Chapter 6: The Skeletal System
Chapter 6: The Skeletal System BIOL 1014
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This 4 page Class Notes was uploaded by Audrey Jennings on Friday September 30, 2016. The Class Notes belongs to BIOL 1014 at University of Louisiana at Monroe taught by Dr. Matthew Overturf in Fall 2016. Since its upload, it has received 24 views. For similar materials see Anatomy and Physiology in Biology at University of Louisiana at Monroe.
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Date Created: 09/30/16
Chapter 6: The Skeletal System Intro: The skeletal system is capable of growth, adapts to stress, and repairs after injury. Components: bone (spongy & compact); cartilage (hyaline, elastic, fibrocartilage); tendons & ligaments (supporting connective tissue) Functions: support, protection, movement, storage of minerals & fat, blood cell production Components: Tendons: connect muscle to bone Ligaments: connect bone to bone Both- dense regular CT; contain bundles of collagen fibers; few nerves & blood vessels Hyaline Cartilage: matrix of collagen for strength & proteoglycans for resiliency; found in joints; make up fetal skeleton; avascular (grow by appositional or interstitial growth) -Appositional growth- new matrix and cells added at surface (outside tissue) -Interstitial growth- cells divide within tissue and add more matrix between cells (inside tissue) Bone: long (femur), short (carpals/tarsals), flat (skull), irregular (sphenoid) -bone matrix 35% organic – collagen & proteoglycans 65% inorganic – hydroxyapatite (calcium phosphate crystals) If collagen is removed, bone becomes brittle. If mineral is removed, bone becomes bendable. Bone Cells: osteoblasts (form); osteocytes (maintain); osteoclasts (break down) Osteoblasts-bone formation through ossification or osteogenesis. (communicate by gap junctions) Osteocytes-mature bone cells surrounded by matrix (can make small amounts of matrix in order to maintain) -Lacunae: small spaces in bone where osteocytes are found -Canaliculi: canals occupied by osteocyte cell processes Nutrients can diffuse through gap junctions. Osteoclasts-resorption of bone Stem Cells=Mesenchyme (become chondroblasts or osteoblasts) Woven Bone: collagen fibers randomly oriented (formed during fetal development and repair) Lamellar Bone: mature bone in sheets called lamellae(rings) Fibers oriented in one direction in each layer, but each layer is oriented in a different direction for strength. Spongy (cancellous) Bone: made up of trabeculae with red marrow filling spaces; oriented along stress lines; covered by endosteum (found in epiphysis) Compact (dense) Bone: (found throughout diaphysis & covering spongy bone) Osteon (Haversian System)- central/Haversian canal containing blood vessels; central canal surrounded by concentric lamellae; lacunae & canaliculi containing osteocyte & fluid; perforating/Volkmann’s canal- blood vessels from periosteum penetrate bone Circumferential lamellae: periphery (surface) of bone Interstitial lamellae: between osteons (within bone) Long Bone Structure: Diaphysis-shaft of compact bone Epiphysis-head/end of bone containing spongy bone Epiphyseal (growth) plate- made up of hyaline cartilage Epiphyseal line- when growth stops Medullary Cavity- contains red marrow in children; gradually changes to yellow marrow in limb bones and skull, rest of skeleton contains red Periosteum- outer, fibrous layer of bone -Sharpey’s fibers: strengthen attachment of tendon to bone Endosteum- inner layer of bone (more cellular than periosteum; lines all internal spaces) Flat Bone Structure: no diaphysis or epiphysis Sandwich: compact bone (bread); spongy bone (ham) Short/Irregular Bone Structure: no diaphysis; similar to structure of epiphysis *Some flat & irregular bones in the skull have sinuses lined by mucous membranes Intramembranous Ossification: results in flat bones -takes place in connective tissue membrane formed from embryonic mesenchyme (forms many skull bones, mandible, and diaphysis of clavicle) Fontanels- “soft spots” unossified Indistinguishable from endochondral bone when remodeled Endochondral Ossification: results in long bones -develop within cartilage template; cartilage calcifies and dies; bone formed on calcified cartilage (spongy bone); compact bone formed underneath periosteum Primary ossification centers form in diaphysis during fetal development. Secondary ossification centers form in epiphysis. (epiphyseal plate) Epiphyseal plate closes between 18-21 years of age. Factors Affecting Bone Growth: genetics, nutrition (vitamin D, protein, vitamin C), hormones (growth hormone, thyroid hormones, & sex hormones) Calcium Homeostasis: Bone is the major site of calcium storage. -parathyroid hormone and calcitonin regulate calcium volume in the blood Bone Remodeling: converts woven to lamellar bone; involves osteoblast and osteoclast activity Bone growth, change in bone shape, adjustment in bone (stress), bone repair, Ca ion regulation Constant cycle of resorption and growth -growth occurs on same side as stress; resorption occurs on opposite side Exercise promotes bone growth. Bone Repair: Fractures -begins with blood clot (hematoma); fibrocartilaginous callus forms a zone of repair, connecting broken ends of bone; osteoblasts enter callus and convert it to osseous callus (new bone). Fractures: Simple or Compound- simple stays within skeletal system; compound pierces skin Complete or Greenstick- complete broken in two pieces; greenstick is partial break (incomplete) Linear (vertical with bone); Transverse (horizontal with bone); Oblique (at an angle); Spiral (twisting fracture) Comminuted- many pieces broken Compact- bone piece driven into another bone piece Compression- excessive vertical force (intervertebral discs) Hairline- incomplete/greenstick fracture where ends don’t separate (crack) Aging: Bone matrix and bone mass decrease, bone becomes brittle, increased susceptibility to fracture -(osteoporosis) common in women Deformity, pain, stiffness (arthritis) Loss of teeth and height