Dissection of the
Superficial Part of the Back
Contents as following :
I. Surface Anatomy
II. Skin Incision
III.Superficial Fascia
IV.Muscle layer
Place the cadaver in the
prone position.
I. Surface Anatomy:
Palpate the following bony landmarks:
1 the external occipital protuberance,
2 the vertebra prominens (spinous process of C7),
3 spinous process of first thoracic vertebra,
4 the crest of the spine of the scapula,
5 the acromion process of the scapula,
6 the superior and inferior angles of the scapula,
7 the iliac crest.
II. Skin Incision:
1. Make a vertical midline skin incision from the
external occipital protuberance downward to the level of
the iliac crest.
2. At the lower end,extend the incision transversely to
the right and left as far as the midaxillary line.
3. At the upper end, extend the incision from the
external occipital protuberance to the acromion process.
4. On the right and left sides, reflect the skin laterally
from the back of the neck, the shoulders, and the back to
the midaxillary lines.
III. Superficial Fascia
(subcutaneous tissue) :
Identify the cutaneous branches of the
posterior rami of the cervical,thoracic,and
lumbar spinal nerves in the underlying
subcutaneous tissue.
1. Locate the greater occipital nerve, which is the
posterior ramus of the second cervical nerve. It
emerges from the trapezius about 2.5cm below and
lateral to the external occipital protuberance.
2.
Clean and study one cutaneous branch of a
posterior ramus of a thoracic spinal nerve.
3. To assist you in finding such a nerve, carefully
look for a blood vessel that follows each of these nerves.
Do not waste time tracing out the cutaneous branches
of all the posterior rami
Now reflect the superficial fascia of the
back in line with the skin incisions, being
carefully not to damage the underlying
muscles, the trapezius and the latissimus
dorsi.
IV. Muscle:
Identify and
clean the trapezius
and latissimus dorsi
muscles and origin
of the posterior part
of the deltoid muscle
Trapezius muscle.
Confirm that this muscle has an extensive
origin from the medial one-third of the superior
nuchal line of the occipitl bone, the occipital
protuberance, the ligamentum nuchae, the spinous
processes of the seventh cervical vertebra and the
spinous processes and supraspinous ligaments of
thoracic vertebrae one to twelve.
Trace the superior muscle fibers to their
insertion on the lateral third of the
clavicle, the middle fibers to their
insertion on the acromion and the spine
of the scapula, and the inferior fibers to
their insertion on the base of the spine of
the scapula.
Cut free the origin of the trapezius from the
skull, the ligamentum nuchae, and the
spinous processes of the vertebrae. Carefully
reflect the trapezius laterally, taking care not
to damage the underlying levator scapulae
and rhomboid muscles.
Identify and preserve the spinal
part of the accessory nerve and
the posterior rami of the third
and fourth cervical nerves, which
supply the trapezius muscle.
Latissimus dorsi muscle.
Confirm that this muscle arises from the posterior
part of the iliac crest, the lumbar fascia, the
spinous processes of the lower six thoracic
vertebrae, and from the lower three or four ribs;
sometimes a few fibers arise from the inferior
angle of the scapula. Note that the fibers sweep
upward and laterally, converging on a tendon that
passes into the axilla to be inserted into the
humerus.
Transect
the
origin
of
the
latissimus dorsi and reflect the
muscle laterally, thus exposing
the underlying serratus posterior
inferior muscle.
Identify and clean the levator
scapulae and rhomboid minor and
rhomboid major muscles. Leave the
levator scapulae intact and trace its
fibers to their insertion on the
medial border of the scapula.
Cut free the origins of the rhomboid minor
and major muscles from the vertebrae and
carefully reflect them laterally to their
insertions on the medial border of the scapula.
Be careful to preserve the underlying serratus
posterior superior muscle, which is
sometimes stuck to the rhomboid muscles.
Identify and clean the dorsal
scapular nerve and the deep branches
of the superficial cervical vessels that
lie deep to the rhomboid muscles,
close to their insertion.
Identify the serratus
anterior muscle at its insertion
along the anterior surface of the
medial border of the scapula.
Define the posterior border of the deltoid muscle
and confirm the origin of this muscle from the spine and
acromion process of the scapula. With a scalpel, cut free the
origin of the deltoid muscle from the spin and acromion
process but leave its attachment to the clavicle intact. Note
that the deltoid fibers pass downward to their insertion on
the deltoid tuberosity of the humerus. To assist you with the
later study, now remove the skin and superficial fascia from
the back of the shoulder and the back of the arm, down as
far as the olecranon process of the ulna.
Identify and clean the
supraspinatus, infraspinatus,
teres minor and teres major,
and the long head of the
triceps muscles.Expose the
boundaries and contents of
the quadrilateral and
triangular spaces.