Skeletal

• skeleton is the structural framework that gives the body its shape and protects the internal organs and soft tissues
• The skeletal system is the framework that helps maintain the body’s shape and enables us to move. The skeletal system is composed of bones, cartilage, and ligaments.
• The skeletal system is the framework that helps maintain the body’s shape and enables us to move. The skeletal system is composed of bones, cartilage, and ligaments.
• Cartilage provides a firm yet flexible support within certain structures, such as the nose, external ear, thoracic cage, and trachea.
• Ligaments, strong bands of fibrous connective tissue, hold bones together.
• Bone is hard and protects the organs it surrounds.
• Skeletal muscles attach to bones by tendons
• There are three types of cartilage: (1) hyaline cartilage, (2) fibrocartilage, and (3) elastic cartilage
• hyaline cartilage is most intimately associated with bone
• Chondrocytes are rounded cells that occupy a space called a lacuna
• Most cartilage is covered by a protective connective tissue sheath called the perichondrium
• By weight, mature bone matrix is normally about 35% organic and 65% inorganic material
• The organic material consists primarily of collagen and proteoglycans.
• The inorganic material consists primarily of a calcium phosphate crystal called hydroxyapatite
• There are three types of bone cells—(1) osteoblasts, (2) osteocytes, and (3) osteoclasts
• Osteoblasts are bone-building cells. which are packaged into vesicles by the Golgi apparatus and secreted by exocytosis.
• The formation of new bone by osteoblasts is called ossification
• Osteocytes account for 90– 95% of bone cells and are very long-lived, with a life span of up to 25 years.
• Osteocytes become relatively inactive, compared with most osteoblasts, but it is possible for them to produce the components needed to maintain the bone matrix.
• Osteocyte cell extensions are housed in narrow, long spaces called canaliculi
• Osteogenesis imperfecta is also known as brittle bone disorder.
• Osteoclasts are bone-destroying cells
• Breakdown of bone is called bone reabsorption
• There are two types of bone formed during ossification: (1) woven bone and (2) lamellar bone.
• Woven bone is the first type of bone that osteoblasts form during ossification. It is fairly weak bone because the collagen fibers are randomly oriented in many directions.
• Lamellar bone is mature bone
• Spongy bone, which appears porous, has less bone matrix and more space
• compact bone has more bone matrix and less space than spongy bone.
• The functional unit of compact bone is an osteon
• the bull’s-eye of the target is the central canal
• The diaphysis is the center portion of the bone.
• The ends of a long bone are called epiphyses
• a hollow center of the bone is called the medullary cavity
• Red marrow is the site of blood cell formation
• yellow marrow is mostly adipose tissue.
• The periosteum is a connective tissue membrane covering the outer surface of a bone
• These bundles of collagen fibers are called perforating fibers
• Sinuses within some of the flat and irregular bones of the skull are air-filled spaces
• Growth hormone from the anterior pituitary increases general tissue growth
• Thyroid hormones are also required for normal growth of all tissues, including cartilage