Category: LIVER

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.