HISTOLOGY OF PANCREAS

PANCREAS Has exocrine & endocrine functions Parts Capsule Septa – lobules Secretions: Enzymes Hormones

EXOCRINE PANCREAS COMPOUND ACCINAR GLAND Pear shaped accini 5-8 pyramidal cells Reticular fibers support accini Inter- lobular CT contains: Blood vessels Nerves Lymphatic

EXOCRINE PANCREAS ACCINI Cells have spherical basal nucleus Basal cytoplasm basophilic – RER mitochondria Golgi apparatus Apical zymogen granules – maximum in fasted person Centroacinar cells

EXOCRINE PANCREAS DUCTS Intercalated ducts NO striated ducts Large intralobular ducts – high cuboidal epithelium Interlobular ducts – columnar epithelium Larger ducts Main duct

SECRETIONS OF EXOCRINE PANCREAS Proteases (trypsinogen & chymotrypsinogen etc.) Amylase Lipase Nucleases (DNAase & RNAase)

MEDICAL APPLICATION ACUTE NECROTIZING PANCREATITIS Proenzyme activated Digest pancreatic tissue Causes: Alcoholism Gall stones Trauma Drugs

MEDICAL APPLICATION Extreme malnutrition e.g. kwashiorkor Atrophy of pancreatic acinar cells Loss of RER Digestive enzyme production hindered

ENDOCRINE PANCREAS (ISLETS) Embedded within accini 100-200µm diameter > 1 million islets Abundant in tail

ISLETS OF LANGERHANS Reticular fibers surround each islet Small polygonal cells Cells lightly stained Arranged in anastomosing cords Fenestrated capillaries between cords Autonomic fibers

ISLETS OF LANGERHANS CELLS OF ISLETS A /α cells- glucagon, at periphery B /β cells- insulin, at center- numerous D /δ cells- somatostatin, scattered F /PP cells- pancreatic polypeptide Enterochromaffin cells- motilin,secretin, substane -P

BLOOD SUPPLY Rich arterial supply Major BV run in interlobular CT Intralobular BV Arterioles pass to islets Extensive capillary network First supply peripheral cells Blood from islets pass to supply exocrine tissue Hormones effect acinar function

COMPARISON PAROTID GLAND PANCREAS

MEDICAL APPLICATION INSULIN DEPENDENT / TYPE I DIABETES (juvenile) Autoimmune disease Partial or total destruction of β cells Lack of insulin INSULIN INDEPENDENT DIABETES / TYPE II Adult onset Associated with obesity Failure of cell to respond to insulin TUMOURS OF ISLETS May secrete anyone of the hormones May secrete more than one hormone