Uploaded February 2022 | Updated September 2026, 1 week ago

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Small correction: The rectus abdominis originates from the pubic crest and symphysis and inserts into the xiphoid process and costal cartilages of ribs 5–7. I mistakenly swapped the origin and insertion in the video. Apologies for the error!

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Content
0:00 Introduction
0:08 Division of the Abdominal Muscles
1:27 Quadratus Lumborum
1:53 Pyramidalis
2:22 Rectus Abdominis
2:52 Transverse Abdominal Muscle
3:49 Internal Oblique
4:21 Cremaster Muscle
5:00 External Oblique

Muscles of the Abdomen
- Lateral Group
○ External Oblique
○ Internal Oblique
○ Transverse Abdominal
- Anterior Group
○ Rectus Abdominis
○ Pyramidalis
- Posterior Group
○ Quadratus Lumborum

Posterior Group:
Quadratus Lumborum
musculus wadratus lumborum
Origin:
Iliac Crest
Iliolumbar Ligament
Insertion:
12th Rib
Costal process of L1-L4
Function:
Extension of trunk
(Bilteral Contraction)
Lateroflexion of trunk
(Unilateral Contraction)

Anterior Group:
Pyramidalis
musculus pyramidalis
O: Superior Pubic Ramus
I: Linea Alba
F:
Tenses linea alba and strengthens the rectus sheath

Rectus Abdominis
musculus rectus abdominis
O:
Xiphoid Process
Costal Cartilage of 5th – 7th Rib
I:
Body of Pubis between pubic symphysis and pubic tubercle
F:
Ventral Flexion of Trunk
Expiration Muscle

Lateral Group
Transverse Abdominal
musculus transversus abdominis
O:
Inguinal ligament
Iliac Crest
Thoracolumbar Fascia
7th – 12th Rib
I: Linea Alba
F:
Rotation of the trunk
Expiration Muscle

Internal Oblique
musculus obliquus internus abdominis
O:
Inguinal ligament
Iliac Crest
Thoracolumbar Fascia
I:
Linea Alba
10th – 12th Rib
F:
Ventral flexion of trunk (Bilateral Contraction)
Tilts the trunk to the side
(Unilateral Contraction)
Expiration Muscle

Cremaster
musculus cremaster
- Formed by Internal Oblique and Transverse Abdominal Muscles

External Oblique
musculus obliquus externus abdominis
O: 5th – 12th Ribs
I:
Linea Alba
Iliac Crest
F:
Ventral flexion of trunk (Bilateral Contraction)
Tilts the trunk to the side
(Unilateral Contraction)
Expiration Muscle