The Upper Limb L1

(1) The Pectoral Region:

Naturally, the upper limbs are connected to the axial skeleton or trunk by means
of bones known as Pectoral Girdle, (pectoral=shoulder) right & left.

* Bones of the shoulder girdle & arm:

The pectoral girdle consists of the clavicle & the scapula (shoulder blade), which
articulate with one another at the acromioclavicular joints, so the scapulae &
clavicles connect the upper limbs with trunk.
The scapula invaded with different types of muscles, these muscles act as shock-
absorper.
The essential functional requirement of the pectoral girdle is the mobility over the
thorax to assist the mobility of shoulder joint.

[1] Clavicle: it's a long, slender, S-like shaped bone that lies horozintally across
the root of the neck. It articulates with the sternum & first costal cartilage
medially & with the acromion process of the scapula laterally.
The clavicle acts to hold the arm away from the trunk. It also transmits forces
from the upper limb to theaxial skeleton & provides attachment for muscles.
It's subcutaneous throughout it's length; it's medial two thirds are convex forward
& it's lateral third is concave backward.

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[2] Scapula: it's a flat, irregular, triangular bone that lies on the posterior thoracic
wall between 2nd & 7th ribs.
It's triangular bone has three Borders(margins): lateral(thick), medial & superior;
it has three Angles: acromion, superior & inferior;
It has two Surfaces: anterior(ventral, costal) & posterior(dorsal).
The posterior surface, the spine of the scapula projects backward. The
lateral end of the spine is free & forms the acromion, which articulates with the
clavicle. The superolateral angle of the scapula forms the pear-shaped fossa
glenoid cavity or fossa, which articulates with the head of the humerus at the
shoulder joint. The coracoid process projects upward & forward above the
glenoid cavity & provides attachment for muscles & ligaments. Medial to the
base of the coracoid process is the suprascapular notch. The posterior surface is
divided by the spine into supraspinous fossa above & an infraspinous fossa
below.
The anterior surface of the scapula is concave & forms the shallow
subscapular fossa.
The inferior angle of the scapula can be palpated easily in the living subject
& marks the level of the seventh rib & the spine of the seventh thoracic vertebra.

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[3] Humerus: it's one of the long bones in the body, it forms the skeleton of the
arm. It consist of proximal end which articulates with the scapula at the shoulder
joint,& a distal end which articulates with the radius & ulna at the elbow joint &
roughly cylindrical body or shaft.
The upper end of the humerus has a head which is a hemispherical in shape
(forms about 1/3 of a sphere)& articulates with the glenoid cavity of the scapula.
Immediately below the head is the anatomic neck. Below the neck are the greater
& lesser tuberosities, separated from each other by the intertubercular or
bicipital groove(site of insertion of the tendon of long head of biceps muscle).
Where the upper end of the humerus joins the shaft is a narrow surgical neck
(because fractures here are fairly common).
About halfway down the lateral aspect of the shaft is a roughened elevation
called the deltoid tuberosity. Behind & below the tuberosity is a spiral groove or
radial groove (which accommodates the radial nerve).
The lower end of the humerus possesses the medial & lateral epicondyles (for
the attachment of muscles & ligaments), the rounded capitulum for articulation
with the head of radius, & the pulley-shaped trochlea for articulation with the
trochlear notch of ulna.
Above the capitulum is the radial fossa, which receives the head of the radius
when the elbow is flexed. Above the trochlea anteriorly is the coronoid fossa,
which during the same movement receives the coronoid process of the ulna.

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Above the trochlea posteriorly is the olecranon fossa, which receives the
olecranon process of the ulna when the elbow joint is extended.

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Muscle attachment :-
The muscular attachment between the pectoral girdle & the trunk are of two types
1- Direct attachment
2- Indirect attachment

{1} Direct attachment: is provided by the following muscles that are inserted to
the clavicle & scapula from the axial skeleton:
1- Pectoralis minor, it's a thin triangular muscle
2- Trapezius
3- Rhomboideus
4- Levator Scapulae
5- Serratus Anterior, it's a large thin muscle that covers the lateral chest wall.

{2} Indirect attachment: to the axial skeleton is provided by the great muscles
of the axillary folds:
1- Pectoralis Major, it's a thick triangular muscle.
2- Latissimus Dorsi
* Also muscular attachment of the upper limbs & the pectoral girdle to the
skeleton indirectly include following muscles:
3- Deltoid muscle
4- Short scapular muscles: a- Supraspinatus
b- Infraspinatus
c- Teres Major
d- Teres Minor
e- Subscapularis
5- Biceps Brachii
6- Coracobrachialis
7- Long head of Triceps brachii

* Joints:-
(1) Sternoclavicular joint: it's a synovial double-plane joint with a capsule
occurs between the sternal snd of the clavicle, the manubrium sterni & the 1 st
costal cartilage.

(2) Acromioclavicular joint: it's a synovial plane joint with a capsule occurs
between the acromion of the scapula & the lateral end of the clavicle.

(3) Shoulder joint: it's a synovial ball & socket joint with a capsule occurs
between the rounded head of the humerus & the shallow, pear-shaped glenoid
cavity of the scapula.

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 The superficial part of the Back and the Scapular region:
 Muscles
1- Trapezius, it's a large, flat, triangular muscle that extends over the back
of the neck & thorax.

2- Latissimus Dorsi, it's a large, flat, triangular muscle that extends over
the lumbar region & the lower part of the thorax.
3- Levator Scapulae
4- Rhomboid Minor
5- Rhomboid Major
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6- Deltoid, it's thick, triangular & covers the shoulder joint. It forms the
rounded contour of the shoulder.
7- Supraspinatus
8- Infraspinatus
9- Teres Minor
10- Teres Major
11- Subscapularis

* Rotator Cuff : four muscles- the supraspinatus, the infraspinatus, the

teres minor & the subscapularis_ form what is termed the rotator cuff.
The tone of these muscles assists in holding the head of the humerus in the
glenoid cavity of the scapula during movements at the shoulder joint.
Therefore, they assist in stabilizing the shoulder joint. The cuff lies on the
anterior, superior, & posterior aspects of the joint. The cuff is deficient
inferiorly & this is a site of potential weakness.

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