Category: HISTOLOGY

HISTOLOGY OF VASDEFERENS

HISTOLOGY OF VASDEFERENS

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HISTOLOGY OF URINARY BLADDER

HISTOLOGY OF URINARY BLADDER

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IDENTIFICATION POINTS

  • MUCOSA LINED BY TRANSITIONAL EPITHELIUM.
  • SUBMUCOSA IS ABSENT.
  • MUSCULAR LAYER CONTAINING DETRUSOR MUSCLES.

INTRODUCTION

– IT IS A MUSCULAR BAG LIKE STRUCTURE WHICH TEMPORARILY STORES URINE FOR VOIDING.

– NORMAL STORING CAPACITY IS 200-300ml.

STRUCTURE

MUCOSA:

INNER MOST LAYER OF URINARY BLADDER LINED BY TRANSITIONAL EPITHELIUM WITH LAMINA PROPRIA RICH IN BLOOD VESSELS UNDERNEATH IT. MUCOSA IS THROWN INTO MANY FOLDS WHICH EXPANDS TO COLLECT MORE QUANTITY OF URINE WITHIN THE BLADDER.

MUSCULAR LAYER:

IRREGULAR CONSISTING OF INNER LONGITUDINAL,MIDDLE CIRCULAR AND OUTER LONGITUDINAL MUSCLE LAYERS. FEW MUSCLE FIBERS AROUND THE INTERNAL URETHRIC ORIFICE FORM AN INTERNAL URETHRAL SPHINCTER WHICH CONTROL THE OUTFLOW OF URINE FROM THE BLADDER.

ADVENTITIA:

OUTERMOST PROTECTIVE COVERING LAYER MADE UP OF DENSE IRREGULAR CONNECTIVE TISSUE.

FUNCTIONS:

  • TRANSITIONAL EPITHELIUM PREVENTS THE ENTRY OF URINE AND ITS TOXIC SUBSTANCES INTO THE URINARY BLADDER. HERE THE CELLS ALSO DECREASE IN SIZE AND LAYERS TO ACCOMMODATE LARGE QUANTITY OF URINE.
  • PROMINENT MUSCULAR COAT IS RESPONSIBLE FOR MICTURITION PROCESS BY PRODUCING POWERFUL CONTRACTIONS.
  • ADVENTITIA IS PROTECTIVE AND SUPPORTIVE IN NATURE.

CLINICAL:

  • USUALLY TRANSITIONAL EPITHELIUM  LINING THE URINARY BLADDER IS 4-6 CELL LAYER-THICK. IF IT INCREASES MORE THAN 6 CELL-LAYER THICK, THEN IT IS SUGGESTIVE OF CARCINOMA OF URINARY BLADDER.
HISTOLOGY OF URETER(TS)

HISTOLOGY OF URETER(TS)

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IDENTIFICATION POINTS

  • STAR SHAPED LUMEN.
  • MUCOSA LINED BY TRANSITIONAL EPITHELIUM.
  • INNER LONGITUDINAL,MIDDLE CIRCULAR AND OUTER LONGITUDINAL MUSCULAR COAT.

INTRODUCTION

– URETER IS A MUSCULAR COAT LIKE STRUCTURE WHICH CONNECTS THE KIDNEY TO URINARY BLADDER.

STRUCTURE

MUCOSA:

INNER MOST LAYER OF URETER LINED BY TRANSITIONAL EPITHELIUM WITH LAMINA PROPRIA BENEATH IT. MUCOSA IS THROWN INTO MANY FOLDS WHICH GIVES A STAR SHAPED LUMEN APPEARANCE TO THE LUMEN.

MUSCULAR LAYER:

IT IS FOUND BELOW THE LAMINA PROPRIA. CONSISTS OF INNER LONGITUDINAL,MIDDLE CIRCULAR AND OUTER LONGITUDINAL MUSCLE LAYERS.

ADVENTITIA:

OUTERMOST PROTECTIVE COVERING LAYER MADE UP OF DENSE IRREGULAR CONNECTIVE TISSUE.

FUNCTIONS:

  • TRANSITIONAL EPITHELIUM PREVENTS THE ENTRY OF URINE AND ITS TOXIC SUBSTANCES INTO THE URETER BY DIFFUSION.
  • MUSCULAR LAYER IS RESPONSIBLE FOR PERISTALSIS IN URETER WHICH PUSHES THE URINE FROM KIDNEY TO URINARY BLADDER.
  • ADVENTITIA IS PROTECTIVE AND SUPPORTIVE IN FUNCTION.

CLINICAL:

  • FORMATION OF STONES IN THE KIDNEY IS CALLED RENAL CALICULI AND IS MORE COMMON IN URETER. IT IS CHARACTERISED BY INTENSE COLIC PAIN IN THE LOIN.
HISTOLOGY OF SUPRA RENAL GLAND

HISTOLOGY OF SUPRA RENAL GLAND

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IDENTIFICATION POINTS

  • OUTER MOST CAPSULE WITH TRABACULAE.
  • CORTEX SHOWING ZONA GLOMERULOSA,ZONA FASICULATA AND ZONA RETICULARIS.
  • MEDULLA SHOWING SINUSOIDS AND SYMPATHETIC GANGLION CELLS.

INTRODUCTION

– SUPRA RENAL GLANDS ARE A PAIR OF ENDOCRINE GLANDS SITUATED IN THE POSTERIOR ABDOMINAL WALL ABOVE THE UPPER POLE OF BOTH KIDNEYS.

– AS THESE ARE LOCATED ABOVE THE KIDNEY, HENCE CALLED SUPRA RENAL GLAND.

– IN MANY ANIMALS THEY ARE FOUND ADJACENT TO THE KIDNEYS HENCE THEY ARE ALSO CALLED ADRENAL GLAND.

STRUCTURE

CORTEX:

SUPERFICIAL OUTER PART WHICH IS 10 TIMES WIDER THAN MEDULLA. IT CONSISTS OF THREE DIFFERENT LAYERS:-

1.ZONA GLOMERULOSA:

  • OUTER MOST LAYER OF CORTEX WHICH CONSTITUTES ABOUT 1/5th OF TOTAL CORTEX.

CELL SHAPE: POLYHEDRAL OR COLUMNAR.

ARRANGEMENT: ACINUS LIKE GROUPS OR INVERTED U-FORM OR HORSE-SHOE SHAPED.

CYTOPLASMIC NATURE: BASOPHILIC.

  • THESE CELLS CONTAIN PROMINENT SMALL NUCLEI WITH  RICH SMOOTH ENDOPLASMIC RETICULUM AND GOLGI COMPLEX. MITOCHONDRIA ARE ELONGATED IN NATURE.

2.ZONA FASICULATA:

  • INTERMEDIATE LAYER OF CORTEX, CONSTITUTES ABOUT 3/5th OF TOTAL CORTEX.

CELL SHAPE: POLYHEDRAL OR COLUMNAR.

ARRANGEMENT: CORD LIKE IN TWO ROWS.

CYTOPLASMIC NATURE: BASOPHILIC.

  • THESE CELLS ARE ALSO CALLED SPONGIOCYTES, CONTAIN LARGE PROMINENT NUCLEI WITH RICH SMOOTH ENDOPLASMIC RETICULUM. GOLGI COMPLEX ARE BEST DEVELOPED IN THE CELLS OF ZONA FASICULATA WITH SPHERICAL MITOCHONDRIA.
  • EXTENSIVELY VACUOLATED CYTOPLASM WITH STORAGE OF CHOLESTROL AND VIT-C.

3.ZONA RETICULARIS:

  • INNERMOST LAYER OF CORTEX, CONSTITUTES ABOUT 1/5th OF TOTAL CORTEX.

CELL SHAPE: POLYHEDRAL OR COLUMNAR.

ARRANGEMENT: NETWORK LIKE.

CYTOPLASMIC NATURE: OFTEN ACIDOPHILIC.

  • AS CELLS FORM NETWORK , IT IS CALLED ZONA RETICULOSA.
  • CELLS ARE RICH IN SMOOTH ENDOPLASMIC RETICULUM,GOLGI APPARATUS AND CONTAINS SMALL AMOUNT OF FAT IN IT.MITOCHONDRIA WITH TUBULAR CISTERNAE.

MEDULLA:

INNERMOST PART OF SUPRA RENAL GLAND, CONSTITUTES ABOUT 1/10th OF TOTAL GLAND.

CELL SHAPE: POLYHEDRAL OR COLUMNAR.

ARRANGEMENT: CLUMPS AND IRREGULAR CORDS WITH SINUSOIDS.

CYTOPLASMIC NATURE: BASOPHILIC.

  • THE CELLS OF MEDULLA ARE CONSIDERED AS THE MODIFIED POST GANGLIONIC SYMPATHETIC NEURONS.
  • THESE CELLS ARE RICH IN SECRETORY GRANULES WITH ABUNDANT ROUGH ENDOPLASMIC RETICULUM AND GOLGI COMPLEX.

FUNCTIONS:

  • ZONA GLOMERULOSA- SECRETE MINERALOCORTICOIDS. Eg: ALDOSTERONE AND 11-DEOXY-CORTICOSTERONE.
  • ZONA FASICULATA- SECRETE GLUCOCORTICOIDS. Eg: CORTICOSTERONE AND CORTISOL(HYDROCORTISONE).
  • ZONA RETICULARIS- SECRETE SEX HORMONES(ANDROGENS AND ESTROGENS) AND SMALL AMOUNT OF GLUCOCORTICOIDS.
  • CELLS OF ADRENAL MEDULLA- SECRETE CATECHOLAMINES(ADRENALINE,NORADRINALINE AND DOPAMINE).

THEY ACT AS NEUROTRANSMITTERS AND ALSO PLAY AN IMPORTANT ROLE IN CARDIAC FUNCTION AND MAINTENANCE OF NORMAL BLOOD PRESSURE.

CLINICAL:

  • HYPERSECRETION OF GLUCOCORTICOIDS CAUSES CUSHING’S SYNDROME.
  • HYPOSECRETION OF GLUCOCORTICOIDS CAUSES ADDISON’S DISEASE.
  • PHEOCHROMOCYTOMA IS A CONDITION  RESULTING DUE TO EXCESS SECRETION OF CATECHOLAMINES FROM MEDULLA.
HISTOLOGY OF KIDNEY

HISTOLOGY OF KIDNEY

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IDENTIFICATION POINTS

  • OUTER CORTEX AND INNER MEDULLA.
  • CORTEX CONTAINING RENAL CORPUSCLES,PROXIMAL AND DISTAL CONVOLUTED TUBULES.
  • MEDULLA CONTAINING LOOP OF HENLE AND COLLECTING DUCTS.

INTRODUCTION

– KIDNEY IS A PAIR OF EXCRETORY ORGAN LOCATED IN THE POSTERIOR ABDOMINAL WALL BEHIND THE PERITONEUM.

STRUCTURE

CAPSULE:

OUTER MOST PROTECTIVE COVERING MADE UP OF DENSE IRREGULAR CONNECTIVE TISSUE. EXTERNAL TO IT THERE IS A CONDENSATION OF PERIPHERAL FAT AS PERINEPHRIC PAD OF FAT , WHICH IN TURN IS SURROUNDED BY SHEATH CALLED RENAL FASCIA.

CORTEX:

OUTER PART OF KIDNEY FOUND BELOW THE CAPSULE. IT MAINLY CONTAINS GLOMERULUS,BOWMAN’S CAPSULE,DCT AND PCT.

MEDULLA:

INNER PART OF KIDNEY FOUND BELOW THE CORTEX. MEDULLA IS RICH IN LOOP OF HENLE,COLLECTING DUCTS AND PAPILLARY DUCTS(DUCTS OF BELLINI).

CLINICAL:

  • NEPHROTIC SYNDROME IS A DISEASE OF KIDNEY CHARACTERISED BY MASSIVE PROTEINURIA,HYPOALBUMINEMIA AND EDEMA.
  • INFLAMMATION OF GLOMERULUS- GLOMERULONEPHRITIS.
  • INABILITY OF THE KIDNEY TO MAINTAIN THE HOMEOSTASIS OF BLOOD AND BODY FLUIDS IS KNOWN AS RENAL FAILURE.

 

HISTOLOGY OF GALL BLADDER

HISTOLOGY OF GALL BLADDER

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IDENTIFICATION POINTS

  • ABSENCE OF SUBMUCOSA AND MUSCULARIS INTERNA.
  • PRESENCE OF FIBRO MUSCULAR COAT.
  • ABSENCE OF GLANDS AND GOBLET CELLS.

INTRODUCTION

– GALL BLADDER IS A MUSCULAR SAC LIKE STRUCTURE SITUATED IN FOSSA OF GALL BLADDER(VISCERAL SURFACE OF LIVER ).

– DIFFERENT PARTS OF GALL BLADDER ARE FUNDUS, BODY AND NECK.

– DEVELOPS IN 4th WEEK OF INTRAUTERINE LIFE FROM ‘PARS CYSTICA’ WHICH IS A PART OF HEPATIC BUD.

STRUCTURE

MUCOSA:

LINED BY SIMPLE COLUMNAR EPITHELIUM WITH FINE MICROVILLI. IT IS HIGHLY FOLDED INTO MANY RUGAE. SUBMUCOSA AND MUSCULARIS MUCOSA ARE ABSENT.

LAMINAPROPRIA:

LOOSE CONNECTIVE TISSUE LAYER BENEATH THE EPITHELIUM.

FIBROMUSCULAR COAT:

CIRCULARLY ARRANGED SMOOTH MUSCLE CELLS WITH FEW ELASTIC FIBRES IN IT.

SEROSA:

MADE UP DENSE IRREGULAR CONNECTIVE TISSUE WITH FEW BLOOD VESSELS IN IT.

FUNCTIONS:

  • STORES BILE.
  • CONCENTRATES THE BILE.
  • DECREASES THE pH OF BILE.
  • CONCENTRATION OF GALL BLADDER MAINTAINS THE PRESSURE IN THE BILLIARY SYSTEM WHICH IS ESSENTIAL FOR THE RELEASE OF BILE INTO SMALL INTESTINE.

CLINICAL:

  • INFLAMMATION OF GALL BLADDER IS CALLED CHOLECYSTITIS.
  • SURGICAL REMOVAL OF GALL BLADDER IS CALLED CHOLECYSTECTOMY.
  • FORMATION OF GALL STONES IN GALL BLADDER RESULTS IN CHOLELITHIASIS.
HISTOLOGY OF LIVER

HISTOLOGY OF LIVER

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IDENTIFICATION POINTS

  • HEPATIC LOBULES WITH CENTRAL VEIN.
  • RADIATING HEPATIC CORD CELLS.
  • PORTAL TRIADS.

INTRODUCTION

– LIVER IS THE LARGEST EXOCRINE GLAND SITUATED IN THE RIGHT HYPOCHONDRIUM AND A PART OF LEFT HYPOCHONDRIUM IN ABDOMEN.

– IT HAS TWO LOBES. RIGHT LOBE IS BIGGER THAN LEFT LOBE AND BOTH ARE CONNECTED BY ‘FALCIFORM LIGAMENT’.

– DEVELOPMENT OF LIVER STARTS IN 3rd WEEK OF INTRAUTERINE LIFE. IT ARISES FROM CAUDAL END OF FOREGUT AS A HEPATIC BUD AND LATER GROWS AS ‘PARS- HEPATICA’ TO FORM LIVER.

STRUCTURE

CAPSULE:

THIN LAYER OF CONNECTIVE TISSUE COVERING THE LIVER  CALLED ‘GLISSON’S CAPSULE’. IT ALSO COVERS THE BLOOD VESSELS THUS ENTER THE LIVER THROUGH ‘PORTA HEPATIS’ AND DIVIDES THE LIVER INTO NUMEROUS LOBULES.

STROMA:

CONSISTS OF THIN LAYER OF RETICULAR FIBRES SURROUNDING THE HEPATIC CORD CELLS AND SINUSOIDS.

PARENCHYMA:

REPEATED UNITS OF HEPATIC LOBULES FORM WHOLE OF THE LIVER PARENCHYMA.

IT IS EXPLAINED AS FOLLOWS:-

1.HEPATIC LOBULE:

HEXAGONAL MICROSCOPIC AREA OF LIVER, COVERED BY THIN CONNECTIVE TISSUE SEPTUM CALLED ‘INTERLOBAR SEPTUM’.

  • THERE IS A CENTRAL VEIN AT THE CENTRE OF HEPATIC LOBULE AND HEPATIC CORDS ARE RADIATING FROM THE CENTRAL VEIN.
  • HEPATOCYTES ARE HEXAGONAL IN SHAPE PRESENT IN HEPATIC CORDS.
  • 85-90% OF LIVER PARENCHYMA IS MADE UP OF HEPATOCYTES AND  10-15% IS MADE UP OF SINUSOIDAL EPITHELIUM.
  • ‘VON-KUPFFER CELLS’ ACT AS MACROPHAGES OF LIVER AND ARE PRESENT IN THE SINUSOIDS.

2.BILE CANALICULI:

  • THESE STRUCTURES CONNECT ONE HEPATOCYTE WITH ANOTHER HEPATOCYTE.

3.PERISINUSOIDAL SPACE OF DISSI:

  • IT IS A MINUTE POTENTIAL SPACE FOUND IN BETWEEN ENDOTHELIUM OF SINUSOIDS AND HEPATIC CORD CELLS. IT CONTAINS:-
  1. RETICULAR FIBRES
  2. MICROVILLI OF HEPATIC CORD CELLS AND
  3. PERISUNUSOIDAL LIPOCYTES OR LTO CELLS OR STELLATE CELLS.

4.SPACE OF MALL:

  • BLOOD VESSELS AND HEPATIC DUCTS ARE COVERED BY A NARROW INTERVAL SPACE IN THE PORTAL CANALS CALLED ‘SPACE OF MALL’.

5.PORTAL CANAL:

  • SPACE BETWEEN HEPATIC LOBULES FILLED WITH CONNECTIVE TISSUE. IT CONTAINS THE PORTAL TRIAD.
  • PORTAL TRIAD CONSTITUTES PROPER HEPATIC ARTERY,BILE DUCT AND PORTAL VEIN.

6.PORTAL LOBULE:

  • IT IS A TRUE FUNCTIONAL UNIT OF LIVER WHERE A SINGLE BRANCH OF PORTAL VEIN SUPPLIES THE THREE ADJOINING HEPATIC LOBULES.

7.PORTAL ACINUS:

  • DIAMOND SHAPED AREA FOUND BETWEEN TWO CENTRAL VEINS OF HEPATIC LOBULE, WHERE THE COENERS OF DIAMOND IS FORMED BY HEPATIC TRIAD.
  • BASED ON BLOOD SUPPLY IT IS DIVIDED INTO THREE ZONES

  ZONE 1: CLOSE TO ARTERIAL AND PORTAL BLOOD VESSELS  WITH RICH BLODD SUPPLY.

ZONE 2: INTERMEDIATE AREA FOUND BETWEEN ZONE 1 AND ZONE 3, WITH MODERATE BLOOD SUPPLY.

ZONE 3: AREA OF HEPATIC CORD CELLS SURROUNDING THE CENTRAL VEIN FORMS ZONE 3. IT HAS POOR BLOOD SUPPLY.

FUNCTIONS:

  • STROMA ACTS LIKE FRAMEWORK OF LIVER BY SUPPORTING THE HEPATOCYTES AND SINUSOIDS.
  • LIVER IS THE ACTIVE SITE FOR METABOLISM OF CARBOHYDRATES,PROTEINS,LIPIDS,VITAMINS,DRUGS AND HORMONES.
  • SECRETES BILE JUICE AND EXCRETES BILE PIGMENTS.
  • CHIEF ORGAN OF HEAT PRODUCTION.
  • HEAMOPOITIC ORGAN IN FOETAL LIFE.
  • FORMS A PART OF RETICULO-ENDOTHELIAL SYSTEM.
  • DETOXIFICATION CENTRE.

CLINICAL:

  • ENLARGEMENT OF LIVER (HEPATOMEGALY), SEEN IN FATTY LIVER DISEASE.
  • JAUNDICE DUE TO INCREASED BILLIRUBIN LEVEL IN BLOOD.
  • VIRAL INFECTION CAUSING INFLAMMATION OF LIVER CALLED HEPATITIS.
  • CIRRHOSIS OF LIVER WHERE NECROSIS AND FIBROSIS OF HEPATIC LOBULE IS SEEN.
  • CHRONIC VENOUS CONGESTION WHRER , ZONE 3 LIVER CELLS ARE AFFECTED.

 

HISTOLOGY OF PANCREAS

HISTOLOGY OF PANCREAS

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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.