The pectoral region
University of Babylon College of Medicine Dr.HaythemAli Alsayigh M.B.CH.B.-F.I.M.B.S. Surgical Clinical Anatomy Objective • Study the Bones and Joints A. Clavicle (collarbone) B. Scapula (shoulder blade) C. Humerus D. Radius E. Ulna F. Carpal bones G. Metacarpals H. Phalanges
Upper Limb II. Joints and Ligaments A. Acromioclavicular joint B. Sternoclavicular joint C. Shoulder (glenohumeral) joint D. Elbow joint E. Proximal radioulnar joint F. Distal radioulnar joint G. Wrist (radiocarpal) joint H. Midcarpal joint I. Carpometacarpal joints J. Metacarpophalangeal joints K. Interphalangeal joints Some clinical problems Fracture of the clavicle Calcification of the superior transverse scapular ligament Fracture of the greater tuberosity Fracture of the lesser tuberosity Fracture of the surgical neck Fracture of the shaft Supracondylar fracture Fracture of the medial epicondyle Colles' fracture of the wrist and a reverse Colles' fracture (Smith's fracture). Guyon's canal syndrome Guyon's canal (ulnar tunnel The pectoral region
Pectoralis major Rectus sternalis Morphology of body wall muscles Deltopectoral triangle Pectoralis minor Subclavius Clavipectoral fascia Serratus anterior The pectoral region
The pectoral region is located on the anterior aspect of the thorax It contains muscles that belong to the upper limb. The pectoral muscles
The pectoral muscles are 4 muscles; these are pectoralis major, pectoralis minor, subclavius, and serratus anterior. Pectoralis major
This is a large, powerful, fan-shaped (triangular) muscle. It is attached by means of two heads to the front of the chest Pectoralis major Clavicular head
arises from the medial half of the clavicle Pectoralis major Sterno-costal head
is attached to the anterior surface of the sternum and to the upper six costal cartilages Pectoralis major Insertion
The muscle fibers converge to be inserted into the lateral lip of the intertubercular groove of the humerus Pectoralis major Trilaminar insertion
The clavicular head is inserted by the anterior lamina of the tendon Pectoralis major Trilaminar insertion
the manubrial fibers are inserted into the intermediate lamina of insertion Pectoralis major Trilaminar insertion
the sterno-costal fibers arising below the sternal angle are inserted into the posterior lamina of the tendon Pectoralis major insertion
The fibers which arise lowest of all are inserted highest of all Pectoralis major insertion
this produces the rounded appearance of the anterior axillary fold Pectoralis major
Nerve supply Pectoralis major Action
The muscle is an adductor of the arm at the shoulder joint Pectoralis major Action
The muscle is a medial rotator of the arm at the shoulder joint Pectoralis major Action
The clavicular head alone flexes the humerus Pectoralis major Action
From a fixed insertion, the muscle acts as an accessory muscle of respiration and in climbing Pectoralis major test
To test the integrity of the muscle, the arm is abducted to 90o or more and the patient pushes forwards against resistance Absence of pectoralis major Rectus sternalis
One body in 20 (5%) shows the presence of vertical musculoaponeurotic fibers on the surface of pectoralis major alongside the sternum Morphology of the body wall muscles
The body wall of all vertebrates consists of three layers of muscles Morphology of the body wall muscles
embryologically, pectoral muscles are derived from upper limb myotomes Morphology of the body wall muscles
morphologically, pectoral muscles belong to the outer layer of the three primitive layers of the body wall, represented in the abdomen by the external oblique Morphology of the body wall muscles
Towards the midline, ventrally and dorsally, the three layers change direction to make muscles that run longitudinally. Morphology of the body wall muscles
Ventrally, the longitudinal muscle is formed by fusion together of all three layers Morphology of the body wall muscles
It begins behind the symphesis menti as the geniohyoid, thyrohyoid, sternohyoid, omohyoid, and sternothyroid. Morphology of the body wall muscles
Then the rectus abdominis begins and extends to the symphysis pubis Morphology of the body wall muscles
There is a gap where the sternum and costal cartilages intervene Morphology of the body wall muscles
Traces of the ventral rectus muscle appear in this gap in front of the sternal fibers of pectoralis major forming the rectus sternalis muscle Delto-pectoral triangle
1/3 Since deltoid muscle is attached to the 1/2 lateral third of the clavicle and pectoralis major to the medial half, there is a small part of the clavicle to which neither muscle is attached. Delto-pectoral triangle
This part forms the base of a triangular space (delto-pectoral triangle) between the two muscles, deltoid and pectoralis major Delto-pectoral triangle
The delto-pectoral triangle may be visible in thin people. Delto-pectoral triangle
It contains lymph nodes called infraclavicular lymph nodes; it also contains the Cephalic v . termination of the cephalic vein Delto-pectoral triangle The floor of the triangle is formed by deep fascia called the clavi-pectoral fascia Pectoralis minor
This is a small triangular muscle that is largely covered by pectoralis major Pectoralis minor
It arises from the 3rd, 3 4th, and 4 5th ribs (not costal 5 cartilages); and is inserted into the coracoid process of the scapula Pectoralis minor Its nerve supply is the same as that of pectoralis major namely medial and lateral pectoral nerves. Lateral pectoral The medial nerve pectoral nerve passes through Medial pectoral pectoralis minor nerve to reach the overlying pectoralis major
Nerve supply Action of pectoralis minor
The muscle stabilizes the scapula and can pull it forwards against the thoracic wall (protraction). The muscle is elongated in full abduction of the arm; its subsequent contraction assists gravity in restoring the scapula to the rest position Action of pectoralis minor
The muscle is of no great functional importance; however, it is an important anatomical and surgical landmark being a landmark to the underlying axillary artery Chest, cross section at T4 Chest: axial CT
Note pectoralis major Pectoralis major pectoralis minor Pectoralis minor Subclavius
This is a small unimportant muscle that as its name indicates lies inferior to the clavicle Subclavius
It arises from the first costo-chondral junction and is inserted into the subclavian groove on the inferior surface of the clavicle the muscle thus lies almost horizontally Action of subclavius
The muscle acts to stabilize the clavicle during shoulder movement.
Prime mover
fixator Action of subclavius
It may prevent the jagged ends of a fractured clavicle from damaging the adjacent subclavian vein.
Nerve supply of subclavius
nerve to subclavius
A branch of the brachial plexus (roots of C5 &6) Clavipectoral Costo-coracoid ligament fascia
This is a sheet of deep fascia filling in the space between the clavicle and pectoralis minor (hence the name) Clavipectoral fascia
The fascia splits twice to enclose two muscles above to enclose subclavius below to enclose pectoralis minor Clavipectoral fascia
At the inferior border of pectoralis minor, the two layers of fascia rejoin and extend downwards as the suspensory ligament of the axilla The suspensory ligament of the axilla
Is attached to the deep fascia of the floor of the axilla. By its tension, it maintains the axillary hollow Clavipectoral fascia
The clavi-pectoral fascia is almost completely covered by pectoralis major and deltoid muscles; a small portion of it appears at the floor of the delto-pectoral triangle Clavipectoral fascia
Four structures two passing inwards and two passing outwards pierce the clavi- pectoral fascia Clavipectoral fascia
Passing inwards are lymphatic vessels from the infraclavicular ymph nodes to the apical group of axillary lymph nodes and the cephalic vein draining into the axillary vein Clavipectoral fascia Passing outwards are the acromio- thoracic axis (artery) which is a branch of the axillary artery and the lateral pectoral nerve
Lateral pectoral nerve On the cadaver note that the medial pectoral nerve pierces pectoralis minor while the lateral pectoral nerve pierces the clavi-pectoral fascia Lateral pectoral nerve at a position more medial to the lateral Medial pectoral pectoral nerve. nerve In other words, the relation of the pectoral nerves in the pectoral region is the reverse of their names The names of these medial laterall pectoral n. pectoral n. nerves (medial and lateral) are derived Pectoralis minor from their origin from the cords of the brachial plexus (medial and lateral cords
Axillary v. respectively) rather Medial than their relation in cord Axillary a. lateral cord the pectoral region
posterior cord Serratus anterior
This muscle was given its name because of the sow- toothed appearance (L. Serratus = a sow) of its origin where the muscle arises by 8 digitations from the upper eight ribs lateral to their angles Serratus anterior
Since external oblique muscle arises from the lower eight ribs, then the lower 4 external digitations of serratus oblique anterior inter-digitate with the upper 4 digitations of external oblique Serratus anterior
The muscle forms a flat sheet that is attached to the anterior aspect of the medial border of the scapula Serratus anterior
The muscle is supplied by the long thoracic nerve, a branch of the brachial plexus Serratus anterior action
The muscle acting as a whole protracts the scapula (i.e. moves the scapula forwards) and is used by boxers to deliver a straight left Serratus anterior action
acts as a fixator of the scapula during movements of the humerus
Prime mover
fixator Serratus anterior action
The lower fibers are very strong, they pull forwards on the lower angle of the scapula and thus rotate the scapula so that the glenoid cavity faces upwards (as in raising the arm above the head) Serratus anterior action
this is similar to the coupled action of the upper and lower fibers trapezius Serratus anterior action
In quadrupeds, serratus anterior suspends the trunk between the forelimbs