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In-Depth Information
2000; Schultz, 2001 ). Junqueira and Carneiro (2003) describe histological indications of oste-
omalacia in bone. Osteomalacia is a nutritional deficiency of vitamin D causing inadequate
calcification of new bone concurrent with partial resorption of existing bone ( Junqueira
and Carneiro, 2003 ). In addition, hyperparathyroidism is a hormonal imbalance described
by Robling and Stout (2008) as a condition where an excess of the parathyroid hormone is
released. Though it does not have a direct effect on bone remodeling, it does affect the acti-
vation frequency ( Robling and Stout, 2008 ). They noted that individuals suffering from
hyperparathyroidism have a greater number of osteons than healthy individuals.
Osteoporosis (a loss of bone density typically associated with aging) causes intracortical
bone thinning and results in increased porosity within the bone. Jowsey (1977) discovered
that bone depositional rates remained the same while resorption rates rapidly increased
with osteoporosis. This is caused by an extended lag time between the resorption and forma-
tion stages of ARF remodeling ( Frost, 1964; Recker, 1983; Martin and Burr, 1989 ).
Schultz (2001, 2003, 2012) states that paleohistopathology is valuable in disease diagnoses.
Essentially, if a disorder initiates a bony response, these reactions are visible histologically.
Inflammatory processes, lesions, bony tumors, and certain types of bone disease are mani-
fested at the microscopic level and may even be visible before macroscopic indicators are
observable ( Schultz, 2003 ). Paleohistopathology can also enable the discernment between
lytic removal versus deposition of bone (see Smith [Chapter 7], this volume). Also, refer to
Schultz (2001) for comprehensive treatment of the different pathologies recognizable
histologically.
Physical Activity and Biomechanics
Bone responds to both mechanical and nonmechanical factors. The bone remodeling
process is constant and is partly regulated by the body's hormonal system, a process inde-
pendent of mechanical adaptation. Aside from physiology, bone is also subject to forces
and stress of varying magnitudes (Kroman and Symes [Chapter 8], this volume; Petrtyl
et al., 1996; Hughes-Fulford, 2004 ). Once bone modeling is complete, biomechanical stressors
and forces still affect the gross morphology of bone. Bone adapts to its mechanical environ-
ment and does so through ARF remodeling or damage repair. These effects will be visible at
the microscopic level ( Currey, 1959; Ascenzi and Bonucci, 1967, 1968 ).
Wol ff 's law ( Wolff, 1892; Petrtyl et al., 1996; Hughes-Fulford, 2004 )statesthatbonecan
adapt or remodel in response to forces or demands placed upon it from mechanical factors.
Studies have additionally been conducted to research how habitual action (or inaction),
obesity, loading, and other biomechanical factors affect the skeleton at the macroscopic
level ( Ribot et al., 1987; Frost, 1997; Beaupre et al., 2000; Moore and Schaefer, 2011 ). Research
indicates that obese individuals exhibit an increase in overall bone mass and a reduction in
bone loss with age ( Wheatley, 2005 ; Miyabara,etal.,2007;Moore,2008 ). Obesity in post-
menopausal women provided for a higher bone mineral density than for women consid-
ered to be healthy or thin ( Ribot et al., 1987 ). Frost (1997) suggests that because
overweight individuals require stronger muscle forces to move, these forces cause extra
strain and stress on bone, resulting in increased levels of bone remodeling and more
secondary osteonal bone. This topic is discussed further in the chapter on medical imaging
and functional morphology (Moore [Chapter 14], this volume).
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