Introduction Human skeleton initially cartilages and fibrous membranes

Introduction • Human skeleton initially cartilages and fibrous membranes • Hyaline cartilage is the most abundant cartilage • By age 25 the skeleton is completely hardened • 206 bones make up the adult skeleton (20% of body mass) • 80 bones of the axial skeleton • 126 bones of the appendicular skeleton 1

Bone Classification Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. • Bone Classification: • Long Bones (b) • Short Bones • Sesamoid Bones • Flat Bones • Irregular Bones • Wormian Bones (sutural) (c) (d) 2 (a) (e)

Classification of Bones · Long bones · Typically longer than wide · Have a shaft with heads at both ends · Contain mostly compact bone • Examples: Femur, humerus Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 5. 4 a

Classification of Bones · Short bones · Generally cube-shape · Contain mostly spongy bone · Examples: Carpals, tarsals Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 5. 4 b

Classification of Bones on the Basis of Shape Figure 5. 1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 5. 4 c

Classification of Bones · Flat bones · Thin and flattened · Usually curved · Thin layers of compact bone around a layer of spongy bone · Examples: Skull, ribs, sternum Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 5. 5 a

Classification of Bones · Irregular bones · Irregular shape · Do not fit into other bone classification categories · Example: Vertebrae and hip Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 5. 5 b

Classification of Bones on the Basis of Shape Figure 5. 1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 5. 5 c

Parts of a Long Bone • Epiphysis • Distal • Proximal • Diaphysis • Metaphysis • Compact bone • Spongy bone • Articular cartilage • Periosteum • Endosteum • Medullary cavity • Trabeculae • Bone marrow • Red marrow and yellow marrow Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Epiphyseal plates Articular cartilage Proximal epiphysis Spongy bone Space containing red marrow Endosteum Compact bone Medullary cavity Yellow marrow Diaphysis Periosteum Distal epiphysis Femur 9

Microscopic Structure • Bone cells are called osteocytes • in a lacuna • Osteocytes transport nutrients and wastes by cellular processes in canaliculi • The extracellular matrix of bone is largely collagen and inorganic salts • Collagen gives bone resilience & strength • Inorganic salts make bone hard 10

Compact Bone • Osteon • Central canal • Perforating canal aka Volkmann’s canal • Osteocytes • Lamellae • Lacunae • Bone matrix • Canaliculi Endosteum Nerve Blood vessels S bo pon ne gy aka Haversian System C bo om ne pa ct Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Osteon Central canal containing blood vessels and nerves Periosteum Pores Central canal Perforating canal Compact bone Nerve Blood vessels Nerve Trabeculae Bone matrix Canaliculus Osteocyte Lacuna (space) 11

Microscopic Anatomy of Bone Figure 5. 3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide

Microscopic Anatomy of Bone · Lacunae · Cavities containing bone cells (osteocytes) · Arranged in concentric rings · Lamellae · Rings around the central canal · Sites of lacunae Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 5. 3 Slide

Microscopic Anatomy of Bone · Canaliculi · Tiny canals · Radiate from the central canal to lacunae · Form a transport system Figure 5. 3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide

Spongy Bone • Spongy bone is aka cancellous bone Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Spongy bone Compact bone (a) Remnant of epiphyseal plate Spongy bone Compact bone (b) (c) Spongy bone Compact bone a: © Ed Reschke; b, c: Courtesy of John W. Hole, Jr. 15

Bone Development and Growth • Parts of the skeletal system begin to develop during the first few weeks of prenatal development • Bones replace existing connective tissue in one of two ways: • As intramembranous bones • As endchondral bones 16

Intramembranous Bones • These bones originate within sheetlike layers of connective tissues • They are the broad, flat bones • Skull bones (except mandible) • Are known as intramembranous bones 17

Endochondral Bones • Bones begin as hyaline cartilage • Form models for future bones • These are most bones of the skeleton • Are known as endochondral bones 18

Endochondral Ossification • Hyaline cartilage model • Epiphyseal plate • Primary ossification center • Osteoblasts vs. osteoclasts • Secondary ossification centers Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Cartilaginous model Developing periosteum Remnants of epiphyseal plates Secondary ossification center Compact bone developing Spongy bone Epiphyseal plates Blood vessel Calcified cartilage (a) (b) Medullary cavity (c) Medullary cavity Compact bone Medullary cavity Remnant of epiphyseal plate Epiphyseal plate Primary ossification center Secondary ossification center (d) Articular cartilage Spongy bone Articular cartilage (e) (f) 19

Growth at the Epiphyseal Plate Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. • First layer of cells Bone tissue of epiphysis • Closest to the end of epiphysis • Resting cells • Anchors epiphyseal plate to epiphysis • Zone of resting cartilage 1 Zone of resting cartilage 2 Zone of proliferating cartilage 3 Zone of hypertrophic cartilage • Second layer of cells 4 Zone of calcified cartilage • Many rows of young cells Ossified bone of diaphysis • Undergoing mitosis • zone of proliferating cartilage (a) (b) b: © The Mc. Graw-Hill Companies, Inc. /Al Telser, photographer 20

Growth at the Epiphyseal Plate Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. • Third layer of cells Bone tissue of epiphysis • Older cells • Left behind when new cells appear • Cells enlarging and becoming calcified • zone of hypertrophic cartilage 1 Zone of resting cartilage 2 Zone of proliferating cartilage 3 Zone of hypertrophic cartilage • Fourth layer of cells 4 Zone of calcified cartilage • Thin Ossified bone of diaphysis • Dead cells • Calcified extracellular matrix • zone of calcified cartilage (a) (b) b: © The Mc. Graw-Hill Companies, Inc. /Al Telser, photographer 21

Homeostasis of Bone Tissue • Bone Resorption – action of osteoclasts and parathyroid hormone aka parathormone aka PTH • Bone Deposition – action of osteoblasts and calcitonin • Occurs by direction of the thyroid and parathyroid glands Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Developing medullary cavity Osteoclast 22 © Biophoto Associates/Photo Researchers, Inc.

Factors Affecting Bone Development, Growth and Repair • Deficiency of Vitamin A – retards bone development • Deficiency of Vitamin C – results in fragile bones • Deficiency of Vitamin D – rickets, osteomalacia • Insufficient Growth Hormone – dwarfism • Excessive Growth Hormone – gigantism, acromegaly • Insufficient Thyroid Hormone – delays bone growth • Sex Hormones – promote bone formation; stimulate ossification of epiphyseal plates • Physical Stress – stimulates bone growth 23

Bone Function • Bones shape, support, and protect body structures 24

Support, Protection, and Movement • Support, Movement & Protection • Gives shape to head, etc. • Supports body’s weight • Protects lungs, etc. • Bones and muscles interact • When limbs or body parts move 25

Blood Cell Formation • Also known as hematopoiesis • Occurs in the red bone marrow 26

Inorganic Salt Storage • Calcium • Phosphate • Magnesium • Sodium • Potassium 27