DIGESTIVE SYSTEM
Pancreas, Liver, Gall Bladder
Pancreas
• An elongated retroperitoneal gland
• About 12–15 cm (5–6 in.) long and 2.5 cm (1 in.)
thick.
• Lies posterior to the greater curvature of the
stomach, somewhat obliquely, sloping from the head
upwards towards the tail on the posterior abdominal
wall.
• Crosses the bodies of L1-L2 vertebra at the level of
the transpyloric plane.
• 4 Parts: Head, Neck, Body and Tail.
• Head: The expanded and broadest portion of the
pancreas embraced by the C-shaped curve of the
duodenum.
- Uncinate process: A hook-shaped projection from
the inferior part of the head, extends medially to the
left, posterior to the SMA.
• Neck: is short (1.5–2 cm) and overlies the superior
mesenteric vessels, which form a groove in its
posterior aspect. Anteriorly, covered with
peritoneum, and is adjacent to the pylorus of the
stomach.
• Body: Continues from the neck and lies to the left of
the superior mesenteric vessels, passing over the
aorta and L2 vertebra, continuing just above the
transpyloric plane posterior to the omental bursa.
• Tail: Passes anterior to the left kidney The tail is
relatively mobile and lies within the two layers of the
splenorenal ligament and thus reaches the hilum of
the spleen with the splenic vessels.
Pancreatic Ducts
• Main pancreatic duct: Begins in
the tail, runs through the
parenchyma of the head. The
main pancreatic duct and
common bile duct unite to form
the short, dilated
hepatopancreatic ampulla (of
Vater), which opens on an
elevation of the duodenal
mucosa known as the major
duodenal papilla.
Sphincter of the hepatopancreatic ampulla (sphincter of
Oddi): consists of smth muscle which regulate the passage
of pancreatic juice & bile into the through the
hepatopancreatic ampulla.
• Accessory pancreatic duct:
Opens into the duodenum
at the summit of the minor
duodenal papilla, about 2.5
cm (1 in.) superior to the
hepatopancreatic ampulla.
Function:
- produces enzymes to digest
all categories of digestible
foods.
- Alkaline fluid(bicarbonate)
-Secretes insulin and glucagon introduced with enzymes
to egulate blood sugar level. neutralizes acidic chyme
Histology of the Pancreas
• The pancreas is made up of small clusters of
glandular epithelial cells.
• Exocrine portion: Consists of about 99% of the
clusters, called acini. The cells within acini secrete
pancreatic juice(a mixture of fluid and digestive
enzymes ) through duct system
• Endocrine portion: Consists of 1% of the
clusters, called
pancreatic islets (islets
of Langerhans).
- These cells secrete the
hormones glucagon,
insulin, somatostatin, and
pancreatic polypeptides
into the circulation (blood
vessels) to circulate to
target cells
Blood supply
Splenic artery, which supplies the neck, body and tail.
Superior and inferior pancreaticoduodenal arteries:
supply the head.
Venous return: - by small veins into the splenic vein.
- superior pancreaticoduodenal vein drain the head into the
portal vein
- Inferior pancreaticoduodenal vein drain the head into the
superior mesenteric vein.
Lymph drainage
• To the left of the neck it drains into the pancreaticosplenic
nodes which accompany the splenic artery.
• The head drains from its upper part into the coeliac group
and from its lower part and uncinate process into the
superior mesenteric group of preaortic lymph nodes.
Nerve supply
• Parasympathetic vagal fibres: from the posterior
vagal trunk and coeliac plexus which are capable of
stimulating exocrine secretion. But hormonal control
is more important than the neural.
• Sympathetic vasoconstriction: spinal cord segments
T6–10 via splanchnic nerves and the coeliac plexus
Liver
• Largest gland in the body,
weighs about 1500 g and
receives about 1500 mL of
blood per minute.
• Wedge-shaped, &
• lies inferior to the
diaphragm and occupies
most of the right
hypochondriac and part of
the epigastric regions of the
abdominopelvic cavity.
Almost completely covered
by visceral peritoneum
NB: Of all the organs of the
body It is second only to the
skin in size.
• 2 surfaces
• Diaphragmatic: - boldly
convex and subdivided into
anterior, superior, posterior
and right surfaces
• Visceral: Has Hilum of the
liver( porta hepatis); a
transverse fissure is located
for entry and exit of HPV,
HA, lymphatics, hepatic
nerve plexus and hepatic
ducts.
.
Border
• Sharp inferior border:
Separates the right and
anterior surfaces from
the visceral surface
• Ligaments: Falciform
ligament - a fold of the
mesentery, extends from
the undersurface of the
diaphragm btw the two
principal lobes of the
liver to the superior
surface of the liver, helps
to suspend the liver in
the abdominal cavity.
• Ligamentum teres (round
ligament): Attached to the
free margin of the falciform
ligament, a remnant of the
umbilical vein of the fetus,
carried well-oxygenated and
nutrient-rich blood from the
placenta to the fetus, this
fibrous cord extends from the
liver to the umbilicus.
• Ligamentum venosum: A
fibrous remnant of the fetal
ductus venosus, which
shunted blood from the
umbilical vein to the IVC,
short-circuiting the liver.
• Coronary ligaments(Rt &
lft): narrow extensions of
parietal perioneum. Lft
forms lft triangular
ligament which enclose
the bare area, and rt forms
rt triangular ligament .
• Fxn. The liver’s digestive
Bile salts. Bile lack enzymes but
function is to produce bile.
its bile salts emulsify fats by
• Bile: is a yellow-green,
physically breaking large fat
globules into smaller ones, thus watery solution containing
providing more surface area for bile salts, bile pigments,
cholesterol, phospholipids,
the fat-digesting enzymes to
& a variety of electrolytes.
work on.
• Lobes
Anatomical divisions include- a large Right lobe and a
smaller Left lobe demarcated by the falciform ligament
anteriorly and the fissures for the ligamentum teres
and ligamentum venosum on the visceral surface.
Caudate lobe: Lies between the inferior vena cava and
the fissure for the ligamentum venosum.
Quadrate lobe: Lies between the gallbladder fossa and
the fissure for the ligamentum teres. NB: Both lobes
were consequently considered to be part of the right
lobe.
Functional division: into right and left halves is by an
oblique plane that runs through the centre of the bed
of the gallbladder and the groove for the IVC.
Bile
 Produced by hepatocytes
 Composition
 Bile salts
 Bile pigment (mostly bilirubin from the breakdown
of hemoglobin)
 Cholesterol
 Phospholipids
 Electrolytes
Role of the Liver in Metabolism
 Several roles in digestion
 Detoxifies drugs and alcohol
 Degrades hormones
 Produce cholesterol, blood proteins (albumin and clo
tting proteins)
 Plays a central role in metabolism
Histology of the liver
• Hepatocytes: - are the major functional cells and
perform a wide array of metabolic, secretory, and
endocrine functions.
• - Are specialized epithelial cells with 5 to 12 sides
that make up abt 80% of the volume of the liver.
They secrete bile(which serves as both an excretory
product and a digestive secretion.)
- Hepatic laminae: are plates of hepatocytes one cell
thick bordered on either side by the endothelial-lined
vascular spaces(hepatic sinusoids). The hepatic laminae
are highly branched, irregular structures.
• Bile canaliculi: Are small ducts between hepatocytes
that collect bile produced by the hepatocytes. From
bile canaliculi – bile ductules - bile ducts. The bile
ducts merge to form the larger right and left hepatic
ducts, which unite and exit the liver as the common
hepatic duct.
• Hepatic sinusoids: - Are highly permeable blood
capillaries between rows of hepatocytes that receive
oxygenated blood from branches of the hepatic
artery and nutrient-rich deoxygenated blood from
branches of the hepatic portal vein.
- Hepatic sinusoids converge and deliver blood into a
central vein - hepatic veins - IVC
- Stellate reticuloendothelial (Kupffer) cells: Are
fixed phagocytes lining the hepatic sinusoids
which destroy worn-out white and red blood
cells, bacteria, and other foreign matter in the
venous blood draining from the gastrointestinal
tract.
• Portal triad: Constitute a bile duct, branch of the
hepatic artery, and branch of the hepatic portal
vein.
• Biliary tract
- The extrahepatic biliary tract consists of the 3
hepatic ducts (right, left and common), the
gallbladder and cystic duct, and the common bile
duct.
•
• And portal triad located at 3
corners of the hexagon.
NB: Model is based on
description of liver of adult pig
3 Anatomical and
functional units: Organization of
hepatocytes, bile duct
system, and hepatic
sinusoids.
• 1. Hepatic lobule: Each lobule shaped like
a hexagon with a
central vein, rows of
hepatocytes and
hepatic sinusoids
radiate out from the
central vein.
2. Portal lobule:- is
triangular in shape and is
defined by three imaginary
straight lines that connect 3
central veins that are closest
to the portal triad(center).
- the bile duct of a portal
triad is taken as the center
of the portal lobule.
- This model emphasized the
This model has not gained exocrine function of the liver,
that is, bile secretion.
widespread acceptance.
3. Hepatic acinus:- the
preferred structural and
functional unit of the liver.
- oval mass that includes
portions of two
neighboring hepatic
lobules.
- the short axis of the
hepatic acinus is defined
by branches of the portal
The long axis of the acinus is
triad that run along the
defined by two imaginary
curved lines, whichconnect the border of the hepatic
two central veins closest to the lobules.
short axis
Blood supply
• Arterial (oxygenated) blood is furnished by the
hepatic artery
• Venous blood is carried to the liver by the portal
vein.
• 3 main hepatic veins drain into IVC.
• The lymphatics of the liver drain into 3 or 4
nodes that lie in the porta hepatis (hepatic
nodes).
• Nerve supply: - Sympathetic; by way of the
coeliac ganglia
- vagus; fibres form hepatic branch reach porta
hepatis
Functions of the Liver
• Lipid metabolism
• Protein metabolism
• Processing of drugs and
hormones
• Excretion of bilirubin
• Synthesis of bile salts
• Storage: prime storage
site for certain vitamins
(A, B12, D, E, and K) and
minerals (iron and
copper), which are
released from the liver
when needed elsewhere
in the body.
• Phagocytosis
• Activation of vitamin :
The skin, liver, and
kidneys participate in
synthesizing the active
form of vitamin D.
• Carbohydrate
metabolism.
Gallbladder
• a globular or pear-shaped viscus, abt 7–10 cm long,
with a capacity of about 50 mL.
• lies in the gallbladder fossa on the visceral surface of
the right lobe of the liver, adjacent to the quadrate
lobe.
• Function: Stores and concentrates the bile secreted by
the liver
• 3 Parts: fundus, body and neck.
The neck continues into the cystic duct.
•
•
•
-
Histology of the gallbladder
a fibromuscular sac
Mucous membrane: - is a lax areolar tissue lined with
a simple columnar epithelium.
Epithelium
Body: Epithelium is projected into folds which produce
a honeycomb appearance
Neck and Cystic duct :folds are arranged in a more or
less spiral manner (the ‘spiral valve’ of Heister).
The epithelial cells actively absorb water and solutes
from the bile and concentrate it.
Mucus is secreted by the columnar epithelium
No goblet cells
Mucus secreting glands are present only in the neck.
Blood supply
• Cystic artery: a branch of the right hepatic which
runs across the triangle formed by the liver,
common hepatic duct and cystic duct (Calot's
triangle), to reach the gallbladder.
• Multiple small veins in the gallbladder bed into
hepatic veins, one or more cystic veins drain the
neck into right branch of portal vein.
• Lymph drainage: Drain to nodes in the porta
hepatis - and to a node situated at the anterior
boundary of the epiploic foramen. From these
nodes lymph passes to the coeliac group of
preaortic nodes.