Human Anatomy Vol 1

SCAPULAR REGION

Spine of scapula

Acromion

1 The anterior border and adjoining surface of the

lateral one-third of the clavicle (Fi9.6.2).

2 The lateral border of the acromion where four septa

of origin are attached (Fig.6.2).

3 Lower lip of the crest of the spine of the scapula.

fnse r?

The deltoid tuberosity of the humerus where three septa

of insertion are attaihed.

fUerve $ Iy

Axillary nerve (C5, C6).
The acromial part of deltoid is an example of a
multipennate muscle. Many fibres arise from four septa
of origin that are attached above to the acromion. The
fibres converge on to three septa of insertion which are
attached to the deltoid tuberosity (Fig.6.2).

,4cfi"ons

1 The multipennate acromial fibres are powerful
abductors of the arm at the shoulder joint from
beginning to 90'.
A multipennate arrangement allows a large number
of muscle fibres to be packed into a relatively small

Table 6.1:

Muscle

1. Supraspinatus (Fig. 6.3)


2. lnlraspinatus


3. Teres minor


4. Subscapularis (multipennate)


5. Teres major

lntermuscular

septum of origin

(multipennate

fibres)

lntermuscular

septum of

insertion

Deltoid tuberosity

Fig. 6.2: The origin and insertion of the deltoid muscle

volume. As the strength of contraction of a muscle is

proportional to the number of muscle fibres present

in it (and not on their length), a multipennate muscle

is much stronger than other muscles having the same

volume.

Attachments of muscles of scapular region (except deltoid)

Origin from lnserlion into

Medial two-thirds of the supraspinous fossa Upper impression on the greater tubercle

of the scapula of the humerus

Medial two-thirds of the infraspinous fossa Middle impression on the greater

of the scapula tubercle of the humerus

Upper twothirds of the dorsal surface of the Lowest impression on the greater

lateral border of the scapula tubercle of the humerus

Medial two-thirds of the subscapular fossa Lesser tubercle of the humerus

Lower one-third of the dorsal sudace of lateral Medial lip of the bicipital groove of the

border and inferior angle of the scapula humeru

Posterior

fibres

Anterior

fibres

Table 6.2: Nerve supply and actions of muscles of scapular region (except deltoid)

Muscle

1. Supraspinatus
   (Fig. 6.3)


2. Infraspinatus


3. Teres minor


4. Subscapularis
   (Fis. 6.a)


5. Teres major

Nerue supply

Suprascapular nerve (C5, CO)

Suprascapular nerve (C5, CG)

Axillary nerve (C5, C6)

Upper and lower subscapular nerves

(c5, c6)

Lower subscapular nerve (C5, C6)

Actions

. Along with other short scapular muscles it steadies the
head of the humerus during movements of the arm. lts action
as abductor of shoulder joint from 0-15' is controversial.
Both supraspinatus and deltoid are involved in initiation of
abduction and continuation of abduction.
. Lateral rotator of arm (see above)
Same as infraspinatus
Medial rotator and adductor of arm

Same as subscapularis

lt

E

I

o

CL

CL

c

.o

o

ao