Muscles: Abdomen Flashcards
What are the muscles of the posterior wall of the abdomen?
- Psoas major
- Quadratus lumborum

Psoas Major
COURSE:
- Th. 12, L 1-4 side, L 1-5 cost. proc. > lesser trochanter
ACTION:
- flex and ext. rotate hip
INNERVATION:
- lumbar plexus

Quadratus Lumborum
COURSE:
- internal lip iliac crest & iliolumbal ligament > rib 12, L 1-4 costal processes
ACTION:
- expiration
- flexes spine
INNERVATION:
- lumbar plexus
What muscles form the lateral abdominal wall?
(in order from superficial to deep)
- external obliques
- internal obliques
- transverse abdominals

external obliques
COURSE:
- outside ribs 5-12 (interdigitated w/ serratus and latissimus) > iliac crest & inguinal ligament (via aponeurosis)
ACTION:
- ante/lateral trunk flexion
- lift pelvis
- abd. rotation (to opposite side)
- abd. pressure
INNERVATION:
- intercostal, iliohypogastric and ilioinguinal nerves

interal oblique
COURSE:
- int. line iliac crest, thoracolumbal fascia & inguinal lig. > 3 caudal ribs, linea alba
ACTION:
- ante/lateral flexion
- abd. rotation (own side)
- raise pelvis and abd. pressure
INNERVATION:
- intercostal, iliohypogastric and ilioinguinal nerves

Transverse Abdominis
(forms linea semicircularis (of Douglas))
COURSE:
- int. lip iliac crest & thoracolumbal fascia (direct), inguinal lig. & inside caudal 6 ribs (tendinously) > linea alba (via apo.)
ACTION:
- fixes abd. wall & provides pressure
INNERVATION:
- intercostal, iliohypogastric, ilioinguinal & genitofemoral nerves
What muscles form the medial (anterior group) of abdominal muscles?
- rectus abdominis
- pyramidalis

rectus abdominis
COURSE:
- outer surface costal cartilages 5-7, xipohoid process, interv. ligaments > pubic crest & symph.
ACTION:
- ante/lateral flexion
- raise pelvis
- expiration
INNERVATION:
- intercostal nerves
What is the small green muscle shown here?

Pyramidalis
(absent in 10%)
COURSE:
- pubic symph & crest > linea alba
ACTION:
- tense linea alba
INNERVATION:
- subcostal nerve
What is this line called?
What does it mark?
(Bonus: clinical significance)

Linea Semilunaris
- marks lateral border of rect. abd.
- formed by aponeurosis of int. oblique
(clinically, site of Spigelian hernia)
What is the line marked by the black pointer?
3 names
significance?

Arcuate Line
or Linea Semicircularis or Douglas’ line
- marks the lower limit of the posterior layer of the rectus sheath
(in other words, below this line the aponeuroses of the 3 lateral abdominal muscles only form an anterior sheath around the rectus abdominis)
What does this drawing represent?
Identify its labeled structures.

Rectus Sheath (above arcuate line)
- linea alba
- aponeurosis
- external oblique
- internal oblique
- transvere abominis
- transversalis fascia
- peritoneum
- round ligament of liver
- rectus abdominis
What does this drawing represent?
Identify its numbered structures.

Rectus Sheath (below arcuate line)
- urachus
- external oblique
- internal oblique
- transverse abdominis
- transversalis fascia
- peritoneum
- inferior epigastric artery and vein
- umbilical artery
- middle umbilical fold
- medial umbilical fold
- lateral umbilical fold
- skin
Identify the structures.

- tendinous intersections (of rect. abd.)
- external obliques
- internal obliques
- rectus abdominis
- linea alba
- transverse abdominis
- arcuate line
- semilunar line
- aponeurosis
What are the fascia (and other layers) of the abdomen from superficial to deep?
Skinny Fingers Scratch All My Tricky Places
- Skin
- Fat (subcutaneous)
- Scarpa’s fascia (AKA CT lamellae)
- Superficial Abdominal Fascia
- Muscles (and their fascia)
- Transversalis Fascia
- Peritoneum
What is the layer just deep to the subcutaneous fat of the abdomen?
2 names.
Scarpa’s Fascia
- AKA CT Lamellae
- permeates the fatty tissue and has a weblike appearance
What is the thin layer covering the entire abdomen which thickens medially along the midsagittal plane?
What is the thickening?
Superficial Abdominal Fascia
Linea Alba
What is the layer just deep to the abdominal muscles?
It is especially taut in one area… what area? Name?
Transversalis Fascia
- loose in all areas except…
Umbilical Fascia
- surrounding the umbilicus
The transverse fascia fuses with what ligament to form what?
This serves as the posterior wall of what important area?
it fuses with the **inguinal ligament to form the ** iliopubic tract
which is the posterior wall of the inguinal canal