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The Skeletal System

The Skeletal System is the framework of the body, consisting of 206 bones as well as a network of tendons that is made of tough band of fibrous collagen tissue connecting a muscle to bone, ligaments connecting bones to joint and cartilage that allows some flexibility of movement. The skeletal system serves 4 functions: (1) Giving the body its shape (2) Protecting the vital internal organs (3) Allowing for movement (4) Storing minerals and producing blood cells

The skeletal system has 6 basic components: the skull, spinal column, thorax, pelvis, and the upper and lower extremities. The bones of the adult skeleton are classified by size and shape (long, short, flat, or irregular). The skull rest at the top of the spinal column and houses and protects the brain. It has 2 parts: the cranium and the face. The cranium forms the top, back, and the sides of the skull plus the forehead. The interlocking bones of the cranium are the occipital, 2 parietal, 2 temporal, and the frontal- are typical flat bones. The outer layer of the cranium is thick and tough.

The inner layer is thinner and more brittle. Even though this arrangement provides maximum strength, lightness, and elasticity, the cranium may still be fractured. The brain is commonly lacerated by the bony projections and ridges on the front (anterior) and the lower (inferior) surfaces of the skull. Impact can also bruise the brain and cause it to bleed and swell. Because the cranium cannot expand, bleeding and swelling within the cranium may compress brain tissue, causing it to malfunction and possibly death.

The Face

The face is the area between the brow and the chin. The face has 14 bones, 13 are immovable and interlocking. The immovable bones of the face form the bony settings of the eyes: nose, cheeks, and the mouth. Among them are the orbits (eye socket), nasal bone (bed of the nose), maxillae (fused bone of the upper jaw), and the zygomatic bone (cheekbone). The mandible (lower jaw) freely moves on hinge joints. The mandible is shaped like a horseshoe, and is the largest and the strongest bone of the face.

The spinal column, also called vertebral column, is the main support system of the body. Ribs originate from it to form the chest (thoracic) cavity. The rest of the human skeletal is either directly or indirectly connected to the spine as well.

The spinal column is made up of irregular shaped blocks of bone called vertebrae that has great deal of mobility. Lying on top of one another they form the spinal column . Damage to the spinal cord will cause loss of sensation or movement distal to the injury, as for injury to the vertebrae (spinal column) will produce only pain. Intervertebral disk is a fluid-filled pad of tough elastic cartilage located between each two vertebrae. It acts as shock absorber and allows movement of the spine. They are extremely susceptible to injuries such as, improper lifting of heavy objects, or twisting and grinding. Spinal Column

The spinal column is composed of 33 vertebrae disk, which are divided into 5 parts: cervical, thoracic, lumbar, sacral, and the coccyx. (1) Cervical spine, C1-C7 (neck). The first 7 vertebrae that form the cervical spine, and most prone to injury. (2) Thoracic spine, T1-T12 (upper back). The 12 thoracic vertebrae that are directly below (inferior) the cervical spine and forms the upper back. Vertebrae is support by the 12 pairs of thoracic ribs that are attached to the spine posteriorly. (3)

Lumbar spine, L1-L5 (lower back. This are the next 5 vertebrae forms the lower back, and are the least mobile of the vertebrae. Lower back injuries mostly involves muscles, not vertebrae. (4) Sacral spine, S1-S5 (the back wall of the pelvis). The next 5 vertebrae that are fused together to form the rigid part of the front (posterior) side of the pelvis. (5) Coccyx (tailbone). This are the last 4 vertebrae, which are fused together and do not have the protrusions characteristic of the other vertebrae.

The Thorax

The thorax (or chest), is composed of the ribs, the sternum (the breastbone, and the thoracic spine. The 24 ribs are somewhat flexible arches of bone, which are arranged in 12 pairs and are attached to the front (posteriorly) by ligaments to the thoracic vertebrae. The first 7 pairs of ribs are attached to the sternum by cartilage, which are called the true ribs.

The next 3 pairs are attached to the ribs above them with cartilage. The posterior (front) ends of the last 2 pairs(the floating ribs) are not attached to the sternum. These last 5 pairs of ribs are referred to as false ribs. The sternum is a flat, narrow bone in the middle of the front (anterior) chest. The clavicle referred to as the collarbone is attached to the manubrium, which is the top (superior) portion of the sternum. The ribs are attached to the body of the sternum or also known as the middle segment. The lower (inferior) portion of the sternum is called the xiphoid process.

The Pelvis

The pelvis is a doughnut shaped structure consisting of several bones, including the sacrum and the coccyx. The iliac crest forms the wings of the pelvis, located at each side of the pelvis. The pubis is in the front (anterior) and lower (inferior) portion of the pelvis, and the ischium is in the back (posterior) and lower (inferior) portion of the pelvis. The pelvis forms the floor of the abdominal cavity. The pelvic cavity supports the intestines and houses the bladder, rectum, and internal reproductive organs in the human body.

Lower Extremities

The legs from the hip to the toes form the lower extremities. The hip joint is on each lateral side of the hip. The joint is made up of the pelvic socket, called the acetabulum, which fits the head of the femur (thighbone). The bottom of the femur is flat with 2 projections that help form the hinged knee joint, which only allows angular movement. The patella (kneecap) protects and stabilize the joint of the knee and keeps the condyle of the tibia and the femur aligned.

The condyle is a rounded protuberance at the end of some bones, forming an articulation with another bone. The tibia (shin) and the fibula are the two bones of the lower leg. The weight-bearing bone located at the anterior and medial side of the leg is the tibia. Its broad upper surface receives the rounded end of the distal femur to form the joint of the knee. The smaller distal end of the tibia forms the medial malleolus of the ankle.

Fibula is attached to the tibia at the top and is located at the lateral side of the leg parallel to the tibia. The ankle joint socket is formed by the bony prominences at the ends of the tibia and fibula. The medial and lateral malleolus are the knobby surface landmarks of the ankle joint. Tarsals are group of bones, including the calcaneus (heel bone) that makes up the proximal portion of the foot. There are 5 metatarsals that forms the substance of the foot, and 14 phalanges on each foot that forms the toes (2 on each big toe and 3 in each other toe).

The Upper Extremities

The upper extremities, includes the shoulders, arms, forearms, wrist, and hands. Each clavicle and scapula form a shoulder girdle, the tip is called the acromion. The arm is attached to the trunk of the shoulder girdle by a muscle and extend from it to the arms, thorax, neck, and the head. The humerus is the largest bone of the upper extremity and is located at the proximal portion of the arm. Its shaft is roughly cylindrical, its upper end is round, and its lower end is flat.

The round head of the humerus fits into a shallow cup in the shoulder blade, forming a ball and socket joint that is freely movable and easily dislocated joint in the human body. The distal end of the humerus and the proximal end of the radius and the ulna forms the hinged elbow joint. The radius is called, the lateral bone of the forearm; and the ulna is called, the medial bone of the forearm.

The radius is located on the dumb side and the ulna is located on the little-finger side of the forearm. The olecranon is part of the ulna, which forms the bony prominence of the elbow. The ulna can be felt through the skin with fingertips, while the upper two-thirds of the radius cannot be felt because it is sheathed in the muscle tissue. Only the lower third of the radius can be felt through the skin. There are 8 bones in the wrist called carpals. The structural strength of the hand comes from the metacarpals. The bones make up the fingers and thumbs are phalange (3 in each finger, 2 per thumb.

The Joints

The place where two bones meet is called joint. Some joints are immovable (the skull), other joints are slightly movable (the spine), and the remaining joints are movable, such as the elbows and knees. Movable joints allows changes of position and motion as follow below: • Flexion: bending toward the body or decreasing the angle between the bones of the body.

• Extension: away from the body or decreasing the angle between the bones the bones of the body. • Abduction: movement away from the midline. • Adduction: movement toward the midline. • Circumduction: combination of the four preceding motions as is possible with the shoulder joint. • Pronation: turning the forearm so the palm of the hand is turn toward the back. • Supination: turning the forearm so the palm of the hand is turned toward the front.

The structure of the joint determines the type of movement that is possible for the particular body part to move. The most common types of joint are the ball- and –socket joint and hinged joint. The following are different types of joint: • Ball-and socket joint: type of joint that permits the widest range of motion-flexion, extension, abduction, adduction, and rotation.

• Hinged Joint: type of joint that permits flexion and extension. Elbow joints have forward movement (the anterior bone surfaces approach each other), while the knee joints have backward movement (the posterior bone surfaces approach each other). • Pivot Joint: type of joint that allows turning motion, and includes the joints between the head and neck at the first and second cervical vertebrae and those of the wrist. • Gliding Joint: where one bone slides across another to the point where surrounding structures restrict the motion. Gliding joint connect the small bones in the hands and the feet.

• Saddle Joint: joint shaped to permit combinations of limited movements along perpendicular planes. An example of saddle joint is the ankle, which allows the foot to turn inward slightly as it moves up and down. • Condyloid Joint: modified ball-and-socket joint that permits limited motion in two directions. Examples includes, the wrist that allows the hand to move up and down and from side to side, but not to rotate completely.

Bone Injuries Fun Facts:

Fractures to the bone causes the loss of continuity in the structure of a bone. When a bone is fractured, the sharp fragments may inure the surrounding tissues. It is important to know that bone s are also living tissue and have rich blood supply. When bone is fractured the vessels within the bone may be torn or ruptured from the sharp edges or fragments from the fractured bone. It sometimes can lead to severe bleeding from the bone itself rather than the surrounding vessels or tissue. A person can lose about 1,000 to 2,000 mL of blood from a fractured femur.

Bleeding from a pelvic fracture may cause up to 2,000mL blood into the pelvic cavity. Always remember, when aiding patient with pelvic fracture note that they may go through the shock state. Your bones are the framework of the body that gives its shape, support the body, and protects its vital internal organs from easily being injured. Without the bones of the body, the human body is like a jellyfish without shape.


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