Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Skeletal system includes: Bones of the skeleton Cartilages, ligaments and other connective tissues that stabilize and connect Functions of skeletal system Support Storage of minerals and lipids Blood cell production Protection Leverage SECTION 6-1: Introduction to the skeletal system

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Bone shapes SECTION 6-2: Classification of Bones Irregular Sesamoid Sutural Long Flat Short Bone Structure Compact bone (dense) Spongy bone (cancellous)

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.1 Figure 6.1 Classification of Bones by Shape

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Diaphysis Epiphyses Metaphysis Articular cartilage Marrow cavity Filled with red or yellow marrow A typical long bone includes Articular cartlilage

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.2 Figure 6.2 Bone Structure

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Osseous tissue 1.solid matrix- Crystals of hydroxyapatite Ca3(PO4)2+ Ca(OH)2 2.Collagen- 2.Vascular- SECTION 6-3: Bone Histology

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 4. Wrapped a. Endosteum b. Periosteum i. fibrous layer ii. Cellular layer(osteogenic)- iii. Sharpey’s Fibers SECTION 6-3: Bone Histology

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 1.Osteocytes = mature bone cells -Maintain, repair bone 2. Osteoblasts= synthesize new matrix - become osteocyte 3. Osteoclasts=dissolve bone matrix -multicuncleated, differentiate from WBC 4.Osteoprogenitor =cells differentiate into osteoblasts, repair fractures Cells in bone:

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.3a Figure 6.3 The Histology of Compact Bone

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.3b, c Figure 6.3 The Histology of Compact Bone

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Basic unit of compact bone is an osteon Osteocytes arranged around a central canal Perforating canals extend between adjacent osteons Spongy bone contains trabeculae Compact bone and spongy bone

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.4 Figure 6.4 The Structure of Osseus Tissue

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.5 Figure 6.5 The Distribution of Forces on a Long Bone Bones and stress Compact bone located where stresses are limited in direction Spongy bone located where stresses are weaker or multi-directional

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Ossification = converting other tissue to bone 1. Intramembranous 2. Endochondral Calcification = depositing calcium salts within tissues SECTION 6-4: Bone development and growth

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Calcification deposition of Ca++ salts w/in a tissue

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 1. Intramembraneous Ossification Bones form w/in a thin CT membrane Used to form flat bones (cranium, mandible, clavicle)

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Begins with osteoblast differentiation Dermal bones produced Begins at ossification center Intramembranous ossification forming bone: red cartilage: blue

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Steps of Intramembraneous Ossification in cranium 1.Mesenchymal cells form a thin CT membrane covering brain 2.Some mesenchymal cells differentiate into osteoblasts in the center of each membrane.(Occurs 6 weeks after fertilization) 3.Osteoblasts secrete these locations(called primary centers of ossification) 4. Ossification spreads in all directions

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Steps of Intramembraneous Ossification in cranium birth ossification is not complete, membrane remains as sutures and fontanels(soft spots) Fetal skulls at weeks gestation; fontanels typically close at 6 months

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Fontanelles indentations of fibrous membrane between bones of fetal skull Intramembranous ossification is not complete until months anterior posterior sphenoid mastoid

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.7 Figure 6.7 Intramembranous Ossification

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Cartilage model gradually replaced by bone at metaphysis Increasing bone length Timing of epiphyseal closure differs Appositional growth increases bone diameter Endochondral ossification

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Bone Growth 1. Appositional- increases diameter, while medullary cavity hollowed out -

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.10b Figure 6.10 Appositional Bone Growth

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Bone Growth 2. Interstitial- occurs at epiphyseal plates a. Chondroblasts produce new cells that are pushed toward epiphysis b. At the diaphysis end of plate older cartilage is converted into bone isci4online/bone/bone_growth4.swf

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.9 Figure 6.9 Bone Growth at an Epiphyseal Cartilage

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings continually changing Remodeling Exercise Hormone levels Growth hormone and thyroxine increase bone mass Calcitonin and PTH control blood calcium levels SECTION 6-5: Dynamic Nature of Bone

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.12 Figure 6.12 A Chemical Analysis of Bone

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 99% body’s calcium in the skeleton Calcium ion concentration maintained by bones GI tract and kidneys Calcitonin and PTH regulate blood calcium levels Calcitonin decreases blood calcium levels PTH increases blood calcium levels The skeleton is a calcium reserve

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Effects on bone growth 1.Growth hormone- produced by pituitary gland; targets growth plate activity a. Excess causes giagantism

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings b. Low levels cause pituitary dwarfism normally proportioned treatment with growth hormone

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Effects on bone growth 2. Testosterone- produced by the testes and adrenal glands in males and by the adrenal glands in females -Responsible for the growth “spurt’ at puberty -Overproduction in males causes closure of the epiphyseal line (Caution for anabolic steroid users)

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Effects on bone growth 3.Estrogen- produced by the ovaries in females; -stimulates osteoblasts -promotes closing of the epiphyseal line - MENOPAUSE causes bone loss!!!

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Effects of aging include 1. Osteopenia (inadequate ossification) begins between ages 30 and 40, osteoblast activity declines, while osteoclast activity remains level, Women lose 8% of bone mass per decade, while men lost only 3% in the same time period 2. Osteoporosis SECTION 6-7: Aging and the Skeletal System

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Osteoporosis When the loss of bone mass compromises normal function a person is diagnosed with osteoporosis. When the loss of bone mass compromises normal function a person is diagnosed with osteoporosis

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.16 Figure 6.16 The Effects of Osteoporosis

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Effects on bone growth 4. Parathyroid hormone- produced by the parathyroid glands in the neck -Stimulates the osteoclasts to Ca++ to be released from the bone to enter the blood -Ca++ necessary for muscles and nerves to function properly

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.13a Figure 6.13 Factors that Alter the Concentration of Calcium Ions in Body Fluids

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Effects on bone growth 5. Calcitonin- produced by the thyroid gland - Inhibits osteoclasts so Ca++ remains in the bone, promotes ostepoblasts

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.13b Figure 6.13 Factors that Alter the Concentration of Calcium Ions in Body Fluids

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Effects on bone growth 6. Vitamin D- some is produced in the skin ; Most is ingested in food -Necessary for the absorption of Ca++ from the intestine into the blood -Osteomalacia (Rickets in children) causing softened, weakened bones Main symptom is pain when weight is put on the affected bone

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Bone Fractures (Breaks) Bone fractures are classified by: Simple(closed) vs. compound(open)

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Types of Bone Fractures Linear the fracture is parallel to the long axis of the bone Transverse the fracture is perpendicular to the long axis of the bone

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Types of Bone Fractures Greenstick incomplete fracture where one side of the bone breaks and the other side bends common in children

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Types of Bone Fractures Comminuted bone fragments into three or more pieces common in the elderly

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Types of Bone Fractures Spiral ragged break when bone is excessively twisted common sports injury

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Types of Bone Fractures Depressed broken bone portion pressed inward typical skull fracture

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Types of Bone Fractures Compression bone is crushed; common in porous bones

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Types of Bone Fractures Epiphyseal epiphysis separates from diaphysis along epiphyseal line; occurs where cartilage cells are dying

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 1.Fracture hematoma 2.Internal and External callus 3.Cartilage replaced by bone 4.Osseous callus removed Bone graft- a transplant of bone to stimulate repair Fracture repair

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.14 Steps in the Repair of a Fracture Figure 6.14