Skeletal System Definitions

Pivot Joint

A joint in which a section of a cylinder of one bone fits into a corresponding cavity on the other, permitting rotating movement, as in the proximal articulation between the radius and ulna. Also called rotary joint, trochoid joint.

Tarsals

A set of seven irregularly shaped bones. They are situated proximally in the foot, in the ankle area.

Gliding Joint

Gliding joints, such as the ones between the carpals of the wrist, are found where bones meet as flat surfaces and allow for the bones to glide past one another in any direction.

Hinge Joint

Hinge joints, such as the elbow and knee, limit movement in only one direction so that the angle between bones can increase or decrease at the joint. The limited motion at hinge joints provides for more strength and reinforcement from the bones, muscles, and ligaments that make up the joint.

Phalanges

Small bones that make up the fingers and toes

Cranium

The bones of the superior portion of the skull are known as the cranium and protect the brain from damage.

vertebrae

The bones that make up the spinal column

Pectoral girdle

The clavicle and scapula, known collectively as the pectoral girdle, attach to the axial skeleton at the sternum. The pectoral girdle bones move the shoulder joint in many different directions to improve the flexibility of the upper limbs. These bones and the muscles that move them allow you to elevate, depress, abduct, adduct, and rotate the shoulder joint to give the arms an extremely free range of motion.

Clavicle

The clavicles, or collarbones, are a pair of long bones that connect the scapula to the sternum. The name clavicle comes from the Latin word for "little key" and describes the shape of the clavicle as an old-fashioned skeleton key.

femur

The femur, or thigh bone, is the longest, heaviest, and strongest bone in the entire human body. All of the body's weight is supported by the femurs during many activities, such as running, jumping, walking, and standing. Extreme forces also act upon the femur thanks to the strength of the muscles of the hip and thigh that act on the femur to move the leg

Fibula

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 stabilizing 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.

humerus

The humerus is the only bone of the upper arm. It is a long, large bone that extends from the scapula of the shoulder to the ulna and radius of the lower arm. The proximal end of the humerus, known as the head, is a round structure that forms the ball of the ball-and-socket shoulder joint. On its distal end, the humerus forms a wide, cylindrical process that meets the ulna and radius to form the inner hinge of the elbow joint. The pectoral, deltoid, latissimus dorsi, and rotator cuff muscles attach to the humerus to rotate, raise, and lower the arm at the shoulder joint.

Mandible

The mandible (lower jawbone) consists of a horizontal horseshoe-like body with a flat ramus projecting upward at each end.

metacarpals

The metacarpal bones are 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 a thick layer of fibrous, connective tissue pads the bones; on the back of the hand, they can be seen and felt through the skin.

Patella

The patella is the technical name for the kneecap, the triangular-shaped bone at the front of the knee joint. The patella is held in place by muscles, the lower end of which surrounds the patella and is then attached to the upper part of the tibia (shin) by patellar tendons. The patella protects the knee joint.

pelvic girdle

The pelvic girdle consists of paired hipbones, connected in front at the pubic symphysis and behind by the sacrum; each is made up of three bones—the blade-shaped ilium, above and to either side, which accounts for the width of the hips; the ischium, behind and below, on which the weight falls in sitting; and the pubis, in front.

radius

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.

scapula

The 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.

Ball and socket joint

The shoulder and hip joints form the only ball and socket joints in the body. These joints have the freest range of motion of any joint in the body - they are the only joints that can move in a full circle and rotate around their axis. However, the drawback to the ball and socket joint is that its free range of motion makes it more susceptible to dislocation than less mobile joints.

Skull

The skull is composed of 22 bones that are fused together except for the mandible.

vertebral column

The spine, also known as the vertebral column or spinal column, is a column of 26 bones in an adult body - 24 separate vertebrae interspaced with cartilage, and then additionally the sacrum and coccyx

sternum

The sternum, commonly known as the breastbone, is a long, narrow flat bone that serves as the keystone of the rib cage and stabilizes the thoracic skeleton. Several muscles that move the arms, head, and neck have their origins on the sternum. It also protects several vital organs of the chest, such as the heart, aorta, vena cava, and thymus gland that are located just deep to the sternum.

Tibia

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.

ulna

The ulna is the longer, larger and more medial of the lower arm bones. Many muscles in the arm and forearm attach to the ulna to perform movements of the arm, hand and wrist. Movement of the ulna is essential to such everyday functions as throwing a ball and driving a car.

carpals

These bones also form the flexible wrist joint with the proximal row of the carpals.There are eight small carpal bones in the wrist 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 proximal end, where it articulates with the ulna and radius at the wrist.

Metatarsals

These bones connect the phalanges to the tarsals. There are five in number - one for each digit.

Skeletal System

all of the bones and cartilage of the body that collectively provide the supporting framework for the muscles and organs

ribs

protective rib cage around the vital thoracic organs such as the heart and lungs. The rib cage also anchors the bones of the head, neck, shoulders, and arms to the trunk of the body. Powerful muscles that move the head and arms attach to these bones as well. The bones of the chest and their joints also support the upper body's weight.