The Skeletal System Chapter 6
Skeletal System Introduction Functions of the skeleton Framework of bones The skeleton through life
Functions of the Skeleton Support Protection Movement Storage areas Minerals Lipids Hemopoiesis Red marrow
Histology of Bones Bone = osseous tissue (connective tissue) Intercellular substance Hydroxyapatite crystals Collagenous fibers
Human Anatomy, 3rd edition Anatomy of a Long Bone Diaphysis – shaft Epiphysis – extremity of bone Articular cartilage – covers epiphysis Periosteum – covering around surface of bone Medullary cavity – marrow cavity in diaphysis Endosteum – lines medullary cavity Human Anatomy, 3rd edition Prentice Hall, © 2001
Human Anatomy, 3rd edition The Periosteum Two layers Fibrous layer Osteogenic layer Osteoblasts Human Anatomy, 3rd edition Prentice Hall, © 2001
Human Anatomy, 3rd edition The Endosteum Single layer Osteoclasts Osteoblasts Human Anatomy, 3rd edition Prentice Hall, © 2001
Structure of Bone Tissue Pores Living cells Channels for blood vessels Decrease weight of bone Degree of porosity Spongy (cancellous) bone Compact bone Human Anatomy, 3rd edition Prentice Hall, © 2001
Human Anatomy, 3rd edition Compact Bone Haversian system (Osteon) Volkmann’s canals Haversian canals Lamellae Lacunae Canaliculi Human Anatomy, 3rd edition Prentice Hall, © 2001
Human Anatomy, 3rd edition Spongy Bone Composed of trabeculae Penetrated by blood vessels from periosteum Human Anatomy, 3rd edition Prentice Hall, © 2001
Ossification Embryo skeleton 2 types Begins as cartilage & membrane Bone formation begins about 6 weeks after fertilization 2 types Intramembranous ossification Endochondral ossification
Ossification 1st stage – embryonic mesenchyme cells migrate into future bone sites Become chondroblasts or Become osteoblasts
Intramembranous Ossification Mostly in flat bones Osteoblasts in the fibrous membrane secrete intercellular substances (matrix) Matrix becomes mineralized Formation of spongy bone Original layer of connective tissue remains as periosteum
Intramembranous Ossification FG05_05A.JPG Title: A Three-Dimensional View of the Intramembranous Ossification Notes: Stepwise formation of intramembranous bone from mesenchymal cell aggregation to spongy bone; spongy bone might form compact bone. Keywords: ossification, osteocyte, matirx, osteoblast, osteod, mesenchyme, stem cell, spicules, osteoblast
Intramembranous Ossification FG05_05B.JPG Title: A Three-Dimensional View of the Intramembranous Ossification Notes: Stepwise formation of intramembranous bone from mesenchymal cell aggregation to spongy bone; spongy bone might form compact bone. Keywords: ossification, osteocyte, matirx, osteoblast, osteod, mesenchyme, stem cell, spicules, osteoblast
Intramembranous Ossification FG05_05C.JPG Title: A Three-Dimensional View of the Intramembranous Ossification Notes: Stepwise formation of intramembranous bone from mesenchymal cell aggregation to spongy bone; spongy bone might form compact bone. Keywords: ossification, osteocyte, matirx, osteoblast, osteod, mesenchyme, stem cell, spicules, osteoblast
Endochondral Ossification Occurs within a hyaline cartilage model Occurs in most bones of the body Periosteum forms at about week 8 Calcification begins in center of diaphysis Primary ossification center Secondary ossification centers at epiphyses Medullary cavity forms
Endochondral Ossification FG05_07A.JPG Title: Endochondral Ossification Notes: Steps in the formation of a long bone. Keywords: chondrocytes, matrix, epiphysis, diaphysis, osteogenic, marrow, periosteal, spongy bone, metaphysis, ossification
Endochondral Ossification FG05_07B.JPG Title: Endochondral Ossification Notes: Light micrograph showing the zones of cartilage ad the advancing osteoblasts at a epiphyseal plate. Keywords: osteoblasts, osteoid, marrow cavity, epiphyseal cartilage matrix, cartilage cells, zone of proliferation, zone of hypertrophy
Fetus. 10 weeks
Fetus, 16 weeks
Remaining Cartilage Articular cartilage Epiphyseal plate Bone grows in length
Homeostasis Remodeling Factors affecting bone growth Different rates in body Balance between osteoclasts and osteoblasts Factors affecting bone growth Calcium & phosphorus in diet Vitamins A, C, & D Hormones Growth hormone, thyroxine Calcitonin Parathyroid hormone Sex hormones
Fracture Repair Hematoma formation Formation of fibrocartilagenous callus Formation of bony callus Remodeling of bony callus
Fracture Repair FG05_11.JPG Title: Fracture Repair Notes: Steps involved in the repair of a fracture. Keywords: spongy bone, callus, periosteum, hematoma
Disorders Vitamin deficiencies Scurvy Rickets Osteoporosis
Scurvy http://www.pathguy.com/lectures/nejm_scurvy.gif
Scurvy Blood Vessels
Rickets http://bioe.eng.utoledo.edu/adms_staffs/akkus/2003_WEB_PROJECTS/hormone/vitamin_d.htm
Osteoporosis