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Basic Anatomy for the Artist

Lesson #1

A comprehensive study of human anatomy for artists:

This series considers the body as a whole in both subtle and extreme action. The skeletal structures and the muscle forms are closely related in the drawings to the form one sees on the surface. Wherever possible the landmarks are shown where bones give form on the surface, to help either for quick sketching, or more developed drawings, paintings, or sculptures.

For more precise anatomical information, a definite line is used to delineate the figures in the drawings. This is useful for outline pattern drawing and for the use of the line brought within the figure to show the form. For those interested in creating the illusion of a solid form in space, a hard line on the edge can sometimes deny the continuation of that form.

Foremost in the consciousness should be the fact that what one sees and interprets is light being reflected from a surface. It becomes necessary then to look at the graduations of shadow as the form recedes from the light, and for painters to observe the color changes.

Sometimes the lighting will be such that a part of the body will merge with the background completely, because of color juxtaposition or an identical tonal effect. Then it is decision time for expressing what you see, or what you know is there, or combining them. At such times an abstraction can emerge, and be developed as a form continuous with its environment. In this context those meanings of the word abstract are: to consider, apart from the concrete, something visionary, a negation of one or more objects in consequence of the mind's concentration on another.

MUSCLE STRUCTURE AND ACTION

The two components of skeletal muscle are a fleshy part composed of muscle cells and a fibrous part called a tendon or aponeurosis. Tendons are usually round and cord-like or flat bands. They are designed for strength, consisting mainly of protein fibers called collagen which lie longitudinally in the muscle axis, and are plaited. There are also a low percentage of elastic fibers which allow for about 4% contraction. When a tendon needs a wide areas of attachment it becomes sheet-like and is then called an aponeurouis. The collagen fibers extend into the bone which results in extra bone growth being stimulated in these areas called tubercles, tuberosities, and process.

Muscle cells are arranged into bundles of many cells and these bundles can shorten to about one half their length. Muscle cells are specialized to perform one function, and that is to contract. When the bundles shorten they therefore become thicker. When they thicken the form on the surface will bulge more, which they do when a muscle is producing action. All the bundles of a muscle do not have to act at one time. This explains why a slow change of form may be seen on the surface as more and more cells are stimulated into contraction to provide the action demanded.

Muscles have different arrangements of their cell bundles and also their tendons according to the demands of the power expected. Bundles of cells are arranged in long parallels if the action is to be maintained through a long distance. If greater power is needed, the muscle bundles are arranged in short diagonal bundles with far more numerous cells.

Muscles act on the skeleton to move it because they span joints. The usual plan is that the fleshy part is attached by fibers to one bone, and the tendon of this muscle span a joint and inserts into another bone. There is also the design where the fleshy part is in the middle and tendons on either end span a joint. When the fleshy part contracts, the bone, which is the more moveable, is drawn toward the other bone.

There is an exception in the face apart from the two muscles which control the jaw joint. Muscles of the face have two different designs: circular muscles which surround the eyes and mouth openings, and long muscles whose muscle bundles interweave at the edges of the circular ones, and pull the circular ones when they contract. There are also muscles which attach to the skin and move it and cause puckering.

THE MUSCLES OF THE FACE AND THEIR ACTIONS

There are two main muscles of the face. Orbicularis Oculi encircles the eye and Orbicularis Oris encircles the mouth. They are called sphincters because when they contract they close an opening.

The other muscles of the face which are interwoven into the edges of these two muscles, when they contract, pull on them and create action and the expression of the face. These muscles are:

• Frontalis which covers the frontal bone. When it contracts it pulls up orbicularis oculi and creates the horizontal frown lines on the forehead.
• Levator Labii Alaeque Nasi lifts the upper lip.
• Levator Labii interweaves with orbicularis oris. It lifts the lip.
• Levator Anguli Oris lifts the corner of the mouth.
• Zygomaticus Minor and Zygomaticus Major lift the corner of the mouth and are called the "smiling muscles".
• Risorius, attaching to the parotid gland, pulls horizontally on the corner of the mouth and is called the "grinning muscle".
• Depressor Labii pulls the lip down.
• Depressor Anguli Oris pulls the corner of the mouth down.

There are also two muscles attached to the skin:

• Corrugator, arising from the frontal bone, its muscle bundles pass up through frontalis muscle to attach to the skin. They cause the frowning furrows at the top of the nose when they contract.
• Mentales, a pair of cone-shaped muscles whose apices are attached to the front of the jaw and whose muscle bundles are attached to the skin of the chin. They can be felt as two rounded forms. A dimple in the chin is an indentation between two cones. The mentales move and pucker the skin in this area.

STRUCTURES CONCERNING THE EYES AND THEIR ACTIONS

The eyeball lies protected within the anterior half of the cone of bone, the Orbital Cavity. The eyelids also protect it, especially the upper one. This position in the skull places the eyes in the front plane of the head.

The eyeball is about 25mm in diameter, the white part called the sclera making up five-sixths of the ball. The anterior one-sixth is the transparent cornea which projects like a little dome. Behind the cornea is the flat disc called the iris. This is composed of muscle tissue which can contract to close and also open the pupil, which is the hole in the iris which allows light to enter. Radial bundles of muscle cells open it, and these striations are visible, and there are also muscle bundles running circularly around the pupil forming a sphincter.

The orbital cavity is filled in its posterior half by the optic nerve, fat, the muscle which control eye movements, and the vessels and nerves. The fat serves to cushion the eye if it is struck. In an emaciated person with fat depletion, the eye will sink into the orbit.

The eyelids are composed of soft tissue which take the form to a great extent of the eyeball under them. The upper lid is capable of much greater movement. The muscle which turns the eyeball upward, the Superior Rectus, is a laminated section of the muscle to the upper lid, the Lavator Palpebrae. They have the same nerve supply so they work together. The upper lid can also work, under the will, by itself. Also, when the eye looks down the upper lid comes down with it.

GENERAL INFORMATION: The Medial canthus (corner) of the eye is usually lower than the Lateral Canthus so the eye is set on a diagonal which runs downward toward the nose. This is to enable the film of tears which bathes the eye constantly to drain into tear ducts which open into the upper and lower lids at the medial canthus.

NOTE: When drawing the eye it helps greatly if one thinks first of the sphere behind the lids. Then the lids can be put in working over and around that round form.

See you next time!