Chapter 10
The Muscular System
351
10
MUSCLE
DESCRIPTION
ORIGIN (O) AND
INSERTION (I)
ACTION
NERVE
SUPPLY
Latissimus dorsi
(lah-tis
9
ı˘-mus dor
9
si)
(
latissimus
5
widest;
dorsi
5
back)
Broad, flat, triangular
muscle of lower back
(lumbar region); extensive
superficial origins; covered
by trapezius superiorly;
contributes to the posterior
wall of axilla
O—indirect attachment
via lumbodorsal fascia
into spines of lower
six thoracic vertebrae,
lumbar vertebrae, lower
3 to 4 ribs, and iliac
crest; also from scapula’s
inferior angle
I—spirals around teres
major to insert in floor
of intertubercular sulcus
of humerus
Prime mover of arm
extension; powerful
arm adductor; medially
rotates arm at shoulder
;
depresses scapula;
plays important role in
lowering arm in a power
stroke, as in striking
a blow, hammering,
swimming, and rowing;
with arms fixed overhead,
it pulls the rest of the
body upward and
forward
Thoracodorsal nerve
(C
6
–C
8
)
MUSCLE GALLERY
Table 10.9
(continued)
Clavicle
Deltoid
Sternum
Pectoralis
major
Lateral head
Long head
Medial head
Coracobrachialis
Triceps brachii:
Biceps brachii
Brachialis
Brachio-
radialis
(a) Anterior view
Supraspinatus*
Spine of scapula
(b) Posterior view
Deltoid (cut)
Greater tubercle
of humerus
Infraspinatus*
Teres minor*
Teres major
Triceps brachii:
Latissimus dorsi
Humerus
Olecranon
of ulna
Lateral head
Long head
Anconeus
Figure 10.15
Muscles crossing the shoulder and elbow joints, causing movements
of the arm and forearm, respectively.
(For related images, see
A Brief Atlas of the Human
Body
, Figures 35 and 36.)
(a)
Superficial muscles of the anterior thorax, shoulder, and arm,
anterior view.
(b)
Muscles of the posterior thorax and arm. The triceps brachii muscle of the
posterior arm is shown in relation to the deep scapular muscles. The deltoid muscle of the
shoulder and the trapezius muscle have been removed.
*Rotator cuff muscles
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