56 57 58 ## BONE 59 60 1. Histologic features of bone 61 ■ Types of bone (Fig. 1.1; Table 1.1) 62 ■ Microscopic classification: lamellar, woven 63 ■ Woven: immature or pathologic bone; random organization; not stress-oriented; high rate of turnover; more osteocytes per unit; weaker 64 ■ Lamellar: normal bone; secondary bone created via remodeling of woven bone; organized; stress-oriented; less flexible; stronger 65 ■ Macroscopic classification: cortical, cancellous 66 ■ Cortical (compact) bone 67 ■ 80% of skeleton 68 ■ Characterized by slow turnover rate, higher Young's modulus of elasticity, more stiffness 69 70 Consists of tightly packed osteons 71 (Haversian systems) 72 Contain arterioles, venules, capillaries, nerves 73 Connected by Haversian or Volkmann 74 canals 75 Cement lines define the outer border of 76 an osteon 77 Interstitial lamellae form between 78 osteons 79 Fibrils connect lamellae but do not 80 cross cement lines 81 Nutrition provided by intraosseous 82 circulation through canals and canaliculi 83 (cell processes of osteocytes) 84 ancellous (spongy or trabecular) bone 85 20% of skeleton 86 87 88 89 90 ![A diagram illustrates bone structure, including cortical, cancellous, and immature regions, alongside labeled cross-sections and a detailed view of Haversian canals.](https://cdn.orris.care/cdss_images/4c49d5ab68aa34eb0f4dbf737952709e9f9fa998bd1e9d2e1b20571b423cccf4.png) 91 92 *CORTICAL BONE DETAIL* 93 94 *FIG. 1.1 Types of bone. Cortical bone consists of tightly packed osteons. Cancellous bone consists of a meshwork of trabeculae. In immature bone, unmineralized osteoid lines the immature trabeculae. Pathologic bone is characterized by atypical osteoblasts and architectural disorganization. (Colorized from Brinkner, M. R., & Miller, M. D. (1999). Fundamentals of orthopaedics (p. 2). Philadelphia: Saunders.)* 95 96 97

Table 1.1 Types of Bone.
MICROSCOPIC APPEARANCE	SUBTYPES	CHARACTERISTICS	EXAMPLES
Lamellar	Cortical	Structure is oriented along lines of stress	Femoral shaft
Woven	Cancellous	Strong	Distal femoral metaphysis
	Cancellous	More elastic than cortical bone	Distal femoral metaphysis
	Immature	Not stress oriented	Embryonic skeleton
	Immature		Fracture callus
	Pathologic	Random organization	Osteogenic sarcoma
	Pathologic	Increased turnover	Fibrous dysplasia
	Weak
	Flexible

98 99 Modified from Brinker, M. R., et al. (1999). Fundamentals of orthopaedics. p. 1). Philadelphia: Saunders. 100 101 Characterized by high turnover rate (more remodeling), smaller Young's modulus, more elasticity [... Output truncated due to length. 647 tokens/2087 characters removed ...]