Intertransversarii Thoracis 1–9
Back · Trunk
The intertransversarii thoracis are small, inconstant muscular slips found between the transverse processes of adjacent thoracic vertebrae, where they are the least developed of the intertransverse muscles. Each runs from the transverse process of one thoracic vertebra to the transverse process of the vertebra above. Because the thorax is splinted by the rib cage, movement here is limited, and these slips act chiefly as weak lateral flexors of the thoracic spine and as segmental stabilisers of adjacent vertebrae. They are supplied by the posterior (dorsal) rami of the thoracic spinal nerves.
Origin, Insertion, Action & Nerve
Origin
Transverse process of a thoracic vertebra
Insertion
Transverse process of the adjacent vertebra above
Action
Laterally flexes the thoracic spine and stabilizes adjacent vertebrae
Nerve
Posterior (dorsal) rami of thoracic spinal nerves
Attachments explained
The Intertransversarii Thoracis 1–9 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
Transverse process of a thoracic vertebra
Insertion
Transverse process of the adjacent vertebra above
Action & function
When the Intertransversarii Thoracis 1–9 contracts, it produces the following movement: Laterally flexes the thoracic 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 Thoracis 1–9 receives its nerve supply from the Posterior (dorsal) rami of thoracic spinal nerves.
Because a muscle can only contract when its nerve is intact, injury to the Posterior can weaken or paralyse the Intertransversarii Thoracis 1–9, impairing the movements it normally produces (laterally flexes the thoracic 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 Thoracis 1–9 (the OIANS method)
Set the thoracic intertransversarii in context by comparing them with their cervical and lumbar counterparts. In the thorax the ribs restrict lateral bending, so these muscles are poorly developed and often incomplete, which explains why their action is described as weak lateral flexion and stabilisation rather than powerful movement.
Simplify the innervation by noting that the thoracic region does not have the divided anterior and posterior arrangement seen in the neck; here a single set of intertransverse slips is supplied by posterior (dorsal) rami. Remembering this uniformity spares you the branching detail required for the cervical group.
Frequently asked questions
Where is the Intertransversarii Thoracis 1–9 located?
The Intertransversarii Thoracis 1–9 is a muscle of the Back group, located in the Trunk.
What is the origin of the Intertransversarii Thoracis 1–9?
Transverse process of a thoracic vertebra
What is the insertion of the Intertransversarii Thoracis 1–9?
Transverse process of the adjacent vertebra above
What movements does the Intertransversarii Thoracis 1–9 produce?
Laterally flexes the thoracic spine and stabilizes adjacent vertebrae
What nerve supplies the Intertransversarii Thoracis 1–9?
Posterior (dorsal) rami of thoracic spinal nerves
Is the Intertransversarii Thoracis 1–9 free to study in OIANS?
The Intertransversarii Thoracis 1–9 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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