Pancreas and spleen and retroperitoneal space pdf - Abdomen

Basic Anatomy

uncinate process.

sels and is called the

head extends to the left behind the superior mesenteric ves

the concavity of the duodenum (Fig. 5.58). A part of the

of the pancreas is disc shaped and lies within

head

The

creas is divided into a head, neck, body, and tail (Fig. 5.58).

the peritoneum. It crosses the transpyloric plane. The pan

lated and situated on the posterior abdominal wall behind

epigastrium and the left upper quadrant. It is soft and lobu

The pancreas is an elongated structure that lies in the

carbohydrate metabolism.

which play a key role in

glucagon,

insulin

hormones

produces the

pancreatic islets (islets of Langerhans),

and carbohydrates. The endocrine portion of the gland,

contains enzymes capable of hydrolyzing proteins, fats,

exocrine portion of the gland produces a secretion that

The pancreas is both an exocrine and endocrine gland. The

Location and Description

the lumen constantly open.

the “spiral valve.” The function of the spiral valve is to keep

the neck of the gallbladder. The fold is commonly known as

201

Pancreas

the

and

lumen of gallbladder

FIGURE 5.54

Longitudinal sonogram of the upper part of the

of Dr. M.C. Hill.)

abdomen showing the lumen of the gallbladder. (Courtesy

Development of the Liver and Bile Ducts

may not be recognized when performing a cholecystectomy, and

The gallbladder drains directly into the bile duct. The condition

leave the narrow stem that would normally form the cystic duct.

from the hepatic bud develops into the gallbladder and fails to

In the absence of the cystic duct, the entire outgrowth of cells

Rarely, the outgrowth of cells from the hepatic bud bifurcates so

Occasionally, the outgrowth of cells from the hepatic bud fails

atresia should be attempted when possible. If the atresia cannot

Jaundice appears soon after birth; clay-colored stools and very

comes to occupy the greater part of the abdominal cavity; the

and the

common hepatic duct

now become canalized to form the

a point halfway along the second part of the fully formed duode

entodermal cells (Figs. 5.41 and 5.55). The site of origin lies at the

Liver
The liver arises from the distal end of the foregut as a solid bud of

apex of the loop of the developing duodenum and corresponds to

num. The hepatic bud grows anteriorly into the mass of splanch-

nic mesoderm called the septum transversum. The end of the

bud now divides into right and left branches, from which col-

umns of entodermal cells grow into the vascular mesoderm. The

paired vitelline veins and umbilical veins that course through the

septum transversum become broken up by the invading columns

of liver cells and form the liver sinusoids. The columns of ento-

dermal cells form the liver cords. The connective tissue of the

liver is formed from the mesenchyme of the septum transversum.

The main hepatic bud and its right and left terminal branches

right and left hepatic ducts. The liver grows rapidly in size and

right lobe becomes much larger than the left lobe.

Gallbladder and Cystic Duct
The gallbladder develops from the hepatic bud as a solid out-

growth of cells (Fig. 5.41). The end of the outgrowth expands

to form the gallbladder, while the narrow stem remains as the

cystic duct. Later, the gallbladder and cystic duct become cana-

lized. The cystic duct now opens into the common hepatic duct

to form the bile duct.

Biliary Atresia
Failure of the bile ducts to canalize during development causes

atresia. The various forms of atresia are shown in Figure 5.56.

dark-colored urine are also present. Surgical correction of the

be corrected, the child will die of liver failure.

Absence of the Gallbladder

to develop. In these cases, there is no gallbladder and no cystic

duct (Fig. 5.57).

Double Gallbladder

that two gallbladders are formed (Fig. 5.57).

Absence of the Cystic Duct

the bile duct may be seriously damaged by the surgeon (Fig. 5.57).

Accessory Bile Duct
A small accessory bile duct may open directly from the liver into

the gallbladder, which may cause leakage of bile into the peri-

toneal cavity after cholecystectomy if it is not recognized at the

time of surgery (Fig. 5.57).

Congenital Choledochal Cyst
Rarely, a choledochal cyst develops because of an area of

weakness in the wall of the bile duct. A cyst can contain 1 to 2 L

of bile. The anomaly is important in that it may press on the bile

duct and cause obstructive jaundice (Fig. 5.57).

E M B R Y O L O G I C N O T E S

202

CHAPTER 5

The Abdomen: Part II—The Abdominal Cavity

stomach

ventral mesentery

first part of
duodenum

second part of
duodenum

dorsal
mesentery

hepatic bud

gallbladder

ventral

pancreatic bud

third part

of duodenum

stomach

dorsal pancreatic bud

fourth part of duodenum

gallbladder

dorsal

mesentery

dorsal

mesentery

ventral

mesentery

ventral

pancreatic bud

dorsal

pancreatic bud

liver

remains of

ventral

mesentery

gallbladder

ventral pancreatic bud

dorsal pancreatic bud

peritoneum will fuse here

and then disappear

first part of duodenum

FIGURE 5.55

Development of the duodenum in relation to the ventral and dorsal mesenteries. Stippled area, foregut; cross

hatched area, midgut.

atresia of bile duct

atresia of hepatic duct

atresia of entire

extrahepatic apparatus

atresia of hepatic ducts

FIGURE 5.56

Some common congenital anomalies of the

denal arteries (Fig. 5.26) supply the pancreas.

The splenic and the superior and inferior pancreaticoduo

Arteries

frequently communicates with the main duct.

(Figs. 5.51 and 5.58). The accessory duct

duodenal papilla

minor

num a short distance above the main duct on the

the upper part of the head and then opens into the duode

of the pancreas, when present, drains

accessory duct

The

duct drains separately into the duodenum.

(Fig. 5.51). Sometimes, the main

major duodenal papilla

duodenum at about its middle with the bile duct on the

the way (Fig. 5.58). It opens into the second part of the

the length of the gland, receiving numerous tributaries on

begins in the tail and runs

main duct of the pancreas

The

Pancreatic Ducts

hilum of the spleen (Figs. 5.4 and 5.27)

muscle, the left suprarenal gland, the left kidney, and the

origin of the superior mesenteric artery, the left psoas

and splenic veins, the inferior vena cava, the aorta, the

From right to left: the bile duct, the portal

Posteriorly:

sac, and the stomach (Figs. 5.4 and 5.6)

the attachment of the transverse mesocolon, the lesser

From right to left: the transverse colon and

Anteriorly:

and comes in contact with the hilum of the spleen (Fig. 5.4).

passes forward in the splenicorenal ligament

The

(Fig. 5.4). It is somewhat triangular in cross section.

runs upward and to the left across the midline

body

The

enteric artery from the aorta (Fig. 5.26).

ning of the portal vein and the origin of the superior mes

connects the head to the body. It lies in front of the begin

is the constricted portion of the pancreas and

neck

The

biliary ducts.

-
-

tail

Relations

■

Blood Supply

Basic Anatomy

(Figs. 5.4 and 5.11).

colic flexure. The left kidney lies along its medial border

The stomach, tail of the pancreas, and left

Anteriorly:

tail of the pancreas).

splenicorenal ligament (carrying the splenic vessels and the

sels). The peritoneum also passes to the left kidney as the

ach (carrying the short gastric and left gastroepiploic ves

omentum (ligament) to the greater curvature of the stom

5.61), which passes from it at the hilum as the gastrosplenic

The spleen is surrounded by peritoneum (Figs. 5.5 and

cannot be palpated on clinical examination (Fig. 5.61).

pole extends forward only as far as the midaxillary line and

long axis lies along the shaft of the 10th rib, and its lower

the diaphragm close to the 9th, 10th, and 11th ribs. The

notched anterior border. It lies just beneath the left half of

lymphoid tissue in the body. It is oval shaped and has a

The spleen is reddish and is the largest single mass of

Location and Description

ply the area.

Sympathetic and parasympathetic (vagal) nerve fibers sup

Nerve Supply

and superior mesenteric lymph nodes.

gland. The efferent vessels ultimately drain into the celiac

Lymph nodes are situated along the arteries that supply the

Lymph Drainage

The corresponding veins drain into the portal system.

Veins

203

Spleen

-
-

Relations

■

body

right lobe
of liver

bile duct

second part
of duodenum

major duodenal
papilla

head of pancreas

main pancreatic duct

uncinate process

neck

tail

spleen

left hepatic duct

right hepatic duct

neck

accessory pancreatic duct

fundus of
gallbladder

body

cystic duct

FIGURE 5.58

Different parts of the pancreas dissected to reveal the duct system.

absence of cystic duct

abnormally long cystic duct

congenital absence

of gallbladder

double gallbladder

accessory bile duct

choledochal cyst

FIGURE 5.57

Some common congenital anomalies of the

gallbladder.

204

CHAPTER 5

The Abdomen: Part II—The Abdominal Cavity

Diagnosis of Pancreatic Disease

atic enzymes that produce the signs and symptoms of acute

Because the pancreas lies behind the stomach and trans

The deep location of the pancreas sometimes gives rise to prob-

lems of diagnosis for the following reasons:

■

Pain from the pancreas is commonly referred to the back.

■

verse colon, disease of the gland can be confused with that

of the stomach or transverse colon.

■

Inflammation of the pancreas can spread to the peritoneum

forming the posterior wall of the lesser sac. This in turn can

lead to adhesions and the closing off of the lesser sac to form

a pseudocyst.

Trauma of the Pancreas

The pancreas is deeply placed within the abdomen and is well

protected by the costal margin and the anterior abdominal wall.

However, blunt trauma, such as in a sports injury when a sudden

blow to the abdomen occurs, can compress and tear the pan-

creas against the vertebral column. The pancreas is most com-

monly damaged by gunshot or stab wounds.

Damaged pancreatic tissue releases activated pancre-

peritonitis.

Cancer of the Head of the Pancreas and the Bile Duct

Because of the close relation of the head of the pancreas to

the bile duct, cancer of the head of the pancreas often causes

obstructive jaundice.

The Pancreatic Tail and Splenectomy

The presence of the tail of the pancreas in the splenicorenal

ligament sometimes results in its damage during splenectomy.

The damaged pancreas releases enzymes that start to digest

surrounding tissues, with serious consequences.

C L I N I C A L N O T E S

Development of the Pancreas

Basically, congenital fibrocystic disease in the pancreas is

Ectopic pancreatic tissue may be found in the submucosa of the

This opens on the summit

als, the two ducts join and form a common dilatation, the

through the duodenal wall, although in close contact, and open

(Fig. 5.52). In some individuals, they pass separately

wall of the second part of the duodenum to open on the summit of

duct are joined to one another. They pass obliquely through the

As seen from development, the bile duct and the main pancreatic

The inferior part of the head and the uncinate process of the

Continued growth of the entodermal cells of the now-fused

num. The proximal part of the dorsal pancreatic duct may persist

the distal part of the dorsal pancreatic duct. The main pancreatic

is derived from the entire ventral pancreatic duct and

main pan

Fusion also occurs between the ducts, so that the

the left side of the duodenum, results in the ventral bud’s coming

of the stomach and duodenum, together with the rapid growth of

A canalized duct system now develops in each bud. The rotation

bud, close to the junction of the foregut with the midgut (Fig. 5.41).

mesentery. The ventral bud arises in common with the hepatic

short distance above the ventral bud and grows into the dorsal

mal cells that arise from the foregut. The dorsal bud originates a

The pancreas develops from a dorsal and ventral bud of entoder-

into contact with the dorsal bud, and fusion occurs (Fig. 5.59).

creatic duct

duct joins the bile duct and enters the second part of the duode-

as an accessory duct, which may or may not open into the duo-

denum about 0.75 in. (2 cm) above the opening of the main duct.

ventral and dorsal pancreatic buds extends into the surround-

ing mesenchyme as columns of cells. These columns give off

side branches, which later become canalized to form collecting

ducts. Secretory acini appear at the ends of the ducts.

The pancreatic islets arise as small buds from the develop-

ing ducts. Later, these cells sever their connection with the duct

system and form isolated groups of cells that start to secrete
insulin and glucagon at about the 5th month.

pancreas are formed from the ventral pancreatic bud; the supe-

rior part of the head, the neck, the body, and the tail of the pan-

creas are formed from the dorsal pancreatic bud (Fig. 5.59).

Entrance of the Bile Duct and Pancreatic Duct

into the Duodenum

the major duodenal papilla, which is surrounded by the sphinc-
ter of Oddi

separately on the summit of the duodenal papilla. In other individu-

hepato-

pancreatic ampulla (ampulla of Vater).

of the duodenal papilla.

Anular Pancreas
In anular pancreas, the ventral pancreatic bud becomes fixed so

that, when the stomach and duodenum rotate, the ventral bud

is pulled around the right side of the duodenum to fuse with the

dorsal bud of the pancreas, thus encircling the duodenum (Fig.

5.60). This may cause obstruction of the duodenum, and vomit-

ing may start a few hours after birth. Early surgical relief of the

obstruction is necessary.

Ectopic Pancreas

stomach, duodenum, small intestine (including Meckel’s diver-

ticulum), and gallbladder, and in the spleen. It is important in that

it may protrude into the lumen of the gut and be responsible for

causing intussusception.

Congenital Fibrocystic Disease

caused by an abnormality in the secretion of mucus. The mucus

produced is excessively viscid and obstructs the pancreatic

duct, which leads to pancreatitis with subsequent fibrosis. The

condition also involves the lungs, kidneys, and liver.

E M B R Y O L O G I C N O T E S

Basic Anatomy

205

dorsal bud

region of rapid growth

ventral bud

bile duct

forms main pancreatic duct

forms accessory pancreatic duct

duodenum

FIGURE 5.59

The rotation of the duodenum and the unequal growth of the duodenal wall lead to the fusing of the ventral and

dorsal pancreatic buds.

narrowed lumen of duodenum

fixed ventral pancreatic bud

dorsal bud

dorsal pancreatic bud

duodenum

ventral pancreatic bud

FIGURE 5.60

Formation of the anular pancreas, producing duodenal obstruction. Note the narrowing of the duodenum.

splenic
vessels

splenicorenal
ligament

gastrosplenic
omentum

costodiaphragmatic

recess

diaphragm

liver

stomach

transverse colon

left lung

spleen

notched anterior
border

FIGURE 5.61

Spleen.

Shows relation of spleen to adjacent structures.

It is oval shaped and has a notched anterior border.

206

CHAPTER 5

from the celiac plexus.

The nerves accompany the splenic artery and are derived

Nerve Supply

and then drain into the celiac nodes.

a few lymph nodes along the course of the splenic artery

The lymph vessels emerge from the hilum and pass through

Lymph Drainage

form the portal vein.

creas, the splenic vein joins the superior mesenteric vein to

and the body of the pancreas. Behind the neck of the pan

The splenic vein leaves the hilum and runs behind the tail

Veins

about six branches, which enter the spleen at the hilum.

border of the pancreas. The splenic artery then divides into

artery. It has a tortuous course as it runs along the upper

The large splenic artery is the largest branch of the celiac

Arteries

ribs (Figs. 5.11 and 5.61).

phragmatic recess); left lung; and 9th, 10th, and 11th

The diaphragm; left pleura (left costodia

Posteriorly:

The Abdomen: Part II—The Abdominal Cavity

■

Blood Supply

ment prevent a direct downward enlargement of the organ.

Splenic Enlargement

A pathologically enlarged spleen extends downward and

medially. The left colic flexure and the phrenicocolic liga-

As the enlarged spleen projects below the left costal margin,

its notched anterior border can be recognized by palpation

through the anterior abdominal wall.

The spleen is situated at the beginning of the splenic vein,

and in cases of portal hypertension it often enlarges from

venous congestion.

Trauma to the Spleen

Although anatomically the spleen gives the appearance of

being well protected, automobile accidents of the crushing

or run-over type commonly produce laceration of the spleen.

Penetrating wounds of the lower left thorax can also damage

the spleen.

C L I N I C A L N O T E S

Retroperitoneal Space

two branches of the renal artery, the ureter, and the third

hilum transmits, from the front backward, the renal vein,

The

renal sinus.

hilum extends into a large cavity called the

(Fig. 5.64). The

hilum

of renal substance and is called the

each kidney is a vertical slit that is bounded by thick lips

much as 1 in. (2.5 cm). On the medial concave border of

both kidneys move downward in a vertical direction by as

With contraction of the diaphragm during respiration,

ney because of the large size of the right lobe of the liver.

The right kidney lies slightly lower than the left kid

the costal margin (Fig. 5.63).

side of the vertebral column; they are largely under cover of

toneum high up on the posterior abdominal wall on either

The kidneys are reddish brown and lie behind the peri

urethra.

The urine leaves the body in the

located within the pelvis.

urinary bladder,

to the

ureters

which passes down the

urine,

products leave the kidneys as

maintaining the acid–base balance of the blood. The waste

the water and electrolyte balance within the body and in

ucts of metabolism. They play a major role in controlling

The two kidneys function to excrete most of the waste prod

Location and Description

Urinary Tract

and gonadal blood vessels.

roperitoneal space also contains the ureters and the renal

descending parts of the colon, and the duodenum. The ret

for the suprarenal glands, the kidneys, the ascending and

variable amount of fatty connective tissue that forms a bed

a definite layer of fascia. In front of the fascial layers is a

Each of these muscles is covered on the anterior surface by

muscles and the origin of the transversus abdominis muscle.

medial to lateral by the psoas and quadratus lumborum

The floor or posterior wall of the space is formed from

the iliac crests below (Fig. 5.62).

12th thoracic vertebra and the 12th rib to the sacrum and

wall behind the parietal peritoneum. It extends from the

The retroperitoneal space lies on the posterior abdominal

Kidneys

Development of the Spleen

dorsal mesentery (Fig. 5.46). In the earliest stages, the spleen

The spleen develops as a thickening of the mesenchyme in the

consists of a number of mesenchymal masses that later fuse.

The notches along its anterior border are permanent and indi-

cate that the mesenchymal masses never completely fuse.

E M B R Y O L O G I C N O T E S

(continued)

The part of the dorsal mesentery that extends between

hypertrophy after removal of the major spleen and be respon

icorenal ligament. Their clinical importance is that they may

the hilum of the spleen and the greater curvature of the

stomach is called the gastrosplenic omentum; the part that

extends between the spleen and the left kidney on the poste-

rior abdominal wall is called the splenicorenal ligament. The

spleen is supplied by a branch of the foregut artery (celiac

artery), the splenic artery.

Supernumerary Spleen
In 10% of people, one or more supernumerary spleens may be

present, either in the gastrosplenic omentum or in the splen-

sible for a recurrence of symptoms of the disease for which

splenectomy was initially performed.