Anterolateral Abdominal Wall Flashcards
Borders of the abdominal cavity?
Superiorly - extends into the thoracic cage at the 4th intercostal space
Inferiorly - runs continuously with the pelvic cavity, although it is arbitrarily separated at the plane of the pelvic inlet
Contents?
Contains digestive organs and part of the urogenital system (e.g. kidney, ureters and spleen.
The abdomen can be subdivided into nine regions by planes. What are these planes?
There are two saggital (vertical) planes and two transverse (horizontal planes).
Sagittal - extend for the mid-clavicular point to the mid-inguinal point (mid-way between the ASIS and pubic tubercle).
Transverse - the two transverse planes are commonly seen as:
1) sub-costal plane (between inferior border of the 10th costal cartilages)
2) trans-tubercular plane (between iliac tubercles, at the level of L5).
The transverse planes can also be seen as the transpyloric plane and interspinous plane.
1) transpyloric plane - located halfway between the superior border of the manubrium and the pubic symphysis, at the level of L1.
2) interspinous plane - ASIS on each side.
The abdomen can also be subdived into quadrants by two planes. What are these?
1) Transverse transumbilical plane
2) Vertical median plane
What are the 9 subdivisions of the abdomen?
Right upper - Right hypochondrium
Middle upper - Epigastric
Left upper - Left hypochondrium
Right middle - Right flank
Middle - Umbilical
Left middle - Left flank
Right lower - Right inguinal
Middle lower - Pubic
Left lower - Left inguinal
Boundaries of the anterolateral wall?
Superiorly - costal cartilages of ribs 7-10 and the xiphisternum
Inferiorly - inguinal ligament
Fascia of the anterolateral wall?
The subcutaneous tissue of this wall is susceptible of the lower anterior abdominal wall. In morbid obesity it can be many inches thick.
Above the umbilicus is a single sheet of connective tissue that runs continuous with other superficial fascia in different parts of the body.
There are three types of fascia below the umbilicus (from superficial to deep):
1) Superificial fatty subcutaneous layer (Camper’s fascia)
2) Deep membranous layer of subcutaneous tissue (Scarpa’s fascia). This fascia continues inferiorly into the perineal area as Colle’s fascia but not into the thighs.
3) Superficial, intermediate and deep investing fascia that is located between the obliques and transverse abdominis.
How many muscles are there in anterolateral wall of the abdomen?
5.
There are 3 flat muscles and 2 vertical muscles.
What are the flat muscles?
Function?
1) External oblique
2) Internal oblique
3) Transverse abdominis
They function to strengthen the wall of the abdomen to prevent organs from herniating.
In the anteromedial aspect of the abdominal wall, each flat muscles form an aponeurosis which covers the vertical rectus abdominis muscles and become intertwined in the middle to form a structure called the linea alba. The linea alba extends from the xiphisternum to the pubic symphysis.
External oblique
Origin - ribs 5-12
Insertion - iliac crest and pubic tubercle
Action - contralateral rotation of the torso
Innervation - thoracoabdominal nerves (T7-T12) and subcostal nerve (T12)
Internal oblique
Origin - inguinal ligament, iliac crest and lumbdorsal fascia
Insertion - ribs 10-12
Actions - bilateral contraction compresses abdomen and unilateral contraction ipsilateral rotates the torso.
Innervation - thoracoabdominal nerves (T7-11) and the subcostal nerve (T12) and branches of the lumbar plexus.
Transversus abdominis
Origin - inguinal ligament and costal cartilages 7-12, iliac crest
Insertion - conjoint tendon, xiphisternum, linea alba and the pubic crest
Actions - compression of the abdominal contents
Innervation - thoracoabdominal nerves (T7-11) and the subcostal nerve (T12).
What are the vertical muscles?
1) Rectus abdominis
2) Pyramidalis
They are located in the midline of the anterlateral wall.
Rectus abdominis
Origin - pubic crest
Insertion - xiphisternum and costal cartilages of 5-7
Actions - assists in compressing abdominal viscera, stabilises pelvis when walking and depresses the ribs.
Innervation - Thoracoabdominal nerves (T7-T11)
Pyrimidalis
Origin - pubic crest and pubic symphysis
Insertion - linea alba
Actions - tenses the linea alba
Innervation - subcostal nerve (T12)
Clinical relevance: surgical incisions in the abdominal wall
1) Midline - an incision is made thorugh the linea alba and extends the length of the abdomen. Minimal blood loss as the linea alba is poorly vascularised.
2) Paramedian - performed laterally to the linea alba, providing access to the kidney, spleen and adrenals.
3) Kocher - begins at the xiphoid process and extends laterally to the right costal margin for gall bladder pathology.
