The internal oblique is a muscle of the anterior abdominal wall. It is a broad, sheet-like muscle, located deep to the external oblique. It plays an important role in abdominal wall functions and rotation of the torso.
The internal oblique muscle originates from the inguinal ligament, iliac crest and lumbodorsal fascia. It inserts onto ribs 10-12.
The internal oblique muscle is capable of both bilateral and unilateral contractions. When it is bilaterally contracted, it compresses the abdomen. On the other hand, when it is unilaterally contracted, it ipsilaterally rotates the torso.
The internal oblique muscle is innervated by branches of the thoracoabdominal nerves (T7-T11) and the subcostal nerve (T12), as well as branches of the lumbar plexus.
The internal oblique is supplied by the lower posterior intercostal and subcostal arteries, as well as the superior and inferior epigastric arteries, superficial and deep circumflex arteries, and posterior lumbar arteries.
Fig 1 – Lateral view of the abdominal wall. The internal oblique is visible – note that its fibres are perpendicular to those of the external oblique. It is important to note the difference in orientation between the two muscles of the abdominal wall, as this provides important information about their function.
The internal oblique, along with the external oblique, is one of the primary muscles that make up the abdominal wall. The abdominal wall plays an important role in protecting the organs of the abdominal cavity from external forces, and in providing support for the torso. As part of the trio of muscles that make up the abdominal wall, the internal oblique helps to provide stability and protect vital organs.
The internal oblique also plays an important role in core stability. Core stability is essential for movement of the body as a whole, and for many activities such as walking, running, and lifting. The internal oblique muscle helps to provide stability to the spine and torso by supporting the abdominal wall and helping to keep the trunk upright and in proper alignment.
The internal oblique muscle is also important for twisting and rotation of the torso. When one side of the internal oblique is contracted, it helps to rotate the torso towards the side of the contraction. This can be useful for activities such as twisting and turning when trying to reach an object, or when performing sports such as golf or tennis.
The internal oblique muscle is an important part of the abdominal wall, providing stability and protection for the organs, as well as aiding in rotation of the torso. It is innervated by thoracoabdominal and lumbar plexus nerves, and is supplied by several arteries. Understanding the anatomy and function of the internal oblique is important for health professionals, such as physical therapists and athletic trainers, in order to provide proper treatment and rehabilitation.
