Intertransversarii Mediales Lumborum 1–5
Back · Trunk
The intertransversarii mediales lumborum are the medial intertransverse muscles of the lumbar spine, lying closer to the vertebral arch than the lateral group. Each slip runs from the mammillary process of one lumbar vertebra to the mammillary process of the vertebra immediately above, distinguishing its bony attachments from the lateral muscles that use the transverse processes. Placed lateral to the vertebral bodies, they laterally flex the lumbar spine to the acting side and stabilise adjacent vertebrae during movement. Unlike the lateral group, the medial lumbar intertransversarii are supplied by the posterior (dorsal) rami of the lumbar spinal nerves.
Origin, Insertion, Action & Nerve
Origin
Mammillary process of a lumbar vertebra
Insertion
Mammillary process of the adjacent vertebra above
Action
Laterally flexes the lumbar spine and stabilizes adjacent vertebrae
Nerve
Posterior (dorsal) rami of lumbar spinal nerves
Attachments explained
The Intertransversarii Mediales Lumborum 1–5 is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Mammillary process of a lumbar vertebra
Insertion
Mammillary process of the adjacent vertebra above
Action & function
When the Intertransversarii Mediales Lumborum 1–5 contracts, it produces the following movement: Laterally flexes the lumbar spine and stabilizes adjacent vertebrae.
As part of the Back group of the Trunk, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Intertransversarii Mediales Lumborum 1–5 receives its nerve supply from the Posterior (dorsal) rami of lumbar spinal nerves.
Because a muscle can only contract when its nerve is intact, injury to the Posterior can weaken or paralyse the Intertransversarii Mediales Lumborum 1–5, impairing the movements it normally produces (laterally flexes the lumbar spine and stabilizes adjacent vertebrae). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Intertransversarii Mediales Lumborum 1–5 (the OIANS method)
Distinguish this muscle from the lateral lumbar intertransversarii by its attachments. The medial set uniquely uses the mammillary processes rather than the transverse processes, a detail that is easy to recall because mammillary and medial both begin with m. From that placement the familiar lateral flexion action follows.
Pair the medial attachment with the medial rule for innervation: these muscles take posterior (dorsal) rami, grouping them with the true deep back muscles and against the ventral-ramus lateral lumbar group. Holding the medial pair, mammillary processes and dorsal rami, together as a unit is the surest way to avoid confusing them with their lateral neighbours.
Frequently asked questions
Where is the Intertransversarii Mediales Lumborum 1–5 located?
The Intertransversarii Mediales Lumborum 1–5 is a muscle of the Back group, located in the Trunk.
What is the origin of the Intertransversarii Mediales Lumborum 1–5?
Mammillary process of a lumbar vertebra
What is the insertion of the Intertransversarii Mediales Lumborum 1–5?
Mammillary process of the adjacent vertebra above
What movements does the Intertransversarii Mediales Lumborum 1–5 produce?
Laterally flexes the lumbar spine and stabilizes adjacent vertebrae
What nerve supplies the Intertransversarii Mediales Lumborum 1–5?
Posterior (dorsal) rami of lumbar spinal nerves
Is the Intertransversarii Mediales Lumborum 1–5 free to study in OIANS?
The Intertransversarii Mediales Lumborum 1–5 is always free to browse. Its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory. Quiz and Flashcard practice for the Trunk is part of the one-time Lifetime upgrade, though; only the Upper Limb decks are free to test yourself on.
Related muscles
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