Bones Flashcards
Bone classifications.
206 bones in two groups. Axial and appendicular skeleton. Axial: axis of body (skull, vertebral column and thoracic cage). Appendicular: upper and lower limbs and girdles.
Function of bones
Support, protection, movement, mineral storage and blood cell formation (hematopoiesis). Overall body shape and form.
Types/shapes of bones
Long bones, short bones, sesamoid bones (patella), flat bones and irregular bones.
Bone anatomy.
Bones are dominated by Osseous tissue. It contains nerves, connective tissue, muscle and is highly vascularized. Bones contain markings on the surface such as depressions, projections and openings. Compact bone: dense outer layer of each bone. Spongy bone (cancellous bone): internal to compact bone and contains honeycomb of trabeculae.
Long bone anatomy.
Has diaphysis (shaft) and epiphysis (ball/head). Diaphysis is compact bone that surrounds the medullary cavity. Diaphysis can contain red or yellow marrow. Epiphysis has toxically and distal ends. Compact bone on outside. Spongy bone on inside. Epiphysis has articular cartilage (hyaline cartilage on joint surface). Epiphyseal plate: disk of hyaline cartilage that allows for growth during childhood, turns into a faint line in adults.the periosteum is a membrane that covers entire bone surface except for the articular surfaces. Has two layers. Fibrous (outer) and osteogenic (inner). Osteogenic contains osteoblasts and osteoclasts. Endosteum: membrane on in we bone surface.
Nutrient foramen and sharpey’s fibers.
Nutrient foramen is the point of entry on the diaphysis for the periosteum. Sharpey’s fibers anchor the periosteum to the bone.
Short bone anatomy.
Short, irregular and flat are all similar. External layer is compact bone covered by periosteum. Internal is spongy bone covered by Endosteum. Bone marrow covers the spongy bone. Does not contain diaphysis or epiphysis. In flat bones, spongy bone is called diploe.
Microscopic compact bone.
Filed with passages for blood/lymph vessels and nerves. Osteon-haversion system: the structural and functional unit of compact bone. Lamella: hollow tubes of bone matrix, contain college fibers that alternate orientation. Haversion canals/central canal: central nerve/vessel fibers in osteon. Volkmann’s canals: right angles to haversion canals. They connect central canals to periosteum and medullary cavity. Canaliculi: channels that connect the lacunae (contain mature bone cells). Lacunae are located between in between the lamellae. Interstitial lamellae: incomplete, gap filling remnants of reconstruction. Circumferential lamellae: in between periosteum and Endosteum, extend around circumference of diaphysis.
Microscopic anatomy of spongy bone
Poorly organized, trabeculae align along stress lines, irregular lamellae in trabeculae. Osteocytes connected by canaliculi. No osteons.
Chemical composition of bone.
Contains organic and inorganic compounds. Organis: cells and oateoids. Osteoids are 1/3 of the matrix-ground substance and collagen fibers. Hydroxyapatites: 65% of bone tissue, contain mineral salts (calcium and phosphorus) and small crystals deposited around collagen fibers.
Bone development
Aka ossification or osteogenesis. Embryo- formation of skeleton. Bone growth, bone remodeling and repair. Two types; intramembranous ossification and endochondral ossification
Intramembranous ossification.
Bones develop from fibrous membrane. Produces membrane bones (cranial bones, scapula and all flat bones) 1. Ossification center appears in fibrous connective tissue 2. Bone matrix (osteoid) secreted by osteoblasts 3. Spongy bone and periosteum form-vascularization 4. Bone collar of compact bone forms along with appearance of red marrow
Endochondral ossification
Replacement of cartilage model. Produces cartilage (endochondral) bones including all bones below the skull except the scapula. Cartilage is removed as ossification occurs. Ossification begins in the center of cartilage model at the primary ossification center. 1. Bone collar forms around diaphysis of cartilage model 2. Cartilage in center of diaphysis calcifies and cavitates. Kills Chondrocytes and matrix but the cartilage still grows on the ends. 3. Periosteal bud invades and spongy bone forms. The bud contains nutrient artery and vein, lymphatic, nerve fibers, red marrow elements, osteoblasts and osteoclasts 4. Diaphysis elongates and medullary cavity forms. (Primary ossification center enlarges, osteoclasts create marrow cavity, epiphysis push out by growth at Epiphyseal plate) 5. Epiphyses ossify after birth (secondary ossification center).
Bone growth.
Interstitial growth of long bones during infancy and youth. Appositional growth to add thickness, most stop growth during adolescence. Some grow through life.
Longitudinal bone growth
Occurs at Epiphyseal plate. The Chondrocytes die, matrix calcifies, osteoblasts and osteoclasts lay down osteoid. This eventually leads to epipheseal plate closure. Events are similar to endochondral ossification.
