REGIONAL ANATOMYREGIONAL ANATOMY

WENZHU YAN

Department of Anatomy,liaoning Medical CollegeDepartment of Anatomy,liaoning Medical College

Chapter 6 THE ABDOMEN

Section 1 Introduction 

The abdomen is the region of the trunk between the thorax and the pelvis.

It consists of the abdominal wall, the abdominal cavity and abdominal viscera.

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Section 2 The Anterolateral Abdominal Wall

Main Contents Ⅰ.The Superficial Structures 1.The skin The skin of anterior lateral abdominal wall contained more elastic fibers. Surgeons use the skin flap with vessels for plastic surgery.

2. The superficial fascia The superficial fascia on lower abdominal wall differentiates usually into two layers. Between them are superficial vessels, nerves and lymph nodes. The superficial layer （ Camper’s fascia ） . The deep layer （ Scarpa’s fascia ）

（ 1 ） The superficial blood vessels

1 ） The superficial epigastric artery

2 ） The superficial iliac circumflex artery

3 ） The superficial veins

the thoracoepigastric vein,

the lateral thoracic vein

the superficial epigastric vein

The umbilical venous network

the paraumbilical vein

（ 2 ） The cutaneous nerves The abdominal wall is supplied segmentally by all the lower six pairs of the intercostals nerves and the first lumbar nerve.

The 7th intercostals nerve distributes the area about the level of the xiphoid process.

The 10th usually runs to the level of the umbilicus.

The first lumbar nerve distributes the area above the inguinal ligament and the pubic symphysis.

（ 3 ） The lymphatic vessels

the lymphatic vessels above the level of the

umbilicus flow into the axillary lymph nodes, the

vessels below the level of umbilicus drain into the

superficial inguinal lymph nodes. They also anastomose

with the lymphatics of the liver by the lymph vessels

within the round ligament of liver.

Ⅱ） The Deep Structures 1.The muscles

（ 1 ） The rectus

abdominis and its sheath

The Rectus abdominis is a

long strip—like muscles.

The sheath of rectus

abdominis is enclosed by

aponeuroses of the obliquus

and transverse muscles.

The sheath of rectus abdominis

（ 2 ） The obliquus externus abdominis

（ 3 ） The obliquus internus

abdominis

The inguinal falx （ conjoined

tendon ） is a common

aponeurosis joined by the

obliquus internus abdominis and

transversus abdominis.

（ 4 ） The transverses abdominis

2. The transverse fascia

It is a thin layer between the extraperitoneal fascia and transverses abdominis.

In the inguinal region it is thick.

3. The extraperitoneal fascia （ extraperitoneal fatty tissue ）

This is a loose connective tissue with fat between the transverse fascia and parietal peritoneum.

This space extends to the retroperitoneal space and the inferior peritoneal space of the pelvis.

4. The parietal peritoneum It is the inner most layer of the anterolateral abdominal wall and a part of the peritoneum actually.

Ⅲ. Clinical Notes 1.The superficial epigastric veins The superficial epigastric venous network above

the level of the umbilicus flows into axillary vein via the lateral thoracic and the thoracoepigastric veins, and below the umbilicus, it flows into the great saphenous vein.

The veins around the umbilicus flow into the portal vein through the paraumbilical vein.

These venous networks and veins belong respectively to the superior, inferior venae cavae and the portal system.

If venous flow through the liver is impeded, the portal hypertension dilates the veins of the portal system, including the paraumbilical vein which can cause varicosities of the abdominal wall （ the caput medusa ） .

2.The abdominal incisions （ 1 ） The median incision It is made through the

linea alba. It provides an almost bloodless operation, but incisional hernia and gaping of wound may occur.

（ 2 ） The paramedian incision It is placed 2.5 ～ 4.0cm lateral and parallel to the median line. The passing layers are: skin, superficial fascia, the anterior layer of the sheath of rectus abdominis, the posterior layer of the sheath of rectus abdominis,

transverse fascia, extraperitoneal fascia and

parietal peritoneum. The rectus abdominis is not incised, so the vessels, nerves and muscles are less damaged.

（ 3 ） The rectus incision The incised layers are the same as the paramedian incision but with an additional incision of rectus abdominis. The incision hurts more vessels, nerves and muscles.

（ 4 ） The McBurney’s incision The oblique skin incision centered at McBurney’s point （ two-thirds of the way laterally along the line from the umbilicus to the anterior iliac spine ） .

the obliquus internus abdominis and transversus abdominis are then split in the line of their fibers, and retreated without their having to be divided. On closing the incision, these muscles snap together again, leaving a virtually undamaged abdominal wall. It is routinely used to the appendix operation.

（ 5 ） The transverse and oblique incisions Incision cutting through the abdominal muscles do not damage their richly anastomosing nerve supply and heal without weakness. They are useful in exposing sigmoid colon or cecum, and by displacing the peritoneum medially to expose the extraperitoneal structures such as the ureter, sympathetic trunk and the external iliac vessels.

Section 3 The Inguinal Region  Ⅰ.Main Contents Ⅰ ） The Layers of the Inguinal Region The skin The superficial fascia The aponeurosis of the obliquus externus abdominis The superficial inguinal ring The lateral crus The medial crus. The intercrural fibers The external spermatic fascia The inguinal ligament The reflected ligament The lacunar ligament

2.The obliquus internus abdominis and transversus abdominis

These muscles have a free lower border, which arches over the spermatic cord.

The cremaster which surround the spermatic cord and the testis

The conjoined tendon or inguinal falx.

3.The iliohypogastric nerve and the ilioinguinal nerve

distribute to the skin of the scrotum or labia major. These two nerves also have muscular branches to distribute to this region except the cutaneous innervations

the genital branch of the genitofemoral nerve runs along the medial side of the spermatic cord and distributes to the dartos muscle and the cremaster.

4.The transverse fascia

the deep inguinal ring

the internal spermatic fascia

5.The extraperitoneal fascia

the inferior epigastric

the deep circumflex iliac

blood vessels

（ 1 ） The inferior epigastric artery

（ 2 ） The deep circumflex iliac artery

It arises from the external iliac artery at about the same level of the inferior epigastric artery. The artery runs laterally under the inguinal ligament.

6.The inguinal triangle（ Hesselbach’s trangle ） The inferior epigastric artery laterally, the lateral border of the rectus abdominis medially and the medial half of the inguinal ligament inferiorly bound an area, known as Hesselbach’s trangle.

7.The parietal peritoneum

The median umbilical fold is formed by the remains of the urachus

The two medial umbilical fold lie on either side of the median umbilical fold. These folds are formed by the obliterated distal part of the umbilical artery.

The most lateral fold on each side is the lateral umbilical fold which contains the inferior epigastric vessels.

The lateral inguinal fossa lies

laterally to the lateral umbilical

fold and corresponds to the deep

inguinal ring.

The fossa between the medial

and lateral inguinal folds is

known as the medial inguinal

fossa. Its inferomedial part is

opposite the superficial ring.

Ⅱ） The Inguinal Canal It is a oblique passage

about 4cm long, and has two openings and four walls.

1. The deep inguinal ring

It is the entrance of the inguinal canal. It lies a finger breadth above the midpoint of the inguinal ligament.

2. The superficial inguinal ring It is a triangular defect in shape of the aponeurosis of the obliquus externus abdominis.

The medial crus （ margin ） of the ring attaches to pubic towards the medial end of the pubic crest. The lateral crus of the ring attaches to the pubic crest.

3.The walls of the inguinal canal

Anterior wall : the aponeurosis of obliquus externus abdominis, and laterally is reinforced by muscle fibers of obliquus internus abdominis

Posterior wall :the reflected ligament, conjoined tendon （ inguinal falx ） and transverse fascia.

Superior wall : arched fibers of the obliquus internus abdominis and transverses abdominis.

Inferior wall : the inguinal ligament.

4. The contents of the inguinal canal

the spermatic cord in male or the round ligament in female and ilioinguinal nerve in both.

Ⅱ.Clinical Notes 1.The anatomical basis of the hernias and the

hydrocele （ 1 ） Direct and indirect inguinal hernias In the indirect （ oblique ） inguinal hernia the

abdominal contents enter the deep ring and traverse the inguinal canal to emerge from the superficial ring, they are sometimes eongenital or acquired.

But in a direct inguinal hernia the viscus protrudes immediately forward toward the superficial ring. And therefore the neck of hernia involves the wall in the region of the Hesselbach’s triangle.

（ 2 ） The hydrocele A dircted or indirect inguinal hernia is often confused with a hydrocele of tunica vaginalis of testis if it enters the scrotum and along which the abdominal organs descend.

The communicating hydrocele of testis occurs when the upper part of the vaginal process opens and communicates upwards to the abdominal cavity, sometimes, accompanying an oblique hernia. But a common hydrocele of tunica vaginalis of testis does not communicate with the abdominal cavity.

 

Section 4 The Peritoneum and Peritoneal Cavity

Ⅰ.Introduction

  The peritoneum

The parietal peritoneum

The visceral peritoneum.

The peritoneal cavity.

The greater sac,

The omental bursa or lesser sac

the neck or communication between the greater sac and the lesser sac is the omental （ epiploic ） foramen. Based on the covering of the peritoneum, the viscera in the abdominal and pelvic cavities can be divided into three kinds:

①The intra—peritoneal organs: the spleen, stomach, jejunum, ileum, cecum, transverse

colon and sigmoid colon. ②The meso—peritoneal organs: gallbladder, liver, ascending colon, uterus and urinary

bladder.

③The extra—peritoneal organs: The viscera are covered by peritoneum only on their one aspect,

such as pancreas, ureter, kidney, suprarenal gland, and the descending and transverse parts of the duodenum.Such organs lie posterior to the peritoneum, known as retroperitoneal position.

 

Ⅱ.Main Contents The omental （ epiploic ） foramen （ the foramen

of Winslow ） Its anterior wall is formed by the right margin of the

lesser omentum, which contains between its two layers in this situation the bile duct, the hepatic portal vein and the proper hepatic artery.

The inferior vena cava lies behind the omental foramen.

The caudate process of the liver forms the roof of the omental foramen.

The upper border of the superior part of the duodenum is the inferior wall of the omental foramen.

Section 5 The Supracolic compartment  Main Contents  Ⅰ ） The Stomach 1. Divisions the cardiac part the fundus of stomach the body of stomach the pyloric part.

2. Position and relation

Position

the left hypochondriac and the epigastric regions.

The cardiac orifice lies on the left side of the 11th thoracic vertebra and the pylorus on the right side of the 1st lumbar vertebra

relation Its anterior surface is

behind the left lobe of the liver, the diaphragm and the anterior abdominal wall.

Its posterior surface is separated by the omental bursa from a number of structures. These form the“stomach bed”.

They are the diaphragm, spleen, pancreas, left kidney, left suprarenal gland, the transverse colon and its mesocolon.

3. The ligaments of the stomach

the hepatogastric ligament.

the greater omentum the

gastrosplenic （ gastrolienal ） ligament the gastrophrenic ligament

（ 1 ） The arteries The arteries of the stomach are derived from the celiac trunk.

1 ） The left gastric artery and right gastric artery

The point between the left first branch and second branch of the left gastric artery of the stomach is a landmark of incision of the stomach in the gastrectomy.

4. The blood vessels, lymphatic drainage and nerves

2 ） The right and left gastroepiploic arteries

3 ） The short gastric arteries

4 ） The posterior gastric artery In recent reports, it is found in about 60 ～ 80 ％ of cases.

It arises from the splenic artery and supplies the posterior upper part of the stomach where the gastrophrenic ligament attaches.

In operation, it should be protected from damage. This artery gives nutrition to the remnant of the stomach after subtotal gastrectomy.

（ 2 ） The veins

The right and left gastric

the right gastroepiploic vein.

The left gastroepiploic and the short gastric veins.

1 ） The right and left gastric lymph nodes

2 ） The suprapyloric and subpyloric lymph nodes

3 ） The right and left gastroepiploic lymph nodes

4 ） The splenic lymph nodes

（ 3 ） The lymphatic drainage

（ 4 ） The nerves The sympathetic nerve

comes from the celiac ganglia which gives rise to postganglionic fibers that accompany the arteries to the stomach.

The parasympathetic nerve is derived from branches of the anterior and posterior vagal trunks.

The anterior vagal trunk, derived mainly from the left vagus nerve. it gives off hepatic and duodenal branches that leave the stomach within the hepatoduodenal ligament.

The rest of anterior vagal trunk continues along the lesser curvature of the stomach, giving rise to anterior gastric branches supplying the anterior surface of the stomach.

“crow’s foot” to supply the pyloric antrum and the anterior wall of the pyloric canal.

The posterior vagal trunk, derived mainly from the right vagus nerve

The posterior vagal trunk gives off a celiac branch

The posterior gastric branches

“crow’s foot” which supply the pyloric antrum and the posterior wall of the pyloric canal.

Ⅱ） The Duodenum

1. Position and shape

The duodenum is continuous proximally with the pylorus of the stomach, and distally with the duodenojejunal junction.

It is is related to the upper three lumbar vertebrae and the head of the pancreas.

2. Divisions and relations （ 1 ） The superior part Its relations are: posteriorly, the inferior vena

cava, common bile duct, hepatic portal vein and gastroduodenal artery;

anteriorly, the quadrate lobe of the liver and gallbladder;

superiorly, the neck of the gallbladder and lesser omentum;

inferiorly, the pancreas.

（ 2 ） The descending part

The common bile duct and pancreatic duct pierce the posteromedial wall obliquely just below the middle of the descending part.

the major duodenal papilla,

the minor duodenal papilla.

Its relations include: posteriorly, the right kidney, right renal vessels and the right ureter; anteriorly, the transverse colon and its mesocolon; medially, the pancreas, pancreatic duct and common bile duct; laterally, the ascending colon.

（ 3 ） The horizontal part It is about 10 ～ 12cm long and passes transversely to the left of the third lumbar vertebra.. It is retroperitioneal.

Its relations are: posteriorly, the inferior vena cava, abdominal aorta and right ureter; anteriorly the supeior mesenteric vessels and the root of the mesentery; superiorly, the head of the pancreas. Tight stretching of the superior mesenteric artery over this part of duodenum is considered responsible for certain duodenal obstructions.

（ 4 ） The ascending part

It runs upwards, slightly to the left of the abdominal aorta to the level of the second lumbar vertebra where it terminates by bending abruptly forwards and to the right as the duodenojejunal flexure, which is fixed to the right crus of the diaphragm by the suspensory ligament of duodenum. It is the landmark for the origin of the jejunum during operation.

3. The blood vessels, lymphatic drainage and nerves

（ 1 ） The arteries The principal blood supply is from the two arcades formed by the superior and inferior pancreaticoduodenal arteries.

The superior pancreaticoduodenal artery. The inferior pancreaticoduodenal artery .

Ⅲ） The Liver

Position

There are “H” shaped deep grooves on the visceral surface: the left longitudinal groove contains the ligamentum teres （ anteriorly ） and the ligamentum venosum （ posteriorly ） ; the right longitudinal groove is the fossa for gallbladder and the sulcus for vena cava.

The cross-bar of the “H” is the porta hepatis （ or the first porta hepatis ）

The porta hepatis and hepatic pedicle

The second porta hepatis

In the superior margin of the sulcus for vena cava on the diaphragmatic surface of the liver lies the second porta hepatis where the right, left and intermediate hepatic veins leave the liver and enter the inferior vena cava.

The third porta hepatis

In the inferior part of the sulcus for vena cava

where the inferior vena cava receives several small

veins （ the short hepatic veins ） from the visceral

surface of the right half and the caudate lobe of the

live is the third porta hepatis.

The hepatic pedicle The structures entering or leaving the （ first ） porta hepatis are bounded together by the connective tissue in the free border of the hepatoduodenal ligament, at the anterior margin of the omental foramen. Where these structures form the hepatic pedicle.

At this level the common bile duct lies anteriorly and to the right, while the proper hepatic artery lies anteriorly just to the left of the common bile duct; the hepatic portal vein lies behind them.

Close to the （ first ） porta hepatis the proper hepatic artery, hepatic portal vein and common bile duct are each represented by two branches, a right and a left.

The right and left hepatic ducts lie anteriorly, the

right and left arterial branches lie in the middle, while

the right and left branches of the hepatic portal vein lie

posteriorly. The relations of these structures to each

other and to the cystic duct, and the variations which

may occur here are of great surgical importance.

4.The lobes and segmentations

the liver is divided into a right lobe, a quadrate lobe, a left lobe and a caudate lobe by the right and left longitudinal grooves and the porta hepatis, the quadrate lobe is anterior to the porta hepatis and the caudate lobe is posterior to the porta hepatis.

The segments of the liver The common hepatic duct, hepatic portal vein and hepatic artery divide into right and left branches to the right and left halves of the liver. These branches further split into smaller branches to form the Glisson’s system.

On the basis of the Glisson’s system, the liver is divided into two halves, five lobes and eight segments.

Two halves of the liver are the right and left halves.

Five lobes are: the right half includes the right anterior lobe and the right posterior lobe, the left half is consist of the left lateral lobe, the left medial lobe, and the caudate lobe.

Eight segments are

the caudate lobe （Ⅰ） ,the superior and inferior segments of the left lateral lobe （Ⅱ and Ⅲ） ,the left medial lobe （Ⅳ） ,the superior and inferior segments of the right anterior lobe （Ⅷ and Ⅴ） ,and the superior and inferior segments of the right posterior lobe （Ⅶ and Ⅵ） .

the extrahepatic bile ductsⅣ)

the pancreasⅤ)

the spleenⅥ)

section 6 the infracolic compartment

1.Verniform appendix

2.The hepatic portal vein

Section7 The retroperitoneal space

1.kidney

relation

Renal capsule

The ureter

Thank youThank you for your attention!for your attention!

Department of Anatomy,liaoning Medical CollegeDepartment of Anatomy,liaoning Medical College