There are many ways to approach the study of the human figure in motion. One great way to start is to gain a good grasp of the human skeletal system. In this chapter, we will look at the primary bones—their locations and their basic landmarks. Understanding the basic shapes and placement of bones serves many purposes for the artist. First, bones provide the framework to which the muscles are attached. Second, the lengths of the bones, particularly the long bones, help indicate the general proportions of a person (short, average, or tall stature). Third, portions of bones located close to the surface of the skin can be utilized as essential landmarks in the depiction of the human figure. Finally, bones’ interactions at the joints—which we will cover extensively in the next chapter—are vital for understanding the mechanics of movement.
Bones are classified into four categories—long bones (bones of the limbs), short bones (carpal and tarsal bones of the wrist and foot), flat bones (sternum, ribs), and irregular bones (vertebrae, portions of cranial bones). The characteristics of these different types will be introduced as we examine the various bones of the skeleton.
Anatomy Vocabulary Basics
A number of essential anatomical terms are used repeatedly throughout this book. The first with which you should become familiar is the anatomical position—the standard international reference position used to locate the various sections and structures of the human body. The anatomical position is a standing, erect position of the entire body, with both feet on the ground next to each other and the head facing forward. The arms are positioned at the sides with the palms facing forward.
Other terms describe the locations of the various body parts (including bones and muscles) in relation to one another when the figure is standing in the anatomical position. Some of these terms are also used to describe the particular view that an observer has of the figure or a particular body part. Here is a basic list:
· Anterior means “in front of”—that is, toward the front of the body. An anterior view is a view of the front of the body or a body part.
· Posterior means “in back of”—that is, toward the back of the body. A posterior view is a view of the back of the body or a body part.
· Lateral means “side”—that is, away from the midline (or central axis) of the body. A lateral view is a side view of the body or a body part.
· Medial means “middle”—that is, toward the midline (or central axis) of the body. A medial view is a view of the medial surface of a body part (such as a foot).
· Superior means “above,” referring to structures closer to the head or toward the top of a body part. A superior view is a view from above.
· Inferior means “below,” referring to structures closer to the feet or toward the bottom of a body part. An inferior view is a view from below.
· Dorsal pertains to the back of the hand and the upper side of the foot.
· Palmar pertains to the palm of the hand.
· Plantar pertains to the sole of the foot.
· Proximal means “in proximity to”—that is, nearer a limb’s point of origin on the torso. It can also pertain to structures of the fingers and toes.
· Distal means “distant from”—that is, farther from a limb’s point of origin on the torso. It can also pertain to structures of the fingers and toes.
The Main Bones of the Human Figure
The human skeleton consists of two basic parts—the axial skeleton and the appendicular skeleton. The axial skeleton is the group of bones that forms the central axis of the body; its primary function is to support and protect the internal organs. The bones of the axial skeleton include the cranium, the bones of the vertebral column (including the sacrum and coccyx), and the rib cage.
The appendicular skeleton is the group of bones forming the appendages of the body (upper and lower limbs), including the shoulder girdle and pelvic girdle. The primary functions of the appendicular skeleton are to support and move the axial skeleton and to allow movement of the limbs. Appendicular bones include the humerus, ulna, and radius of the upper limbs; the femur, tibia, and fibula of the lower limbs; the bones of the hands and feet; the scapula and clavicle; and the two hip bones (os coxae) of the pelvis.
The following two drawings show the basic bones and their locations, as seen from both anterior (front) and posterior (back) views of the figure. Learning the placement of the bones will help you identify the bony landmarks you may see as a live model takes various poses.
BASIC BONES OF THE SKELETON—ANTERIOR VIEW
BASIC BONES OF THE SKELETON—POSTERIOR VIEW
When drawing the human figure, artists look for various surface landmarks. These can be soft surface forms, such as muscles, tendons, ligaments, and fatty tissue, or hard surface forms, which are places where evidence of the skeleton can be seen on the surface of the body. Hard surface forms are also known as bony landmarks—parts of bones (ridges, bumps, depressions) that are positioned close to the skin, creating visual landmarks on the surface form.
The following drawings provide a general guide to where the main bony landmarks are, as seen from both the anterior and posterior views. Whether you can see these skeletal clues on a live model will depend on both the pose and the model’s body type. On some figures, fatty tissue may obscure much of the evidence of the bones, while on leaner figures it will be easier to see bone definition at several places on their bodies.
BONY LANDMARKS OF THE SKELETON—POSTERIOR VIEW
BONY LANDMARKS OF THE SKELETON—ANTERIOR VIEW
The cranium, or skull, consists of two portions: One portion, resembling an ostrich egg, houses the brain and creates the dome of the skull. This portion consists of eight separate bones that are fused together. The second portion contains fourteen individual facial bones, which are positioned in the front region of the cranium. The facial bones are also fused together, with the exception of the movable lower jawbone, which is called the mandible.
Variations in the many bony components of the cranium are remarkable from one person to another. The width of the cranium can range from very narrow to rather wide. When viewed from the side, a face can appear almost flat, or the profile can project out strongly. The forehead can be almost vertical, like a steep cliff, or can curve gracefully. Cheekbones can be prominent or hardly noticeable. The nose, depending on the projection of the nasal bone, can be flattish or pronounced. The mandible (lower jaw) can be small, with a delicate chin, or robust, with a broad chin. When drawing a face, it is always a good idea to look for these bony landmarks, as they play a large role in creating the individual’s unique facial characteristics.
The following drawing shows the basic bones of the cranium. Many of the bones’ features are covered by facial muscles, which are themselves obscured by a layer of subcutaneous fatty tissue. But knowing the placement of these bones will greatly help you understand where certain facial muscles or soft-tissue forms attach.
BONY LANDMARKS OF THE CRANIUM
Anterior and lateral (side) views
In the next drawing, portions of a face have been superimposed over a three-quarter view of the cranium, showing how the eyes are contained within the eye sockets and how the cartilage of the ear is positioned.
THE CRANIUM, WITH SOME FACIAL FEATURES SUPERIMPOSED
Anterior three-quarter view
The following drawing shows the profile of the cranium and, next to it, an ostrich egg with superimposed facial bones. When drawing a head in profile, it can be helpful to think of the braincase as an ostrich egg to avoid clipping the width of the cranium from front to back, which beginning artists tend to do. The width of the cranium will, of course, appear to lessen as the head rotates toward you.
THE BRAINCASE RESEMBLING AN OSTRICH EGG
Now, let’s look at a few individual components of the cranium. The frontal bone, commonly called the forehead, is a bony plate situated at the upper front of the cranium above the eye sockets. It is similar in shape to the back of a crab, as shown in this drawing shown here. The outer borders, which are called the temple lines (superior temporal lines), are helpful in indicating the plane change that occurs from the front of the head to the side. The brow ridge(superciliary arch) is the slightly thickened portion above the eye sockets; males tend to have thicker brow ridges than females. The glabella is a smooth prominence above the root of the nose. The frontal eminences are two large, slightly bulging forms positioned side by side in the general forehead region. These eminences can be subtle or quite robust, depending on the individual.
The eye sockets, also called orbits, are two large bony hollows, each containing the sphere of the eyeball. Situated between the eye sockets is the area where the structure of the nose begins, commonly called the root of the nose.The nose is made up of a combination of bone and soft-tissue forms (cartilage). The bone segment, called the nasal bone, actually consists of two bones positioned side by side and forming the bony bridge of the nose. The nasal bone can be thought of as a bony canopy that protrudes over the nasal cavity and serves as an attachment site for the nasal cartilage and muscles. The nasal cavity is an inverted heart-shaped aperture that contains some of the sinuses. It is divided in half within by the nasal septum, which is a structure consisting of both bone and cartilage.
The endless variations in nose shapes are influenced by three components: the bridge of the nasal bone, the nasal cavity, and the cartilage that attaches to the bony part of the nose. If the nasal bone has a high bridge, the nose structure juts out more from the front plane of the face, whereas a low bridge produces a flatter nose. A narrow nasal cavity produces a nose that is narrow and sometimes more angular, while a wider nasal cavity creates a broader nose. The drawing on the following page shows three basic shapes of the nasal bones and three basic widths of the nasal cavity. These bony features can affect the overall shape of the soft-tissue forms of the nose, which are the nasal cartilage (lateral cartilage and greater alar cartilage) and the wings of the nose (lesser alar cartilage and fibrous fatty tissue).
NASAL BONE AND NASAL CAVITY
Anterior views of different noses
The cheekbones, called the zygomatic bones in anatomical terminology, are projections of bone near the lower, outer parts of the eye sockets. The cheekbone has two portions: the zygomatic process, which is part of the outer portion of the eye socket, and the zygomatic arch, which is a thin strip of bone (comprised of two sections) that continues along the side of the head toward the ear. The zygomatic bones mainly serve as an anchoring site for muscles. Many artists emphasize this bone by placing a rich highlight on the upper plane of the structure.
THE FRONTAL BONE RESEMBLING THE BACK OF A CRAB
Frontal bone, anterior view
Dungeness crab (Metacarcinus magister)
The maxilla (upper jaw) is actually two joined bones that together form the upper dental arch and parts of the lower orbits (eye sockets), nasal cavity, and hard palate. The section containing the dental arch is U-shaped, which fits over the U-shaped dental arch of the mandible. The external portion of the maxilla bones is covered with muscles and subcutaneous fatty tissue, making it hard to detect on the surface. When observing some expressions of the mouth, such as a broad, toothy grin with parted lips, you will see the gums, which attach directly on the maxilla.
The mandible (lower jaw) is the only movable bone in the whole cranium. Overall, it is shaped much like a horseshoe, as shown in the lower drawing opposite. The ramus (pl., rami) extends upward from the body of the mandible, its shape rather flat and rectangular. At the upper part of the ramus on the side closest to the teeth is a shark-fin shape called the coronoid process. On the side of the ramus closest to the ear canal is a pronglike structure called the condylar process. This structure is part of the temporomandibular joint, or TMJ, the only moveable joint in the cranium.
The outer edges of the mandible and the chin region give the only surface evidence of this bony structure when the jaw is closed, because the rest is covered by muscles and glandular and fatty tissues. There are two lines along the outer edge of the mandible: a shorter line that aligns with the ear and a longer one that sweeps into the chin region. The angle of mandible is the corner where these two lines come together. Depending on how the soft-tissue forms attach to the jaw area, the outer edges of the mandible may be more angular or more smoothly curving. The chin area, referred to anatomically as the mental protuberance, is a bony mass covered with muscles that flesh out the actual chin shape. Chins can be wide or narrow and can recede back or project forward.
THE MANDIBLE RESEMBLING A HORSESHOE
Mandible, superior view
The teeth are positioned in the dental arches, which are located in both the maxilla and mandible bones. The basic structure of a tooth consists of a bone-like material called dentin, which is covered by enamel,an ivory-like material that is the hardest substance in the entire body. Each tooth has three portions: a crown, neck, and root. Each is individually rooted in a tooth socket, anatomically known as the alveolus; the gingiva (gum) usually obscures the structure of the neck. The crown—the exposed portion of the tooth—is the structure that interests artists most when they depict the teeth in open-mouthed expressions.
When depicting a person who is smiling with parted lips, it is essential for the artist to understand the shape and placement of the teeth located on the front portion of the dental arches. On smiles with parted lips, you generally see six frontal teeth on the upper arch. Make sure to position the two large front teeth on each side of the midline of the head; otherwise, the teeth will look out of alignment. When observing faces with widely opened mouths, you will see part of one of the dental arches (sometimes both) curving within the structure of the mouth. The perspective of the curving arch depends on your particular viewpoint of the head. If a head with a wide-open mouth is tilting down, portions of the lower dental arch are usually seen curving upward. When the head is tilting back with a wide open mouth, the upper dental arch is partially seen, curving downward (see this page).
The relationship between the upper dental arch and the lower dental arch when the jaw is closed is called dental occlusion. The alignment of the upper and lower teeth can influence the soft-tissue forms of the lower face, especially the lips. Teeth that line up with their front edges nearly touching are in an edge to edge occlusion, which tends to produce a more vertical alignment between the upper and lower lips when seen in a profile view. But this alignment shifts if the upper teeth slightly overlap the lower teeth (an overbite) or the teeth in the lower dental arch slightly protrude past the upper teeth (an underbite). These three basic alignments are shown in the next drawing. Malocclusion is the term for a noticeable overlapping or overcrowding of the teeth and possible misalignment in the mandible, producing more extreme versions of the overbite and underbite conditions. Malocclusions greatly affect the softer forms of the lower face.
DENTAL OCCLUSIONS—THREE TYPES
The Vertebral Column
The vertebral column, also called the spine or backbone, consists of twenty-four individual vertebrae (sing., vertebra) placed atop each other and (with the exception between the first two neck vertebrae) separated by fibrous pads called intervertebral discs. As the name vertebral column suggests, it can be thought of as a supporting column for the head. The vertebral column also bears the weight of the upper body, protects the spinal cord, and allows for movement. For artists, the vertebral column is an important structural landmark indicating any rotating, tilting, or twisting action within the rib cage and pelvis regions. The position of the vertebral column is one of the first clues for assessing the line of action (see this page), especially in gesture poses.
The following-hand drawing depicts the structure of the vertebral column as seen in a lateral (side) view. The vertebral column is divided into four distinct regions: cervical, thoracic, lumbar, and sacral. The cervical (neck) region contains seven vertebrae, the thoracic (rib cage) region twelve vertebrae, and the lumbar (small of the back) region five vertebrae, totaling twenty-four vertebrae. The sacral region contains the fused vertebrae of the sacrum bone and the coccyx (tailbone). Each individual vertebra on the chart is assigned a letter and number to designate its location and the region it belongs to: For example, C1 means the first vertebra of the cervical region.
VERTEBRAL COLUMN—LATERAL VIEW
From this side view you can see how the vertebrae are not stacked absolutely vertically, as they appear to be from a front or back view, but create a series of subtle curves. The four curves correspond to the four regions of the vertebral column. When you observe a standing figure from the side, you can sense these curves very easily. Many novice artists depict the side of the figure too stiffly, giving the spine a ramrod appearance. But recognizing these curves helps give the figure’s spine a sense of natural, rhythmic flow.
Each vertebra has two basic components, a bony cylindrical drum (called the body) and a bony arch (vertebral arch). On the arch component there are many projecting bony structures. These include the spinous process, which projects in the posterior direction, and the two transverse processes, which project on either side of the arch. These projecting shapes serve as attachment sites for ligaments and tendons of the various muscles of the back and usually cannot be seen on the surface, with the exception of a few of the spinous processes, which sometimes appear on the surface as small beads, especially when the figure bends forward at the waist.
First lumbar vertebra (L1)
The drawing above shows two views of a lumbar vertebra. Although there are some differences in shape between the cervical, thoracic, and lumbar vertebrae, their features are basically similar—except for the first two cervical vertebrae (C1, C2), as we shall see shortly.
Now let’s look briefly at the individual regions of the vertebral column to learn something about their distinctive characteristics. The first region, the cervical vertebrae, consists of the seven vertebra of the neck. The upper two cervical vertebrae are called the atlas and the axis. These two vertebrae, while not noticeable on the surface form, are important in the movement of the head, as we shall see in the next chapter.
THE ATLAS VERTEBRA NAMED AFTER THE TITAN OF GREEK MYTHOLOGY
Atlas vertebra (C1), three-quarter posterior superior view
The atlas cervical vertebra (C1) helps support the cranium. Its transverse processes, extending horizontally on each side of the vertebra, are attachment sites for various ligaments and tendons. From the first two following drawings, you can see how the atlas vertebra got its name. It was named for Atlas, the Titan of Greek mythology who supported the world or heavens. The Farnese Atlas is a second-century Roman copy of a Hellenistic sculpture depicting Atlas holding a celestial sphere.
THE AXIS VERTEBRA RESEMBLING A SADDLE TREE
Axis cervical vertebra (C2), three-quarter posterior superior view
The axis cervical vertebra (C2) is positioned beneath the atlas vertebra (C1). The small, spherelike shape of bone projecting upward like a saddle horn is called the dens or odontoid process and articulates with the anterior tubercle of the atlas vertebra sitting just above it. Looking at the previous two drawings, you can see how the axis vertebra is shaped somewhat like a saddle tree, a structural device within saddles that keeps the rider from putting too much pressure on the horse’s spine.
For artists, the other important cervical vertebra is the seventh vertebra (C7), also called the vertebra prominens. That’s because the spinous process of this vertebra appears as a small bony bump at the back of the neck. This small form might seem insignificant, but it is actually a vital bony landmark. In back and side views of the figure, it tells you where the neck anatomically ends and where the rib cage begins.
The second region of the vertebral column consists of the twelve thoracic vertebrae—the vertebrae of the thorax, or rib cage. These are the vertebrae to which the ribs attach, creating the birdcage shape of the rib cage.
The third region consists of the five lumbar vertebrae. These comparatively massive vertebrae, which define what is commonly called the small of the back, are the bony transitional structure connecting the rib cage and pelvis, and they help bear the weight of the rib cage and cranium and all the various associated soft-tissue structures (muscles and organs). When viewing the lumbar vertebrae from the front of a skeleton, it is possible to see a resemblance to an ancient Greek column, as shown in next the drawing.
LUMBAR VERTEBRAE RESEMBLING A GREEK COLUMN
LEFT: Lumbar vertebrae (L1-L5), anterior view
RIGHT: Greek column (Doric order)
Finally, we reached the last region of the vertebral column, called the sacral region, which consists of the sacrum and coccyx (tailbone). The sacrum and coccyx serve not only as the base of the vertebral column but also as the middle portion of the pelvis.
The sacral region is an important bony landmark for locating the general placement of the pelvis. The bone is covered with ligaments and a thin layer of subcutaneous tissue that softens the bony triangular shape when seen on the living model. The sacrum is easily identifiable, with its upper portion flanked by two small depressions in the skin (sacral dimples) and its apex pointing downward toward the gluteal cleft (the separation of the gluteus maximus muscles). The coccyx curves inward and is usually hidden by the gluteus maximus muscles (buttocks); it can be seen only on extremely thin individuals.
The sacrum bone resembles the head of an elephant, as can be seen in the following drawing. In Hindu tradition, the body’s energy centers are called chakras, and the first, or root, chakra is located at the base of the spine, at the sacrum bone and coccyx. Ganesha, a Hindu god with the head of the elephant, symbolically resides in the root charkra, so it’s interesting that the sacrum bone, from the anterior view and even in side views, looks so much like an elephant’s head.
THE SACRUM RESEMBLING AN ELEPHANT’S HEAD
Sacrum, anterior view
Head of an elephant
The Thorax (Rib Cage)
The thorax, or rib cage, consists of twelve pairs of ribs, together creating a cagelike structure. The first seven pairs of ribs (called true ribs) connect to the first seven thoracic vertebrae, swinging around to attach, via cartilage, into the sternum (breastbone) in the front. The costal cartilage (or rib cartilage) is a small, sturdy bar of hyaline cartilage attaching directly into the sternum to allow slight gliding movements during respiration. The next three pairs (called false ribs) also attach to the thoracic vertebrae, but as they swing around toward the front they do not attach directly into the sternum. Instead, their cartilage joins together and then joins into the cartilage of the last true rib. This fusion of cartilage is a branchlike structure that creates most of the thoracic arch (rib cage arch). The rib cage arch, comprised entirely of cartilage, can be seen on the surface in certain poses, such as when the figure is reaching upward or intentionally pulling in the abdominal muscles.
The last two pairs of ribs, called floating ribs, begin from the thoracic vertebrae like the others, but they are not long enough to attach into the sternum or even to “share a ride” with the rib cage arch.
THE THORAX (RIB CAGE)—ANTERIOR VIEW
The sternum, or breastbone, is a long, thin bone composed of three sections that together resemble a small sword or dagger. In fact, the older term for the body of the sternum was gladiolus, which is related to the word gladiator, and the sternum actually looks a lot like a dagger used in ancient Roman times, as seen in the following drawing.
THE STERNUM RESEMBLING A DAGGER
LEFT: Sternum, anterior three-quarter view
RIGHT: Roman dagger
The sternum, positioned in the front-central portion of the rib cage, is the bony structure into which the ribs attach as they swing around from the thoracic vertebrae. The cartilage of the ribs attaches into small depressions called costal notches on the outer sides of the sternum. The sternum consists of three components: the manubrium, the body of the sternum, and the xiphoid process. At the top of the manubrium is the suprasternal notch, commonly called the pit of the neck, which is an essential landmark when depicting the head and neck region, marking the transition between the neck and rib cage in front views. A slight plane change between the manubrium and the body of the sternum, called the sternal angle, is an essential for sculptors. The sternum is considered an important bony landmark for all figurative artists because it can indicate exactly what position the rib cage is in in any frontal or three-quarter pose—especially useful for depicting any rotation or tilting action within the torso region.
The Shoulder Girdle of the Rib Cage
The shoulder girdle consists of two clavicles (collarbones) and scapulae (shoulder blades), which form a somewhat bony ring encompassing the rib cage. The girdle is instrumental in allowing movement of the upper limb. Various muscles from the torso and arm attach into the shoulder girdle to help move the scapula bones, clavicles, and humerus bones to different positions.
The two clavicles, or collarbones, are slightly curved bones, somewhat serpentine in shape. Although the bones appear straight in some poses, the serpentine shape is apparent in a three-quarter view or if the model is bending in a forward direction. The clavicles are positioned on either side of the top portion (manubrium) of the sternum with the suprasternal notch (pit of the neck) in between. The inner end (medial end, sternal end) of each clavicle appears as a small protrusion on the surface. At the outer end (lateral end, acromial end) of the clavicle, the form is flatter yet appears near the skin as a small bump, located slightly above the flat plateau of the acromion process of the scapula. The next drawing shows the clavicles’ serpentine appearance, especially in the farther clavicle.
PLACEMENT OF THE CLAVICLES
Three-quarter view of torso, with sternum, acromion process of scapula, humerus, and rib cage
The two scapulae (sing., scapula) are elongated, triangularly shaped bones, slightly curved to glide over the curved rib cage. Although the Latin name scapula (pron., SKAP-yoo-lah) means shoulder blade,the Greek root skapteinmeans “to dig”—most likely a reference to the scapula’s trowel-like shape, which is especially apparent when viewed from its anterior surface (ventral surface, costal surface), as can be seen in the following drawing. There is archeological evidence that people of Paleolithic times used the scapulae of large animals as digging tools.
THE SCAPULA RESEMBLING A GARDEN TROWEL
LEFT: Left scapula, anterior view
RIGHT: Garden trowel
Viewed from the back, the scapula has a projection of bone in the upper region that appears as a tilting ledge. This spine of the scapula is an attachment site for the deltoid and trapezius muscles. On the body’s surface this bony ledge catches light along its length, making it easy to identify its location. The outer end of the spine of the scapula, called the acromion process, is a broad, flat surface that attaches to the outer (lateral) end of the clavicle. The acromion process acts as a protective bony canopy over the shoulder joint. The outer ends of the shoulder girdle are similar to the epaulettes of a military uniform, with the top of each acromion appearing as a circular shape with a flat plane. These regions can also appear as round bony masses at the ends of the shoulders, depending on the position of the upper arms (see this page).
A shallow depression called the glenoid fossa is located on the outer portion of the scapula, below the acromion process. This is the socket for the head of the humerus bone of the upper arm. A small projecting bony shape near the upper part of the glenoid fossa is called the coracoid process; it is shaped like a small, blunt beak. It serves as an attachment site for muscles. The outer edge of the scapula, closest to the vertebral column, is called the medial borderor vertebral border. Look for this border when trying to locate the position of the scapula on a living model. At times you will also see the bottom corner, called the inferior angle. The other elongated border of the scapula is called lateral border. This border is hard to detect on the surface because it is covered over by muscles. The supraspinous fossa is positioned above the spine of the scapula and appears as a cradle-like bony structure. The infraspinous fossais a large depression below the spine of the scapula.
Left scapula, posterior view
In the life study on the following page, you can see the general shape and position of the scapula bones with the surrounding muscular forms and bony landmarks. Because of the position of the arms in this pose, the vertebral (outer) borders and inferior angles (lower tips) of the scapulae are projecting close on the surface, making it easy to see the shoulder blades’ location.
MALE FIGURE HOLDING HIS HANDS BEHIND HIS BACK
Graphite pencil, ballpoint pen, watercolor wash, and white chalk on toned paper.
Bones of the Upper Limb
The bones of the upper limb consist of the humerus of the upper arm and the ulna and radius of the lower arm. The next drawing shows the features and bony landmarks of these bones.
BONES OF THE UPPER LIMB—THREE VIEWS
The following drawing, an anterior three-quarter view of a skeleton torso with arms overhead, shows how the shoulder girdle encircles the rib cage and how the upper arms (humerus bones) move in relation to the bones of the scapula, as well as the placement of the lower arms (radius and ulna bones).
BONES OF THE UPPER AND LOWER ARM WITH RIB CAGE AND SHOULDER GIRDLE
Anterior three-quarter view with arms overhead
The single bone of the upper arm, the humerus (pron., HYOO-murr-us) is a typical long bone, with a long shaft that expands at each end into a broader mass. The upper portion, called the head of the humerus,has a spherelike shape that fits into the shallow depression (glenoid fossa) of the scapula, creating the ball-and-socket joint of the shoulder. The shaft of the humerus is completely covered by muscles and soft tissue. Located midway along the bone is a small textured area called the deltoid tuberosity. This is the attachment site for the deltoid muscle. At the lower end of the humerus, the bone flares outward into a wide base. Two bony expansions, called the medial epicondyle and lateral epicondyle, are the prominent projections. The medial (inner) epicondyle is usually noticeable on the surface form as a small bump located near the inner side of the elbow (olecranon). When the lower arm is bent, the lateral (outer) epicondyle is also seen on the surface as a small bony protrusion, but when the arm is straightened it usually becomes concealed by muscles of the radial group—the large mass of muscle that crosses the elbow joint region. A noticeable indentation, or dimple, in the skin is seen where the lateral epicondyle is located.
THE HUMERUS—THREE VIEWS
At the lower end of the humerus and between the epicondyles are two additional bony structures. One is the trochlea, a spool-like structure, and next to it a spherelike shape called the capitulum. Although hidden from our view on the living model they are important for understanding joint movement, as we will see in the next chapter.
The Ulna and Radius
The lower arm contains two bones: the slightly larger one is called the ulna, and the other is the radius. These two bones are positioned parallel to each other when the arm is in the anatomical position or when the hand is supinated, meaning that the palm is facing forward or upward. When trying to locate the position of these two bones in the living model, it is helpful to remember that the radius is always on the thumb side of the wrist and the ulna bone always on the little finger side of the wrist, no matter what the hand or lower arm is doing.
ULNA AND RADIUS—THREE VIEWS
The ulna (pron., ULL-nah) has a noticeable landmark, commonly called the elbow but known in anatomical terminology as the olecranon. It appears as a bony protrusion at the elbow joint. Also located at the upper portion of the ulna is the trochlear notch (not seen on the surface). Shaped much like a crescent wrench (see the following drawing), it hooks around the bottom portion of the trochlea of the humerus bone, creating the hinge joint of the elbow region.
THE ULNA RESEMBLING A CRESCENT WRENCH
When the whole arm is straight, the olecranon is level with the medial and lateral epicondyles of the humerus. When the lower arm bends or flexes, the olecranon swings slightly downward and becomes more noticeable on the surface. In the bent-arm position, the elbow bump of the olecranon is lower than the epicondyles, and the three forms have a triangular configuration. The following drawing shows how the elbow’s appearance changes as the arm moves.
ELBOW (OLECRANON OF ULNA)
Along most of the length of the ulna is a sharp edge called the posterior border of the ulna. This tends to create a skin furrow from the elbow to the wrist. At the base of the ulna is the head of the ulna, which appears as a small bony bump on the little-finger side of the wrist. A small extension of bone from the head of the ulna is called the styloid process of the ulna.
The radius is a slender bone positioned next to the ulna. At the upper portion is the head of the radius, shaped like a small wheel. It is held close to the capitulum of the humerus by a ligament that acts like a supporting strap, letting the head of the radius rotate or spin under the ball-like shape of the capitulum. Slightly farther down from the head of the radius is a small protrusion of bone called the bicipital tuberosity (radial tuberosity), which is an attachment site for the tendon of the biceps brachii muscle. At the lower end of the radius the bone expands slightly and has a pointy projection called the styloid process of the radius.
In the life study shown next, we see the arms in a relaxed position with the model’s chin gently resting against one hand. The accompanying skeletal diagram shows the slight rotation of the radius rolling over the ulna in the model’s left arm.
WOMAN WITH RELAXED ARMS
Graphite pencil, watercolor wash, and white chalk on toned paper.
Bones of the Hand
The hand consists of several bones, which are conveniently grouped in three sections: the carpal bones (wrist region), the metacarpals (main structure of the hand block), and the phalanges (finger and thumb bones).
The carpal bones, commonly called the wrist bones, comprise eight individual bones, divided into two rows. The first row (proximal row) contains the scaphoid, lunate, triquetral, and pisaform carpal bones. The second row (distal row) contains the trapezium, trapezoid, capitate, and hamate carpal bones. Because numerous ligaments attach to and between the carpal bones, and layers of muscles and tendons overlay them, it is hard to detect the carpal bones individually on the surface. However, the pisaform carpal bone marks where the heel of the hand terminates, and at the wrist below the thumb eminence is a subtle bony bump formed by the scaphoid carpal bone.
BONES OF THE HAND
Right hand, dorsal view
Located beyond the group of the carpal bones are the metacarpals, five elongated bones making up the general block-shaped structure of the hand. The bony landmarks of the metacarpals that are most clearly seen are the knuckles, which are the heads of the metacarpal bones. These are also known as the metacarpo-phalangeal joints, or MCP joints. The knuckles appear as small bony shapes when the fingers bend or the hand clenches into a fist.
Right hand, dorsal view
The finger and thumb bones are called the phalanges (pl., pron. fah-LAN-jeez; sing., phalanx, pron. FAY-links or FAY-lanks). With the exception of the thumb, each finger has three phalanges. The phalanx closest to the finger’s attachment on the hand is known as the proximal phalanx, and the phalanx farthest away is called the distal phalanx. The phalanx between these two bones is called the middle phalanx.
Right hand, dorsal surface
Study of Hand with Guitar, shows various surface forms of the hand, including the metacarpal heads (knuckles), as well as a few tendons. Some veins can also be seen. The accompanying skeletal diagram shows the location of the bones of the hand in this particular pose.
STUDY OF HAND WITH GUITAR
Graphite pencil and white chalk on toned paper.
The pelvis consists of three main bones: the triangularly shaped bone called the sacrum and two large wing-shaped bones, commonly called the hip bones (anatomical name, os coxae). These three pelvic bones are held together at their joints with layers of ligaments; however, the entire pelvis should be considered as a unit, not as individually movable bones. When the pelvis is tilting, the whole pelvis tilts.
THE PELVIS—ANTERIOR VIEW
The term pelvis comes from a Latin word meaning “basin,” and the pelvis resembles a shattered ancient bowl, reassembled but with pieces still missing, as shown in the drawing at bottom right. In fact, the pelvis does function as a vessel for various soft-tissue structures, such as the intestinal tract, as well as serving as a protective bony chamber for a developing fetus.
THE PELVIS RESEMBLING A FRAGMENTED BOWL
Pelvis, three-quarter anterior view
Ancient bowl, partly reassembled
A few bony landmarks on the pelvis are worth noting because they are either seen on the surface or, if hidden, serve as important attachment sites for muscles. Most of these landmarks comes in pairs. The ilium is the large, fan-shaped structure in the upper part of each hip bone. Along the top of the entire length of the ilium is a narrow rim called the iliac crest. In the anterior view of the pelvis, the iliac crest abruptly ends, and this segment is called the anterior superior iliac spine, or ASIS. There are two of these structures—one on each ilium bone—and they occasionally appear on the surface as two small bony protrusions on the front of the hips. The two ASIS structures, along with the sacrum and iliac crest, are the only bony evidence of the pelvis seen on the living model, but these landmarks are harder to detect in people who have substantial fatty tissue.
At the other end of the iliac crest is the posterior superior iliac spine, or PSIS. Each PSIS lies near a noticeable depression or dimple in the skin. These two dimples correspond to the top border of the sacrum of the pelvis.
Differences between the Male and Female Pelvis
The female pelvis is wider, with a slightly lower ilium, than the male pelvis. Because the female pelvis is wider, the hip sockets (acetabula) are placed farther apart. The neck of the femur is at a more pronounced angle, making the shaft of the femur descend more obliquely in the female than in the male. The protrusion of the greater trochanter will be more evident on the male; on the female it is slightly overlapped with subcutaneous fatty tissue, making it harder to detect on the surface. However, the greater trochanter can be seen in a lean female with minimal fatty tissue. The sacrum is wider in the female, while in the male it is not just narrower, but the coccyx projects inward at a sharper angle. The pubic arch—the inverted V-shaped structure on the lower portions of the ischium bones—is wider in the female, narrower in the male. These differences provide only a general guide, however, because some characteristics can be seen in either sex, depending on the individual. Some women have narrow hips, and some men wider hips.
STUDY OF MALE PELVIS AND LEGS, ANTERIOR AND POSTERIOR VIEWS
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STUDY OF FEMALE PELVIS AND LEGS, ANTERIOR AND POSTERIOR VIEWS
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The ischium bones, at the bottom portion of the pelvis, look like bagels or doughnuts because of the large opening (called the obturator foramen) in the center of each. These bones are not seen on the surface but are essential attachment sites for several upper leg muscles. These are the bones we sit on, and they have a smooth rocking-chair surface along their bottom edge. The pubic bones are a pair of bones that make up the bony bridge in the front lower portion of the pelvis and are separated by a fibrous pad called the pubic symphysis. An inverted V-shaped arch called the pubic arch is created by the ischium and the lower part of the pubic bones. A cuplike socket on the pelvis, called the acetabulum, is the location for the head of the femur. This is the ball-and-socket joint of the hip. As was mentioned in the section on the vertebral column, the sacrum serves as the base of the vertebral column, but it also functions as the middle portion of the pelvis.
Bones of the Lower Limb
The bones of the lower limb are the femur (in the upper leg, or thigh), the tibia and fibula (lower leg), and the patella (kneecap). The following drawing shows the features and bony landmarks of these bones.
BONES OF THE LOWER LIMB—THREE VIEWS
LEFT: Left lower limb, lateral view
CENTER: Left lower limb, anterior view
RIGHT: Left lower limb, posterior view
The upper leg consists of a large, elongated bone called the femur (pron., FEE-mur), sometimes referred to as the thigh bone. Three views of the femur are shown next.
The femur shaft descends at a slight angle within the thigh. It is smoother on the front (anterior) region, looking much like a large stalk of bamboo. On the back of the femur, however, there is a craggy vertical ridge called the linea aspera. Various muscles of the upper leg attach along this long ridge. At the upper portion of the femur is the head of the femur, which is shaped like a golf ball, as shown in the next drawing. It fits inside the cuplike socket (acetabulum) of the pelvis. The neck of the femur is an extension of bone projecting at a tilt from the head of the femur. The head and neck of the femur are not visible on the live model because of the multiple layers of ligaments and muscles in the region.
THE HEAD OF THE FEMUR RESEMBLING A GOLF BALL
As the neck joins the shaft of the femur, the bone becomes a large, textural mass called the greater trochanter. On the surface of the greater trochanter is a series of bumps and ridges, which are attachment sites for the gluteal muscles of the hip region. In certain positions of the upper leg, the greater trochanter can occasionally be seen as a large bump on the side of the hip of a live model. In other views, the bump of the greater trochanter is hidden because of the gluteal muscles converging in this region, and a large depression in the skin will appear instead. Below the greater trochanter but on the opposite side of the femur shaft is a small projection of bone called the lesser trochanter.This form, an attachment site for muscles, cannot be located on the surface form.
PATELLA AND KNEE REGION
Left knee region, anterior view
At the base of the femur are two massive expansions of bone, called the condyles. The outer one is called the lateral condyle of the femur, and the one on the inner side is called the medial condyle of the femur.The condyles are slightly flat on their sides, yet very knoblike in the back, where they have the appearance of two caster wheels, as shown in the following drawing. When the knee bends, these forms roll on top of the tibia, much like wheels. While the condyles are harder to detect in the standing leg, the upper portions of the femur’s condyles can usually be detected on a live model when the legs are bent, as in a sitting pose. In an anterior view of the femur bone, the condyles are separated by a smooth surface called the patellar surface of the femur, which articulates with the patella. In a posterior view, the two condyles are separated by a large depression called the intercondylar fossa.
THE CONDYLES OF THE FEMUR RESEMBLING A PAIR OF CASTERS
THE PATELLA RESEMBLING A SCALLOP SHELL
The patella, or kneecap, is a small, somewhat triangular bone that resembles a scallop shell, as shown.
It is the human body’s largest sesamoid bone—meaning a bone that is encased within a tendon (in this case, the tendon of the quadriceps muscles). On a living model, the top ridge of the patella can appear as a small shelf that catches light; this ledge grows more noticeable when the knees are flexed dramatically, as in a squatting pose. As a sesamoid bone, the patella helps reduce the friction between the femur and the tendon of the quadriceps during knee flexion. The patella also serves as a protective shield for the exposed bottom portion of the femur when the leg is bent. As the lower leg bends or flexes, the patella glides slightly downward. It can be seen in front, three-quarter, and side views of the leg.
The life study shown next, showing the lower torso of a seated figure, indicates the prominent landmarks of the knee region. The accompanying skeletal diagram shows the positions of the bones in the same pose.
STUDY OF SEATED LEGS IN A THREE-QUARTER VIEW
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Shown in the following drawing are two bones in the lower leg: the larger one is the tibia, and the slender one positioned next to it is called the fibula. Unlike the two bones of the lower arm, these bones never cross over each other. The fibula is always positioned in the outer region of the lower leg.
The tibia, or shin bone, is the second largest bone in the body, after the femur. At its upper frontal region are the medial and lateral condyles of the tibia. They appear as a singular, triangular shape with a small bony protrusion, called the tibial tuberosity, located at the inverted apex of this bony triangle. The tibial tuberosity is the attachment site for the patellar ligament. On the front shaft of the tibia is a sharp, curved edge called the anterior border of the tibia. It is usually seen as a slight curve beginning near the medial (inner) condyle and descending toward the inner ankle. The curve is accentuated by the tibialis anterior muscle (the muscle on the front of the tibia), which runs obliquely down the shaft of the tibia. At the lower end of the tibia is part of the ankle joint, which contains a blunt projection of bone on the inner side of the tibia called the medial malleolus, commonly known as the inner ankle.
TIBIA AND FIBULA—THREE VIEWS
The fibula, or calf bone, is the slender bone alongside the tibia and serves as an attachment site for various muscles. A sheetlike membrane called the interosseous membrane attaches between the tibia and fibula. The fibula can be thought of as a lateral strut or a flying buttress, stabilizing the ankle joint. At its upper region, the head of the fibula, shaped like a bony marble, is where a strong, cordlike tendon from a hamstring muscle called the biceps femoris attaches. Both the tendon and the head of the fibula can usually be seen on the live model, most notably when the lower leg is bending in a side view. As the thin and angular shaft of the fibula descends from the head, the bone twists vertically, adding strength to its slender form. In general, the shaft cannot be seen on the surface form because it is covered with muscles running along its length. At its base, the fibula expands into a small triangular mass called the lateral malleolus (outer ankle), seen as a bony landmark on a living model. When observed from the front or back, the outer ankle bone is at a lower level than the inner ankle bone of the tibia.
The sketchbook studies of the upper and lower legs and the accompanying skeletal diagram show the positions of the tibia and fibula in three different poses. Even though you cannot see the shaft of the fibula on the surface of the leg, you usually can see the head of the fibula and the outer ankle (lateral malleolus), which are at opposite ends of the fibula. Connecting these two ends in your mind helps keep you aware of the fibula’s structure and placement and can help you depict the leg in a stable, realistic way.
SKELETAL DIAGRAM, SHOWING LOCATIONS OF TIBIA AND FIBULA
SKETCHBOOK STUDIES OF LEGS
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Medial malleolus (inner ankle)
Left foot, anterior view
The medial malleolus (inner ankle) is higher than the lateral malleolus (outer ankle).
Left foot, medial view
The medial malleolus (inner ankle) of the tibia is broader and has a blunt end.
Lateral malleolus (outer ankle)
Left foot, lateral view
The lateral malleolus (outer ankle) of the fibula is narrower and has a tapered end.
The ankle is actually made up of two different bones: the lower portions of the fibula and tibia. These forms are important bony landmarks of the lower leg and foot region and their correct placement is very important. Many beginning artists draw the ankle bones directly across from each other when seen in front or back views, but the outer ankle bone (lateral malleolus of the fibula) is actually lower than the inner ankle bone (medial malleolus of the tibia). In the lateral (outer) side view of the foot, the outer ankle bone appears lean, with a tapered end. On the medial (inner) side view of the foot, the inner ankle bone appears broader, with a blunt end. All these features of the ankle are shown in the drawings above.
Bones of the Foot
The bones of the foot belong to three groups—the tarsal bones, the metatarsal bones, and the phalanges (toe bones)—and are similar in structure to the bones of the hand. All the bones composing these three groups can be seen in the following drawings.
BONES OF THE FOOT—LATERAL VIEW
BONES OF THE FOOT—SUPERIOR VIEW
Tarsal bones is the collective term for the group of seven bones of the foot (comparable to the carpals of the hand) that form the posterior half of the foot, also called the hind foot. Directly beneath the two bones of the lower leg (tibia and fibula) is the second-largest tarsal bone, called the talus. These three bones (tibia, fibula, and talus) form the ankle joint.
The calcaneus, commonly known as the heel bone, is the largest tarsal. Only a small portion of the heel bone can be seen on the living model because it is mostly covered with muscles and layers of fibrous-fatty tissue. It is sometimes noticeable directly below the attachment of the Achilles tendon. The other tarsal bones are the navicular, cuboid, and three bones sitting side by side, called the cuneiform bones.
Positioned between the tarsal bones and the phalanges are five elongated bones called the metatarsals. Each has a shaft with a base and head at opposite ends. These bones, along with some of the tarsal bones, help form the general arch of the foot. The heads of the metatarsals might appear on the surface as small bony bumps when the toes are dynamically flexing or curling. The medial (inner) surface of the first metatarsal (of the large toe) can be seen as a slight ridge long the inner side of the foot. On the fifth metatarsal (of the little toe) is a small projection called the tuberosity of the fifth metatarsal. Sometimes this will be seen as a small bump midway along the outer edge of the foot.
The phalanges (sing., phalanx) are the toe bones. The great toe has two individual bones, while each of the lesser toes has three individual bones. The phalanx closest to the toe’s attachment on the foot is called the proximal phalanx; the farthest away is called the distal phalanx; and the intermediate phalanges on the four lesser toes are known as the middle phalanges. The joints of the first two toes can usually be detected because of these toes’ size and length. On the other toes it is harder to see any evidence of the bones, since they are mainly obscured by fatty tissue on the toes’ sides and bottoms.
STUDY OF SEATED LEGS IN THREE-QUARTER VIEW
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