Pectoral Muscles Flashcards
What are the two heads of the pectoralis major and where do they attach?
The muscle has two heads –a clavicular head (attaches to the clavicle), and a sternocostal head (attaches to the sternum and ribs). Fibres from both heads attach to the edge of the intertubecular groove of the humerus.
What is the role of the pectoralis major?
Together, they act to adduct and medially rotate the humerus at the shoulder. The clavicular head also performs flexion.
What nerves innervate the pectoralis major?
The pectoralis major is innervated by the medial and lateral pectoral nerves, which are derived from thebrachial plexus.
Where does the pectoralis minor lie?
The pectoralis minor muscle is much smaller than the pectoralis major, and lies posterior (underneath) to it.
Where does the pectoralis minor originate from?
The muscle has a triangular shape, originating from the anterior surfaces of ribs 3 – 5.
Where does the pectoralis minor attach?
The fibres then converge to attach to the corocoid process of the scapula. Attaching to the scapula forms a ‘bridge’, which vessels passing into the upper limb must travel underneath
What effect does contraction of the pectoralis minor have on the shoulder?
Contraction of the pectoralis minordepresses the shoulder (an inferior motion)
Which nerve innervates the pectoralis minor?
It is innervated by themedial pectoral nerve
Where is the serratus anterior found?
The serratus anterior is found more laterally in the chest and, forms the medial wall of the axilla.
Where does the serratus anterior originate?
The muscle consists of several strips, which originate from ribs 2-8.
Where does the serratus anterior attach?
They attach to the costal (rib facing) surface of the medial border of the scapula.
What is the action of the serratus anterior?
The main action of the serratus anterior is to rotate the scapula, allowing the arm to be raised over 90 degrees. It also holds the scapula against the ribcage – this is particularly useful when upper limb reaches anteriorly (e.g punching).
What nerve innervates the serratus anterior?
It is innervated by the long thoracic nerve.
