Why are bony landmarks important

Patella Patella. Radius Carpal articular surface. Radial styloid process. Radial tuberosity. Scapula Acromion. Coracoid process. Glenoid cavity. Inferior angle. Infraspinous fossa. Lateral border. Medial border. Spine of scapula. Subscapular fossa. Superior angle. Suprascapular notch. Supraspinous fossa. Tarsals Calcaneal tuberosity. Medial cuneiform. Middle cuneiform.

Lateral cuneiform. Sustentaculum tali. If we learn to identify the surface landmarks of the bones we will have a firm foundation for all our subsequent anatomical study. From this masterful study by Poynter we can see how important a study of the bones was to the masters of the past. Students in the 19th century academies were expected to be able to draw any element of the figure entirely from memory.

This requires a great deal of anatomical study. One of the best practices for this study is to draw the a skeleton in the same orientation as your figure study, as Poynter did. At LARA we encourage students to engage in this practice as it offers a sure path to a solid understanding of the figure and its forms. When life drawing, proper observation of the bony landmarks helps us to get a good hold of the proportions and structure of our figure.

The bones offer the truth of proportion. If the proportion of the bones in our drawings is incorrect our figure will look strange. As we can see in the two wonderful studies below, though the body type of the two models may differ greatly, identifying and controlling bony landmarks remains of utmost importance.

The thoracic cage includes the 12 pairs of ribs , and the sternum , the flattened bone of the anterior chest. The appendicular skeleton includes all bones of the upper and lower limbs, plus the bones that attach each limb to the axial skeleton. There are bones in the appendicular skeleton of an adult. The bones of the appendicular skeleton are covered in a separate chapter. Skip to main content. Chapter 6: The Skeletal System.

Search for:. Divisions of the Skeletal System. Learning Objectives Distinguish between the axial skeleton and appendicular skeleton Define the axial skeleton and its components Define the appendicular skeleton and its components.

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.

The ulna pron. 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.

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. 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. 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.

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. The finger and thumb bones are called the phalanges pl.

With the exception of the thumb, each finger has three phalanges. The phalanx between these two bones is called the middle phalanx. 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. 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.

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.

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. 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. 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. 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.

The upper leg consists of a large, elongated bone called the femur pron. 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. 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. 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. 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 patella, or kneecap, is a small, somewhat triangular bone that resembles a scallop shell, as shown. 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.