Download The Thoractic Wall

The Thoracic Wall
Surface Anatomy:
Before starting your dissection,
inspect and palpate the following
surface landmarks with the cadaver
in the supine position; later
examine the same landmarks on
yourself. Identification of
landmarks is easier on the living
than on the preserved cadaver.
1.Suprasternal Notch.
2.Sternal Angle (Angle of Louis).
3. Xiphisternal Joint.
4. Subcostal Angle.
5. Costal Margin.
6. Clavicle.
7. Ribs.
8. Nipple.
9. Axillary Folds.
Dissection of
Pectoral
Region
skin incision
Make a skin incision along the full length of both
clavicle. Then incise the skin in the midline from the
suprasternal notch to the xiphisternal junction; continue
the incision along the costal margin to the midaxillary
line on each side.
Make circular incisions around the nipples.
Reflect the skin from the midline anteriorly to the
midaxillary line on each side. Leave the large skin flaps
attached at the midaxillary lines.
Mammary Gland.
The mammary gland lies in the superficial fascia
covering the anterior chest wall.
In the child and in men it is rudimentary. In the
femal after puberty it enlarges and assumesits
hemispherical shape.
In the youngadult female it overlies the second to
the sixth ribs and their costal cartilages and
extends from the lateral margin of the sternum to
the midaxillary line. Its upper lateral edge extends
round the lower border of the pectoralis major and
enters the axilla.
In middle-aged multiparous women the
breast may be large and pendulous. In older
women past the menopause the adipose
tissue of the breast may become reduced in
amount and hemispherical shape lost; the
breasts then become smaller, and the
overlying skin is wrinkled.
Examine the mammary gland in the male and the
female. Note that the nipple is surrounded by a
pigmented area called the areola. Incise the nipple in
the female and extend the incision into the breast.
Observe that the breast tissues divided up into 15 to
20 compartments by fibrous septa and that the greater
part of the breast substance is made up of fatty tissue.
After removing the fat with the scalpel handle,
identify one or two of the lactiferous ducts and trace
them to the nipple. Identify the thin sheet of muscle,
the platysma, as it arises from the fascia covering the
pectoralis major and passes superiorly over the
clavicle into the neck.
Cutaneous nerves and blood
vessels.
Identify the supraclavical nerves as
they descend from the neck beneath
the platysma. These supply the skin
of the shoulder and upper part of the
thorax down to the level of the
second costal cartilage.
Identify the anterior and lateral cutaneous branches
of an intercostal nerve.
With the scalpel handle, firmly stroke the superficial
fascia along the course of these nerves, thus removing
the overlying fat. Very often the small blood vessels that
accompany the nerves are first identified and lead the
dissector to the nerves. Do not dissect out all the
cutaneous nerves, but spend some time tracing out a
representative sample.
Pectoralis Major.
Expose and clean the entir anterior surface of the
pectoralis major muscle. Identify the clavicular
and sternocostal origins of this muscle. Follow the
tendon to its insertion in the floor of the bicipital
groove of the humerus. Recognize the
deltopectoral triangle, an interval between the
deltoid and pectoralis major muscles and the
clavicle. Identify the cephalic vein as it enters the
triangle from the upper limb.
Serratus Anterior.
Expose the digitations of origin of the serratus
anterior from the upper eight ribs.
This important muscle passes round the thoracic
wall to be inserted into the medial border of the
scapula. Identify the anterior layer of the rectus
sheath..
Cut the pectoralis major free from its origins on the
clavicle, sternum, ribs, and anterior layer of the rectus
sheath. Reflect the pectoralis major laterally to expose
the underlying pectoralis minor, the clavipectoral fascia,
and the subclavius muscle. Identify the lateral pectoral
nerve as it pierces the clavipectoral fascia to enter the
pectoralis major muscle. Also identify the medial
pectoral nerve as it pierces the pectoralis minor to enter
the pectoralis major.
Pectoralis Minor.
Clean the origin of the pectoralis
minor from the third, fourth, and
fifth ribs. Trace the fibers laterally
as they converge to be inserted
into the medial border of the
coracoid process.
Clavipectoral Fascia.
Identify this strong sheet of connective
tissue, which is split above to enclose the
subclavius muscle and is attatched to the
clavicle. Inferiorly, it splits to enclose the
pectoralis minor muscle and continues
downward to join the fascial floor of the
armpit.
Identify the thoracoacromial vessels and cephalic
vein as they pierce the clavipectoral fascia. Cut the
pectoralis minor muscle free from its origin on the
ribs and reflect it laterally. Recognize the lateral
thoracic vessels along the lateral border of the
pectoralis minor muscle. Do not attempt to dissect
the contents of the axilla. This area forms part of
the dissection of the upper limb.