Tricep Posterior pronation

Here we have a posterior view of the brachium with emphasis on the Triceps and the first stages of Pronation.. Also we got a bit of info on the extensor tendons,( extensor digitorum, indicies, and policis longus)  and how their branchings  insert into the phalanges.

Isonomia and the Gravitational Vector

.... In terms of artistic anatomy, understanding where the muscles originate and insert on the bone and how these muscles exert their influence on surface anatomy, is important for communicating how the veiwer "reads" the drawing. The nervous system is constantly firing off electrical impulses to the muscles to initiate flexion, as a way to counteract gravitational forces exerted down through the physical body.These forces are expressed as vectors which are channeled down through the skeleton to the earth's core or more specifically through whatever surface the body is resting on. In every movement there is a coordinated series of muscle flexion, all utilizing to various degrees the three types of levers, mechanisms of physics which describe how soft tissue can exert force across bone to achieve movement.To initiate movement through an invisible gravitational field means that the physical body,( or brain more accurately) has to coordinate how multiple muscles and groups of muscles must inititate flexion at precisely the right moment to achieve the desired movement. Very much like how retro rockets on a space craft  initiate movement along a path with the precise directional pulses of rockets.

"From the time a child leaves its mother's arms and begins to stand and walk alone, there is a force with which it, in common with the rest of mankind, is always contending; this force is gravity. We are battling with this force from morning till night, yielding to it partially as opportunity offers to assume a sitting position, and finally yielding to it completely, as we do each night when we sink to rest in a horizontal position. But this force not only acts upon the body as a whole throughout the day, but upon each individual part of the body. Thus the head tends to drop forward, the shoulders to round over and droop forward, the back to curve, the chest to become flattened and compressed, the knees to bend, the arch of the foot to break down, etc. This is nature's attempt to seek an equilibrium . . . and the only way that this downward tendency can be overcome is by the constant exertion of muscular force." l Sargent, 122, 

Triceps

From last weeks Ecorche class..."The Triceps"

• The primary function of the triceps is to extend the elbow, which results in straightening the arm. 
• The secondary function of the triceps is fulfilled only by the long head of the muscle, which is to adduct the arm (or to bring the arm down towards the body). The triceps shares this function with the latissimus dorsi (back muscles).

Interesting to note the placement of the Long Head and how it traverses the medial and lateral heads. On flexion it bulges out prominently at the tricep tendon sheath- a flat band of tendon that angles from the elbow up and lateraly. Check it out.