liver anatomy and physio

1. Liver: Anatomy and Physiology
Dr. Himanshu Jangid

2. Liver : Introduction
 The liver is the largest of the abdominal viscera, occupying a
substantial portion of the upper abdominal cavity.
 It performs a wide range of metabolic activities necessary for
homeostasis, nutrition and immune defence.
 It is composed largely of epithelial cells (hepatocytes), which are
bathed in blood derived from the hepatic portal veins and hepatic
arteries.
 Hepatocytes are also associated with an extensive system of minute
canals, which form the biliary system into which products are
secreted.

3.  The liver lies in the upper right part of the abdominal
cavity.
 It occupies most of the right hypochondrium and
epigastrium,
 frequently extends into the left hypochondrium as far as
the left lateral line.
 In adults the liver weighs 2% of body mass.
 an overall wedge shape

4.  The liver capsule plays an important part in maintaining
the integrity of its shape.
 Once the capsule is lacerated, the liver tissue is
easily parted and provides only limited support for
surgical sutures.
 These features, in combination with its exceptional
vascular supply, make the liver prone to potentially lethal
injuries if it is split open.

5. EXTERNAL FEATURES
 The liver is attached to the anterior abdominal wall,
diaphragm and other viscera by several ligaments, which
are formed from condensations of the peritoneum :
 Falciform ligament
 Coronary ligament
 Triangular ligaments
 Lesser omentum

7. Porta hepatis
 The Porta hepatis is the area of the inferior surface
through which all the neurovascular and biliary
structures, except the hepatic veins, enter and leave the
liver.
 It is situated between the quadrate lobe in front and the
caudate process behind.
 Right and left hepatic bile ducts emerge from it.
 All these structures are enveloped in the perivascular
fibrous capsule - hepatobiliary capsule of Glisson - a
sheath of loose connective tissue which surrounds the
vessels

8. The porta hepatis

9. LOBATION AND SEGMENTATION
 The liver has four lobes or eight segments, depending
on whether it is defined by its gross anatomical
appearance or by its internal architecture.

10. Gross anatomical lobes
 Right lobe
 The right lobe is the largest in volume and
contributes to all surfaces
 Quadrate lobe
 The quadrate lobe is only visible from the inferior
surface. it is functionally related to the left lobe.
 Caudate lobe
 this lobe is said to arise from the right lobe, but it is
functionally separate
 Left lobe
 The left lobe is the smaller of the two 'main' lobes

11. Couinaud segments

12. Couinaud segments
 The liver is divided by the 'principal plane' into two
halves of approximately equal size.
 The principal plane is defined by an imaginary
parasagittal line from the gallbladder anteriorly to the
inferior vena cava posteriorly.
 The usual functional division of the liver into right and left
lobes lies along this plane.
 The liver is further subdivided into segments,
 each supplied by a
 principal branch of the hepatic artery,
 portal vein and bile duct.

13.  Segments I, II, III and IV make up the functional left lobe,
 Segments V, VI, VII and VIII make up the functional right
lobe.
 Segment I corresponds to the gross anatomical caudate
lobe and segment IV to the quadrate lobe.

14. VASCULAR SUPPLY
• Two sources provide blood to the liver
o Hepatic artery
 Celiac trunk of aorta
o Portal vein
• Blood exits the liver via the central vein
• 25% of cardiac output
• Blood flow into the liver is controlled by number of
factors
• Muscular sphincters
• Number of different stimuli, including the autonomic nervous
system, circulating hormones, bile salts, and metabolites

16. Portal vein
• Portal vein is a valveless
structure that is formed by
the confluence of the
superior mesenteric vein
and the splenic vein.
 75% of the total liver
blood supply by volume
 2 PV in liver
 Left 2,3,4
 Right 5,6,7,8
• Portal vein is formed by the
union of the superior
mesenteric vein and the
splenic vein at the level of the
second lumbar vertebra
behind the head of pancreas
• Portal vein is contained within
the hilum of the liver

17. Portal vein
• The portal vein gives rise to branching septal veins,.
• Blood from the septal veins enters directly into the
parenchymal sinusoids between hepatocytes.
•
• Sinusoids are lined by fenestrated and discontinuous
endothelial cells
o extrasinusoidal space of Disse, into which protrude abundant
microvilli of hepatocytes
 Kupffer and presinusoidal stellate cells

19. The portal vein and its tributaries (semi-diagrammatic). Portions of the stomach,
pancreas and left lobe of the liver and the transverse colon have been removed.

20.  The portal vein supplies the liver with 5% of its resting
oxygen consumption but significantly more of its
metabolic nutrition.
 Progressive occlusion of the hepatic artery rarely
results in complete necrosis of the liver, which is due
principally to the blood supply derived from the
portal vein.

21. Hepatic Artery
• Provides the remaining 25% of the blood flow to the liver
 Large amount of variability
• Common hepatic artery arises from the celiac axis,
• ascends in the hepatoduodenal ligament, and gives rise to the right
gastric, gastroduodenal, and proper hepatic arteries;
• the proper hepatic artery then divides into the right and left hepatic
arterial branches in the liver hilum
• Right artery off SMA (#1 variant)

24. Hepatic veins
 The liver has two venous systems.
 The portal system conveys venous blood from the
majority of the gastrointestinal tract and its associated
organs to the liver.
 The hepatic venous system drains blood from the liver
parenchyma into the inferior vena cava.

25.  The hepatic veins convey blood from the liver to the
inferior vena cava.
 The right hepatic vein drains segments V, VI, VII and VIII.
 The left hepatic vein drains segments II and III with some
drainage from segment IV.
 The hepatic veins have no valves.

26. Arrangement of the hepatic venous territories. Multiple lower group veins may be
present. Individual segments may drain into more than one hepatic venous territory.

27. INNERVATION
 The liver has a dual innervation.
 Hepatic nerves, which arise from the hepatic plexus and
contain sympathetic and parasympathetic (vagal) fibres
 Supply the parenchyma.
 They enter the liver at the porta hepatis and largely
accompany the hepatic arteries and bile ducts.

28. INNERVATION
 The capsule is supplied by some fine branches of the
lower intercostal nerves, which also supply the parietal
peritoneum,
 particularly in the area of the 'bare area' and superior
surface.
 This is seen clinically when distension or disruption of the
liver capsule causes quite well localized sharp pain.

29. HEPATIC PLEXUS
 The hepatic plexus is the largest derivative of the coeliac
plexus.
 It also receives branches from the anterior and posterior
vagi.
 These branches not only supply vasomotor fibres to the
hepatic vessels and biliary tree, but also innervate the
hepatocytes directly and are involved in the control of
some homeostatic mechanisms.
 The vagal fibres are motor to the musculature of the
gallbladder and bile ducts and inhibitory to the sphincter
of the bile duct.

30. REFERRED PAIN
 Pain arising from the parenchyma of the liver is poorly
localized.
 In common with other structures of foregut origin, pain is
referred to the central epigastrium.
 Stretch of or involvement of the liver capsule by
inflammatory or neoplastic processes rapidly produces
well-localized pain of a 'somatic' nature.

31. Functional Anatomy of Liver
• Liver is composed of
hexagonal shaped units-
lobules
• Radiate from central
vein to the periphery
• Between the rows of
hepatocytes are
sinusoids which supply
blood

33. Functional Anatomy of Liver
 In the mature liver, hepatocytes are arranged mainly
in plates - or cords,
 Between the plates are venous sinusoids, which
anastomose with each other via gaps in the
hepatocyte plates.
 Bile secreted by the hepatocytes is collected in a
network of minute tubes (canaliculi).

34. Portal Triad
Branches of portal vein, hepatic
artery and the biliary ducts bound
together in the perivascular fibrous
capsule

35. CELLS OF THE LIVER
 Cells of the liver include
 hepatocytes,

 hepatic stellate cells - also known as perisinusoidal
lipocytes, or Ito cells - sinusoidal endothelial cells,
 macrophages (Kupffer cells),
 the cells of the biliary tree - cuboidal to columnar
epithelium - and
 connective tissue cells of the capsule and portal tracts.

37. Functions of the Liver
 Formation and secretion of bile
 Nutrient and vitamin metabolism
 Glucose and other sugars
 Amino acids
 Lipids
 Fatty acids
 Cholesterol
 Lipoproteins
 Fat-soluble vitamins
 Water-soluble vitamins

38.  Inactivation of various substances
 Toxins
 Steroids
 Other hormones
 Synthesis of plasma proteins
 Acute-phase proteins
 Albumin
 Clotting factors
 Steroid-binding and other hormone-binding proteins
 Immunity
 Kupffer cells

39. Bile
 About 500 mL is secreted per day.
 Some of the components of the bile are reabsorbed in the
intestine and then excreted again by the liver
(enterohepatic circulation).

40. Composition of Human Hepatic Duct Bile

41.  The glucuronides of the bile pigments, bilirubin and biliverdin,
are responsible for the golden yellow color of bile.
 The bile salts are sodium and potassium salts of bile acids,
and all those secreted into the bile are conjugated to glycine or
taurine, a derivative of cysteine.
 The bile acids are synthesized from cholesterol.

42.  Primary bile acids
 Formed in the liver are cholic acid and chenodeoxycholic acid.

 Secondary bile acids
 In the colon, bacteria convert cholic acid to deoxycholic acid
and chenodeoxycholic acid to lithocholic acid.

43. Enterohepatic Circulation
Enterohepatic circulation of bile salts. The solid lines entering the portal system represent bile salts of
hepatic origin, whereas the dashed lines represent bile salts resulting from bacterial action.

44. Functions of the Gallbladder
 In normal individuals, bile flows into the gallbladder when the
sphincter of Oddi is closed.
 In the gallbladder, the bile is concentrated by absorption of
water.
 The degree of this concentration is shown by the increase in
the concentration of solids
 liver bile is 97% water, whereas the average water content of
gallbladder bile is 89%.

45.  When the bile duct and cystic duct are clamped, the
intrabiliary pressure rises to about 320 mm of bile in 30
minutes, and bile secretion stops.
 However, when the bile duct is clamped and the cystic duct is
left open, water is reabsorbed in the gallbladder, and the
intrabiliary pressure rises only to about 100 mm of bile in
several hours.
 Acidification of the bile is another function of the gallbladder.

46. Comparison of Human Hepatic Duct Bile and
Gallbladder Bile.

47. Regulation of Biliary Secretion
 Cholagogues:
 Substances that cause contraction of the gallbladder
 When food enters the mouth, the resistance of the sphincter
of Oddi decreases.
 Fatty acids and amino acids in the duodenum release CCK,
which causes gallbladder contraction.

48. Effects of Cholecystectomy
 The periodic discharge of bile from the gallbladder aids
digestion but is not essential for it.
 Cholecystectomized patients maintain good health and
nutrition with a constant slow discharge of bile into the
duodenum.
 Bile duct becomes somewhat dilated, and more bile tends to
enter the duodenum after meals than at other times.
 Cholecystectomized patients can even tolerate fried foods,
although they generally must avoid foods that are particularly
high in fat content.

49.  Choleretics:
 Substances that increase the secretion of bile
 The production of bile is increased by stimulation of the
vagus nerves and by the hormone secretin, which
increases the water and HCO3
– content of bile.
 Bile salts themselves are among the most important
physiologic choleretics.