The skeletal system serves many important functions; it provides shape, support, protection, allows movement when combined with the muscular system, it produces blood from the marrow and stores important minerals such as calcium and phosphorus.
There are 206 bones in the adult human body.
Vital organs are protected by the skeletal system. The brain is protected by the surrounding skull, as the heart and lungs are encased by the sternum and rib cage.
LOWER LIMB BONES
OS COXA
The os Coxa consists of three bones :
These three bones fuse together in adulthood to form the hip bone.
The ilium forms the superior portion of the os coxa, the ischium the lower posterior portion, and the pubis the lower anterior portion. The left and right os coxa bones meet anteriorly at the pubis symphysis joint and articulate posteriorly with the sacrum. Inferior to the sacrum is the coccyx.
Together, the right and left os coxae form the pelvic girdle. Making up the pelvis (or bony pelvis) are the os coxae, sacrum and coccyx.
Patella
The Patella is the lens-shaped bone (sometimes described as “triangular”) that forms the kneecap.
It is located in the tendon on the quadriceps femoris muscle of the thigh where it lies in front of the knee-joint between the femur and the tibia.
The functions of the Patella include :
Tibia (shin bone)
The tibia, sometimes known as the shin bone, is the larger and stronger of the two lower leg bones. It forms the knee joint with the femur and the ankle joint with the fibula and tarsus. Many powerful muscles that move the foot and lower leg are anchored to the tibia. The support and movement of the tibia is essential to many activities performed by the legs, including standing, walking, running, jumping and supporting the body’s weight.
The tibia is located in the lower leg medial to the fibula, distal to the femur and proximal to the talus of the foot. It is widest at its proximal end near the femur, where it forms the distal end of the knee joint before tapering along its length to a much narrower bone at the ankle joint.
Fibula (pin)
The fibula is the long, thin and lateral bone of the lower leg. It runs parallel to the tibia, or shin bone, and plays a significant role in stabilising the ankle and supporting the muscles of the lower leg. Compared to the tibia, the fibula is about the same length, but is considerably thinner. The difference in thickness corresponds to the varying roles of the two bones; the tibia bears the body’s weight from the knees to the ankles, while the fibula merely functions as a support for the tibia.
At the fibula’s proximal end, just below the knee, is a slightly rounded enlargement known as the head of the fibula. The head of the fibula forms the proximal (superior) tibiofibular joint with the lateral edge of the tibia. From the proximal tibiofibular joint, the fibula extends slightly medially and anteriorly in a straight line toward the ankle. Upon reaching the ankle, the fibula swells into a bony knob known as the lateral malleolus, which can be seen and felt protruding from the outside of the ankle joint. At the medial malleolus, the fibula forms the distal (inferior) tibiofibular joint with the tibia and also the talocrural (ankle) joint with the tibia and talus of the foot.
While the fibula moves very little relative to the tibia, the joints that it forms contribute significantly to the function of the lower leg. The proximal and distal tibiofibular joints permit the fibula to adjust its position relative to the tibia, increasing the range of motion of the ankle. The lateral malleolus also forms the lateral wall of the talocrural joint and reinforces the ankle joint.
Many muscles of the thigh and lower leg attach to the fibula through tendons. One of the hamstrings, the biceps femoris muscle, has its insertion at the head of the fibula and pulls on the fibula to flex the leg at the knee. Eight other muscles – including the three fibularis (peroneus) muscles, the soleus, and several flexors and extensors of the toes – have their origins on the fibula as well.
An interesting fact about the fibula is that it can be harvested for tissue to graft onto other bones in the body. The fibula bears so little body weight that it typically has more bone mass than is needed to support the leg, making it a good tissue donor. The bony tissue harvested from the fibula is most commonly grafted onto the mandible to replace bone lost during oral cancer surgery. Skin and blood vessels covering the fibula are grafted along with the osseous (bone) tissue to maintain blood supply to the bone and to close the wound in the face. The remaining tissue in the leg can be sutured together to heal around the donor site.
Tarsals
The tarsals are a group of bones located in the foot and ankle area. There are seven tarsals in each ankle/foot, and they form a part of the appendicular skeleton. The tarsals articulate with each other and the tibia, fibula, and the metatarsals to form the ankle joint. The functions of the tarsals include supporting movement, creating insertion points for muscles, tendons, and ligaments, and storing some minerals, such as calcium and phosphorus.
The tarsals include the talus, navicular, intermediate cuneiform, medial cuneiform, lateral cuneiform, cuboid, and calcaneus. Conditions that can afflict the tarsals include infection, trauma, fracture, osteoporosis, osteomyelitis and dislocations.
Metatarsal Bone
Metatarsals are part of the bones of the mid-foot and are tubular in shape. They are named by numbers and start from the medial side outward. The medial side is the same side as the big toe.
They are called the first metatarsal, second metatarsal, third metatarsal, fourth metatarsal, and the fifth metatarsal. The first metatarsal is the strongest of the group.
These bones are found between the phalanges of the toes and the tarsal bones. Each bone's base will move with at least one of the tarsal bones where the tarsometatarsal joint is located. The metatarsal bones are connected to the bones of the toe, or phalanges, at the knuckle of the toe, or metatarsophalangeal joint.
Metatarsals are convex in shape (arch upward), are long bones, and give the foot its arch. They work with connective tissues, ligaments and tendons, to provide movement in the foot.
These bones can become fractured, strained, or inflamed from misuse or overuse. Immobilization of the foot (e.g. via casting) can help heal metatarsal fractures and sprains.
Phalanges (Foot)
The distal phalanges (foot) are located at the end of each toe. Three phalangeal bones make up each digit, articulating with each other at bending joints. The distal phalanges come at the end, right below the toenail.
The distal phalanges articulate with the intermediate phalanges, which are joined to the proximal phalanges. Those bones, in turn, connect to the metatarsals of the foot.
The toe bones within the foot are similar to that of the fingers of the hand. After all, both the hand and the foot are comprised of five total digits. However, the phalanges of the foot bear subtle but distinct differences. The hand features a thumb, which is structurally different from the fingers. The foot's big toe is structurally the same as the other toes. Also, finger bones tend to be longer, while the toe bones tend to be flatter and stubbier.
The distal phalanges provide a home for both the toenail and the fleshy pad on the underside of each toe. Since they come at the end of the toe, they are sometimes referred to as the terminal phalanges.
UPPER LIMB BONES
Clavical
The clavicle or collarbone (os clavicula) is located superior to the first rib and runs horizontally from the sternum to the scapula.
A superior view of the clavicle shows it is shaped somewhat like an “S”. the medial end curves anteriorly and the lateral end curves posteriorly.
Along with the scapula, the clavicle forms the shoulder or pectoral girdle, which connects the humerus (arm) to the axial skeleton.
The clavicle functions like a strut or lever arm to help support (suspend) the humerus and scapula and maintain their position relative to the rib cage.
Scapula
Together, the scapula and clavicle form the shoulder girdle (or pectoral girdle), which supports movements of the humerus.
The triangular-shaped scapula (os scapula) is a relatively flat bone and is therefore often referred to as the shoulder blade.
The anterior surface of the scapula faces the posterior ribs and its position is loosely maintained by the muscles t hat attach to it s surface and ligament connections to the clavicle.
Humerus
The humerus (= arm bone) is a long bone that extends from the shoulder to the elbow.
At its proximal end, the humerus (os humerus) articulates with the scapula (= part of the pectoral girdle).
Distally, the medial surface of the humerus articulates with the ulna and the lateral surface articulates with the radius.
Radius and Ulna
The radius is the more lateral and slightly shorter of the two forearm bones. It is found on the thumb side of the forearm and rotates to allow the hand to pivot at the wrist. Several muscles of the arm and forearm have origins and insertions on the radius to provide motion to the upper limb. These movements are essential to many everyday tasks such as writing, drawing, and throwing a ball.
The radius is located on the lateral side of the forearm between the elbow and the wrist joints. It forms the elbow joint on its proximal end with the humerus of the upper arm and the ulna of the forearm
Although the radius begins as the smaller of the two forearm bones at the elbow, it widens significantly as it extends along the forearm to become much wider than the ulna at the wrist. A short cylinder of smooth bone forms the head of the radius where it meets the capitulum of the humerus and the radial notch of the ulna at the elbow. The head of the radius allows the forearm to flex and pivot at the elbow joint. Just distal to the head, the radius narrows considerably to form the neck of the radius before expanding medially to form the radial tuberosity, a bony process that serves as the insertion of the biceps brachii.
Distal to the elbow, the body of the radius continues in a straight line along the lateral side of the forearm before suddenly widening just above the wrist joint. At its wide distal end, the radius terminates in three smooth, concave surfaces that form the wrist joint with the ulna and the carpals of the hand. Two of these concavities meet with the scaphoid and lunate bones of the carpals to form the radiocarpal portion of the wrist joint. On the medial side, the ulnar notch of the radius forms the distal radioulnar joint with the ulna, allowing the radius to rotate around the ulna to supinate and pronate the hand and wrist. The styloid process – a small, pointy extension of bone – protrudes from the lateral edge of the radius to anchor the radial collateral ligament of the wrist.
One of the most important functions of the radius is anchoring the muscles of the upper arm and the forearm. The biceps brachii muscle of the upper arm forms its insertion at the radial tuberosity to flex and supinate the forearm at the elbow. The supinator, pronator teres, and pronator quadratus muscles of the forearm also form insertions on the radius to supinate and pronate the hand and wrist by rotating the distal end of the radius around the ulna. Several muscles that move the hand and digits – including the flexor pollicis longus and flexor digitorum superficialis muscles – also have their origins on the radius.
Carpals
Femur
The femur is the major bone of the upper-leg, and is also known non-medically as the thigh bone. It is a long bone that goes between the hip and the knee.
The narrowed end of the femur carries the head of the femur and is the most common site of fracture in the leg in elderly women.
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