Anatomy and Physiology

1

R. Sutcliffe & O. Tucker

Liver segmental anatomy 2

Hepatic artery anatomy 6

Liver resection planes 7

Liver physiology 8

Gallbladder anatomy 10

Biliary anatomy 13

Pancreatic anatomy 14

Pancreatic physiology 15

Anatomy and physiology

Chapter 1

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2 CHAPTER 1 Anatomy and physiology

Liver segmental anatomy

The liver is the largest solid organ (weight 1.2–1.6kg), and lies in the

right upper quadrant of the abdomen below the right hemidiaphragm.

Peritoneal attachments: falciform ligament, coronary ligament, and

left and right triangular ligaments (see Fig. 1.3).

The Glissonian capsule is a fi brous covering over the liver, except the

bare area, where the liver is in direct contact with the diaphragm.

Liver segments

Anatomical divisions are based on vascular and biliary anatomy not

surface markings (see Figs 1.1 and 1.2).

The arterial supply to the liver is via the common hepatic artery

(branch of coeliac axis), which usually runs to the left of the common

bile duct, before dividing into left and right branches. There is consider-

able anatomical variation of the hepatic arteries (Hepatic artery

anatomy b p. 6).

The mid-plane of the liver separates the right lobe (supplied by

right hepatic artery and right portal vein) from the left lobe (supplied

by left hepatic artery and left portal vein). The principal plane

(see Fig. 1.1) intersects the gallbladder fossa anteriorly and the

inferior vena cava fossa posteriorly.

The left and right hepatic ducts (fi rst-order ducts) drain bile into the

common hepatic duct from each lobe.

Second-order ducts and arteries divide each lobe into two sections.

right lobe => anterior and posterior sections;

left lobe => medial and lateral sections.

The left intersectional plane corresponds to the umbilical fi ssure

and the attachment of the falciform ligament to the liver. The right

intersectional plane does not have a surface marking.

Third-order divisions of the liver are also known as Couinaud’s

segments.

right anterior section => segments 5 and 8

right posterior section => segments 6 and 7;

left lateral section => segments 2 and 3;

left medial section => segment 4.

The caudate lobe is distinct from the left and right lobes, and is also

referred to as segment 1. It lies between the porta hepatis and the

inferior vena cava. It receives a blood supply from both left and right

hepatic arteries, and bile drains into both left and right hepatic ducts.

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3

7

6

8

5

4

2

3

Principalplane

Fig. 1.1 Principal plane.

Fig. 1.2 Liver segments. LHV: left hepatic vein, MHV: middle hepatic vein, RHV:

right hepatic vein.

– Left hepatic vein– Middle hepatic vein– Right hepatic vein

LHVMHVRHV

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65

4 3

2

8

RHV LHV

MHV

LIVER SEGMENTAL ANATOMY



The portal vein drains blood from the gastrointestinal tract

(from lower oesophagus to rectum), pancreas, and spleen. It is formed

by the union of the splenic and superior mesenteric veins posterior to

the neck of the pancreas. The inferior mesenteric vein invariably drains

into the splenic vein.

The right portal vein supplies the right lobe and its branches

correspond to those of the right hepatic artery.

The left portal vein is initially horizontal and changes direction at the

ligamentum venosum to become vertical (umbilical portion, in the

umbilical fi ssure). The vertical portion is a remnant of the umbilical

vein, and gives branches to segment 4 (to its right), and segments 2

and 3 (to its left).

The hepatic veins drain blood from the liver into the inferior vena

cava, and lie between sections or lobes:

left hepatic vein – between s2 and s3 then left intersectional plane;

middle hepatic vein – mid-plane (between s4 and s5/8);

right hepatic vein – right intersectional plane (between s5/8

and s6/7).

10% of patients have a large inferior right hepatic vein in addition to a

superior right hepatic vein.

The caudate lobe drains blood directly into the IVC, via several small

veins.

See Fig. 1.3.

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5

G

G

FL

LTL

IVC

R

L

PH

BA

UC

LC

RTL

Posterior view

Anterior view

Fig. 1.3 Peritoneal attachments of the liver. G: gallbladder, FL: falciform ligament,

LTL: left triangular ligament, IVC: inferior vena cava, R: right lobe, L: left lobe,

PH: porta hepatis, BA: bare area, UC: upper layer of coronary ligament, LC: lower

layer of coronary ligament, RTL: right triangular ligament.

LIVER SEGMENTAL ANATOMY



Hepatic artery anatomy

An accessory artery indicates that the proper hepatic artery

(left, right, or common) is also present.

A replaced artery indicates that the proper artery is absent.

An accessory or replaced left hepatic artery arises from the left

gastric artery and runs in the lesser omentum.

An accessory or replaced right hepatic artery arises from the

superior mesenteric artery, and passes behind the common bile duct

to run along its right posterolateral border into the liver.

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Liver resection planes

Anatomical liver resections follow anatomical planes (Fig. 1.4).

Transection through umbilical fi ssure/falciform ligament

(left intersectional plane):

left lateral sectionectomy (or ‘segmentectomy’);

extended right hepatectomy.

Transection through mid-plane:

left hepatectomy;

right hepatectomy.

Transection through right intersectional plane:

extended left hepatectomy;

right posterior sectionectomy.

Fig. 1.4 Resection planes.

Extended right hepatectomyLeft lateral segmentectomy

Right hepatectomyLeft hepatectomy

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LIVER RESECTION PLANES



Liver physiology

The liver parenchyma is arranged into lobules, which contain several

acini. An acinus is arranged around terminal branches of the hepatic

artery and portal vein.

Hepatocytes receive their blood supply via the hepatic sinusoids, which

are fenestrated capillaries lined by endothelial cells. Sinusoids are lined

by Kupffer cells (part of reticulo-endothelial system), hepatic stellate

cells, and liver-associated lymphocytes.

Bile canaliculi drain bile from hepatocytes into a network of cholangi-

oles and larger ducts, before entering the common hepatic duct

Liver function

The liver has substantial reserve capacity, which allows signifi cant damage

(e.g. cirrhosis) to occur before symptoms develop. A signifi cant volume

of liver (up to 60%) can be resected safely, without patients developing

liver failure, provided that the future liver remnant is of good quality and

an adequate volume (see Complications after liver resection, Early, Small-

for-size syndrome b p. 190).

Metabolism:

carbohydrates (gluconeogenesis, glycogenesis, glycogenolysis);

protein;

lipids;

bilirubin;

hormones;

haemoglobin;

drugs;

lactate.

Synthesis:

albumin;

clotting factors (fi brinogen, prothrombin, V, VII, IX, XI, protein C,

protein S, antithrombin);

cholesterol;

triglycerides;

bile;

lipoproteins;

caeruloplasmin;

transferrin;

complement;

glycoproteins.

Storage

glycogen;

vitamin B12;

iron;

copper.

Foetal erythropoiesis.

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9LIVER PHYSIOLOGY



Gallbladder anatomy

The gallbladder is a hollow organ that concentrates and stores bile.

It lies in the gallbladder fossa on the inferior aspect of the right lobe.

It has a rounded fundus, a body, and an infundibulum. Gallstones may

become impacted in Hartmann’s pouch.

The presence of fat in the duodenum stimulates the release of

cholecystokinin (CCK), which causes contraction of the gallbladder and

secretion of bile through the cystic duct, common bile duct, and into

the duodenum.

Calot’s triangle is bordered by the gallbladder, the common hepatic

duct and the liver (Fig. 1.5). The peritoneal covering of the gallbladder

extends onto the anterior and posterior aspects of Calot’s triangle and

onto the portal structures. The arterial supply of the gallbladder is via

the cystic artery, which usually arises from the right hepatic artery and

lies within Calot’s triangle. Occasionally, the cystic artery has anterior

and posterior branches before entering the gallbladder.

The cystic duct joins the common hepatic duct to form the common

bile duct, usually about 5cm above the duodenum. Rarely, an accessory

cystic duct (duct of Luschka) drains bile intrahepatically through the

gallbladder fossa, and is susceptible to injury during cholecystectomy

(Fig. 1.6).

Venous drainage of the gallbladder occurs via multiple small veins that

enter the portal vein, either through the gallbladder fossa or Calot’s

triangle

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L

CHDCD CA

PH

G

R

Fig. 1.5 Calot’s triangle. PH: porta hepatis, R: right lobe of liver, G: gallbladder,

L: liver, CD: cystic duct, CHD: common hepatic duct, CA: cystic artery.

GALLBLADDER ANATOMY



(a) (b)

(c) (d)

RHD

LHD

CHD

CD

CBD

GB

Fig. 1.6 Gallbladder anatomical variation. (a) Normal (GB: gallbladder; CD: cystic

duct; CBD: common bile duct; CHD: common hepatic duct; RHD: right hepatic duct;

LHD: left hepatic duct). (b) Cystic duct draining into RHD. (c) Right posterior

sectoral duct draining into gallbladder. (d) Short or absent cystic duct.


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Biliary anatomy

The left and right hepatic ducts unite at the base of segment 4,

anterior to the portal vein bifurcation. The common hepatic duct

passes inferiorly in the right edge of the hepatoduodenal ligament,

to the right of the common hepatic artery, and joins the cystic duct

to become the common bile duct.

The common bile duct (diameter 3–7mm) passes behind the fi rst part

of the duodenum, enters the head of the pancreas, and terminates at

the ampulla of Vater.

Many anatomical variants of biliary anatomy have been described

(Fig. 1.7).

The blood supply of the biliary tree is derived principally from the

hepatic artery, which explains the presence of biliary complications that

develop after hepatic artery thrombosis in liver transplant recipients.

Fig. 1.7 Hepatic duct anatomical variation. (a) Normal anatomy (RA: right anterior

sectoral duct, RP: right posterior sectoral duct, LHD: left hepatic duct). (b) Right

anterior and posterior sectoral ducts drain directly into confl uence (c) Right

posterior sectoral duct drains into left hepatic duct. (d) Right anterior sectoral

duct drains into common hepatic duct.

RA

RP

LHD LHD

RA

RP

RA

RP

LHD

RA

RP

LHD

(a) (b)

(c) (d)

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BILIARY ANATOMY



Pancreatic anatomy

The pancreas is a retroperitoneal organ, which is separated from the

stomach anteriorly by the lesser sac. It consists of a head, neck, body

and tail. The head of the pancreas lies within the C-shaped duodenum.

The neck lies at the level of the fi rst lumbar vertebra (transpyloric

plane of Addison), anterior to the confl uence of the portal, superior

mesenteric and splenic veins, and connects to the body and tail. The

tail of the pancreas is closely related to the splenic hilum within the

lienorenal ligament.

The uncinate process of the pancreas originates from the embryological

dorsal pancreas and fuses with the pancreatic head (ventral pancreas).

It lies posterior to the superior mesenteric artery and vein.

Exocrine secretions (see Fig.1.8) enter the pancreatic duct (diameter

1-3mm) that joins with the accessory pancreatic duct and the common

bile duct to form a common channel that terminates at the ampulla of

Vater (postero-medial border of the second part of the duodenum).

The arterial supply of the pancreas is via branches of the coeliac axis

(gastroduodenal artery => superior pancreatico-duodenal artery),

superior mesenteric artery (inferior pancreatico-duodenal artery) and

branches directly from the splenic artery.

Venous drainage is via tributaries into the splenic, portal and superior

mesenteric veins.

Lymphatic drainage of the pancreas occurs via lymph nodes located

along the arterial supply (coeliac axis and superior mesenteric artery).

Fig. 1.8 Anatomical relationships of the pancreas. D: duodenum, S: spleen,

CBD: common bile duct, PD: pancreatic duct, DJ: duodeno-jejunal fl exure, PV: portal

vein, SMV: superior mesenteric vein, HA: hepatic artery, SA: splenic artery,

SMA: superior mesenteric vein, CA: coeliac axis.

LGACBD

D

PD

HA

Aorta

CA

DJ

S

SA

SMASMV

PV

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Pancreatic physiology

Exocrine: acinar cells secrete bicarbonate (regulated by secretin) and

inactive pro-enzymes (regulated by CCK), which are activated in the

duodenum (e.g. trypsin, amylase, lipase, chymotrypsin). Bicarbonate

neutralizes gastric acid, and enzymes digest dietary proteins, lipids, and

carbohydrate to allow absorption. Lipid absorption is facilitated by bile

acids (secreted in bile).

Endocrine: Islets of Langerhans consist of alpha, beta, delta, and

PP cells, which secrete glucagon, insulin, somatostatin, and pancreatic

polypeptide, respectively.

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PANCREATIC PHYSIOLOGY


Anatomy and Physiology

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