Disorders of skeleton

Disorders of skeleton

      Skeletal deformation may be hereditary e.g.., arthritis may be hormonal e.g.., osteoporosis or may be due to nutritional deficiency e.g.., osteomalacia and rickets. Here we will describe slipped disc spondolysis, sciatica arthritis. 

Common disorders of skeleton 

Slipped disc 

          Each intervertebral disc is a cushion like pad which consists of nucleus pulposus and annulus fibrosus. Nucleus pulposus is an inner semifluid which acts as a rubber ball to give a diac it's elasticity and compressibility. Annulus fibrosus is the strong outer ring of fibrocartilage, which holds together successive vertebrae. The discs act as shock absorber. Severe or sudden trauma to spines may result in herniation of one or more discs. 

           The herniated disc or slipped disc usually involves rupture of annulus fibrosus followed by protrusion of the spongy nucleus pulposus. If protrusion presses on spinal cord or on spinal nerves, generate severe pain or even destruction of these nervous structures. "Slipped disc " is misleading as it is not the whole disc that slides out of the position. 

Spondylosis 

      It is the immobility amd fusion of vertebral joint. Cervical spondylosis results from chronic cervical degeneration, with herniation of disc and aging. 

Sciatica 

        Sciatica refers to pain, weakness, numbness, or tingling in the leg. It is caused by injury to or pressure on the sciatic nerve. Common causes of sciatica include : Slipped disk, pelvic injury or fracture and tumors. 

Arthritis

          It is the inflammation of joints. The typical symptoms of arthritis include pain after walking which may later occur even at rest, creaking sounds in joint, difficulty in getting up from a chair and pain on walking up and down stairs. There are different types of arthritis. Osteoarthritis is a progressive disease in which the articular cartilages gradually soften and disintegrate. It affects knee, hip and intervertebral joints.

             Rheumatoid arthritis is the result of an autoimmune disorder in which synovial membrane becomes inflamed due to faulty immune system. Gouty arthritis results from a metabolic disorder in which an abnormal amount of uric acid is retained in the blood and sodium urate crystals are deposited in the joints. The most common joint affected is the joint of the big toe. 

Bone fractures 

          A fracture is the medical term for a broken bone. They occur when the physical force exerted on the bone is simple stronger than the bone itself. So bones break when they fracture cannot withstand a force a trauma applied to them. 

Common types of fractures 

           Simple fracture or closed fractures are those in which the skin is intact. If the bone ends penetrate the skin and form a wound are called compund fracture or open fracture. When a fracture damages the adjacent organs it is called complicated fracture. 

Bone repair 

        Bone is a living tissue that undergoes repair following fracture. The repair process of a simple fracture takes place in four major steps. 

Haematoma or clot formation 

             When a bone breaks, blood vessels in the bone, and perhaps in surrounding tissues, are torn and haemorrhage. As a result, a haematoma, a mass of clotted blood, forms at the fracture site. Soon, bone cells deprived of nutrition die, and the tissue at the site becomes swollen, painful , and inflamed. 

Fibrocartilaginous callus formation 

        Within a few days, several events lead to the formation of fibrocartilaginous or soft callus. Capillaries grow into the haematoma and phagocytic cells invade the area and begin cleaning up the debris. A fracture ruptures the periosteum and stimulates the production and release of the numerous osteoblasts. These osteoblasts in conjunction with cartilage forming cells secrete a porous mass of bone and cartilage called callus (or cartilaginous callus) surrounding the break. The callus replaces the original blood clot and holds the ends of the bones together. This process takes 3-4weeks . 

Bony callus formation or callus ossification 

         Within a week, after the formation of soft callus, if is gradually converted into a hard bony callus of spongy bone. Bony callus formation continues until a firm union is formed about two months later. Osteoclasts breakdown the cartilage while osteoblasts replace it with bone. 

Bone remodelling 

          It takes place when a compact bone is formed across the fracture line to connect both sides. Usually, more bone is produced at the site of a healing fracture than needed to replace the damaged tissue. However, ostelclasis eventually remove the excess and the final result of the repair is bone shaped very much like the original. The final structure of the remodeled area resembles that of the original unbroken bony region because it responds to the same set of mechanical stressors. 

Cardiac muscles

       These are found only in heart. They branch extensively, cardiac muscles are striated like skeletal muscle, but each cell usually contains one nucleus located near the centre. Adjacent cells join together to form branching fibres by specialised cell-to-cell attachments called intercalated discs, which have gap like junctions that allow action potentials to pass from cell to cell. 

Skeletal muscles

         These muscles are attached to the bone and are responsible for movements of body parts and whole body  movements(locomotion). 

Structure of  Skeletal Muscles

            Skeletal muscles or striated muscles show alternate light and dark regions under microscope. Skeletal muscles are composed of muscle fibers are enclosed by collagen fibres and connective tissue. At the ends of the muscle the collagen and connective tissue forms tendons which attach the muscle to skeletal elements. Each skeletal muscle fibre is a single cylindrical cell, enclosed by a plasma membrane like structure called sarcolemma and has several nuclei. The sarcolemma of muscle fibre cell penetrates deep into the cell to form a hollow elongated tube, the transverse tubule (T-tubule) . The cytoplasm of the muscle fibre is called sarcoplasm. It contains sarcoplasmic reticulum. Within the muscle fibers are numerous thin myofibrils which possess characteristic cross striations. 

Muscle disorders

         There are many problems related to muscle which are generally called muscle disorder. Some common muscle disorders e.g., muscle fatigue, cramp and tetany are discussed here. 

Muscle fatigue

              When the muscles lose the ability to contract, the Physiological state of muscles is called muscle fatigue. The other factors which contribute to muscle fatigue are accumulation of lactic acid and ionic imbalance. The cause of extreme fatigue is lactic acid which causes muscle pH to drop and the muscle to ache. 

Cramp 

         It is also know as titanic contraction of entire muscle. It lasts for just few seconds to several hours, causing the muscle to become taut (tightly drawn) and painful. It is most common in thigh and hip muscles. It usually occurs at night or after exercise. It reflects low blood sugar level, electrolyte depletion, dehydration, irritability of spin cord and neurons. 

Tetany 

      In tetany the body shakes from continuous muscle contraction and convulsion occur due to calcium imbalance. It results in the excitability of neurons and results in loss of sensation. If untreated the symptoms progress to spasm of larynx, paralysis and ultimately death occurs. 

                     Dr. Mahalakshmi Raghunath

                     Reference:

                     Author:Dr.N.Senthil kumar