Session 1: The Anterior abdominal Wall and Peritoneal Cavity

Question 1

What does the diaphragm separate?

Answer 1

It separates the abdominal cavity from the thorax

Question 2

What does the diaphragm contain?

Answer 2

apertures that allow structures to pass between the thorax and abdomen.

Question 3

What is inferior to the abdominal cavity?

Answer 3

The pelvic cavity and it is also continuous with it.

Question 4

What does the abdominal cavity contain?

Answer 4

organs of the GI tract (stomach, small and large intestine)
the hepatobiliary system (liver and gallbladder)
the urinary system (kidneys and ureters)
the endocrine system (pancreas and adrenal glands)

The abdomen also contains the spleen (a haematopoietic and lymphoid organ) and of course the great vessels (abdominal aorta and inferior vena cava) and their branches.

Question 5

What is the abdominal wall composed of?

Answer 5

composed of skin, subcutaneous tissue and muscles and their associated aponeuroses (flat tendons).

Five lumbar vertebrae contribute to the posterior wall

Question 6

What is the function of the abdominal wall?

Answer 6

protect the abdominal viscera
* increase intra-abdominal pressure (e.g. for defecation and childbirth)
* maintain posture and move the trunk

Question 7

What is the abdominal wall lined with?

Answer 7

a serous membrane called parietal peritoneum

Question 8

What are the bony landmarks of the abdominal cavity?

Answer 8

Xiphisternum
* Costal margin
* Iliac crests
* Anterior superior iliac spines (ASIS)
* Pubic tubercles
* Pubic symphysis (a fibrocartilaginous joint).

Question 9

What are the four quadrants?

Answer 9

Right upper quadrant
Left upper quadrant
Right lower quadrant
Left lower quadrant

Question 10

Which lines divide the quadrants?

Answer 10

• a vertical line that runs down the midline through the lower sternum, umbilicus, and the pubic symphysis
• a horizontal line that runs across the abdomen through the umbilicus.

Question 11

What are the nine regions?

Answer 11

the anterior abdominal wall can also be divided into nine regions
Smaller so more precise

Question 12

Name the nine regions

Answer 12

Right hypochondrium
Epigastrium
Left hypochondrium
Right flank
Umbilical region
Left flank
Right iliac fossa
Suprapubic region
Left iliac fossa

Question 13

Which lines divide the nine regions?

Answer 13

four imaginary lines:
* the right and left midclavicular lines,
* the subcostal line
* the intertubercular line

Question 14

What other landmarks are associated with the abdominal Wall?

Answer 14

Transpyloric plane:

Transumbilical plane:

Intercristal plane:
McBurney’s point:

Question 15

What muscles comprise the anterolateral abdominal wall?

Answer 15

External oblique (diagonally orientated fibres)
* Internal oblique (diagonally orientated fibres)
* Transversus abdominis (horizontally orientated fibres)
* Rectus abdominis (rectus = straight).

Question 16

What is the rectus abdominis attached to?

Answer 16

The vertical right and left rectus abdominis muscles lie either side of the midline.

Rectus abdominis is attached to the sternum and costal margin superiorly and to the pubis inferiorly and is surrounded by an aponeurotic rectus sheath

Question 17

In which direction do the muscles run?

Answer 17

• External oblique (EO) is most superficial. The fibres of EO run medially and inferiorly, towards the midline.
• Internal oblique (IO) lies deep to EO. The fibres of IO are orientated perpendicular to those of EO (they run medially and superiorly).
• Transversus abdominis lies deep to internal oblique. Its fibres are orientated horizontally.

Question 18

How do the muscles act?

Answer 18

When these muscles contract together, they increase intra-abdominal pressure. Alone, the oblique muscles act as lateral flexors of the lumbar spine.

Question 19

What do these muscles become?

Answer 19

Anteriorly, these muscles become aponeurotic (an aponeurosis is a flat tendon).

Question 20

What forms the rectus sheath?

Answer 20

Rectus abdominis lies within the rectus sheath. The anterior and posterior walls of the rectus sheath are formed by the aponeuroses of EO, IO and transversus abdominis.

Question 21

How is the inguinal ligament formed?

Answer 21

The most inferior part of the external oblique aponeurosis is attached to the anterior superior iliac spine laterally and the pubic tubercle medially, forming the inguinal ligament. Just above the inguinal ligament is the inguinal canal

Question 22

What vessels supply the abdominal wall?

Answer 22

• musculophrenic artery
• superior epigastric artery
• inferior epigastric artery,

Question 23

What is the abdominal wall innervated by?

Answer 23

Thoraco-abdominal nerves T7 – T11.
- continuation of the intercostal nerves T7 – T11. These somatic nerves contain sensory and motor fibres.

Question 24

What is the inguinal canal?

Answer 24

an oblique passageway through the muscles of the anterior abdominal wall and lies superior to the medial half of the inguinal ligament. It passes through each layer of the abdominal wall as it travels medially and inferiorly.

Question 25

What are the borders of the inguinal canal?

Answer 25

Anterior border:
● External oblique aponeurosis
● Laterally only: internal oblique aponeurosis

Posterior border:
● Transversalis fascia
● Medially only: medial fibres of the aponeuroses of the internal oblique and transversus abdominis (which are together known as the conjoint tendon).

Roof:
● Transversalis fascia
● Arching fibres of the internal oblique and transversus abdominis.

Floor:
● Inguinal ligament (the lower border of the external oblique aponeurosis).

The contents of the inguinal canal are different between males and females.

Question 26

What is an abdominal wall hernia?

Answer 26

A hernia is an abnormal protrusion of tissues or organs from one region into another through an opening or defect. Herniae of the anterior abdominal wall may occur if the muscles are weak or have been incised during surgery. A segment of the small intestine may protrude through a defect in the wall, forming a visible and palpable lump under the skin.

Question 27

What is a laparotomy?

Answer 27

the surgical opening of the anterior abdominal wall, undertaken for major operations where good access to the abdomen is needed.

Question 28

What is an abdominal aortic aneurysm?

Answer 28

Abdominal aortic aneurysm (AAA or triple A)
This is an abnormal swelling of the wall of the aorta.
The affected portion of the wall becomes distended, but it is weak and prone to rupture.

Question 29

What is an inguinal hernia?

Answer 29

An inguinal hernia is a protrusion of abdominal contents (normally part of the greater omentum or loops of small intestine) through the anterior abdominal wall into the inguinal canal. Inguinal hernias are indirect or direct.

Question 30

What is the peritoneum?

Answer 30

Peritoneum is a serous membrane that lines the abdominal wall and covers the viscera within it.
Parietal peritoneum lines the abdominal wall.
* It can be seen with the naked eye and is innervated by the somatic nerves that supply the overlying muscles and skin of the abdominal wall.
* Pain from the parietal peritoneum is usually sharp, severe, and well localised to the abdominal wall.

Question 31

What is visceral peritoneum?

Answer 31

Visceral peritoneum covers the abdominal viscera.
* It is adhered to the surface of the viscera and cannot be seen with the naked eye.
* The visceral peritoneum is innervated by visceral sensory nerves. These nerves convey ‘painful’ sensations back to the CNS along the path of the sympathetic nerves that innervate the organ / structure it covers.
* Pain from the visceral peritoneum can be severe. It is usually dull and diffuse (i.e. it cannot be pinpointed to a specific location).
* ‘Painful’ sensations from the visceral peritoneum may be perceived as nausea or distension.

Question 32

What lies between the peritoneum?

Answer 32

Between the parietal and visceral peritoneum lies the peritoneal cavity. In a healthy abdomen, a thin film of peritoneal fluid lies in the peritoneal cavity. It allows the viscera to slide freely alongside each other.

The two layers of peritoneum are continuous with each other. The arrangement of the two layers mirrors the arrangement of the parietal and visceral pleurae.

Question 33

How are the abdominal viscera described?

Answer 33

Depending on the extent to which they are covered by peritoneum, the abdominal viscera are described as:

• Intraperitoneal: almost completely covered by peritoneum e.g. the stomach
• Retroperitoneal: posterior to the peritoneum, hence only covered by peritoneum on their anterior surface e.g. the pancreas and abdominal aorta.

Some retroperitoneal organs are described as ‘secondarily retroperitoneal’. These organs were intraperitoneal in early development but came to be ‘stuck down’ onto the posterior abdominal wall.

Question 34

What are mesenteries?

Answer 34

Mesenteries are folds of peritoneum that contain fat and suspend the small intestine and parts of the large intestine from the posterior abdominal wall. Arteries that supply the intestine (from the abdominal aorta) and veins that drain the gut (tributaries of the portal venous system) are embedded in the mesenteries.

Question 35

What are the greater and lesser omentum?

Answer 35

The greater and lesser omenta are folds of peritoneum that are usually fatty and connect the stomach to other organs.
* The greater omentum hangs from the greater curvature of the stomach and lies superficial to the small intestine.
* The lesser omentum connects the stomach and duodenum (the first part of the small intestine) to the liver. The hepatic artery, the hepatic portal vein, and the bile duct (the ‘portal triad’) are embedded within its free edge.

Question 36

What are ligaments?

Answer 36

Ligaments are folds of peritoneum that connect organs to each other or to the abdominal wall. Some peritoneal ligaments that we will come across later are the:
* falciform ligament, which connects the anterior surface of the liver to the anterior abdominal wall
* the coronary and triangular ligaments, which connect the superior surface of the liver to the diaphragm.

Question 37

What are peritoneal folds?

Answer 37

Peritoneal folds are raised from the internal aspect of the lower abdominal wall and are created by the structures they overlie, like carpet running over a cable. Sometimes they are difficult to see.

Question 38

What are the umbilical folds?

Answer 38

The median umbilical fold lies in the midline and represents the remnant of the urachus, an embryological structure that connects the bladder to the umbilicus.
* Lateral to the median umbilical fold lie the medial umbilical folds. These represent the remnants of the paired umbilical arteries, which returned venous blood to the placenta in foetal life.
* Lateral to the medial umbilical folds are the lateral umbilical folds. The inferior epigastric arteries lie deep to these peritoneal folds. They supply the anterior abdominal wall.

Question 39

What is the peritoneal cavity divided into?

Answer 39

The peritoneal cavity is divided into two regions of unequal size.
* The smaller lesser sac (also called the omental bursa) is a space that lies posterior to the stomach and anterior to the pancreas.
* The larger greater sac is the remaining part of the peritoneal cavity.
* The greater and lesser sacs communicate with each other via a passageway that lies posterior to the free edge of the lesser omentum, the epiploic foramen (also called the omental foramen).

Question 40

How does the viscera of the abdominal cavity develop?

Answer 40

The viscera of the abdominal cavity do not develop in the locations that we see them in the adult. The gastrointestinal system develops from the embryonic gut tube which lies in the midline of the abdominal cavity, suspended from the posterior abdominal wall by the dorsal mesentery. Major branches of the abdominal aorta that supply the developing gut tube travel through the dorsal mesentery. The ventral mesentery connects the stomach to the anterior abdominal wall. As the liver grows within it, the anterior part of the ventral mesentery becomes the falciform ligament and the posterior part becomes the lesser omentum.

During development, organs grow, migrate, and rotate towards their final positions. As they do so, they ‘pull’ their peritoneal attachments with them. Growth, migration, and rotation of organs during development is responsible for the formation of the lesser sac and results in some organs being ‘pushed’ onto the posterior abdominal wall and becoming retroperitoneal.

Question 41

What is peritonitis?

Answer 41

Peritonitis describes infection and inflammation of the peritoneum. It may be localised (i.e. to the region of peritoneum adjacent to an inflamed / infected organ) or generalised (affecting the whole peritoneum). Peritonitis may be caused by inflammation of an organ (e.g. the pancreas) or rupture of a hollow viscus (e.g. the stomach or bowel). Rupture of the intestine allows faecal matter and bacteria to contaminate the peritoneum. Because the peritoneum has a large surface area and is semi-permeable, peritonitis can lead to sepsis and is hence a life-threatening condition. Peritonitis is extremely painful.

Question 42

What are peritoneal adhesions?

Answer 42

In a healthy abdomen, a thin layer of peritoneal fluid allows the abdominal viscera to slide freely alongside each other. Adhesions are pathological fibrous connections between the parietal and visceral peritoneum. When the peritoneum is irritated (e.g. by infection) it produces fibrin which causes the parietal and visceral peritoneum to adhere to each other. These connections may become fibrous. They can cause chronic abdominal pain and they increase the risk of volvulus (twisting) of the intestine, because it can no longer move freely.

Question 43

What are ascites?

Answer 43

Ascites is an increased volume of peritoneal fluid. It occurs secondary to other pathology, such heart failure, liver failure or intra-abdominal malignancy. The abdomen may become very distended, and it is very uncomfortable. An ascitic drain can be used to remove the fluid and relieve symptoms, but fluid will usually reaccumulate.

Question 44

How can an aneurysm be detected?

Answer 44

An aneurysm may be detected on abdominal examination, felt as a pulsatile mass in the midline of the abdomen. Examination of the abdomen must always include palpitation of the aorta, as detection can be lifesaving. Sudden rupture of an AAA carries an extremely high mortality rate.

Question 45

What occurs in a laparotomy?

Answer 45

A midline sagittal incision of the linea alba involves minimal risk to nerves and muscles. Ideally, muscles are split, rather than cut.

Where possible, keyhole surgery (laparoscopy) is performed, as it is associated with less post-operative pain, faster wound healing and a smaller risk of wound infection and post-operative hernia.

Question 46

What do the muscles form?

Answer 46

The fibres of the aponeuroses fuse with each other, forming a tough midline raphe (= seam) called the linea alba (‘white line’).

The aponeuroses of these muscles also form the rectus sheath, which encloses the rectus abdominis.

Question 47

What forms the six pack?

Answer 47

• It is composed of muscle segments interspersed with horizontal tendinous bands.

When the muscle segments hypertrophy with exercise, they bulge either side of the tendinous bands and can be seen on the anterior abdominal wall as bulges – the ‘six-pack’.

Question 48

What is the rectus abdominis like?

Answer 48

The right and left rectus abdominis muscles lie either side of the linea alba.

Rectus abdominis is a flexor of the lumbar spine.

Question 49

Which nerves specifically innervate the abdomen ?

Answer 49

● The subcostal nerve – this originates from the T12 spinal nerve (so called because it runs along the inferior border of the 12th rib).
● Iliohypogastric and ilioinguinal nerves – both are branches of the L1 spinal nerve.

Question 50

What is the inguinal canal like?

Answer 50

The canal is about five centimetres long in the adult. It extends from the deep inguinal ring laterally (an aperture in the transversalis fascia) to the superficial inguinal ring medially (an aperture in the external oblique aponeurosis).

Question 51

What is an indirect inguinal hernia?

Answer 51

In an indirect inguinal hernia, intra-abdominal contents are forced through the deep inguinal ring and into the canal.

The abdominal contents may even be forced along the canal and through the superficial ring. From here, the hernia may extend into the scrotum in males or into the labia majora in females.

Question 52

What is a direct inguinal hernia?

Answer 52

In a direct inguinal hernia, intra-abdominal contents are forced through the posterior wall of the inguinal canal (i.e. the relatively weak transversalis fascia) and directly through the superficial ring.

The herniated abdominal contents do not pass through the deep inguinal ring in direct inguinal hernias. Although they are less common than indirect hernias, direct inguinal hernias are often easier to reduce.

Question 53

When does a hernia become a surgical
Emergency?

Answer 53

Indirect hernias are more common than direct hernias. They are more likely to get stuck in the canal and become ‘irreducible’. Potentially, herniated tissue can ‘strangulate’ and become ischaemic. This is a surgical emergency.

Question 54

What is the superior epigastric artery a branch of?

Answer 54

continuation of the internal thoracic artery
- descends in the rectus sheath

Question 55

What is the mesenteric artery a branch of?

Answer 55

branch of the internal thoracic

Question 56

What is the inferior epigastroc artery a branch of?

Answer 56

branch of the external iliac artery. It ascends in the rectus sheath and anastomoses with the superior epigastric.

Question 57

What are the arteries that supply the abdominal wall accomplices by?

Answer 57

These vessels are accompanied by deep veins. An extensive network of superficial veins is found in the anterolateral abdominal wall.