SUPERFICIAL MUSCLES OF THE BACK

18. 12. 2012

Kaan Yücel

M.D., Ph.D.

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A TOTAL OF 8 FIGURES IN THE TEXT

Dr.Kaan Yücel http://yeditepeanatomy1.org Superficial muscles of the back

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There are two major groups of muscles in the back:The extrinsic back muscles include superficial and intermediate muscles that produce and control limb and respiratory movements, respectively. The intrinsic (deep) back muscles include muscles that specifically act on the vertebral column, producing its movements and maintaining posture.Muscles in the superficial and intermediate groups are extrinsic muscles because they originate embryologically from locations other than the back. They are innervated by anterior rami of spinal nerves: •Superficial group consists of muscles related to and involved in movements of the upper limb; •Intermediate group consists of muscles attached to the ribs and may serve as a respiratory function.Muscles in the superficial group include: Trapezius Latissimus dorsi Rhomboid major Rhomboid minor Levator scapulae

Rhomboid major, rhomboid minor, and levator scapulae are located deep to trapezius in the superior part of the back. Although located in the back region, for the most part these muscles receive their nerve supply from the anterior rami of cervical nerves and act on the upper limb. The trapezius receives its motor fibers from a cranial nerve, the spinal accessory nerve (CN XI).

The trapezius attaches the pectoral girdle to the cranium and vertebral column and assists in suspending the upper limb. Descending (superior) fibers elevate the scapula (e.g., when squaring the shoulders).Middle fibers retract the scapula (i.e., pull it posteriorly).Ascending (inferior) fibers depress the scapula and lower the shoulder.

The name latissimus dorsi (L. widest of back) was well chosen because the muscle covers a wide area of the back. Latissimus dorsi is a large, flat triangular muscle that begins in the lower portion of the back and tapers as it ascends to a narrow tendon that attaches to the humerus anteriorly. Movements associated with this muscle include extension, adduction, and medial rotation of the upper limb. Latissimus dorsi can also depress the shoulder, preventing its upward movement. The thoracodorsal nerve of the brachial plexus innervates the latissimus dorsi muscle.

From the transverse processes of the upper cervical vertebrae, the fibers of the levator of the scapula pass inferiorly to the superomedial border of the scapula. True to its name, the levator scapulae acts with the descending part of the trapezius to elevate the scapula, or fix it (resists forces that would depress it, as when carrying a load. Levator scapulae is innervated by branches from the anterior rami of spinal nerves C3 and C4 and the dorsal scapular nerve.

The rhomboids (major and minor), which are not always clearly separated from each other, have a rhomboid appearance. The two rhomboid muscles lie deep to the trapezius, inferior to levator scapulae and form broad parallel bands that pass inferolaterally from the vertebrae to the medial border of the scapulae. Rhomboid minor is superior to rhomboid major. The rhomboids retract and rotate the scapula, depressing its glenoid cavity. The dorsal scapular nerve innervates both rhomboid muscles.

The muscles in the intermediate group of back muscles consist of two thin muscular sheets in the superior and inferior regions of the back, immediately deep to the muscles in the superficial group; serratus posterior superior and serratus posterior inferior muscles. These muscles are related to the movements of the thoracic cage, as the superficial muscles are related to the movements of the shoulder (girdle). These two muscles are innervated by the anterior rami of upper thoracic nerves.

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Dr.Kaan Yücel http://yeditepeanatomy1.org Superficial muscles of the back

Most body weight lies anterior to the vertebral column, especially in obese people; consequently, the

many strong muscles attached to the spinous and transverse processes of the vertebrae are necessary to

support and move the column.

There are two major groups of muscles in the back:

The extrinsic back muscles include superficial and intermediate muscles that produce and control limb and

respiratory movements, respectively.

The intrinsic (deep) back muscles include muscles that specifically act on the vertebral column, producing its

movements and maintaining posture.

Muscles in the superficial and intermediate groups are extrinsic muscles because they originate

embryologically from locations other than the back. They are innervated by anterior rami of spinal nerves:

Muscles of the deep group are intrinsic muscles because they develop in the back.

•Superficial group consists of muscles related to and involved in movements of the upper limb;

•Intermediate group consists of muscles attached to the ribs and may serve as a respiratory function.

Figure 1. Superficial and intermediate groups of back muscleshttp://web.uni-plovdiv.bg/stu1104541018/docs/res/anatomy_atlas_-_Patrick_W._Tank/2%20-%20The%20Upper%20Limb.htm

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1. MUSCLES OF THE BACK

2. SUPERFICIAL GROUP OF BACK MUSCLES

Dr.Kaan Yücel http://yeditepeanatomy1.org Superficial muscles of the back

The muscles in the superficial group are immediately deep to the skin and superficial fascia. They are

connected with the shoulder girdle. They attach the superior part of the appendicular skeleton (clavicle,

scapula, and humerus) to the axial skeleton (skull, ribs, and vertebral column). Because these muscles are

primarily involved with movements of this part of the appendicular skeleton, they are sometimes referred to

as the appendicular group. Accordingly, they are also referred as posterior axioappendicular muscles and

produce and control limb movements.

Muscles in the superficial group include:

Trapezius

Latissimus dorsi

Rhomboid major

Rhomboid minor

Levator scapulae

Rhomboid major, rhomboid minor, and levator scapulae are located deep to trapezius in the superior part of

the back. Although located in the back region, for the most part these muscles receive their nerve supply from

the anterior rami of cervical nerves and act on the upper limb. The trapezius receives its motor fibers from a

cranial nerve, the spinal accessory nerve (CN XI).

Each trapezius muscle is flat and triangular, with the base of the triangle situated along the vertebral

column (the muscle's origin) and the apex pointing toward the tip of the shoulder (the muscle's insertion). The

trapezius attaches the pectoral girdle to the cranium and vertebral column and assists in suspending the

upper limb. This large, triangular muscle covers the posterior aspect of the neck and the superior half of the

trunk. It was given its name because the muscles of the two sides form a trapezium (G. irregular four-sided

figure). The muscles on both sides together form a trapezoid.

The fibers of the trapezius are divided into three parts, which have different actions at the

physiological scapulothoracic joint between the scapula and the thoracic wall:

Descending (superior) fibers elevate the scapula (e.g., when squaring the shoulders).

Middle fibers retract the scapula (i.e., pull it posteriorly).

Ascending (inferior) fibers depress the scapula and lower the shoulder.

The superior and inferior fibers work together to rotate the lateral aspect of the scapula upward,

which needs to occur when raising the upper limb above the head. The trapezius also braces the shoulders by

pulling the scapulae posteriorly and superiorly, fixing them in position on the thoracic wall with tonic

contraction; consequently, weakness of this muscle causes drooping of the shoulders.

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Dr.Kaan Yücel http://yeditepeanatomy1.org Superficial muscles of the back

Motor innervation of trapezius is by the accessory nerve [XI], which descends from the neck onto the deep

surface of the muscle. Proprioceptive fibers from trapezius pass in the branches of the cervical plexus and enter

the spinal cord at spinal cord levels C3 and C4.

Figure 2. Trapezius musclehttp://www.teachpe.com/anatomy/muscles/trapezius.php

The name latissimus dorsi (L. widest of back) was well chosen because the muscle covers a wide area

of the back. Latissimus dorsi is a large, flat triangular muscle that begins in the lower portion of the back and

tapers as it ascends to a narrow tendon that attaches to the humerus anteriorly. The posterior axillary fold is

formed by the tendon of latissimus dorsi as it passes around the lower border of the teres major muscle. It

can be easily palpated between the finger and thumb.

This large, fan-shaped muscle passes from the trunk to the humerus and acts directly on the

glenohumeral joint and indirectly on the pectoral girdle. The latissimus dorsi extends, retracts, and rotates

the humerus medially (e.g., when folding the arms behind the back or scratching the skin over the opposite

scapula). As a result, movements associated with this muscle include extension, adduction, and medial

rotation of the upper limb. Latissimus dorsi can also depress the shoulder, preventing its upward movement.

In combination with the pectoralis major, the latissimus dorsi is a powerful adductor of the humerus

and plays a major role in downward rotation of the scapula in association with this movement. In conjunction

with the pectoralis major, the latissimus dorsi raises the trunk to the arm, which occurs when performing

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Trapezius Superior nuchal line External occipital

protuberance Ligamentum nuchae Spinous processes of

C7 to T12

Lateral 1/3 of clavicle

Acromion

Spine of scapula

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ORIGIN INSERTION

Dr.Kaan Yücel http://yeditepeanatomy1.org Superficial muscles of the back

chin-ups (hoisting oneself so the chin touches an overhead bar) or climbing a tree, for example. The latissimus

dorsi is also useful in restoring the upper limb from abduction superior to the shoulder; hence the latissimus

dorsi is important in climbing.

Figure 3. Latissimus dorsihttp://www.becomehealthynow.com/body/muscles/atlas/latissimus.shtml

The superior third of the strap-like levator scapulae lies deep to the sternocleidomastoid; the inferior

third is deep to the trapezius. From the transverse processes of the upper cervical vertebrae, the fibers of the

levator of the scapula pass inferiorly to the superomedial border of the scapula. True to its name, the levator

scapulae acts with the descending part of the trapezius to elevate the scapula, or fix it (resists forces that

would depress it, as when carrying a load.

With the rhomboids and pectoralis minor, the levator scapulae rotates the scapula, depressing the glenoid

cavity (rotating the lateral aspect of scapula inferiorly). Acting bilaterally (also with the trapezius), the levators

extend the neck; acting unilaterally, the muscle may contribute to lateral flexion of the neck (toward the side

of the active muscle).

Figure 4. Levator scapulae Figure 5. Levator scapulae and rhomboid muscleshttp://en.wikipedia.org/wiki/File:Levator_scapulae.png http://home.comcast.net/~wnor/lesson1superficialmusclesofback.htm

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Latissimus dorsi

Spinous processes of T7 to L5

Sacrum Iliac crest Ribs 10 to 12

Floor of intertubercular sulcus of humerus

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ORIGIN INSERTION

Dr.Kaan Yücel http://yeditepeanatomy1.org Superficial muscles of the back

The rhomboids (major and minor), which are not always clearly separated from each other, have a

rhomboid appearance—that is, they form an oblique equilateral parallelogram.

The two rhomboid muscles lie deep to the trapezius, inferior to levator scapulae and form broad

parallel bands that pass inferolaterally from the vertebrae to the medial border of the scapulae. Rhomboid

minor is superior to rhomboid major.

The rhomboids retract and rotate the scapula, depressing its glenoid cavity. They also assist the

serratus anterior in holding the scapula against the thoracic wall and fixing the scapula during movements of

the upper limb. The rhomboids are used when forcibly lowering the raised upper limbs.

Figure 6. Rhomboid major et minorhttp://www.rad.washington.edu/academics/academic-sections/msk/muscle-atlas/upper-body/rhomboid-major-and-minor

Rhomboid major is superior to rhomboid minor.

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Rhomboid major

Spinous processes of T3 to T5 (Rho-Rhomb)

Medial border of scapula between spine and inferior angle

Rhomboid minor

Lower portion of ligamentum nuchae

Spinous processes of C7 and T1 (Rhomboi-Rhomboid)

Medial border of scapula at the spine of scapula

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3. INTERMEDIATE GROUP OF BACK MUSCLES

ORIGIN INSERTION

Dr.Kaan Yücel http://yeditepeanatomy1.org Superficial muscles of the back

The muscles in the intermediate group of back muscles consist of two thin muscular sheets in the

superior and inferior regions of the back; serratus posterior superior and serratus posterior inferior. They lie

immediately deep to the muscles in the superficial group. These muscles are related to the movements ofthe

thoracic cage, as the superficial muscles are related to the movements of the shoulder (girdle).

The intermediate extrinsic back muscles are thin muscles, commonly designated as superficial

respiratory muscles, but are more likely proprioceptive rather than motor in function (Fibers from these two

serratus posterior muscles pass obliquely outward from the vertebral column to attach to the ribs. This

positioning suggests a respiratory function, and at times, these muscles have been referred to as the

respiratory group).

Figure 7. Intermediate group of back muscles: serratus posterior superior et inferiorhttp://home.comcast.net/~wnor/lesson6musclesofback.htm

Table. Extrinsic back muscles [Superficial (appendicular) group & intermediate (respiratory) group of back muscles]Muscle Origin Insertion Innervation FunctionTrapezius Superior nuchal line

External occipital Lateral 1/3 of

clavicleMotor-accessory nerve [XI];

Assists in rotating the scapula during

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Serratus posterior superior

Lower portion of ligamentum nuchae

Spinous processes of C7 to T3

Supraspinous ligaments

Upper border of ribs 2 to 5 just lateral to their angles

Serratus posterior inferior

Spinous processes of T11 to L3

Supraspinous ligaments

Lower border of ribs 9 to 12 just lateral to their angles

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ORIGIN INSERTION

Dr.Kaan Yücel http://yeditepeanatomy1.org Superficial muscles of the back

protuberance Ligamentum nuchae Spinous processes of

C7 to T12

Acromion

Spine of scapula

proprioception-C3 and C4

abduction of humerus above horizontalupper fibers elevate, middle fibers adduct, lower fibers depress scapula

Latissimus dorsi Spinous processes of T7 to L5

Sacrum Iliac crest Ribs 10 to 12

Floor of intertubercular sulcus of humerus

Thoracodorsal nerve (C6 to C8)

Extends, adducts, and medially rotates humerus

Levator scapulae Transverse processes of C1 to C4

Upper portion medial border of scapula superior to root of scapular spine

C3 to C4 and dorsal scapular nerve (C4, C5)

Elevates scapula

Rhomboid major Spinous processes of T3 to T5

Medial border of scapula between spine and inferior angle

Dorsal scapular nerve (C4, C5)

Retracts (adducts) and elevates scapula

Rhomboid minor Lower portion of ligamentum nuchae

Spinous processes of C7 and T1

Medial border of scapula at the spine of scapula

Dorsal scapular nerve (C4, C5)

Retracts (adducts) and elevates scapula

Serratus posterior superior

Lower portion of ligamentum nuchae

Spinous processes of C7 to T3

Supraspinous ligaments

Upper border of ribs 2 to 5 just lateral to their angles

Anterior rami of upper thoracic nerves (T2 to T5)

Elevates ribs 2 to 5

Serratus posterior inferior

Spinous processes of T11 to L3

Supraspinous ligaments

Lower border of ribs 9 to 12 just lateral to their angles

Anterior rami of lower thoracic nerves (T9 to T12)

Depresses ribs 9 to 12 and may prevent lower ribs from being elevated when the diaphragm contracts.

Testing the superficial muscles of the backTo test the trapezius (or the function of the spinal accessory nerve [CN XI] that supplies it), the shoulder is

shruggedx against resistance (the person attempts to raise the shoulders as the examiner presses down on

them). If the muscle is acting normally, the superior border of the muscle can be easily seen and palpated.xShrugged:To raise (the shoulders), especially as a gesture of doubt, disdain, or indifference. Omuz silkmek

To test the latissimus dorsi (or the function of the thoracodorsal nerve that supplies it), the arm is

abducted 90° and then adducted against resistance provided by the examiner. If the muscle is normal, the

anterior border of the muscle can be seen and easily palpated in the posterior axillary fold.

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CLINICAL ANATOMY

Dr.Kaan Yücel http://yeditepeanatomy1.org Superficial muscles of the back

To test the rhomboids (or the function of the dorsal scapular nerve that supplies them), the individual places

his or her hands posteriorly on the hips and pushes the elbows posteriorly against resistance provided by the

examiner. If the rhomboids are acting normally, they can be palpated along the medial borders of the

scapulae; because they lie deep to the trapezius, they are unlikely to be visible during testing.

Auscultatory TriangleThe auscultatory triangle is the site on the back where breath sounds may be most easily heard with a

stethoscope. The boundaries are the latissimus dorsi, the trapezius, and the medial border of the scapula.

Figure 8. Auscultatory trianglehttp://ourhumananatomy.blogspot.com/2010/03/53-triangle-of-auscultation.html

Stiff NeckLevator scapulae

The muscle most often involved with a stiff neck is the levator scapula which connects the neck and

shoulder. The most usual complaint of a "stiff neck" is pain when trying to turn the head to the side where it

hurts, often turning the body instead of the neck to look behind. It is often associated with a headache but not

always.

The most common causes for developing this kind of stiff neck are; turning the head to one side while

typing, long phone calls without a headset, sleeping without proper pillow support with the neck tilted or

rotated, sitting in a chair with armrests too high and exposure of the neck to a cold draft.

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