The scalenus anterior muscle originates from the transverse processes of cervical vertebrae C3-C6. It inserts into the scalene tubercle of the first rib. It functions to bend the neck forward and laterally, and rotate it to the opposite side. It also helps elevate the first rib as an accessory muscle of respiration. It is an important landmark at the root of the neck, deep to the sternocleidomastoid muscle, with relations to structures like the phrenic nerve, arteries, veins, and other muscles in the region.

1. SCALENUS ANTERIOR
V.S.RASHMI PRIYEM
ULTRA’S BEST DENTAL SCIENCE COLLEGE

2.  MOST SUPERFICIAL AND LIES DEEP TO
STERNOCLEIDOMASTOID MUSCLE.
 KEY MUSCLE AT THE ROOT OF NECK BECAUSE
OF ITS INTIMATE RELATIONS TO MANY
STRUCTURES IN THE REGION.
 PROVIDES A USEFUL SURGICAL LANDMARK.

3. ORIGIN
 FROM ANTERIOR TUBERCLES OF TRANSVERSE
PROCESSES OF C3, C4, C5, AND C6
VERTEBRAE.

4. INSERTION
 THE FIBRES CONVERGE AND DESCEND
ALMOST VERTICALLY TO BE INSERTED BY A
NARROW, FLAT TENDON TO THE SCALENE
TUBERCLE ON THE INNER BORDER OF THE 1st
RIB.

5. NERVE SUPPLY
 BY VENTRAL RAMI OF C4, C5, AND C6 SPINAL
NERVES.

6. ACTIONS
 1. ACTING FROM BELOW, BENDS THE NECK
FORWARDS AND LATERALLY AND ROTATES IT
TO THE OPPOSITE SIDE.
 2. ACTING FROM ABOVE, HELPS TO ELEVATE
THE 1st RIB AND THUS ACTS AS AN ACCESSORY
MUSCLE OF RESPIRATION.

7. RELATIONS
IMPORTANT LANDMARK AT THE ROOT OF THE NECK
BECAUSE PHRENIC NERVE PASSES SUPERFICIAL TO IT.

8. ANTERIOR RELATIONS:
 1. PHRENIC NERVE
 2. TWO ARTERIES
 TRANSVERSE CERVICAL ARTERY
 SUPRASCAPULAR ARTERY
 3. TWO VEINS
 ANTERIOR JUGULAR VEIN
 SUBCLAVIAN VEIN

9. ANTERIOR RELATIONS:
 4. TWO MUSCLES
 (A) INFERIOR BELLY OF OMOHYOID
 (B) STERNOCLEIDOMASTOID (CLAVICULAR HEAD)
 5. CAROTID SHEATH LIES VERTICALLY IN
FRONT OF THE MUSCLE.
 6. CLAVICLE CROSSES FROM MEDIAL TO
LATERAL SIDE.

10. POSTERIOR RELATIONS:
 1. ROOTS OF BRACHIAL PLEXUS SEPARATES
THE SCALENUS ANTERIOR FROM SCALENUS
MEDIUS.
 2. SUBCLAVIAN ARTERY PASSES DEEP TO
SCALENUS ANTERIOR, SEPARATING IT FROM
SCALENUS MEDIUS.
 3. SCALENUS MEDIUS MUSCLE (MEDIAL PART).
 4. CERVICAL PLEURA.
 5. SUPRAPLEURAL MEMBRANE.

11. OTHER RELATIONS:
 1. MEDIAL BORDER OF SCALENUS ANTERIOR
FORMS THE LATERAL BOUNDARY OF THE
SCALENOVERTEBRAL TRIANGLE OR TRIANGLE
OF THE VERTEBRAL ARTERY.
 2. LATERAL BORDER OF THE SCALENUS
ANTERIOR IS RELATED TO TRUNKS OF
BRACHIAL PLEXUS.
 3. UPPER PART OF SCALENUS ANTERIOR IS
SEPARATED FROM LONGUS CAPITIS BY THE
ASCENDING CERVICAL ARTERY.