Anterior Abdominal Wall & Inguinal Region Flashcards
What is the definition of the anterior abdominal wall?
A musculomembranous layer that allows movement, protection and stability of the trunk
What are the layers that make up the anterolateral abdominal wall?
From superficial to deep:
- skin
- subcutaneous tissue (fatty)
- muscle layers
- peritoneum
Why does there tend to be more blood lost during surgery in obese patients?
They have more subcutaneous fat
fat requires a blood supply, so there are more blood vessels present supplying the fat
What are the two layers of subcutaneous tissue in the anterolateral abdominal wall?
- Camper fascia
This is a superficial fatty layer of subcutaneous tissue
- Scarpa fascia
This is a deep membranous layer of subcutaneous tissue
What are the 3 muscle layers that form the anterolateral abdominal wall?
- external oblique
- internal oblique
- transversus abdominis
What are the 3 fascia that separate the muscles of the anterolateral abdominal wall?
- superficial fascia
- intermediate fascia
- deep fascia
- transversalis fascia
(after transversus abdominis)
What immediately follows the transversalis fascia?
Extraperitoneal fat followed by parietal peritoneum
By which muscles are the 3 paired muscles of the anterolateral abdominal wall supported by?
- rectus abdominis
2. quadratus lumborum
What is the linea alba?
The region where the aponeuroses from either side of the body interdigitate in the midline
In which direction do the fibres of the external oblique muscles run?
Forwards and downwards
hands in pockets
How is the right external oblique attached to the left external oblique?
Why does it attach in this way?
They are attached through the external oblique aponeurosis
There is no bone in the midline for a tendon to attach on to
How is the external oblique aponeurosis formed?
How would it be described?
A flattened tendinous sheet formed by the left and right external oblique coming towards the midline and interdigitating
What is the fibre orientation of the internal oblique muscles?
Opposite to the external oblique
Upwards and backwards
How is the internal oblique aponeurosis formed?
From the right and left internal oblique muscles coming towards the midline and interdigitating
In which direction do the fibres of the transversus abdominis muscle run?
Do they have an aponeurosis?
In the transverse plane
They have an aponeurosis which forms in the midline
How are the muscles of the anterolateral abdominal wall involved in movement?
They are involved in movement of the trunk through lateral rotation and flexion
How do the muscles of the anterolateral body wall help to keep the body upright?
When they contract, they help to keep the vertebral wall upright as they work alongside muscles in the posterior abdominal wall
What are the other 2 functions of the muscles of the anterolateral abdominal wall?
- they provide some kind of protection to the abdominal viscera
- they act to increase intraabdominal pressure which helps to expel things
(e. g. vomiting and defecation)
Where does the rectus abdominis muscle run from?
It runs from the costal margin down towards the pubic tubercle
There is one on either side
What is present between the muscle bellies of the rectus abdominis muscles?
tendinous intersections
What is the role of the rectus abdominis muscle?
Mainly movement and flexion of the trunk
It is also involved in forced expiration and increasing intra-abdominal pressure
What is the role of the quadratus lumborum muscle?
It works with the anterior muscles to keep the body upright and maintain the posture
Where is the internal thoracic artery found?
It lies on either side of the sternum
What are the 2 branches of the internal thoracic artery and what do they supply?
- musculophrenic artery goes towards the muscles and part of the diaphragm
- superior epigastric artery supplies the superior region of the abdominal wall
What happens to the superior epigastric artery on the anterior abdominal wall?
It forms an anastomosis with the inferior epigastric artery
What is an anastomosis of 2 arteries?
2 arteries are coming from different regions to supply the same area
Where does the inferior epigastric artery arise from?
femoral artery
What other vessels does the femoral artery give rise to?
superficial epigastric artery
deep circumflex arteries
What does the inferior epigastric artery give rise to?
the external iliac artery
As well as the superior epigastric artery, what other arteries supply the anterior abdominal wall?
- posterior intercostal arteries
2. subcostal arteries
What is significant about the anastomosis between the superior and inferior epigastric arteries?
It is significant in collateral circulation
This develops due to coarctation of the aorta
What happens as intercostal nerves continue onto the abdominal wall?
Where are they found?
They become thoracoabdominal nerves
They run between the internal oblique and transversus abdominis muscles
What 3 structures do the thoracoabdominal nerves supply?
What type of nervous supply is this?
- skin overlying abdominal muscles (somatic sensory)
- muscles of the abdominal wall (somatic motor)
- parietal peritoneum (somatic sensory)
Where is the subcostal nerve found?
What is significant about it?
Underneath the 12th rib
It also supplies some of the anterior abdominal wall
What other 2 nerves contribute to the supply of the anterior abdominal wall?
At which vertebral level do they originate?
- iliohypogastric nerve
- ilio-inguinal nerve
Originate at vertebral level L1
What are the 2 branches of the thoracoabdominal nerves and from which vertebral level do they originate?
anterior cutaneous branches and lateral cutaneous branches
Thoracoabdominal nerves originate from vertebral levels T7 - T11
What are the 2 branches of the subcostal nerve and at which vertebral level is it found?
lateral cutaneous branch and anterior cutaneous branch
Found at vertebral level T12
What is the rectus sheath formed from?
The aponeuroses of the three anterolateral muscles
What is the rectus sheath and what does it contain?
It is a fibrous compartment containing:
- rectus abdominis
- epigastric arteries
- tips of the thoracoabdominal nerves
Why is there no tendinous attachment (bone) found in the midline?
There needs to be space for expansion of the abdomen after eating and during pregnancy
A bone would make it more difficult to change the intra-abdominal pressure
Why is a new mother more susceptible to a hernia?
The linea alba expands during pregnancy
The aponeuroses have been stretched leading to potential weakening in the anterior abdominal wall
What is significant about the rectus sheath above and below the level of the umbilicus?
It has a different arrangement above and below the level of the umbilicus
What is the arrangement of the rectus sheath below the level of the umbilicus?
the external oblique aponeurosis, internal oblique aponeurosis and transversus abdominis run anterior to the rectus abdominis
the peritoneum runs posterior to the rectus abdominis
Why are hernias more prevalent below the level of the umbilicus?
The configuration of the rectus sheath makes it weaker
an increase in intra-abdominal pressure will cause organs to move into the weaker area
What is the arrangement of the rectus sheath above the level of the umbilicus?
the external oblique aponeurosis and anterior layer of the internal oblique aponeurosis run anterior to the rectus abdominis
the posterior layer of the internal oblique aponeurosis, transversus abdominis and peritoneum run posterior to the rectus abdominis
What is shown by the arcuate line?
The change in the aponeuroses above and below the level of the umbilicus
What are ligaments?
Structures covered with a small amount of peritoneum
Where is the lateral umbilical ligament found?
Overlying the inferior epigastric artery and its accompanying veins
What is the medial umbilical ligament formed from?
the remnants of the foetal umbilical artery
What is the median umbilical ligament formed from?
the remnants of the foetal urachus
Why is the muscle belly of the rectus abdominis visible below the level of the umbilicus?
Due to the arrangement of the aponeuroses
What is the inguinal region and where does it extend from?
It is an area of the abdominal wall that extends from the anterior superior iliac spine (ASIS) to the pubic tubercle
It is referred to as the ‘groin region’
What is the difference in structures found in the inguinal canal in the male and female?
The inguinal canal contains the spermatic cord in the male and the round ligament of the uterus in the female
What is the inguinal canal?
What is its purpose?
A weakening in the abdominal wall where structures pass out of the abdomen
It serves as a pathway by which structures can pass from the abdominal wall to external genitalia
How is the inguinal ligament formed?
The free edge of the external oblique aponeurosis folds back on itself leading to a thickening of the inferior edge
Where does the inguinal ligament run from?
What does it form?
It runs from the ASIS to the pubic tubercle to form the base of the inguinal canal
Where does the inguinal canal run from and to?
How long is it?
It is around 4 cm long
It is the connection between the deep inguinal ring and the superficial inguinal ring
Where is the superior inguinal ring located?
Adjacent to the pubic tubercle
It is an opening in the external oblique aponeurosis
What structure is formed from the arching fibres of the internal oblique and transversus abdominis muscles?
The conjoint tendon is formed by the 2 sets of arching fibres joining together
what is the role of the conjoint tendon?
It arches over the inguinal canal to form the roof
It attaches to the pubic crest and strengthens the wall of the inguinal canal
What does the spermatic cord consist of?
- ductus deferens
- artery of ductus deferens
- testicular artery
- cremasteric artery
- pampiniform venous plexus
- sympathetic nerve fibres
- genital branch of genitofemoral nerve
- lymphatic vessels
Why is the opening of the inguinal canal larger in males than females?
What is the danger of this?
There are more structures that are passing through the inguinal canal
There is a greater chance of things passing through the canal which shouldn’t
What type of hernia is much more prominent in males than in females?
indirect hernia
Where does protrusion occur in a direct inguinal hernia?
At the level of the superficial ring
Intestines/abdominal contents pass directly through the weakening in the superficial inguinal ring
What is the hernial sac limited by in a direct inguinal hernia?
What does this mean?
the peritoneum and transversalis fascia
as all the structures are covered in peritoneum, they can be pushed back into the correct place
Which area does a direct (acquired) hernia not enter?
The hernia does not usually enter the scrotum
In an indirect hernia, at what level does protrusion occur?
At the level of the deep ring
Abdominal structures first go through the deep ring, then in the inguinal canal, and come out through the superficial ring
Where do abdominal contents leave the abdomen in a direct inguinal hernia?
medial to the inferior epigastric vessels
Where do abdominal contents leave the abdomen in an indirect inguinal hernia?
How can the hernia enter the scrotum?
lateral to the inferior epigastric vessels
they then traverse the canal and can enter the scrotum via the superficial ring
Why are males more susceptible to indirect (congenital) inguinal hernias?
They have a larger inguinal canal and more structures pass through
What type of indirect inguinal hernia may occur in young males and why?
An abdominal organ can protrude into a patent processus vaginalis extending into the inguinal canal
This opening usually closes off
