Download Dr.Kaan Yücel http://yeditepeanatomy1.org Pectoral region

PECTORAL REGION
18. 12. 2012
Kaan Yücel
M.D., Ph.D.
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Axilla & Brachial plexus
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Pectoral region
OR
1. PECTAL
REGION
The pectoral region is external to the anterior thoracic wall and anchors the upper limb to the trunk. It
consists of:
•a superficial compartment containing skin, superficial fascia, and breasts; and
•a deep compartment containing muscles and associated structures.
Nerves, vessels, and lymphatics in the superficial compartment emerge from the thoracic wall, the
axilla, and the neck.
2. MUSCLES OF THE PECTORAL REGION
Four anterior axioappendicular muscles (thoracoappendicular or pectoral muscles) move the pectoral
girdle: pectoralis major, pectoralis minor, subclavius, and serratus anterior. The pectoralis major, pectoralis
minor, and subclavius muscles originate from the anterior thoracic wall and insert into bones of the upper
limb; and the serratus anterior to the scapula.
The pectoralis major muscle is the largest and most superficial of the pectoral region muscles It is a
large, fan-shaped muscle that covers the superior part of the thorax. It directly underlies the breast.
Pectoralis major has clavicular and sternocostal heads. The sternocostal head is much larger, and its
lateral border forms the muscular mass that makes up most of the anterior wall of the axilla. Its inferior
border forms the anterior axillary fold.
The pectoralis major and adjacent deltoid muscles form the narrow deltopectoral groove, in which the
cephalic vein runs.
Producing powerful adduction and medial rotation of the arm when acting together, the two parts of
the pectoralis major can also act independently: the clavicular head flexing the humerus, and the sternocostal
head extending it back from the flexed position.
To test the clavicular head of pectoralis major, the arm is abducted 90°; the individual then moves the arm
anteriorly against resistance. If acting normally, the clavicular head can be seen and palpated.
To test the sternocostal head of the pectoralis major, the arm is abducted 60° and then adducted against
resistance. If acting normally, the sternocostal head can be seen and palpated.
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Figure 1. Pectoralis major
Pectoralis major
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Axilla & Brachial plexus
ORIGIN
INSERTION
Clavicular head:
Medial half of
clavicle
Lateral lip of
intertubercular
sulcus of
humerus
Sternocostal head:
 Anterior surface
of sternum
 Superior six
costal cartilages
 Aponeurosis of
external oblique
muscle
The subclavius and pectoralis minor muscles underlie pectoralis major. Both subclavius and pectoralis
minor pull the tip of the shoulder inferiorly.
Figure 2. Pectoralis minor and subclavius
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The serratus anterior overlies the lateral part of the thorax and forms the medial wall of the axilla. This
broad sheet of thick muscle was named because of the saw-toothed appearance of its fleshy slips or
digitations (L. serratus, a saw). The serratus anterior is one of the most powerful muscles of the pectoral
girdle. It is a strong protractor of the scapula and is used when punching or reaching anteriorly (sometimes
called the “boxer's muscle”).
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Pectoral region
The strong inferior part of the serratus anterior rotates the scapula, elevating its glenoid cavity so the
arm can be raised above the shoulder. It also anchors the scapula, keeping it closely applied to the thoracic
wall, enabling other muscles to use it as a fixed bone for movements of the humerus. The serratus anterior
holds the scapula against the thoracic wall when doing push-ups or when pushing against resistance (e.g.,
pushing a car).
To test the serratus anterior (or the function of the long thoracic nerve that supplies it), the hand of
the outstretched limb is pushed against a wall. If the muscle is acting normally, several digitations of the
muscle can be seen and palpated.
Figure 3. Serratus anterior
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ORIGIN
Serratus anterior
Lateral parts of 1st8th ribs
INSERTION
Medial border of
scapula
3. FASCIAE OF THE PECTORAL REGION
The fascia of the pectoral region is attached to the clavicle and sternum. The pectoral fascia invests the
pectoralis major and is continuous inferiorly with the fascia of the anterior abdominal wall. The pectoral fascia
leaves the lateral border of the pectoralis major and becomes the axillary fascia, which forms the floor of the
axilla.
CLAVIPECTORAL FASCIA
Deep to the pectoral fascia and the pectoralis major, another fascial layer, the clavipectoral fascia,
descends from the clavicle, enclosing the subclavius and then the pectoralis minor, becoming continuous
inferiorly with the axillary fascia.Nerves, vessels, and lymphatics that pass between the pectoral region and
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the axilla pass through the clavipectoral fascia between subclavius and pectoralis minor or pass under the
inferior margins of pectoralis major and minor.
The part of the clavipectoral fascia between the pectoralis minor and the subclavius, the costocoracoid
membrane, is pierced by the lateral pectoral nerve, which primarily supplies the pectoralis major. The part of
the clavipectoral fascia inferior to the pectoralis minor, the suspensory ligament of the axilla, supports the
axillary fascia and pulls it and the skin inferior to it upward during abduction of the arm, forming the axillary
fossa.
The clavipectoral triangle (deltopectoral triangle) is the area in the pectoral region where the cephalic
veina can be found. The triangle is formed by the pectoralis major, deltoid and the clavicle. The deltopectoral
groove is an indentation in the muscular structure between the deltoid muscle and pectoralis major. It is the
location through which the cephalic vein passes and where the coracoid process is most easily palpable.
Figure 4. Clavipectoral fascia
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Pectoral region
Table. Muscles of the pectoral region
Muscle
Pectoralis major
Proximal
Attachment (Origin)
Clavicular head:
Medial half of
clavicle
Distal
Attachment
(Insertion)
Lateral lip of
intertubercular
sulcus of
humerus
Sternocostal head:
InnervationX
Lateral and
medial pectoral
nerves; clavicular
head (C5, C6),
sternocostal head
(C7, C8, T1)
Main Action
Adducts, flexes, and medially
rotates the arm.
Medial pectoral
nerve (C8, T1)
Stabilizes scapula by drawing it
inferiorly and anteriorly against
thoracic wall
Anchors and depresses clavicle
 Anterior surface
of sternum
 Superior six costal
cartilages
 Aponeurosis of
external oblique
muscle
Pectoralis minor
Subclavius
Serratus anterior
3rd-5th ribs near
their costal
cartilages
Junction of 1st rib
and its costal
cartilage
Lateral parts of 1st8th ribs
Coracoid
process of
scapula
Inferior
surface of
middle third of
clavicle
Medial border
of scapula
Nerve to
subclavius (C5,
C6)
Long thoracic
nerve (C5, C6, C7)
Acting alone, clavicular head
flexes humerus and sternocostal
head extends it from the flexed
position
Protracts scapula and holds it
against thoracic wall; rotates
scapula
X The spinal cord segmental innervation is indicated (e.g., “C5, C6” means that the nerves supplying the subclavius are derived from
the fifth and sixth cervical segments of the spinal cord). Numbers in boldface (C5) indicate the main segmental innervation. Damage
to one or more of the listed spinal cord segments or to the motor nerve roots arising from them results in paralysis of the muscles
concerned.
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