Sternalis
Shoulder & Scapula · Upper Limb
The sternalis is an uncommon anatomical variant lying on the front of the chest, running vertically alongside the sternum on top of the pectoralis major. When present it arises from the manubrium of the sternum or the clavicle and attaches variably to the xiphoid process, pectoral fascia, lower ribs, costal cartilages, or rectus sheath. It has no significant functional role and, at most, slightly tenses the pectoral fascia. Its nerve supply is variable, coming from the intercostal or pectoral nerves. Its main importance is clinical: it can be mistaken for a mass on chest imaging or mammography.
Origin, Insertion, Action & Nerve
Origin
Manubrium of the sternum or clavicle
Insertion
Xiphoid process, pectoral fascia, lower ribs, costal cartilages, or rectus sheath
Action
Inconstant variant; may tense the pectoral fascia (no significant functional role)
Nerve
Intercostal nerves (or pectoral nerves), variable
Attachments explained
The Sternalis 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
Manubrium of the sternum or clavicle
Insertion
Xiphoid process, pectoral fascia, lower ribs, costal cartilages, or rectus sheath
Action & function
When the Sternalis contracts, it produces the following movements: Inconstant variant; may tense the pectoral fascia (no significant functional role).
As part of the Shoulder & Scapula group of the Upper Limb, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Sternalis receives its nerve supply from the Intercostal nerves (or pectoral nerves), variable.
Because a muscle can only contract when its nerve is intact, injury to the Intercostal nerves can weaken or paralyse the Sternalis, impairing the movements it normally produces (inconstant variant). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Sternalis (the OIANS method)
Learn the sternalis for what it teaches about variation rather than function. It is an inconstant vertical strip beside the sternum with no meaningful action, so there is no O-I-A logic to reason through; the point is simply to know it exists.
Its clinical value is the reason to remember it: on a mammogram or chest scan it can imitate a mass or a pathological finding. Holding that single fact, a normal variant that mimics disease, is the efficient way to store this muscle.
Frequently asked questions
Where is the Sternalis located?
The Sternalis is a muscle of the Shoulder & Scapula group, located in the Upper Limb.
What is the origin of the Sternalis?
Manubrium of the sternum or clavicle
What is the insertion of the Sternalis?
Xiphoid process, pectoral fascia, lower ribs, costal cartilages, or rectus sheath
What movements does the Sternalis produce?
Inconstant variant; may tense the pectoral fascia (no significant functional role)
What nerve supplies the Sternalis?
Intercostal nerves (or pectoral nerves), variable
Is the Sternalis free to study in OIANS?
Yes. The Sternalis is free in OIANS: its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory, and because it belongs to the Upper Limb it is also covered by the free Quiz and Flashcard decks. The other regions, the "All Muscles" deck, and the Progress and Explore tools are unlocked with a one-time Lifetime purchase.
Related muscles
Study the Sternalis
Test yourself on Upper Limb muscles with interactive quizzes and flashcards in the free OIANS app.
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