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Bones: The Living Framework of the Human Body. Eva L. Murdoch, PhD Assistant Professor Department of Natural Sciences Joliet Junior College. http:// www.youtube.com / watch?v =FufL80hJsP8. The Skeleton. Provides structural support for the entire body Stores minerals - PowerPoint PPT Presentation
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Bones: The Living Framework of the Human Body
Eva L. Murdoch, PhDAssistant Professor
Department of Natural SciencesJoliet Junior College
http://www.youtube.com/watch?v=FufL80hJsP8
The Skeleton
• Provides structural support for the entire body
• Stores minerals
• Protects soft tissues
• Houses red and yellow bone marrow
• Serves as levers, on which skeletal muscles pull to generate motion
Bone Formation and Growth
• Bone formation
– 6 weeks (embryo 0.5”)
• Bone growth
– Continues during development in utero
– Continues through childhood
– Stops at about age 25
• Hormonal regulation
– Growth hormone & Thyroxin – stimulate bone cells to produce bone
matrix growth
– Sex hormones (estrogen & testosterone) speed up bone synthesis at
puberty growth stops within few years
The Human Body
• The human body: collection of cells and cell
products
- Cells: smallest living unit performing vital functions
- Cell products: non-living, often proteins, also
perform vital functions
Bone Tissue
• Living tissue composed of: - Several cell types – osteocytes, osteoblasts,
osteoclasts
- Matrix - cell products (collagen fibers) and inorganic salts (calcium phosphate)
• Matrix: Protein-Crystal Combination:
- Collagen fibers: exceptionally strong protein, when subjected to tension – stronger than steel
- Calcium phosphate crystals: very hard, withstanding compression, but brittle when exposed to twisting
• Bone Cells:
- Osteocytes: maintain protein and mineral content of bone matrix
- Osteoblasts: produce bone matrix- Osteoclasts: remove and recycle
bone matrix
Bone Tissue
Ca3(PO4)2
Ca2+
Ca2+
Ca2+
Ca2+
Ca2+
Ca2+Ca2+
• Bone: – Strong, somewhat flexible and
highly resistant to shattering.– On par with the best steel-
reinforced concrete– Even better, bone undergoes
changes (remodeling), and can repair itself after injury
Bone Tissue
Bone Remodeling
• Maintaining bone mass is a balance between bone cells creating bone matrix and bone cells dissolving bone matrix. − Recycle & renewal of bone matrix
– Maintenance of mineral reserve, supply of minerals in body fluids (blood)
− Involves osteocytes, osteoblasts, and osteoclasts
• Turnover rate: varies − Deposition > removal, bone stronger
− Deposition < removal, bone weaker
• Heavy-metal ion deposition into bone matrix– Lead (Pb), cobalt (Co), uranium (U), plutonium (Pu)
Bone: Calcium Homeostasis• Calcium – essential ion for all cells
− Bones: calcium reserve− Calcium homeostasis: maintenance of
sufficient calcium ion level in blood
1. Calcium: high in blood− Calcitonin: decrease of calcium in blood,
resulting in increased bone production
2. Calcium: low in blood− Parathyroid Hormone: increase of calcium in
blood, due to an increase in bone breakdown
The Effects of Exercise on Bone
• Bone adapts to physical stress:– Mineral crystals in bone matrix create small
electrical currents• Osteoblasts: produce bone matrix• Electrical currents: repair of severe fractures
– Bone surfaces change• Thicker, larger bumps & ridges: muscle
attachment
Bone and Aging
• Bone: thinner & weaker – Osteopenia – b/n ages 30 & 40 women lose
8% of bone mass/decade, men 3%• Mainly at ends of long bones, vertebrae &
jaws• Causing fragile limbs, reduction in height,
and tooth loss – Osteoporosis – age > 45, severe bone loss,
affects: 29% women & 18% man• Fractures due to normal physical activity
(standing)• Accelerated in women: loss of estrogen
– Cancer (bone marrow, breast and other) – risk factor for osteoporosis• osteoclast activating factors
Normal spongy bone
Spongy bone in osteoporosis
Things I can do to slow down the effects of aging and assure optimum bone mass.
• Adequate diet• Weight bearing exercise (daily)• Monitor hormone levels
associated with bone mass