The scalene muscles are a group of three pairs of muscle

Muscle

Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

s in the lateral neck

Neck

The neck is the part of the body, on many terrestrial or secondarily aquatic vertebrates, that distinguishes the head from the torso or trunk. The adjective signifying "of the neck" is cervical .-Boner anatomy: The cervical spine:The cervical portion of the human spine comprises seven boney...

, namely the scalenus anterior

Scalenus anterior

The Scalenus anterior , also known as anterior scalene muscle, lies deeply at the side of the neck, behind the Sternocleidomastoideus.-Anatomy:...

, scalenus medius

Scalenus medius

The Scalenus medius, the largest and longest of the three scalene muscles, arises from the posterior tubercles of the transverse processes of the lower six cervical vertebræ. It descendes along the side of the vertebral column to insert by a broad attachment into the upper surface of the first...

, and scalenus posterior

Scalenus posterior

The Scalenus posterior , the smallest and most deeply seated of the three Scaleni, arises, by two or three separate tendons, from the posterior tubercles of the transverse processes of the lower two or three cervical vertebræ, and is inserted by a thin tendon into the outer surface of the second...

.

They are innervated by the spinal nerves C4-C6.

Origin and insertion

They originate from the transverse processes from the cervical vertebrae

Cervical vertebrae

In vertebrates, cervical vertebrae are those vertebrae immediately inferior to the skull.Thoracic vertebrae in all mammalian species are defined as those vertebrae that also carry a pair of ribs, and lie caudal to the cervical vertebrae. Further caudally follow the lumbar vertebrae, which also...

 of C2 to C7 and insert onto the first and second rib

Rib

In vertebrate anatomy, ribs are the long curved bones which form the rib cage. In most vertebrates, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the chest cavity. They serve to protect the lungs, heart, and other internal organs of the thorax...

s. Thus they are called the lateral vertebral muscles.

Function

The action of the anterior and middle scalene muscles is to elevate the first rib

First rib

The first rib is the most curved and usually the shortest of all the ribs; it is broad and flat, its surfaces looking upward and downward, and its borders inward and outward....

 and laterally flex the neck

Neck

The neck is the part of the body, on many terrestrial or secondarily aquatic vertebrates, that distinguishes the head from the torso or trunk. The adjective signifying "of the neck" is cervical .-Boner anatomy: The cervical spine:The cervical portion of the human spine comprises seven boney...

 to the same side; the action of the posterior scalene is to elevate the second rib and tilt the neck to the same side.

They also act as accessory muscles of inspiration, along with the sternocleidomastoids.

Relations

The scalene muscles have an important relationship to other structures in the neck. The brachial plexus

Brachial plexus

The brachial plexus is a network of nerve fibers, running from the spine, formed by the ventral rami of the lower four cervical and first thoracic nerve roots...

 and subclavian artery

Subclavian artery

In human anatomy, the subclavian arteries are two major arteries of the upper thorax , below the clavicle . They receive blood from the top of the aorta...

 pass between the anterior and middle scalenes. The subclavian vein

Subclavian vein

The subclavian veins are two large veins, one on either side of the body. Their diameter is approximately that of the smallest finger.-Path:Each subclavian vein is a continuation of the axillary vein and runs from the outer border of the first rib to the medial border of anterior scalene muscle...

 and phrenic nerve pass anteriorly to the anterior scalene as it crosses over the first rib.

The passing of the brachial plexus

Brachial plexus

The brachial plexus is a network of nerve fibers, running from the spine, formed by the ventral rami of the lower four cervical and first thoracic nerve roots...

 and the subclavian artery

Subclavian artery

In human anatomy, the subclavian arteries are two major arteries of the upper thorax , below the clavicle . They receive blood from the top of the aorta...

 through the space of the anterior and middle scalene muscles constitute the scalene hiatus (the term "scalene fissure" is also used). The region in which this lies is referred to as the scaleotracheal fossa. It is bound by the clavicle

Clavicle

In human anatomy, the clavicle or collar bone is a long bone of short length that serves as a strut between the scapula and the sternum. It is the only long bone in body that lies horizontally...

 inferior anteriorly, the trachea medially, posteriorly by the trapezius, and anteriorly by the platysma muscle

Platysma muscle

The platysma is a superficial muscle that overlaps the sternocleidomastoid.It is a broad sheet arising from the fascia covering the upper parts of the pectoralis major and deltoid; its fibers cross the clavicle, and proceed obliquely upward and medially along the side of the neck.The anterior...

.

See also

• Muscle
  Muscle
  Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
  
  s
• List of muscles of the human body
• Accessory muscles of respiration

Additional images

The origin of the scalenes is 1st and 2nd ribs
The insertion is the transverse processes of c2-c7.