Human Anatomy Vol 1

UPPER LIMB

lliac crest

Fig.5.1 : Surface landmarks and lines of dissection

Culoneous Neryes

The cutaneous nerves of the back are derived from the

posterior primary rami of the spinal nerves. Their

distribution extends up to the posterior axillary lines.

The following points may be noted.

1 The posterior primary rami of the spinal nerves C1,

C7, C8, L4 and L5 do not give off any cutaneous

branches. A11 twelve thoracic, L1-L3 and five

sacral nerves, however, give cutaneous branches

(Figs 5.2 and 5.3).

2 Each posterior primary ramus divides into medial

and lateral branches, both of which supply the

erector spinae muscles, but only one of them, either

medial or lateral, continues to become the cutaneous

nerves. In the upper half of the body (up to T6), the

medial branches, and in the lower half of the body

(below T6) the lateral branches, of the posterior

primary rami provide the cutaneous branches. Each

cutaneous nerve divides into a smaller medial and a

larger lateral branch before supplying the skin.

3 The posterior primary rami supply the intrinsic

muscles of the back and the skin covering them. The

cutaneous distribution extends further laterally than

the extensor muscles.

4 No posterior primary ramus erter supplies skin or

muscles of a limb. The cutaneous branches of the

posterior primary rami of nerves L7, L2, L3 and

S1-S3 are exceptions in this respect: They turn

Lateral cutaneous branch

Anterior primary ramus

Medial muscular branch

Posterior primary ramus

Dorsal nerve root

Ventral root

Lateral cutaneous branch

Anterior cutaneous branch

Fig.5.2: Course and branches of a lower thoracic nerve

downwards unlike any other nerve and supply the

skin of the gluteal region.

Twelfth rib

Back of scalp

External occipital

protuberance (i)

Acromion (v)

Deltoid

tuberosity (iii)

T12 spine (ii)

Sacrum

.ct
E

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CL
CL
f

c

o

a)

U)o

Dissection

ldentify the attachments of trapezius muscle in the upper

part of back; and that of latissimus dorsi in the lower

paft. Cut vertically through trapezius 5 cm lateral to the

venebral spines. Divide the muscle horizontally between

the clavicle and spine of scapula; and reflect it laterally

to identify lhe accessory nerue and its accompanying

blood vessels, the superticial ceruical ariery and vein.

Look for lhe suprascapular vessels and nerue, deep

to trapezius muscle, towards the scapular notch.

Cut through levator scapulae muscle midway

between its two attachments and clean the dorsal

scapular nerve (supplying the rhomboids) and

accompanying blood vessels. ldentify rhomboid minor

from rhomboid major muscle.

Pull the medial or inner scapular border away from

the chest wall for looking at the serratus anterior muscle'

Define attachments of latissimus dorsi muscle.

Feotures

Muscles connecting the upper limb with the vertebral

column are the lrapezits (Fig. 5.4), the latissimus dorsi,

the levator scapulae, and the rhomboid minor and

rhomboid major. The attachments of these muscles are

given in Table 5.1, and their nerve supply and actions

shown in Table 5.2.