Anatomy of the Scapular Region: Muscles, Nerves, and Arteries | Study notes Acting

The scapular region is on the superior posterior surface of the trunk

and is deﬁned by the muscles that attach to the scapula (shoulder

blade). These muscles can be divided into:

• extrinsic muscles, which join the axial to the appendicular

skeleton (trapezius, latissimus dorsi, levator scapulae, rhomboid

minor, and rhomboid major);

• intrinsic muscles, which join the scapula to the humerus (deltoid,

supraspinatus, infraspinatus, teres minor, teres major, and

subscapularis).

The principal structural support is from the scapula, a flat triangular

bone. The costal (anterior) surface of the scapula overlies ribs II to

VII, and its three borders are superior, medial (vertebral), and

lateral (axillary), The lowest point is the inferior angle, and

the lateral point is the lateral angle. A transverse spine of scapula

divides the posterior surface of the scapula into a smaller

supraspinous fossa above and a larger infraspinous fossa below.

As it continues laterally, this spine forms the acromion (the bony

high point of the shoulder). The subscapular fossa is on the

anterior surface of the scapula. At the lateral angle of the scapula the

shallow, oval-shaped glenoid cavity articulates with the head of the

humerus at the glenohumeral joint.

MUSCLES

The muscles of the scapular region (Figs 17.1 and 17.2) join the

upper limb to the posterior trunk and facilitate many movements at

the shoulder. They can be divided into three groups (Table 17.1).

• The superﬁcial extrinsic muscles join the axial skeleton (chest wall

and rib cage) to the appendicular skeleton (bones of the upper

limb). The two muscles in this group are the trapezius and

latissimus dorsi. The large, triangular trapezius muscle slightly

overlies the broad latissimus dorsi muscle. Together, these

muscles originate from the entire length of the thoracic vertebral

column (CVII, TI to TXII) and insert laterally onto the clavicle,

scapula, and humerus.

• The deep extrinsic muscles (levator scapulae, rhomboid major,

and rhomboid minor) elevate and retract the scapula. The

strap-like levator scapulae muscle is deep to the

sternocleidomastoid muscle (see Chapter 13) and trapezius

muscles and joins the upper medial border of the scapula to the

transverse processes of the upper cervical vertebrae. The

rhomboids also originate on the medial border of the scapula,

with the rhomboid minor being more superior than the

rhomboid major muscle. These muscles attach to the spinous

processes of the upper thoracic vertebrae.

• The deep ‘intrinsic’ or true scapular muscles are the deltoid,

supraspinatus, infraspinatus, teres minor, teres major, and

subscapularis muscle. The deltoid muscle, which has three parts

(clavicular, acromial, and spinal), is superior and forms the

roundness of the shoulder over the glenohumeral joint. Inferior to

deltoid are four scapular muscles – the supraspinatus,

infraspinatus, teres minor, and subscapularis – which originate

from the scapula and insert laterally on the humerus, forming a

protective covering (rotator cuff) over the glenohumeral joint.

184

Scapular region

Figure 17.1 Scapular muscles (posterior view)

Levator scapulae muscle

Rhomboid minor muscle

Rhomboid major muscle

Supraspinatus muscle

Infraspinatus muscle

Teres minor muscle

Teres major muscle

Latissimus dorsi muscle

Posterior circumflex

humeral artery

Circumflex

scapular artery

Axillary nerve

Quadrangular space

Figure 17.2 Scapular region (anterior view)

Posterior circumflex

humeral artery

Subscapularis

muscle

Teres major muscle

Supraspinatus tendon

Coraco-acromial ligament Suprascapular artery

Suprascapular nerve

Thoracodorsal

nerve

Thoracodorsal artery

Inferior subscapular

nerve

Axillary nerve

Biceps brachii

tendon

Ch17.qxd 1/27/05 5:59 PM Page 184

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The scapular region is on the superior posterior surface of the trunk

and is defined by the muscles that attach to the scapula (shoulder

blade). These muscles can be divided into:

skeleton (trapezius, latissimus dorsi, levator scapulae, rhomboid

minor, and rhomboid major);

supraspinatus, infraspinatus, teres minor, teres major, and

subscapularis).

The principal structural support is from the scapula, a flat triangular

bone. The costal ( anterior ) surface of the scapula overlies ribs II to

VII, and its three borders are superior , medial (vertebral), and

lateral (axillary), The lowest point is the inferior angle , and

the lateral point is the lateral angle. A transverse spine of scapula

divides the posterior surface of the scapula into a smaller

supraspinous fossa above and a larger infraspinous fossa below.

As it continues laterally, this spine forms the acromion (the bony

high point of the shoulder). The subscapular fossa is on the

anterior surface of the scapula. At the lateral angle of the scapula the

shallow, oval-shaped glenoid cavity articulates with the head of the

humerus at the glenohumeral joint.

The muscles of the scapular region (Figs 17.1 and 17.2) join the

upper limb to the posterior trunk and facilitate many movements at

the shoulder. They can be divided into three groups (Table 17.1).

and rib cage) to the appendicular skeleton (bones of the upper

limb). The two muscles in this group are the trapezius and

latissimus dorsi. The large, triangular trapezius muscle slightly

overlies the broad latissimus dorsi muscle. Together, these

muscles originate from the entire length of the thoracic vertebral

column (CVII, TI to TXII) and insert laterally onto the clavicle,

scapula, and humerus.

and rhomboid minor) elevate and retract the scapula. The

strap-like levator scapulae muscle is deep to the

sternocleidomastoid muscle (see Chapter 13 ) and trapezius

muscles and joins the upper medial border of the scapula to the

transverse processes of the upper cervical vertebrae. The

rhomboids also originate on the medial border of the scapula,

with the rhomboid minor being more superior than the

rhomboid major muscle. These muscles attach to the spinous

processes of the upper thoracic vertebrae.

supraspinatus, infraspinatus, teres minor, teres major, and

subscapularis muscle. The deltoid muscle, which has three parts

(clavicular, acromial, and spinal), is superior and forms the

roundness of the shoulder over the glenohumeral joint. Inferior to

deltoid are four scapular muscles – the supraspinatus ,

infraspinatus , teres minor , and subscapularis – which originate

from the scapula and insert laterally on the humerus, forming a

protective covering (rotator cuff) over the glenohumeral joint.

17 Scapular region

Figure 17.1 Scapular muscles (posterior view)

Figure 17.2 Scapular region (anterior view)

The rotator cuff muscles rotate the humerus to enable actions

such as throwing a baseball. In conjunction with the latissimus

dorsi muscle, the teres major muscle, which is just inferior to the

rotator cuff muscles, helps form the posterior axillary fold. The

anterior axillary fold is formed by the pectoralis muscles; the axilla

lies between these folds.

The skin of the scapular region receives sensory information from

the medial branches of the posterior rami of cervical nerves C 4 to

C 8 and thoracic nerves T 1 to T 6 (see Chapter 26 ). The skin over the

lateral scapular area overlying the deltoid muscle is innervated by

branches of the superior lateral cutaneous nerve of arm , which is a

branch of the axillary nerve. Motor innervation to the muscles of

the scapular region is almost entirely by branches of the brachial

plexus (see Chapter 16 ):

the anterior ramus of C 5 ;

muscles) is from the superior trunk;

subscapular , thoracodorsal , and axillary ) are branches of the

posterior cord and supply the subscapularis, teres major,

latissimus dorsi, deltoid, and teres minor muscles. Only the spinal

root of accessory nerve [XI], which innervates trapezius, does not

originate from the brachial plexus.

Blood is brought to the scapular region by a network of arteries,

which form the scapular anastomosis:

dorsal scapular , transverse cervical , and suprascapular arteries ,

which are branches of the subclavian artery, and also from the

acromial artery , which is a branch of the axillary artery;

subscapular , circumflex scapular , and posterior circumflex