Human Skeleton

Several factors contribute to the bone density and average mass of the human skeleton including; sex, race, hormonal factors, nutrition, physical activity and lifestyle behaviors. Because of these and other factors affecting an indage – newborn babies have over 270 bones some of which fuse together into a longitudinal axis, the axial skeleton, to which the appendicular skeleton is attached.

The axial skeleton (80 bones) is formed by the vertebral column (26), the rib cage (12 pairs of ribs and the sternum), and the skull (22 bones and 7 associated bones). The upright posture of humans is maintained by the axial skeleton, which transmits the weight from the head, the trunk, and the upper extremities down to the lower extremities at the hip joints. The bones of the spine are supported by many ligaments. The erectors spinae muscles are also supporting and are useful for balance.

The appendicular skeleton (126 bones) is formed by the pectoral girdles (4), the upper limbs (60), the pelvic girdle (2), and the lower limbs (60). Their functions are to make locomotion possible and to protect the major organs of locomotion, digestion, excretion, and reproduction.

Function

The skeleton serves six major functions.

Support

The skeleton provides the framework which supports the body and maintains its shape. The pelvis, associated ligaments and muscles provide a floor for the pelvic structures. Without the rib cages, costal cartilages, and intercostal muscles, the heart would collapse.

Movement

The joints between bones permit movement, some allowing a wider range of movement than others, e.g. the ball and socket joint allows a greater range of movement than the pivot joint at the neck. Movement is powered by skeletal muscles, which are attached to the skeleton at various sites on bones. Muscles, bones, and joints provide the principal mechanics for movement, all coordinated by the nervous system.

Protection

The skeleton protects many vital organs:

The skull protects the brain, the eyes, and the middle and inner ears.
The vertebrae protect the spinal cord.
The rib cage, spine, and sternum protect the human lungs, human heart and major blood vessels.
The clavicle and scapula protect the shoulder.
The ilium and spine protect the digestive and urogenital systems and the hip.
The patella and the ulna protect the knee and the elbow respectively.
The carpals and tarsals protect the wrist and ankle respectively.

Blood cell production

The skeleton is the site of haematopoiesis, which takes place in red blood cells bone marrow.

Storage

Bone matrix can store calcium and is involved in calcium metabolism, and bone marrow can store iron in ferrotin and is involved in iron metabolism. However, bones are not entirely made of calcium, but a mixture of chondroitin sulfateand hydroxyapatite, the latter making up 70% of a bone.

Endocrine regulation

Bone cells release a hormone called osteocalcin, which contributes to the regulation of blood sugar (glucose) and fat deposition. Osteocalcin increases both the insulin secretion and sensitivity, in addition to boosting the number ofinsulin-producing cells and reducing stores of fat.

Disorders

There are many classified skeletal disorders. One of the most common is osteoporosis. Also common is scoliosis, a side-to-side curve in the back or spine, often creating a pronounced "C" or "S" shape when viewed on an x-ray of the spine. This condition is most apparent during adolescence, and is most common with females.

Bone and cartilage disorders

B

Bone spur (Osteophytes)

[edit]C

[edit]F

[edit]G

[edit]P

[edit]R

Renal Osteodystrophy

[edit]S

Salter-Harris fractures

[edit]W

Water on the knee

Osteoporosis

Osteoporosis is a disease of bone, which leads to an increased risk of fracture. In osteoporosis, the bone mineral density (BMD) is reduced, bone microarchitecture is disrupted, and the amount and variety of non-collagenous proteins in bone is altered. Osteoporosis is defined by the World Health Organization (WHO) in women as a bone mineral density 2.5 standard deviations below peak bone mass (20-year-old sex-matched healthy person average) as measured by DXA; the term "established osteoporosis" includes the presence of a fragility fracture.Osteoporosis is most common in women after themenopause, when it is called postmenopausal osteoporosis, but may develop in men and premenopausal women in the presence of particular hormonal disorders and other chronic diseases or as a result of smoking and medications, specifically glucocorticoids, when the disease is craned steroid- or glucocorticoid-induced osteoporosis (SIOP or GIOP).

Osteoporosis can be prevented with lifestyle advice and medication, and preventing falls in people with known or suspected osteoporosis is an established way to prevent fractures. Osteoporosis can also be prevented with having a good source of calcium and vitamin D. Osteoporosis can be treated with bisphosphonates and various other medical treatments.

Osteomyelitis

Osteomyelitis is a bone infection usually caused by bacteria, including mycobacteria, but is sometimes caused by fungi.

Bacteria or fungi can infect bones by spreading through the bloodstream, spreading from nearby tissue, or directly invading the bone.
People have pain in one part of the bone, fever, and weight loss.
Blood tests and x-rays are done, and doctors remove a sample of bone for tests.
Antibiotics are given for weeks, and surgery may be needed.

Osteomyelitis occurs most commonly in young children and in older people, but all age groups are at risk. Osteomyelitis is also more likely to occur in people with serious medical conditions.

When a bone becomes infected, the soft, inner part (bone marrow) often swells. As the swollen tissue presses against the rigid outer wall of the bone, the blood vessels in the bone marrow may become compressed, which reduces or cuts off the blood supply to the bone. Without an adequate blood supply, parts of the bone may die. These areas of dead bone are difficult to cure of infection because it is difficult for the body's natural infection-fighting cells and antibiotics to reach them. The infection can also spread outward from the bone to form collections of pus (abscesses) in adjacent soft tissues, such as the muscle.

Osteochondritis dissecans

is a joint disorder in which cracks form in the articular cartilage and the underlying subchondral bone. OCD is caused by blood deprivation in the subchondral bone. This loss of blood flow causes the subchondral bone to die in a process called avascular necrosis. The bone is then reabsorbed by the body, leaving the articular cartilage it supported prone to damage. The result is fragmentation (dissection) of both cartilage and bone, and the free movement of these osteochondral fragments within the joint space, causing pain and further damage.

Bone Tumor

A bone tumor is an abnormal growth of cells within a bone. A bone tumor may be cancerous (malignant) or noncancerous (benign).

The cause of bone tumors is unknown. They often occur in areas of rapid bone growth. Possible causes include:

Genetic defects passed down through families
Radiation
Injury

In most cases, no specific cause is found.

Osteochondromas are the most common noncancerous (benign) bone tumors, and occur most often in people between the ages of 10 and 20.

Cancers that start in the bones are referred to as primary bone tumors. Cancers that start in another part of the body (such as the breast, lungs, or colon) are called secondary or metastatic bone tumors. They behave very differently from primary bone tumors. Multiple myeloma often affects or involves the bone, but is not considered a primary bone tumor.

Cancerous (malignant) bone tumors include:

Chondrosarcoma
Ewing's sarcoma
Fibrosarcoma
Osteosarcomas

Broken Hips

Luis Roberto Vazquez Gomez

domingo, 22 de julio de 2012

Human Skeleton