Scapula

"Scapula" is the technical name for the shoulder blade. It is a flat, triangular bone that lies over the back of the upper ribs. The rear surface can be felt under the skin. It serves as an attachment for some of the muscles and tendons of the arm, neck, chest and back and aids in the movements of the arm and shoulder. It is well padded with muscle so that great force is required to fracture it. The back surface of each scapula is divided into unequal portions by a "spine." This spine leads to a "head," which bears two processes - the "acromion process" that forms the tip of the shoulder and a "coracoid process" that curves forward and down below the clavicle (collarbone). The acromion process joins a clavicle and provides attachments for muscles of the arm and chest muscles. The acromion is a bony prominence at the top of the shoulder blade. On the head of the scapula, between the processes mentioned above, is a depression called the "glenoid cavity." It joins with the head of the upper arm bone (humerus).

Tarsal Bones

The foot consists of an ankle, an instep, and five toes. The ankle is composed of seven "tarsal bones," forming a group called the tarsus. These bones are arranged so that one of them, the "talus," can move freely where it joins the tibia and fibula (lower leg bones). This is known as the "head of the talus." The remaining tarsal bones are bound firmly together, forming a mass on which the talus rests. The other bones which compose the tarsus are the "calcaneus," the largest of the ankle bones; the "talus;" the "navicular," the "cuboid," the "lateral cuneiform," the "intermediate cuneiform," and the "medial cuneiform." The "calcaneus," or heel bone, is located below the talus where it projects backward to form the base of the heel. It helps to support the weight of the body and provides an attachment for muscles that move the foot.

Carpal Bones

The skeleton of the wrist consists of eight small "carpal bones" that are firmly bound in two rows of four bones each. The resulting mass is the "carpus." The eight bones are the "pisiform," "triangular" or "triquetrum," the "pisiform," "lunate," and "scaphoid" on the upper end of the wrist, where it connects with ligaments and the lower arm bones, and the "hamate," "capitate," "trapezoid," and "trapezium" on the lower side of the hand by the "metacarpals," or first joint of the fingers.

Capsule of The Shoulder Joint

A "capsule" is a membrane or sac enclosing a body part, usually a joint. "Capsular ligaments" are surrounded and reinforced by muscles tendons, and ligaments, which are largely responsible for keeping the adjoining parts together. The "joint capsule" of the shoulder is attached along the outside ring of the genoid cavity and the anatomical neck of the humerus. Although it completely covers the joint, the capsule is very loose and by itself would be unable to keep the bones of the joint in close contact without the aid of the fibers around it. The joint capsule of the elbow has sides which are thickened by ulnar and radial collateral ligaments. The front surface of the capsule is reinforced by fibers from a muscle (brachialis) in the upper arm.

Clavicle

The clavicle is the collarbone. There are two of these bones, each curved al little like an "f," that join the top of the breastbone (sternum) to the shoulder blade (scapula). The clavicles support the arms and transmit force from the arms into the central skeleton.

The Coccyx

The coccyx (or tail) is the lowest part of the vertebral column and is attached by ligaments to the margins of the sacral hiatus. When a person is sitting, pressure is exerted on the coccyx, and it moves forward, acting sort of like a shock absorber. Sitting down with too great a force may cause the coccyx to be fractured or dislocated.

Deep Transverse Metatarsal Ligaments

The deep transverse metatarsal ligaments connect the heads of joint capsules of all the metatarsal heads.

Deltoid Ligament

The deltoid ligament is a ligamentous structure that is triangular in shape and attaches to the medial malleolus of the tibia to the navicular, calcaneus, and talus (anteriorly and posteriorly) bones of the tarsus.

Phalanges

The phalanges are the small bones that make up the skeleton of the fingers, thumb and toes. Each finger and smaller toe has three phalanges; the thumb and big toe each have two. The phalange nearest the body of the hand or foot is call the "proximal" phalange; the one at the end of each digit is the "distal" phalange; and, of course, when there are three, the middle one is called the "middle" phalange.

Condyloid Joints

In a "condyloid joint" (ellipsoidal), an ovoid condyle of one bone fits into an elliptical cavity of another bone, as in the joints between the metacarpals in the hand and the phalanges (finger bones). The five metacarpal bones, one in line with each finger, form the framework of the palm. The metacarpals articulate proximally with the phalanges (bones of the fingers). The ligaments that bind these bones are the "palmar" and "dorsal metacarpal ligaments." This type of joint permits a variety of movements in different planes; rotating movement, however, is not possible.

Ligaments of The Hand and Wrist

On the radial shaft of the smaller forearm bone, just below its head, is a process called the "radial tuberosity." It serves to attach the biceps brachi muscle, which bends the arm at the elbow. At the lower end of the radius, a lateral "styloid process" provides attachments for the "palmar radiocarpal ligament" (on the palm of the hand) and the "dorsal radiocarpal ligament" (on the back of the hand) from the radius into the wrist. At the lower end of the larger forearm bone (ulna), its knob-like head articulates with a notch of the radius (ulnar notch) laterally and with a disk of fibrocartilage below. This disk, in turn, joins a wrist bone (the triquetrum). A medial "styloid process" at the lower end of the ulna provides attachments for ligaments ("palmar ulnocarpal ligament" and "dorsal ulnocarpal ligament") into the wrist. The skeleton of the wrist is made up of eight small "carpal bones" that are firmly bound in two rows of four bones each. The mass that results from these bones is called the "carpus." The carpus is rounded on its nearest surface, where it articulates with the radius and with the fibrocartilaginous disk on the ulnar side. The carpus is rounded convexly in the front, forming a canal (retinaculum) through which tendons, ligaments and nerves extend to the palm. Its distal surface articulates with the metacarpal bones, which are joined to the carpus by the "palmar carpometacarpal ligaments."

Femur

The "femur" is the thigh bone, the longest bone in the body. The lower end joins the tibia (shin) to form the knee joint. The upper end is rounded into a ball (or "head" of the femur) that fits into a socket in the pelvis to form the hip joint. Just below the head is a constriction, or neck, and two large processes - an upper, lateral "greater trochanter" and a lower, medial "lesser trochanter." These processes provide attachments for muscles of the legs and buttocks. The neck of the femur gives the hip joint a wide range of movement, but it is a point of weakness and a common site of fracture.

Fibular Collateral Ligament

The "fibular collateral ligament" consists of a strong, round cord located between the lateral condyle of the femur (thighbone) and the head of the fibula at the knee joint.

Fibula

The fibula is the outer and thinner of the two long bones of the lower leg. It is much narrower than the other bone (the shin), to which it runs parallel and to which it is attached at both ends by ligaments. The upper end of the fibula does not reach the knee, but the lower end descends below the shin and forms part of the ankle. Its main function is to provide attachment for muscles. It doesn't give much support or strength to the leg, which explains why the bone can safely be used for grafting onto other bones in the body.

The Hamate Bone

The hamate bone is located in the wrist, and can be identified by its wedged shape. It is situated above the fourth and fifth fingers. This bone is generally the one fractured when golfers swing and miss their ball, striking the ground with considerable downward force.

Humerus

The humerus is the bone of the upper arm. The smooth, dome-shaped head of the bone lies at an angle to the shaft and fits into a shallow socket of the scapula (shoulder blade) to form the shoulder joint. Below the head, the bone narrows to form a cylindrical shaft. It flattens and widens at the lower end and, at its base, it joins with the bones of the lower arm (the ulna and radius) to make up the elbow. Some people say the "funny bone" is named because it is next to the humerus. It really isn't a bone at all, but is the ulnar nerve, which passes under a prominence of the humerus, where it is vulnerable. To find the funny bone, put the point of the right elbow on a table. Above and to the left of the point is a big knob. When it is struck, the blow pushes the nerve against this knob, causing temporary paralysis. It is no laughing matter, but it is a "funny" feeling.

Pelvis (or Os Coxa)

The pelvis is a ring of bones in the lower trunk of the body, which is bounded by the coccyx (tail bone) and the hip bones. The pelvis protects abdominal organs such as the bladder, rectum and, in women, the uterus. The pelvis is made up of three hip bones, which are joined by rigid sacroilac joints to the sacrum at the back. The hip bones curve forward to join the pubic symphysis at the front. The symphysis pubis is a cartilaginous union between both sides of the pelvis anteriorly. It is significant during childbirth as it is capable of stretching to permit delivery. Attached to the pelvis are muscles of the abdominal wall, the buttocks, the lower back, and the insides and backs of the thighs. Each innominate bone is made up of three fused bones: the ilium, the ischium, and the pubis. Together they form the acetabulum which is a cup-like depression ball and socket joint. The ilium is the uppermost and largest and consists of a wide, flattened plate with a long curved ridge (called the "iliac crest") along its border. The pubis is the smallest pelvic bone. It extends forward from the ischium and around to the pubis symphysis, where it is joined to the other pubic bone by a tough, fibrous tissue. These three bones meet to form a cup-shaped cavity that make up the socket of the hip joint. There are many structural differences between the male and the female pelvis, most of which reflect the role of childbirth in the female. The male pelvis is larger and smaller inside with the pubis symphysis deeper and longer. The female, on the other hand, has a much more delicate, less prominent pelvis that is wider inside and the pubis symphysis shallow and shorter. These and other differences give testimony to the fact that childbirth is a feat of nature indeed.

Iliofemoral Ligament

The "iliofemoral ligament" is a Y-shaped band of very strong fibers that connects the lower front iliac spine of the coxal bone to a bony line (intertrochanteric line) extending between the greater and lesser trochanters of the femur (thighbone). The iliofemoral ligament is the strongest ligament in the body. It helps to prevent extension of the femur when the body is standing erect.

Ligaments of The Sacrum

The sacrum, at the base of the vertebral column, is wedged between the coxal bones of the pelvis and is united to them by fibrocartilage at the "sacroiliac joints." The weight of the body is transmitted to the legs through the pelvic girdle at these joints. The fibrocartilage at the front of the sacrum, which joins it to the ilium is called the "anterior sacroiliac ligament"; at the back, it is called the "posterior sacroiliac ligament." The coccyx, or tail bone, is attached by ligaments to the margins of the sacral hiatus (opening at the tip of the sacrum). These ligaments are called the "anterior" and "posterior sacrococcygeal ligaments." The "sacrospinous ligament" is a thin, triangular sheet attached by its broad base to the lateral margins of the sacrum and coccyx, where its fibers are intermingled with those of the intrapelvic surface of the "sacrotuberous ligament," and by its apex to the spine of the ischium. The sacrotuberous ligament is a broad, flat fan-shaped complex of fibers stretching from the lower back spine of the ilium, the 4th and 5th transverse tubercles and the caudal part of the lateral margin of the sacrum and coccyx to the inner margin of the tuberosity of the ischium. The "iliolumbar ligament" connects the lower lumbar vertebra process to the ilium (the largest portion of the coxal bone).

Ischium

The "ramus" of the ischium is the thin, flattened part of the ischium (lowest part of the coxal bone), which ascends from the lower part of the body and joins the inferior ramus of the pubis - the junction being indicated in the adult by a raised line. The combined rami are sometimes called the "ischiopubic ramus." The ischium is the posterior inferior compart of the pelvis. Posteriorly, bony prominences form the ischial tuberosity or each side of the inner pelvis and support the body's weight in a sitting position. The large opening called the obturator foramen is formed by both the rami of the ischium together with the pubis and creates the opening that allows for the passage of major blood vessels and nerves to the legs and feet.

Syndesmosis Joints

In a "syndesmosis joint," the bones are bound together by long fibers of connective tissue that form the "interosseous ligament." Since this ligament is flexible and may be twisted, the joint may allow some slight movement. An example of a syndesmosis is found at the distal ends of the tibia and fibula (lower leg bones), where these bones are joined to form the tibiofibular articulation. The "interosseous membrane" is a layer of tissue that separates the space between the joints. The "interosseous talocalcaneal ligament" joins the talus (one of the ankle bones) to the calcaneous (heel bone).

Condyles of The Humerus

At the lower end of the humerus (upper arm bone) and the femur, there are two smooth condyles (rounded processes of the bone): a knob-like "capitulum" on the lateral side and a pulley-shaped "trochlea" in the middle. The capitulum unites with the radius (smaller lower arm bone) at the elbow, and the trochlea is a notch which joins ligaments to the head of the ulna (larger lower arm bone). Above the condyles on either side are "epicondyles," which provide attachments for muscles and ligaments of the elbow. The one toward the center of the arm is the "medial epicondyle," and the one to the side is the "lateral epicondyle."

Ischiofemoral Ligament

The "ischiofemoral ligament" is made up of a band of strong fibers that originate on the ischium just behind the "acetabulum." These fibers blend with the fibers of the joint capsule of the hip. The acetabulum is a cup-shaped cavity in which the three parts of the coxal bone fuse.

Structure of A Joint Capsule

Most joints in the human body are freely movable and have much more complex structures than the immovable or even the slightly movable types. The articular (adjoining) ends of bones in a freely movable joint are covered with a think layer of "articular cartilage," which is resistant to wear and produces a minimum of friction when it is compressed as the joint is moved. Joint bones are held together by a tubular "joint capsule" that has two distinct layers. The outer layer consists mostly of dense, white, fibrous connective tissue, the fibers of which are attached to the periosteum around the outside ring of each bone of the joint near its articular end. The outer fibrous layer of the capsule, therefore, completely encloses the other parts of the joint. It is flexible enough, though, to allow movement and strong enough to help prevent the articular surfaces from being pulled apart. Bundles of strong, tough collagenous fibers called "ligaments" reinforce the joint capsule and help to bind the articular ends of the bones together. Some ligaments appear as bulges in the fibrous layer of the capsule, while others are "accessory structures" located outside the capsule. In either case, these structures also prevent too much movement at the joint, because the ligament is relatively inelastic and becomes tightly drawn whenever a normal limit of movement has been achieved in the joint. The inner layer of the joint capsule consists of a shiny, vascular lining of loose connective tissue called "synovial membrane." The membrane covers all of the surfaces within the joint capsule, except the areas which are covered by cartilage. Some freely movable joints are partially or completely divided into two compartments by disks of fibrocartilage called "menisci" located between the articular surfaces. Such a disk is attached to the fibrous layer of the joint capsule at the sides, and its free surface projects into the joint cavity. Certain freely movable joints also have closed, fluid-filled sacs called "bursae" associated with them. Each bursa has an inner lining of synovial membrane, which may be continuous with the synovial membrane of a nearby joint cavity. Bursae act as cushions and aid the movement of tendons which glide over such bony parts or over other tendons. The names of the bursae indicate their locations; for example, a "suprapatellar bursa," a "prepatellar bursa," and a "infrapatellar bursa."

Tibia

The tibia is the inner and thicker of the two long bones in the lower leg. It is also called the shin bone. Its upper end is expanded into "medial" and "lateral condyles," which have concave surfaces and unite with the condyles of the femur. The tibia is the supporting bone of the lower leg and runs parallel to the other, smaller bone (the fibula) to which it is attached by ligaments. The front of the tibia lies just below the skin and can easily be felt. The upper end joins the femur to form the knee joint, and the lower end forms part of the ankle joint. On the inside of the ankle, the tibia widens and sticks out to form a large bony prominence called the "medial malleolus." On the outside of the ankle is a protrusion called the "lateral malleolus," which is sometimes called the ankle bone, and is the most common area for ankle sprains.

Metacarpal

The metacarpal is one of five, long cylindrical bones in the body of the hand. The bones run from the carpal bones of the wrist to the base of each digit of the hand. On the palm of the hand, these are padded by a thick layer of fibrous, connective tissue; on the back of the hand, they can be seen and felt through the skin. The heads of the metacarpal bones form the knuckles.

Metatarsal

The metatarsal is one of five long, cylindrical bones in the foot. The bones make up the central skeleton of the foot and are held in an arch formation by surrounding ligaments. The metatarsal bones are joined to the toe bones at the metatarsophatangeal joint, a fancy name for the knuckles on the toes.

Oblique Popliteal Ligament

The "oblique popliteal ligament" connects the lateral condyle of the femur (thighbone) to the margin of the head of the tibia at the knee.

Ligaments of The Foot

The instep is made up of five, elongated metatarsal bones that join the tarsus (the seven ankle bones). The distant heads of these bones form the ball of the foot. The tarsals and metatarsals are arranged and bound by ligaments to form the arches of the foot. A "tarsometataral ligament" joins the tarsus to the metatarsal bone. A longitudinal arch extends from the "posterior longitudinal ligament" at the heel to the "anterior longitudinal ligament" of the toe, and a transverse arch ("dorsal metatarsal ligament") stretches across the foot. These arches provide a stable, spring base for the body. At times, the tissues that bind the metatarsal become weakened and produce fallen arches or "flat feet." The "plantar ligaments" are in the sole of the foot. The "plantar calcaneonavicular ligament" joins the "navicular" bone in the ankle to the "calcaneus," or heel bone; the "plantar cuboideonavicular ligament" joins the navicular bone to the "cuboid" bone of the ankle. The "plantar metatarsal ligaments" bind the instep across the sole of the foot.

Lower Leg And Ankle Ligaments

The fibula is the long, slender bone beside the tibia. Its ends are slightly enlarged into an upper "head" and a lower "lateral malleolus." The head meets the fibula just below the lateral condyle; but it does not enter into the knee joint and does not bear any body weight. The ligaments which join the fibula to the front of the fibula are called the "anterior tibiofibular ligaments," and the "posterior tibiofibular ligaments" join them behind the knee. The lateral malleolus is joined to the ankle by the "anterior talofibular ligaments," and the "posterior talofibular ligaments." These ligaments form a prominence on the side of the ankle.

Pubic Symphysis

The pubic symphysis is a cartilage-like articulation between the pubic bones. It is a slightly movable joint that contains three ligaments: the superior pubic, the arcuate pubic and the interpubic disk.

Radius

The radius is the shorter of the two long bones of the forearm. The other is the ulna. The radius is the bone on the thumb side of the arm. The shaft of the radius has a broad base that joins the lower end of the ulna and the upper bones of the wrist at a large process called the radial styloid. The disk-shaped head of the radius, which is smaller than the base, joins the lower end of the humerus (bone in the upper arm) to form the elbow joint.

Sacrum

The sacrum is a large triangular bone at the base of the lower spine. Its broad upper part joins the lowest lumbar vertebrae and its narrow lower part joins the coccyx or "tail bone". The sides are connected to the iliums (the largest bones forming the pelvis). The sacrum is a strong bone and rarely fractures. The five vertebrae that make up the sacrum are separated in early life, but gradually become fused together between the eighteenth and thirtieth years. The spinous processes of these fused bones are represented by a ridge of tubercles. The sacrum is wedged between the coxal bones of the pelvis and is united to them by fibrocartilage at the sacroiliac joints. The weight of the body is transmitted to the legs through the pelvic girdle at these joints.

Skull: Baby and Adult

The skull is the bony section of the head. The skull encases and protects the brain, houses the brain senses, provides attachments for muscles of the head and neck, and helps to form the first portions of the respiratory and digestive tracts. The skull rests on the first vertebra, which is called the "Atlas". At birth, the skull is large in comparison to the rest of the body, and a baby's skull is compressible. The "soft spots" in a baby's head harden and grow together until the bones meet and mesh like a jigsaw puzzle. The largest of the six main soft spots is a diamond-shaped area near the middle of the top of the skull. This is the last area to harden and close, usually at about the age of eighteen months. "Skullduggery" is some kind of trick or some unscrupulous behavior.

Temporal Bones

A temporal bone on each side of the skull joins the parietal bone along the "squamosal suture." The temporal bones form parts of the sides and base of the cranium. The superior temporal line is the topmost curved line on the parietal bone and lies above the inferior temporal line. This is where the temporal fascia attach. The inferior temporal line also lies on the parietal bone, and is the site of attachment of the temporal muscle. Located near the lower edge is a gap, the "external auditory meatus," which leads inward to parts of the ear. The temporal bones house the internal structures of the ear and have depressions, the "mandibular fossae," that join the processes of the mandible. Below each external auditory meatus, there are two projections: a rounded "mastoid process" and a long, pointed "styloid process." The mastoid process provides an attachment for certain muscles of the neck, while the styloid process serves as an anchorage for muscles associated with the tongue and pharynx. The mastoid foramen is a prominent opening in the temporal bone which is located behind (or posterior) to the mastoid process. Generally, it provides the opening through which a vein and artery pass. A "zygomatic process" projects from the front of the temporal bone in the region of the external auditory meatus. It joins the zygomatic bone and helps form the prominence of the cheek.

Supraspinal Ligament

The "supraspinal (or supraspinous) ligament" is a strong, fibrous cord which connects together the apices of the spinous processes of the 7th cervical vertebra to the sacrum; at the point of attachment to the tips of the spinous process, fibrocartilage is developed in the ligament. It is thicker and broader in the lumbar (lower back) than in the thoracic region (chest), and intimately blended, in both places, with the neighboring fascia (tissue).

Tibial Collateral Ligament

The tibial collateral ligament is a broad, flat band of tissue that connects the medial condyle of the femur (thighbone) to the medial condyle of the tibia at the knee joint.

Ulna

The ulna is the longer of the two bones of the forearm; the other being the radius. When the palm faces forward, the ulna is the inner bone (the one nearest the body) running down the forearm parallel to the radius. The upper end joins with the radius and extends into a rounded projection that fits around the lower end of the humerus (the upper arm bone) to form the elbow joint. The lower end of the ulna is rounded and forms a joint with the wrist bones and lower end of the radius.