Posterior Triangle

Question 1

Sternocleidomastoid (SCM)

Answer 1

Origin: sternal head, clavicular head

Insertion: mastoid process, superior nuchal line

Action: tilts head to side, extends neck

Nerve: spinal accessory n. (CN XI)

Arter: SCM branch of occipital artery

Question 2

Platysma

Answer 2

Origin: subcutaneous fascia of chest/neck

Insertion: same as above

Action: draws neck skin, corners of mouth

Nerve: cervical branch of facial n. (CN VII)

Artery: facial a.

Question 3

Anterior scalene

Answer 3

Origin: Transverse process (C3-C6)

Insertion: First rib

Action: elevates first rib, flexes and laterally bends neck

Nerve: brachial plexus (C5-C7)

Artery: Ascending cervical a.

Question 4

Middle scalene

Answer 4

Origin: Transverse process (C2-C7)

Insertion: First rib

Action: elevates first rib, flexes and laterally bends neck

Nerve: brachial plexus (C3-C8)

Artery: Ascending cervical a.

Question 5

Posterior scalene

Answer 5

Origin: Transverse process (C5-C7)

Insertion: Second rib

Action: elevates second rib, flexes and laterally bends neck

Nerve: brachial plexus (C7-C8)

Artery: Ascending cervical a.

Question 6

Omohyoid (posterior belly)

Answer 6

Origin: superior border of scapula near suprascapular notch

Insertion: inferior border of hyoid

Action: Depresses, retracts, and steadies the hyoid

Nerve: ansa cervicalis (C1-C3)

Artery: