Skeletal system Chap. 7 Intro. to Bones

Function = framework of body, protect organs, anchor skeletal muscles for movement.   Skeleton = Greek for “ dried up body” a) axial = longitudinal b) appendicular = arms and legs c) joints, cartilage & ligaments Bones = give the body shape Functions = support, protection, movement, storage of fat in cavities and Ca+2 & P, and blood cell formation

BONE CLASSIFICATION ( BASED ON SHAPE) 206 BONES!! Compact = dense, smooth & homogeneous pg. 131 Spongy = small needle like pieces w/ lots of open spaces Long bones : longer than wide. Shaft w/ 2 heads mostly compact = all limbs Short bones : cube-shaped; mostly spongy; ankle, wrist Flat bones : thin, flattened, usually curved. Two thin compact layers w/ spongy in between. Ex: skull, ribs, sternum Irregular : ex. vertebrae, hips  

Bone Markings-- Table 7.2 pg. 142 all T’s = projections except facet projections/ processes (grow out) depressions/ cavities (indentions)

Structure of a Long Bone Fig. 7.1 pg. 132 Diaphysis (shaft) most of length = compact covered with periosteum (fibrous connective) Epiphyses = ends of long bone (thin compact w/ spongy) Articular Cartilage = covers epiphyses, glassy, smooth, slippery; low friction at joints, movement Epiphyseal line/plate = where growing occurred/ occurs In Adults= storage area for fat (yellow marrow) medullary cavity Infants= red marrow ( RBC’s are formed!) ( only found in adult flat bones & epiphyses of long bones

Osteocytes = mature bone cells… found in cavities w/ matrix called lucunae =in circles called lamellae which are central canals called Haversian Canals Each canal = Haversian System or osteon (pg. 108 and 133) Canaliculi = small canals connecting all bone cells to nutrient supply ** bone heals quickly Preforating Canals a.k.a Volkmann’s Canals = run _l_ Haversian & connect to compact bone Bone is one of the hardest materials is light weight & can resist tension = Ca+2 gives hardness; collagen gives flexibility

BONE FORMATION (GROWTH & REMODELING) Osteoblasts vs. Osteoclasts Embryos = hyaline cartilage young child = mostly bone except nose & ribs Ossification = process of bone formation Hyaline cartilage is covered with bone forming cells called Osteoblasts Cartilage is digested away= opening up to medullary cavity with new bone. ** Bones remodel continuously due to… Ca+2 levels in the blood. a. Low osteoclasts eat up matrix releasing Ca=+2 High Ca+2 is deposited in bone 2. Pull of gravity and muscles of skeleton depending on activity of person (where matrix is grown)