SHOULDER AND PELVIC GIRDLE

Similarities:

Both serve as transitions between relatively immovable torso areas and highly moveable arms and legs.

Both show up on the living figure as construction points although only the clavicle is subcutaneous.

Differences:

shoulder girdle: highly moveable; opens towards back; all parts visible on the surface

pelvic girdle: immovable; does not have a moveable joint with the spine; opens towards the front; only a few points visible on the living figure

The shoulder girdle forms a broad line at the top tapering inward along the edges of the scapulae to form a rough triangle. This is the reverse of the ribcage which is narrower at the top and broader at the base.

The clavicle:

The CLAVICLE is in front; the SCAPULA is in back. The joint between the clavicle and the manubrium is very loose allowing great flexibility and motion of the arms.

In most male figures the clavicle is a rising line, lowest at the joint with the manubrium. It is also longer in the male producing broader shoulders. In the female the clavicle is more horizontal. Occasionally the clavicle slopes downward giving the appearance of a long neck — this is rare in the male.

As seen from above the inner part of the clavicle is a convex curve; the outer part is a concave curve. This curve can vary; muscular development and increase the amount of curvature.

The scapula:

The scapula has no joint with the rib cage; it is bound into place by muscles but can slide very freely. At rest, the scapulae are about a neck width apart.

The clavicle and scapula meet at the ACROMION PROCESS; they are lashed together by ligaments which allow some movement.

On the scapula the COROCOID PROCESS springs from the top of the GLENOID FOSSA; it is deeply buried and is an important attachment point for muscles of the arm.

The HUMERUS is lashed to the coracoid process and the acromion process — loosely bound to allow for considerable movement. When the arm is lifted the tubercle of the humerus comes in contact with the acromion process and shifts the entire scapula.

The exterior border of the scapula is usually not visible as it is crossed by several muscles that move the arm. Important construction points on the scapula are: the interior border and inferior angle which are usually visible and the spine of the scapula.

THE PELVIS

The pelvis is an extremely complex bone, one that is very difficult to visualize in space. The OS COXAE (hipbone) roughly resembles a "figure 8" whose upper and lower sections have been twisted at right angles to one another.

At the center of the "8", but below the center of the bone, is the ACETABULUM, a deep socket which receives the head of the femur. The os coxae consists of 3 separate bones that have grown together in the adult: the ILIUM, above; the ISCHIUM, below; the PUBIS, in front. All three have roots in the hub-like acetabulum. The upper loop of the figure 8 is formed by the ilium and the lower loop by the ishcium and pubis together. The two hipbones are joined in front by cartilage. This joint is called the SYMPHYSIS PUBIS.

The pubis is the root of genitals. The ilium expands above the acetabulum into a broad, thin, wing-like shape. The ilium opens outward in front while the ischium opens outward in back and below.

Unlike the shoulder girdle the pelvis must contain organs and so is immovable.

The head of the FEMUR is deeply imbedded in the acetabulum which restricts movement of the thigh to a greater degree than is possible in the arm. A ligament that originates from the anterior superior iliac spine and inserts at the GREAT TROCHANTER further restricts movement. This ligament pulls tight and limits backward movement of the thigh thus allowing us to maintain an upright position.

Important construction points and lines:

the iliac crest - this is subcutaneous almost all the way along the anterior crest in the male living figure and about 2/3 of the way on the female.

the anterior superior iliac spine - almost always shows up on the living figure as a dimple or depression; on a very lean person as a bump

the posterior superior iliac spine - shows as a dimple (part of the sacral triangle)

the sacral triangle - defined by dimples at the posterior superior spines and point where cleft of buttocks begin - this does not change since the bones here are immovable.

the pubic crest - an important construction line since it marks the halfway point of the body; it is level with the great trochanter. On the living figure this is where the pubic hair begins.

the inguinal or ilio-pubic ligament - a ligament from the anterior superior iliac spine to the pubic crest - the fold of the bent leg occurs here. With a pot belly or muscular development this line is more visible.

 

SUMMARY

MALE - angle of thoracic arch 90 degrees; clavicles longer, angled; pelvis narrower, taller

FEMALE - angle of thoracic arch 60 degrees, clavicles shorter and more horizontal; pelvis wider, shallower

THE SHOULDER GIRDLE

THE PELVIC GIRDLE

 

CONSTRUCTION POINTS AND LINES:

Shoulder girdle:

Pelvic girdle:

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