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Superficial Muscles of the Chest

Q: What is the origin and insertion of the serratus anterior muscle?

The serratus anterior (m. serratus anterior) arises from ribs I–IX via 8–9 muscular slips and inserts into the scapula. Origin — 8–9 digitations from ribs I–IX (maximal development is seen near the inferior angle of the scapula).Insertion — Costal surface of the medial border and inferior angle of the scapula.

Q: What are the functions of the serratus anterior muscle?

The serratus anterior (m. serratus anterior) produces scapular movements and aids in respiration. Scapular movement — Pulls the scapula anteriorly and laterally, rotating it upward and outward to allow arm abduction above the horizontal plane.Fixation — Stabilizes and holds the scapula against the thoracic wall during arm elevation.Respiration — Lower digitations act as a powerful inspiratory stabilizer.

Q: What is the innervation of the serratus anterior muscle?

The serratus anterior (m. serratus anterior) is innervated by the long thoracic nerve (n. thoracicus longus) from spinal segments C5–C7. The nerve runs down the superficial surface of the muscle.

Q: Where does the abdominal part of the pectoralis major originate?

The abdominal part (pars abdominalis) originates from the anterior layer of the rectus sheath (vagina musculi recti abdominis).

Q: Which muscle stabilizes the sternoclavicular joint?

This function is performed by the subclavius muscle (m. subclavius), which pulls the clavicle inferiorly and medially, anchoring it firmly against the sternum.

Musculi thoracis

For medical students2 min readUpdated 2026-10-10

Superficial muscles of the chest are a group of skeletal muscles located on the anterior thoracic wall that are functionally and genetically related to the upper limb. They control movements of the pectoral girdle and upper arm, and act as accessory muscles of respiration when the limbs are fixed.

OriginClassified as upper limb muscles (truncopetal and truncofugal).

RespirationAct as accessory inspiratory muscles when the arms are fixed.

InsertionThe pectoralis major muscle features a specific U-shaped tendon.

Blood supplyPrimarily supplied by branches of the thoracoacromial artery.

General Classification of Chest Muscles

Anatomically, the thoracic musculature (mm. thoracis) is divided into two major groups based on embryonic origin and function:

Superficial muscles. These include the pectoralis major, pectoralis minor, subclavius, and serratus anterior. Phylogenetically, they evolved alongside the upper limbs and migrated to the trunk, thereby controlling the pectoral girdle.
Deep (intrinsic) muscles. These include the external, internal, and innermost intercostal muscles, subcostales, transversus thoracis, and levatores costarum. These are true muscles of the thoracic wall, primarily responsible for the mechanics of breathing.

Pectoralis Major Muscle

The pectoralis major (m. pectoralis major) is a large, fan-shaped muscle covering a significant portion of the anterior chest wall.

Based on its origins, it is divided into three parts:

Pars clavicularis (clavicular part) — originates from the medial half of the clavicle.
Pars sternocostalis (sternocostal part) — arises from the anterior surface of the sternum and the cartilages of ribs II–VII.
Pars abdominalis (abdominal part) — originates from the anterior layer of the rectus sheath (vagina musculi recti abdominis).

Insertion: The muscle fibers converge laterally and insert into the crest of the greater tubercle of the humerus (crista tuberculi majoris). A notable feature is that the tendon forms a double U-shaped fold, with the superior fibers inserting more distally than the inferior fibers.

Function: Performs adduction, internal rotation (medial rotation), and flexion of the arm. When the arms are fixed, the muscle pulls the ribs upward, assisting in forced inspiration.

Innervation and Blood Supply: Innervated by the medial and lateral pectoral nerves (nn. pectorales medialis et lateralis, segments C5–Th1). It is supplied by the pectoral branch of the thoracoacromial artery, the lateral and superior thoracic arteries, and anterior intercostal branches.

Pectoralis Minor Muscle

The pectoralis minor (m. pectoralis minor) is a triangular muscle situated deep to the pectoralis major.

Origin: Arises via individual slips from the anterior ends and cartilages of ribs II–V.
Insertion: The tendon attaches to the coracoid process of the scapula.
Function: Primarily pulls the scapula inferiorly and anteriorly. Like the pectoralis major, when the scapula is fixed, it elevates the ribs, acting as an accessory muscle of inspiration.
Innervation and Blood Supply: Innervated by the medial pectoral nerve (C7–Th1), with occasional contribution from the lateral pectoral nerve. Blood supply comes from the thoracoacromial and lateral thoracic arteries.

Subclavius Muscle

The subclavius (m. subclavius) is a small, slender muscle running between the clavicle and the first rib.

Origin: Arises from the bony part of rib I near its cartilage.
Insertion: Attaches to the inferior surface of the middle third of the clavicle (within the subclavian groove, sulcus m. subclavii).
Function: Pulls the clavicle inferiorly and medially. Its primary biomechanical role is stabilizing the sternoclavicular joint during pectoral girdle movements.
Innervation and Blood Supply: Innervated by the subclavian nerve (n. subclavius, segments C5–C6). Supplied by branches of the thoracoacromial and superior thoracic arteries.

Mnemonic

To easily remember the attachments of the pectoralis minor, use the association: 'The MINOR pectoral starts with the SMALL number 2 (ribs II–V) and reaches for the BEAK of the scapula (coracoid process, from Greek korakoeides meaning raven-like/beak).'

Frequently asked questions

What is the origin and insertion of the serratus anterior muscle?

The serratus anterior (m. serratus anterior) arises from ribs I–IX via 8–9 muscular slips and inserts into the scapula.

Origin — 8–9 digitations from ribs I–IX (maximal development is seen near the inferior angle of the scapula).
Insertion — Costal surface of the medial border and inferior angle of the scapula.

What are the functions of the serratus anterior muscle?

The serratus anterior (m. serratus anterior) produces scapular movements and aids in respiration.

Scapular movement — Pulls the scapula anteriorly and laterally, rotating it upward and outward to allow arm abduction above the horizontal plane.
Fixation — Stabilizes and holds the scapula against the thoracic wall during arm elevation.
Respiration — Lower digitations act as a powerful inspiratory stabilizer.

What is the innervation of the serratus anterior muscle?

The serratus anterior (m. serratus anterior) is innervated by the long thoracic nerve (n. thoracicus longus) from spinal segments C5–C7. The nerve runs down the superficial surface of the muscle.

Which arteries supply all the superficial muscles of the chest?

The superficial chest muscles are supplied by the following arteries:

Pectoralis major (m. pectoralis major) — Pectoral branches of a. thoracoacromialis, a. thoracica lateralis, a. thoracica superior, and anterior intercostal arteries.
Pectoralis minor (m. pectoralis minor) — A. thoracoacromialis, a. thoracica lateralis.
Subclavius (m. subclavius) — A. thoracoacromialis, a. thoracica superior.
Serratus anterior (m. serratus anterior) — A. thoracodorsalis, a. thoracica lateralis, and anterior intercostal arteries.

How do the superficial chest muscles contribute to respiration?

When the upper limbs are fixed (e.g., when a person leans hands on a desk during dyspnea), the pectoralis major and minor reverse their fixed points and pull the ribs superiorly, expanding the thoracic cavity for inspiration.

Where does the abdominal part of the pectoralis major originate?

The abdominal part (pars abdominalis) originates from the anterior layer of the rectus sheath (vagina musculi recti abdominis).

Which muscle stabilizes the sternoclavicular joint?

This function is performed by the subclavius muscle (m. subclavius), which pulls the clavicle inferiorly and medially, anchoring it firmly against the sternum.

Go deeper

Anatomy of the Serratus Anterior Muscle
Deep (Intrinsic) Muscles of the Thoracic Wall
External and Internal Intercostal Muscles
Transversus Thoracis and Subcostales Muscles
Topography of the Thoracoacromial Artery