The Pyramidalis Muscle | Origin, Insertion, Innervation, Action, & Variation

The video tutorial discusses the anterior abdominal wall muscles, focusing on the pyramidalis muscle. It covers the identification, function, innervation, and blood supply of the pyramidalis, highlighting its variability among individuals. The pyramidalis is a small, pyramid-shaped muscle that tenses the linea alba and is innervated by the subcostal nerve. It is present in 80% of the population, with variability in presence, size, and number. The tutorial explains how the rectus abdominis compensates for the absence of the pyramidalis.

Which of the following is NOT one of the four main anterior abdominal wall muscles?

• Pyramidalis

• External oblique

• Internal oblique

• Rectus abdominis

What is the primary action of the pyramidalis muscle?

• Flexing the spine

• Supporting the pelvic floor

• Tensing the linea alba

• Rotating the torso

Which nerve is responsible for the innervation of the pyramidalis muscle?

• Phrenic nerve

• Subcostal nerve

• Femoral nerve

• Sciatic nerve

What percentage of the population lacks the pyramidalis muscle entirely?

• 10%

• 20%

• 30%

• 40%

How does the body compensate for the absence of the pyramidalis muscle?

• The transversus abdominis enlarges

• The external oblique enlarges

• The rectus abdominis enlarges

• The internal oblique enlarges