatic arteries) → Branch at every corner of anatomical lobule → Interconnect and flow toward center

Blood gets modified and dumped into central vein

Sinusoids

Discontinuous capillaries for active blood movement

Surround hepatocytes on both sides

Why does the liver modify the blood?

Central vein needs PROPER amount of nutrients to blood

If lacking nutrients hepatocytes will give

If excess nutrients hepatocytes will take

Hepatic vein

Where all central veins connect and dump 80mg% blood

Drains into inferior vena cava which drains into the right atrium/ventricle

Portal vein (histology)

Large lumen, thick tunica adventitia

Hepatic artery (histology)

Small lumen, thick tunica media

Bile duct (histology)

Lined by simple cuboidal epithelium

Portal triad

Portal vein, hepatic artery, and bile duct

Subendothelial space of Disse

Endothelial cells and hepatocytes don’t touch completely, blood gets out and sits in space

Allows for disruption of laminar flow allowing hepatocytes to modify blood

Bile canaliculi

Tubules created by the tight junctions between hepatocytes

Run in opposite direction of blood

Kupffer cells

Macrophages of the liver (APCs)

Way to sample the blood for Ags

Liver functions

• Storage of fat soluble vitamins (KADE)

• Vit B storage

• Nitrogen removal (proteolysis) + urea conversion (travel to kidney → excreted)

• Alpha/beta globulin, albumin, prothrombin, fibrinogen production

• Makes blood in hepatosplenic period of embryology

• Bile production

• Glucose storage

• Detoxification of lipid soluble drugs

Bile production

Bile salts, bilirubin, cholesterol, lecithin

Bile pathway

Bile canaliculi → Bile duct → R/L hepatic duct → Common hepatic duct → Cystic duct → Common bile duct → Pancreatic duct → Hepatopancreatic duct → Drains through Sphincter of Oddi → Duodenum

Glucose storage and retrieval

Glycogenesis + glucogenolysis

Hepatocytes use GLUT-2 (insulin independent) to uptake glucose, insulin promotes phosphorylation → Glycogen

Does insulin promote the uptake of glucose?

Yes, not necessary but promotes

Gluconeogenesis

Create glycogen from noncarbohydrate precursors

Glycogen is created and broken down into glucose

GLUT-4

Insulin dependent

Muscle/fat

GLUT-1 + GLUT-3

Insulin independent

1: RBCs

3: Neurons

Glucokinase vs. Hexokinase

Glucokinase: Used by liver, high activity when hexokinase asymptotes

Hexokinase: Used by brain/muscle, high activity when glucose is low, asymptotes out when brain/muscle gets its needs

Removal and detox lipid soluble drugs

Functional lobule is divided into zones 1, 2, 3

Zones of functional lobules

1: Periportal - First affected in hepatitis

2: Intermediate - Used when zone 1/3 affected, first affected in yellow fever

3: Pericentral - Surround central veins, first affected in alcohol and lipid detoxification damage

Damage to zone 3 causes results

Central vein is surrounded by damaged cells → Blood flow resistance

Esophageal varices

Liver disease causes blood to backflow

Central vein → Portal vein → Mesenteric veins → Submucosa veins

Gall bladder

Store and concentrate bile

Constricts under CCK

Gall bladder layers

1. Mucosa: Simple cuboidal with rugae, lamina propria

2. Musculares: Random arrangement, responds to CCK

3. Serosa: DICT

Rugae

Present only when gall bladder is constricted

Fold of mucosa

R + L hepatic =

Common hepatic duct

Common hepatic + cystic =

Common bile duct

Common bile + pancreatic duct =

Hepatopancreatic duct

Cholecystectomy

Most common abdominal surgery

Pancreas

Head sits in the loop in the duodenum

Majority is exocrine gland (compound tubular acinar) with embedded islets

90% acinar cells, 2% islet cells, and blood cells

Acinar cells of pancreas

Secrete digestive enzymes under influence of CCK from I cells from crypts

Protease: Proteins → AA

Lipase: Fat

Amylase: Carbohydrates → Sugars

Ductal cells of pancreas

Produce bicarbonate under influence of secretin from S cells from crypts

If gall stones are in the common bile duct you get what?

Pancreatitis

Islet of Langerhans

Island of endocrine cells, release directly into fenestrated capillaries

Alpha cells

Produce glucagon

Protects against hypoglycemia

D cells

Produce somatostatin, paracrine inhibition (inhibits cells immediately around them)

Inhibits glucagon and insulin

Beta cells

Produce insulin

Work on GLUT 1-4 receptors for glucose uptake and storage

F cells

Produce pancreatic polypeptide

Digestion of food by inhibiting gastric emptying and biliary secretion