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ART STUDENTS' ANATOMY

Dover Publications, Inc.

LANDMARKS AND PROPORTIONS

There are landmarks evident in various regions of the body essentially important to the artist. These landmarks, as indicated in the figure on the opposite page, deal primarily with bones which cause projections on the surface. The details concerning the landmarks will be considered later in the text.

The human body is composed of the following parts:

The head (caput) includes the SKULL (cranium) and the FACE (facies). The face includes the mouth (os), nose (nasus), and eye (oculus).

The neck (collum) joins the head with the trunk. The sternocleidomastoid muscles, the throat (larynx), and the sternal parts of the clavicles are easily visible.

The trunk (truncus) is divided into the CHEST (thorax) and BELLY (abdomen). On the chest, one can distinguish the rib outline, the nipples of the mammary glands, and the lower border of the sternum, which serves as a line of separation between the thorax and abdomen. On the abdomen, the navel (umbilicus) is recognized as a depression at approximately the mid-abdomen. The inguinal ligament separates the trunk from the lower extremity. The BACK (dorsum) from the neck to the hip bones (coxae) is usually considered the hinder or posterior part of the trunk. The back of the neck is known as the nape (nucha).

The upper extremity (extremitas superior) is divided into four portions: SHOULDER (omos), ARM (brachium), FOREARM (antibrachium), and the HAND (manu), which includes the wrist (carpus).

The lower extremity (extremitas inferior) is also divided into four parts: HIP (coxa), THIGH (femur), LEG (crus), and FooT (pes), which includes the ankle (tarsus).

PROPORTIONS IN THE ADULT MALE

The "head-length" is the usual unit of measurement.

The average body is 7 ½ heads in length.

The shoulders at the greatest width, measures about 2 heud-lengths.

The supra-sternal fossa to the tip of the middle finger measures ½ the height of the body.

The body may be divided into two equal halves as in the diagram·

AB = BC where B represents the pubic arch.

The lower half (BC) may be subdivided into two equal halves:

BD = DC where D represents a point just below the knee.

The trunk (Fig. 1) may be divided into equal thirds as follows:

EF = FG = GB where E is the supra-sternal fossa

F is the xiphoid process of sternum

G is the navel

B is the pubic arch.

PROPORTIONS IN THE ADULT FEMALE

The body is 7 ½ head-lengths. The trunk is slightly greater in length than that of the male, while the length of the lower limbs is slightly shorter. The pelvis is broader in the female, while the width of the shoulders is narrower.

PROPORTIONS IN THE INFANT

The proportions of the infant may be represented in head-lengths as follows:

Birth—1st year 4 head-lengths

4 years 5 head-lengths

9 years 6 head-lengths (see page 125)

15 years 7 head-lengths

(Adult 7 ½ head-lengths)

THE SKELETON AS A WHOLE

The skeleton forms the framework of the body. It includes bones, cartilages, and articulations which bind the bones together.

Functions of Bones.

1. To afford surface for attachment of muscles.

2. To afford protection.

3. To serve as levers.

4. To bear weight.

Shape of Bones. The bones, according to their shapes, are divided into four types:

1. Long bone—Example, humerus.

2. Short bone—Example, wrist bones.

3. Flat bone—Example, scapula.

4. Irregular—Example, vertebra.

Sex of Bones. The male bones are characterized by:

1. Greater development of processes and ridges.

2. Greater broadness.

3. Greater size of the articular surfaces.

Number of Bones. It is impossible to state an exact number of bones for skeletons in general. No two skeletons are identical. However, two hundred separate bones (206) is the usual number of bones, of which one hundred and twenty-six belong to the appendicular skeleton, and seventy-four to the axial skeleton.

Parts of Bones.

Canal—a tunnel.

Condyle—a rounded eminence with articular cartilage.

Crest—a sharp border of bone.

Epicondyle—a projection above a smooth articular surface.

Foramen—a hole.

Fossa—a depression.

Incisure—a notch.

Lip—margin of a groove.

Line—a low ridge.

Plane—a flat surface.

Process—any kind of projection.

Sinus—a cavity in bone with mucous membrane lining.

Spine—a sharp prominence.

Sulcus—a groove.

TrocMea—a pulley.

Tuberosity—a rounded eminence.

THE SKELETON OUTLINED

The skeleton may be outlined as follows:

AXIAL: Skull, Vertebrae, Sternum, Ribs, Hyoid bone.

APPENDICULAR: Superior extremity, Inferior extremity.

Appendicular (Appendicular skeleton is paired throughout)

THE SKELETAL SYSTEM

THE SKULL

The skull (Figs. 9, 10, 11) rests on the summit of the vertebral column. The individual bones composing the skull are joined to each other by sutures. The skull may be divided into two parts as follows: (1) the skeleton of the face, and (2) the cranium, in which the brain is lodged.

The frontal bone forms the forehead, roof of the orbits, and the nasal fossae. It is smooth and subcutaneous, so that the shape of the bone is distinctive. The internal surface of the bone lodges the frontal lobe of the brain which is associated chiefly with the intellect. The frontal eminences are usually more prominent in women and children than in men, and appear as swellings on either side of the forehead. Below the frontal eminences are the superciliary arches which are small in the female and absent in children.

The occipital bone forms the back of the head. The large foramen (foramen magnum) on the base allows transmission of the spinal cord to the cranial cavity. The external occipital protuberance is easily felt as a prominent surface posteriorly. From the protuberance there extends laterally on either side a curved ridge of bone for muscle attachments, termed superior nuchal line.

The parietal bones are quadrilateral in shape and are united together in the mid-line by the sagittal suture to form the vault of the cranium.

The temporal bones are below the parietal bones at the side and base of the skull. Each possesses a nipple-like projection (the mastoid process), and a deep canal (the external auditory meatus of hearing). The mastoid process is not well developed in the infant, accounting for the marked flattening in appearance. (Fig. 144)

The maxillary bones are fused to form the whole upper jaw. Each maxilla assists in forming the roof of the mouth, the floor and lateral wall of the nose, and the floor of the orbits. It lodges the upper teeth, which in the adult consist of permanent teeth. The first set of teeth appear in childhood, and are called deciduous or milk teeth.

The dental formulae may be represented as follows (Figs. 9, 10, 11, 144):

The mandible is the largest and strongest bone of the face. It consists of a horizontal body and two perpendicular parts, the rami, which unite with the ends of the body in the adult at nearly right angles. It lodges the lower teeth and has a dental formula identical to the upper jaw. The mandible articulates with the temporal bone.

The zygomatic bones are small and quadrangular in shape and are situated at the upper part of the face to form the distinct prominences of the cheeks.

The two nasal bones form the bony arch or "the bridge" of the nose by being placed side by side at the middle and upper part of the face.

The sinuses are large air spaces in the frontal, ethmoid, sphenoid, and maxillary bones. They all communicate with the nasal passages.

Differences in skull due to age—see page 149.

THE VERTEBRAL COLUMN

The vertebral column forms the central axis of the skeleton. It is made up of twenty-six vertebrae in the adult as follows:

Cervica l7

Thoracic 12

Lumbar 5

Sacral 1

Coccygeal 1

The Spine. The spinal column is the chief support for the head, the ribs, the upper and lower extremities. The average length of the spine is about 28 inches in the male, and 27 inches in the female. The true or movable part of the spine is made up of the cervical, thoracic, and lumbar portions. The false or fixed part is made up of the sacrum and the coccyx. Spines of all vertebrae incline downwards, a condition peculiar to men and anthropoid apes. The greatest inclination is in the thoracic and least downward inclination is in the lumbar portions.

Curvatures. The vertebral column presents a series of curvatures as follows: PRIMARY CURVES: THORACIC, convex dorsally, SACRAL, convex dorsally. SECONDARY CURVES: CERVICAL, concave dorsally, LUMBAR, concave dorsally. The thoracic and sacral curves are termed Primary because they are present in fetal life. The cervical and lumbar curves are Secondary, and are developed after birth at about three and one-half months, when the child holds up his head; at nine months, when the child sits upright; and at about twelve to eighteen months, when the child begins to walk.

BONY LANDMARKS

The spines of the vertebrae are subcutaneous. The seventh cervical or vertebra prominens is the most prominent in the cervical region. The first thoracic spine may appear more prominent than the seventh cervical. On stooping or bending, the thoracic vertebrae appear like beaded elevations.

CLAVICLE

Shape. Slender, double curved, rounded medially, flattened laterally.

Position. Ventrally at base of neck and beginning of shoulder.

Articulations. Sternum, indirectly medially, acromion laterally.

Divisions. Body, sternal extremity, acromial extremity.

BONY LANDMARKS

The clavicle is subcutaneous throughout, being visible in most people, and easily felt through the skin and fascia. The sternal extremity is always visible.

STERNUM

Shape. Elongated, flattened ventro-dorsally, Roman sword-like.

Position. Thorax (chest), ventro-medially.

Articulations. Clavicle and true ribs.

Divisions. Manubrium (handle), body (little sword), xiphoid process.

BONY LANDMARKS

The middle of the sternum is subcutaneous. The female sternum is shorter and perhaps somewhat broader than that of the male.

THORAX

(Figures 4, 6, 8)

Shape. Barrel like, but smaller at upper than at lower portion.

Comprises.

12 thoracic vertebrae

12 ribs and cartilages

1 sternum (breast bone), which by their articulations make the barrel-shaped cavity. The slope of ribs increases from above downwards. The antero-posterior flattening is a purely human characteristic.

The upper seven ribs are called true ribs because they are attached to the sternum. The lower five ribs are called false ribs because they are not attached directly to the sternum, but by cartilage to the sternum. The eleventh and twelfth ribs are called floating ribs because they are free of cartilage. The thorax of the female is shorter than that of the male. Although the thorax is well covered externally with muscles, excepting the middle of the sternum and the mid-line of the back, the outline of the thorax is evident for the most part.

SCAPULA

Shape. Broad, flat, triangular with prominent transverse ridge on posterior side.

Position. Thorax, dorso-laterally from 2nd to 7th rib.

Articulations. Clavicle proximally, humerus distally.

Divisions. Body, spine, coracoid process, acromion.

BONY LANDMARKS

The bony points which can be felt on the scapula are the acromion, spine, coracoid process, the vertebral border, and the inferior angle.

Shape. Long, more or less round in upper half, triangular in lower half.

Position. Upper arm.

Articulations. Scapula, proximally, ulna and radius, distally.

Divisions. Body, proximal extremity, distal extremity.

BONY LANDMARKS

The medial and lateral epicondyles of the humerus are subcutaneous and easily recognized. The rest of the bone is covered with muscles, although a great part of it can be felt through them.

RADIUS AND ULNA

RADIUS

Shape. Long, slightly curved, rounded proximally, becoming larger distally and somewhat oval.

Position. LATERALLY in forearm.

Articulations. Humerus proximally, ulna proximo-medially, ulna disto-medially, navicular and lunate bones of wrist distally.

Divisions. Body, proximal extremity, distal extremity.

BONY LANDMARKS

The head of the radius is visible on the back of the forearm, while the distal extremity (styloid process) is somewhat prominent and very easily felt just above the wrist.

ULNA

Shape. Long, tapering, triangular proximally, rounded distally.

Position. MEDIAL side of forearm.

Articulations. Humerus proximally, radius proximally and laterally, radius distally and laterally, triangular cartilage distally.

Divisions. Body, proximal extremity, distal extremity.

BONY LANDMARKS

The head of the ulna appears as a rounded knob when the forearm is in the prone (palm down) position. The knob disappears in supination (palm up). The styloid process of the ulna is about one-half inch more proximal than the styloid process of the radius. The ulna may be felt from end to end on the back of the forearm, the olecranon being subcutaneous, prominent, and visible.

PELVIS

(Figures 4, 6, 8, 22, 23)

Shape. Basin-like.

Position. Lower portion of trunk.

Comprises. Two hip-bones, the sacrum, and coccyx.

Differences in Sex. The male and female pelves differ greatly, because the latter is arranged for the function of child-bearing.

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Excerpted from ART STUDENTS' ANATOMY by EDMOND J. FARRIS. Copyright © 1944 Edmond J. Farris. Excerpted by permission of Dover Publications, Inc..
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