Chapter 6 The Skeletal System
Skeletal System Functions Support Storage Protection Leverage/Movement Red and white blood cell production
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 Endosteum Red marrow Yellow marrow Periosteum Outer bone surface Fibrous outer layer Endosteum Lines bone cavities Lines marrow cavities
Long Bone Structure
Flat, Short, Irregular Bones Flat Bones No diaphyses, epiphyses Sandwich of spongy cancellous between dense compact bone Short and Irregular Bone Compact bone that surrounds spongy cancellous bone center No diaphyses and not elongated
Bone Histology Bone cells: Cancellous bone Compact bone Osteocytes (mature bone cells) Osteoblasts (build bone) Osteoclasts (break down bone) Cancellous bone Spongy bone with trabeculae Compact bone Dense bone
Bone Matrix
Bone Cells Osteoblasts Osteocytes Osteoclasts Formation of bone through ossification Osteocytes Mature bone cells Lacunae: Spaces Canaliculi: Canals Osteoclasts Responsible for bone resorption
Cancellous Bone Spongy bone consisting of trabeculae Oriented along lines of stress
Compact Bone Central or haversian canals: Parallel to long axis with vessels Lamellae: Concentric, circumferential units of bone Osteon or haversian system: Basic functional unit of bone Perforating canals: Perpendicular and provide links to vessels
Bone Development Intramembranous ossification Takes place in connective tissue membrane Skull bone formation Endochondral ossification Takes place in cartilage Long bone formation 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 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
Bone Repair
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
Calcium Homeostasis
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