Chapter 7 Skeletal Tissues Mosby items and derived

Types of Bones Structurally, there are four types of bones Ø Long bones Ø Short bones Ø Flat bones Ø Irregular bones Bones serve various needs, and their size, shape, and appearance will vary to meet those needs Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 2

Types of Bones vary in their proportions of compact and cancellous (spongy) bone; compact bone is dense and solid in appearance, whereas cancellous bone is characterized by open space partially filled with needle-like structures Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 3

Types of Bones Parts of a long bone Ø Diaphysis • Main shaft of long bone • Hollow, cylindrical shape and thick, compact bone • Function is to provide strong support without cumbersome weight Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 4

Types of Bones Parts of a long bone Ø Epiphyses • Both ends of a long bone, made of cancellous bone filled with marrow • Bulbous shape • Function is to provide attachments for muscles and give stability to joints Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 5

Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 6

Types of Bones Parts of a long bone Ø Articular cartilage • Layer of hyaline cartilage that covers the articular surface of epiphyses • Function is to cushion jolts and blows Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 7

Types of Bones Parts of a long bone Ø Periosteum • Dense, white, fibrous membrane that covers bone • Attaches tendons firmly to bones • Contains cells that form and destroy bone • Contains blood vessels important in growth and repair • Contains blood vessels that send branches into bone • Essential for bone cell survival and bone formation Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 8

Types of Bones Parts of a long bone Ø Medullary (or marrow) cavity • Tubelike, hollow space in diaphysis • Filled with yellow marrow in adult Ø Endosteum—thin epithelial membrane that lines medullary cavity Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 9

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Types of Bones Short, flat, and irregular bones Ø Inner portion is cancellous bone, covered on the outside with compact bone Ø Spaces inside cancellous bone of a few irregular and flat bones are filled with red marrow Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 11

Bone Tissue Most distinctive form of connective tissue Extracellular components are hard and calcified Rigidity of bone allows it to serve its supportive and protective functions Tensile strength is nearly equal to cast iron at less than one third the weight Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 12

Microscopic Structure of the Bone Compact bone Ø Contains many cylinder-shaped structural units called osteons, or Haversian systems Ø Osteons surround canals that run lengthwise through bone and are connected by transverse Volkmann’s canals Ø Living bone cells are located in these units, which constitute the structural framework of compact bone Ø Osteons permit delivery of nutrients and removal of waste products Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 13

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Microscopic Structure of the Bone Compact bone Ø Four types of structures make up each osteon: • Lamella—concentric, cylinder-shaped layers of calcified matrix • Lacunae—small spaces containing tissue fluid in which bone cells are located between hard layers of the lamella • Canaliculi—ultrasmall canals radiating in all directions from the lacunae and connecting them to each other and to the Haversian canal • Haversian canal—extends lengthwise through the center of each osteon and contains blood vessels and lymphatic vessels Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 15

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Microscopic Structure of the Bone Cancellous bones Ø No osteons in cancellous bone; instead, it has trabeculae Ø Nutrients are delivered and waste products removed by diffusion through tiny canaliculi Ø Bony spicules are arranged along lines of stress, enhancing the bone’s strength Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 17

Microscopic Structure of the Bone Blood supply Ø Bone cells are metabolically active and need a blood supply, which comes from the bone marrow in the internal medullary cavity of cancellous bone Ø Compact bone, in addition to bone marrow and blood vessels from the periosteum, penetrate bone and then, by way of Volkmann’s canals, connect with vessels in the Haversian canals Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 18

Microscopic Structure of the Bone Types of bone cells Ø Osteoblasts • Bone-forming cells found in all bone surfaces • Small cells synthesize and secrete osteoid, an important part of the ground substance • Collagen fibrils line up in osteoid and serve as a framework for the deposition of calcium and phosphate Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 19

Microscopic Structure of the Bone Types of bone cells Ø Osteoclasts • Giant multinucleate cells • Responsible for the active erosion of bone minerals • Contain large numbers of mitochondria and lysosomes Ø Osteocytes—mature, nondividing osteoblast surrounded by matrix, lying within lacunae Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 20