The Pancreas

Felicity Clark

Speciality Registrar

New Cross Hospital

Why is it important ?

Pancreatitis

Diabetes

Common primary FRCA question

What you need to Know

Exocrine Function Endocrine function Insulin Glucagon Somatostatin

Structure of the Pancreas

Loblues 2 types of parenchymal tissue Acinus (80%) Islets of Langherhans (2%) Blood vessels and ducts (15%)

Exocrine Pancreas

Lumen of Acini produce pancreatic secretions

Accumulate in intralobular ducts Drain to the main pancreatic duct Drains directly into the duodenum

Exocrine Pancreas

Control is via hormones gastrin, cholecystokinin and secretin secreted by cells in the stomach and

duodenum in response to distension and/or food

Exocrine Pancreas

2 main classes of exocrine pancreatic secretions Bicarbonate ions – centroacinar cells – Secretin Neutralise acidic chyme Digestive enzymes – Basophilic cells –

Cholecystokinin Proteases – trypsinogen & chymotrypsinogen Pancreatic lipase Pancreatic amylase Secreted as inactive enzymes - zymogens Enteropeptidase activates

Endocrine Pancreas

Islets of Langherhans Insulin Glucagon Somatostatin Pancreatic polypeptide

Insulin

Anabolic 51 amino acids pro- insulin – C peptide removed 2 polypeptide chains – disulphide bridges Beta cells Binds to alpha sub unit of insulin receptor Autophosphorylation of tyrosine kinase Activates protein kinases Gene on short arm of chromosome 11

Effects of Insulin

Carbohydrate metabolism Glucose uptake – liver /skeletal muscle Glycogen storage Glucose utilisation as energy source

Effects of Insulin

Protein metabolism Stimulates amino acid uptake by cells Stimulates protein synthesis Inhibits Gluconeogenesis

Effects of Insulin

Lipid metabolism Inhibits lipolysis Stimulates fatty acid synthesis from

glucose Stimulates glycerol synthesis Promotes carbohydrate metabolism /

sparing fat

Controlling factors - Insulin

Secretion stimulated Hyperglycaemia Amino acids Beta agonists Acetylcholine Glucagon

Secretion inhibited Hypoglycaemia Beta blockers alpha agonists Somatostatin Diazoxide Thiazides Volatiles

Insulin Deficiency

Type 1 DM – Autoimmune Type 2 DM – Insulin resistance Secondary Diabetes –

increased cortisol – cushings increased growth hormone increased glucagon

Insulin deficiency – think DKA

Carbohydrate decreased glucose uptake Hyperglycaemia, Glycosuria Osmotic diuresis

Protein Increased amino acids in plasma Nitrogen loss in urine Dehydration Ketoacidosis Respiratory alkalosis Coma Death

Insulin deficiency – think DKA

Lipids increased Lipolysis Increased free fatty acids Ketogenesis Ketonuria

Insulin excess

Insulinoma (rare) Iatrogenic (can measure C-peptide) Hypoglycaemia Tremor Sweating Tacchycardia Coma Death

Glucagon

Catabolic 29 amino acids Alpha cells Acts as a second messenger via cyclic

AMP Opposes insulin

Effects of Glucagon

Carbohydrate Metabolism Increased Gluconeogenesis Increased glycogenolysis Glucose sparing – beta oxidation of fatty

acids for energy – ketone bodies

Effects of Glucagon

Lipid Metabolism Stimulates Lipolysis

Other effects Increases catecholamine production Direct positive inotrope

Controlling factors- Glucagon

Secretion Stimulated hypoglycaemia increased amino acids beta agonists sepsis stress trauma

Secretion Inhibited Hyperglycaemia decreased amino

acids increased free fatty

acids insulin somatostatin alpha agonists

Somatostatin

delta cells hypothalamus also called growth hormone inhibiting

hormone inhibits insulin and glucagon release inhibits gastric acid production inhibits gallbladder contraction Neurotransmitter – SG - pain