Anatomy of the Anterior Abdominal Wall Flashcards
List the layers of the anterior abdominal wall from external to internal
- Skin
- Subcutaneous tissue
- Muscle and fascia
- Parietal peritoneum
What is the lateral border of rectus abdominus muscle called?
Linea semilunaris
What is “divarication of recti”?
Laxity/weakness of the linea alba after pregnancy. Clinically presents like a hernia, but isn’t
What separates the two vertical strips of rectus abdominis muscle?
Linea alba
What is it that gives the impression of a six pack?
The linea alba and the tendinous intersections of rectus abdominis
In which direction do the fibres of the external oblique muscle run?
Inferomedially - from the armpit down to rectus abdominis
In which direction do the fibres of the internal oblique muscle run?
Superomedially - up from the lateral pelvis towards to the central ribs
In which direction do the fibres of transversus abdominus muscle run?
Horizontally
List the 3 “flat” muscles superficial to deep
External oblique
Internal oblique
Transversus abdominus
What is the rectus sheath formed by?
Formed by the aponeuroses of the 3 flat muscles, which combine at the midline
Explain how the role of the rectus sheath varies above and below the arcuate line
Above the arcuate line, the rectus sheath covers the anterior and posterior surfaces of rectus abdominus.
Below the arcuate line, the rectus sheath covers only the anterior surface of rectus abdominus, meaning the posterior surface of the muscle directly touches the transversalis fascia.
Where is the arcuate line found?
1/3rd of the way between the umbilicus and the pubic symphysis
Using what planes is the abdomen divided into 9 regions?
Vertically - mid-clavicular lines
Horizontally - trans-pyloric plane halfway between xiphoid process of sternum and umbilicus, inter-tubercular plane joins iliac crests
List the 9 regions of the abdomen
Left and right hypochondrium
Left and right flank
Left and right groin
Epigastric, umbilical and pubic
Where would you find the loin region?
On the back, where the ribs end and the lumbar vertebrae begin
What are the 2 types of referred pain?
Visceral and somatic
State the original site of somatic referred pain and the eventual site it is perceived at
Original site = proximal part of somatic nerve
Perceived site = distal part of same dermatome
Give an example of somatic referred pain which may lead to confusion over the diagnosis
Right lower lobar pneumonia may irritate the somatic nerve supplying the right pleura –> pain felt in RIF
Briefly explain the concept of visceral referred pain
Visceral afferent fibres run in the same nerves as somatic afferent fibres, back to a single spinal cord segment. The CNS then perceives the pain as coming from the somatic area supplied by this segment, rather than from the viscera.
Why is early appendicitis felt as central periumbilical pain?
The visceral afferent fibres from the appendix join with the somatic afferent fibres at T10. Hence the pain is felt in the T10 dermatome, around the umbilicus.
Why does the pain in late appendicitis then localise to the RIF?
Once the inflammation involves the parietal peritoneum, somatic neurones supplying this relay the pain in a localised manner
What can cause visceral pain?
Stretch, inflammation and ischaemia only
What does the anterior abdominal wall run between?
Anterior parts of the ribcage and pelvic girdle
