Skeletal

• A bone is an organ made up of several different tissues working together: bone (osseous) tissue, cartilage, dense connective tissue, epithelium, adipose tissue, and nervous tissue. The entire framework of bones and their cartilages constitute the skeletal system. The study of bone structure and the treatment of bone disorders is referred to as osteology
• Support. The skeleton serves as the structural framework for the body by supporting soft tissues and providing attachment points for the tendons of most skeletal muscles.
• Assistance in movement. Most skeletal muscles attach to bones; when they contract, they pull on bones to produce movement.
• Mineral homeostasis (storage and release). Bone tissue makes up about 18% of the weight of the human body. It stores several minerals, especially calcium and phosphorus, which contribute to the strength of bone
• Blood cell production. Within certain bones, a connective tissue called red bone marrow produces red blood cells, white blood cells, and platelets, a process called hemopoiesis
• Triglyceride storage. Yellow bone marrow consists mainly of adi- pose cells, which store triglycerides. The stored triglycerides are a potential chemical energy reserve.
• 1. diaphysis is the bone’s shaft or body—the long, cylindrical, main portion of the bone.

  2. The epiphyses are the proximal and distal ends of the bone.

  3. The metaphyses are the regions between the diaphysis and the epi- physes.
• articular cartilage is a thin layer of hyaline cartilage covering the part of the epiphysis where the bone forms an articulation ( joint) with another bone.
• periosteum is a tough con- nective tissue sheath and its associated blood supply that surrounds the bone surface wherever it is not covered by articular cartilage
• medullary cavity or marrow cavity, is a hollow, cylindrical space within the diaphysis that contains fatty yellow bone marrow and numerous blood vessels in adults. T
• endosteum is a thin mem- brane that lines the medullary cavity. It contains a single layer of bone-forming cells and a small amount of connective tissue
• Osteoprogenitor cells are unspecialized bone stem cells derived from mesenchyme, the tissue from which almost all connective tissues are formed
• Osteoprogenitor cells (os′-tē-ō-prō-JEN-i-tor; -genic = producing) are unspecialized bone stem cells derived from mesenchyme, the tissue from which almost all connective tissues are formed
• Osteocytes (OS-tē-ō-sīts′; -cytes = cells), mature bone cells, are the main cells in bone tissue and maintain its daily metabolism, such as the exchange of nutrients and wastes with the blood
• Osteoclasts (OS-tē-ō-klasts′; -clast = break) are huge cells derived from the fusion of as many as 50 monocytes (a type of white blood cell) and are concentrated in the endosteum
• Compact bone tissue contains few spaces and is the strongest form of bone tissue. It is found beneath the periosteum of all bones and makes up the bulk of the diaphyses of long bones.
• spongy bone tissue, also referred to as trabecular or cancellous bone tissue, does not contain osteons
• process by which bone forms is called ossification
• fracture (FRAK-choor) is any break in a bone. Fractures are named according to their severity, the shape or position of the fracture line, or even the physician who first described them.
• stress fracture is a series of microscopic fissures in bone that forms without any evidence of injury to other tissues.
• Reactive phase. This phase is an early inflammatory phase
• Reparative phase: Fibrocartilaginous callus formation.Blood vessels grow into the fracture hematoma and phago- cytes begin to clean up dead bone cells. Fibroblasts from the periosteum invade the fracture site and produce collagen fibers. In addition, cells from the periosteum develop into chondroblasts and begin to produce fibrocartilage in this region.
• Reparative phase: Bony callus formation. In areas closer to well-vascularized healthy bone tissue, osteoprogenitor cells develop into osteoblasts, which begin to produce spongy bone trabeculae. The trabeculae join living and dead portions of the original bone fragments
• Bone remodeling phase. The final phase of fracture repair is bone remodeling of the callus.
• Open (Compound)

  The broken ends of the bone protrude through the skin. Conversely, a closed (simple) fracture does not break the skin.
• Comminuted. The bone is splintered, crushed, or broken into pieces at the site of impact, and smaller bone fragments lie between the two main fragments.
• GREENSTICK. A partial fracture in which one side of the bone is broken and the other side bends
• Impacted. One end of the fractured bone is forcefully driven into the interior of the other.
• Pott. Fracture of the distal end of the lateral leg bone (fibula), with serious injury of the distal tibial articulation.
• COLLES. Fracture of the distal end of the lateral forearm bone (radius)

  in which the distal fragment is displaced posteriorly.
• Together, the bones, muscles, and joints form an integrated system called the musculoskeletal system. The branch of medical science concerned with the preven- tion or correction of disorders of the musculoskeletal system is called orthopedics
• long bones have greater length than width, con- sist of a shaft and a variable number of extremities or epiphyses (ends)
• Short bones are somewhat cube-shaped and are nearly equal in length and width. They consist of spongy bone tissue except at the surface, which has a thin layer of compact bone tissue
• Flat bones are generally thin and composed of two nearly parallel plates of compact bone tissue enclosing a layer of spongy bone tissue. Flat bones afford considerable protection and provide extensive areas for muscle attachment.
• Irregular bones have complex shapes and cannot be grouped into any of the previous categories
• Sesamoid bones (SES-a-moyd = shaped like a sesame seed) de- velop in certain tendons where there is considerable friction, tension, and physical stress, such as the palms and soles
• Sutural bones (SOO-chur-al; sutur- = seam) are small bones located in sutures (joints) between certain cranial bones
• skull is the bony framework of the head
• frontal bone forms the forehead (the anterior part of the cra- nium), the roofs of the orbits (eye sockets), and most of the anterior part of the cranial floor
• frontal squama, a scalelike plate of bone that forms the forehead of the skull