Anatomy and Physiology

Skeletal System: Bones and Bone Tissue Chapter 6 Skeletal System: Bones and Bone Tissue

Skeletal System Functions Support Protection Movement Storage Blood cell production

Hyaline Cartilage Consists of specialized cells that produce matrix Chondroblasts Chondrocytes Perichondrium Articular cartilage Growth Appositional Interstitial

Bone Shapes Long Short Flat Irregular Upper and lower limbs Carpals and tarsals Flat Ribs, sternum, skull, scapulae Irregular Vertebrae, facial

Long Bone Structure Diaphysis Epiphysis Epiphyseal plate Shaft Compact bone Epiphysis End of the bone Cancellous bone Epiphyseal plate Growth plate Epiphyseal line Bone stops growing in length

Long Bone Structure Medullary cavity Periosteum Sharpey’s fibers Red marrow Yellow marrow Periosteum Outer bone surface Sharpey’s fibers Attachment Endosteum Lines bone cavities

Flat, Short, Irregular Bones Flat Bones No diaphyses, epiphyses Sandwich of cancellous between compact bone Short and Irregular Bone Compact bone that surrounds cancellous bone center No diaphyses and not elongated

Bone Histology Bone matrix Bone cells Organic: Collagen and proteoglycans Inorganic: Hydroxapatite Bone cells Osteoblasts Osteocytes Osteoclasts Stem cells or osteochondral progenitor cells Woven bone: Collagen fibers randomly oriented Lamellar bone: Mature bone in sheets Cancellous bone: Trabeculae Compact bone: Dense

Bone Matrix

Bone Cells Osteoblasts Osteocytes Osteoclasts Formation of bone through ossification or osteogenesis Osteocytes Mature bone cells Lacunae: Spaces Canaliculi: Canals Osteoclasts Responsible for bone resorption

Woven and Lamellar Bone Woven bone Formed During fetal development During fracture repair Remodeling Removing old bone and adding new Lamellar bone Mature bone in sheets called lamellae

Cancellous Bone Consists of trabeculae Oriented along lines of stress

Compact Bone Central or haversian canals: Parallel to long axis Lamellae: Concentric, circumferential, interstitial Osteon or haversian system: Central canal, contents, associated concentric lamellae and osteocytes Perforating or Volkmann’s canal: Perpendicular to long axis

Bone Development Intramembranous ossification Takes place in connective tissue membrane Endochondral ossification Takes place in cartilage Both methods of ossification Produce woven bone that is then remodeled After remodeling, formation cannot be distinguished as one or other

Intramembranous Ossification

Endochondral Ossification

Endochondral Ossification

Endochondral Ossification

Growth in Bone Length Appositional growth Epiphyseal plate zones New bone on old bone or cartilage surface Epiphyseal plate zones Resting cartilage Proliferation Hypertrophy Calcification

Growth in Bone Length

Growth in Bone Width

Factors Affecting Bone Growth Nutrition Vitamin D Necessary for absorption of calcium from intestines Insufficient causes rickets and osteomalacia Vitamin C Necessary for collagen synthesis by osteoblasts Deficiency results in scurvy Hormones Growth hormone from anterior pituitary Thyroid hormone required for growth of all tissues Sex hormones as estrogen and testosterone

Bone Remodeling Coverts woven bone into lamellar bone Bone constantly removed by osteoclasts and new bone formed by osteoblasts

Bone Repair

Calcium Homeostasis

Calcium Homeostasis Bone is the major storage site for calcium in the body Calcium moves into bone as osteoblasts build new bone Calcium moves out of bone as osteoclasts break down bone When osteoclast and osteoblast activity is balanced, the movement of calcium in and out is equal

Effects of Aging on Skeletal System Bone Matrix decreases Bone Mass decreases Increased bone fractures Bone loss causes deformity, loss of height, pain, stiffness Stooped posture Loss of teeth

Bone Fractures