Category: PANCREAS

HISTOLOGY OF PANCREAS

HISTOLOGY OF PANCREAS

IMAG0325IMAG0330

IDENTIFICATION POINTS

  • NUMEROUS SEROUS ACINI.
  • ISLETS OF LANGERHANS ARE PRESENT.
  • INTERLOBAR DUCTS ARE SEEN.

INTRODUCTION

– PANCREAS IS A  J-SHAPED ORGAN SITUATED IN POSTERIOR ABDOMINAL WALL.

– IT IS DIVIDED INTO HEAD,NECK,BODY AND TAIL. CURVED PROJECTION OF HEAD IS CALLED UNCINATE PROCESS.WHERE HEAD IS FITTED IN THE CURVE OF DUODENUM AND TAIL IS POINTED TOWARDS THE GASTRIC SURFACE OF SPLEEN.

STRUCTURE

CAPSULE:

CAPSULE OF THE PANCREAS IS THIN , MADE UP OF DENSE IRREGULAR CONNECIVE TISSUE. CONNECTIVE TISSUE SEPTAE OF THE CAPSULE ENTERS THE PARENCHYMA OF THE GLAND AND DIVIDES THE WHOLE PARENCHYMA INTO NUMEROUS LOBULES.

PARENCHYMA:

IT IS DISTINCT FROM OTHER GLANDS AS IT CONTAINS BOTH EXOCRINE AND ENDOCRINE GLANDULAR CELLS IN IT. THEREFORE PANCREAS IS SAID TO BE A ‘HETEROCRINE GLAND’.

EXOCRINE PART:

COMPRISES ABOUT 70-80% OF THE TOTAL PARENCHYMA OF THE GLAND. MADE UP OF NUMEROUS SEROUS ACINI WITH A SMALLER LUMEN.

ENDOCRINE PART:

COMPRISES ABOUT 20-30% OF THE TOTAL PARENCHYMA OF THE GLAND. PREDOMINANTLY WELL DEVELOPED IN THE TAIL REGION AND IT CONSISTS OF AGGREGATIONS OF NUMEROUS CELLS FORMING MANY CLUSTERS WHICH ARE REFFERED TO AS ‘ISLETS OF LANGERHANS’.

ISLETS OF LANGERHANS CONTAIN 3 TYPES OF CELLS.THEY ARE:-

1.ALPHA-CELLS:

CONSTITUTE ABOUT 25% OF ENDOCRINE PANCREAS. PERIPHERILY SITUATED IN ISLETS OF LANGERHANS AND CAN BE IDENTIFIED BY SMALL SIZE AND PINK CYTOPLASM.

2.BETA-CELLS:

CONSTITUTE ABOUT 70% OF ENDOCRINE PANCREAS. CENTRALLY SITUATED. LARGE CELLS WITH BLUE CYTOPLASM.

3.DELTA-CELLS:

HARDLY ABOUT 5% OF ENDOCRINE PANCREAS. HIGHLY VARIABLE IN SIZE AND CAN OCCUR ANYWHERE IN ISLETS OF LANGERHANS.

FUNCTIONS:

  • SEROUS ACINI OF EXOCRINE PANCREAS SECRETES PANCREATIC JUICE AND MANY DIGETIVE ENZYMES.
  • ALPHA-CELLS SECRETE A HORMONE CALLED GLUCAGON AND HELPS IN INCREASING BLOOD GLUCOSE LEVEL.
  • BETA-CELLS SECRETE INSULIN AND HELPS IN DECREASING THE BLOOD GLUCOSE LEVEL TO NORMAL.
  • DELTA-CELLS PRODUCE FEW LOCAL HORMONES LIKE GASTRIN,SOMATOSTATIN AND VIP(VASO-ACTIVE INTESTINAL POLYPEPTIVE) WHICH PRODUCE LOCAL EFFECTS ON GI-TRACT.

CLINICAL:

  • INFLAMMATION OF EXOCRINE PANCREAS IS TERMED AS PANCREATITIS.
  • DIABETES MELLITUS IS A ENDOCRINE DISORDER OF PANCREAS CHARACTERISED BY INCREASED BLOOD GLUCOSE LEVEL  DUE TO HYPOSECRETION OF INSULIN BY BETA-CELLS OR DUE TO DESTRUCTION OF RECEPTORS FOR INSULIN HORMONE.