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Trebeculae compact bone Step 4 © 2012 Pearson Education, Inc. Diploë Abnormalities in bone growth © 2012 Pearson Education, Inc. Fibrodysplasia ossificans progressiva (FOP) autosomal dominant, Codon 206: Arg à Hist 1 : 2, 000, 000 endothelial cells àmesenchymal cellsà bone © 2012 Pearson Education, Inc. Marfan Syndrome Genetic condition Excessive growth of cartilage Excessive growth of long bones © 2012 Pearson Education, Inc. Aorta stretches Heart enlarged Calcium Homeostasis • The Skeleton as a Calcium Reserve • Calcium ions (Ca2+) are vital to: • Neurons • Muscle cells, especially heart cells • For contraction, longer depolarization • So, how what all is stored in bone? © 2012 Pearson Education, Inc. Limes! Deficient in Vit. C? à low collagen à Scurvy Bone Contains … Composition of Bone Calcium 39% 99% of the body’s Calcium 4% of the body’s Potassium 35% of the body’s Sodium collagen 33% 50% of the body’s Magnesium 80% of the body’s Carbonate 99% of the body’s Phosphate Deficient in Ca2+? à bendy bones à Rickets © 2012 Pearson Education, Inc. Bone Contains … Composition of Bone Calcium 39% collagen 33% Potassium 0.2% Sodium 0.7% 35% of the body’s Sodium Magnesium 0.5% 50% of the body’s Magnesium Carbonate 9.8% 80% of the body’s Carbonate Phosphate 17% © 2012 Pearson Education, Inc. 99% of the body’s Calcium 4% of the body’s Potassium 99% of the body’s Phosphate Calcium Homeostasis • Calcium is closely regulated • Plasma : 9 – 10.5 mg/dL • When Ca2+ levels too high -> Thyroid respond • When Ca2+ levels too low -> Parathyroid hormone © 2012 Pearson Education, Inc. Factors That Decrease Blood Calcium Levels If too high: Ca2+ > 11 mg/dL Thyroid Responds Calcitonin Produced Block Osteoclasts, Osteoblasts go! Loose Ca2+ ! Absorb less! less Bone calcitriol Calcium absorbed slowly Calcium excreted Calcium stored êCa2+ © 2012 Pearson Education, Inc. Increased calcium loss in urine Factors That Increase Blood Calcium Levels Ca2+ < 8.5 mg/dL If too low: Parathyroid Responds PTH Produced Go Osteoclasts! Absorb more! more calcitriol Bone Calcium released Calcium absorbed quickly éCa2+ © 2012 Pearson Education, Inc. Hold Ca2+ ! Calcium conserved Decreased calcium loss in urine Effects of Aging on the Skeletal System • Age-Related Changes • Age à Bones thinner and weaker: Osteopenia • begins @ 30 – 40 • Women lose 8% of bone mass/decade (men 3%) • The epiphyses, vertebrae, and jaws are most affected • fragile limbs • Loss of height • Tooth loss • Normal deterioration • Abnormal? © 2012 Pearson Education, Inc. Effects of Aging on the Skeletal System • Osteoporosis • Severe bone loss • Affects normal function • Over age 45, occurs in: • 29% of women • 18% of men © 2012 Pearson Education, Inc. Figure 6-18 The Effects of Osteoporosis on Spongy Bone © 2012 Pearson Education, Inc. Normal spongy bone SEM × 25 Spongy bone in osteoporosis SEM × 21 Effects of Aging on the Skeletal System • Hormones and Bone Loss • Estrogens maintain bone mass • regulate expression of genes that control: • Function/life span in mature osteoclasts © 2012 Pearson Education, Inc. Effects of Aging on the Skeletal System • Menopause à Estrogens low © 2012 Pearson Education, Inc. 6-10 Effects of Aging on the Skeletal System • Hormones and Bone Loss • Estrogens low à no regulation of osteoclasts • Rampant wicked-weird cells àLoss of bone density © 2012 Pearson Education, Inc. Effects of Aging on the Skeletal System • Bone Loss Treatments • Hormone Replacement Therapy • Premise: just give more estrogen to the patient • Premarin • Pregnant Mare’s Urine • Estrogens à estradiol • Yes! Estrogen levels go up!! • Problem: endometrial cancer © 2012 Pearson Education, Inc. Effects of Aging on the Skeletal System • Bone Loss Treatments • Other Drugs • Premise: just control the osteoclasts • Biphosphonates • Inhibits bone resorption • Bone mineral density é • Vertebral fractures ê • Problem: LOUD ‘gunshot’ femur fractures é • Irregular formation of matrix © 2012 Pearson Education, Inc. Fractures • • Fractures • Cracks or breaks in bones • Caused by physical stress Fractures are repaired in four steps © 2012 Pearson Education, Inc. Figure 6-17 Types of Fractures and Steps in Repair Bleeding hematoma = blood clot Fracture hematoma Dead bone © 2012 Pearson Education, Inc. Bone fragments Spongy bone of external callus Periosteum Figure 6-17 Types of Fractures and Steps in Repair internal callus external callus Fracture hematoma cleanup Dead bone © 2012 Pearson Education, Inc. Bone fragments Spongy bone of external callus Periosteum Figure 6-17 Types of Fractures and Steps in Repair callus à bone Type of ossification? External callus Osteoblasts and osteocytes remodel Internally ends meet Internal callus © 2012 Pearson Education, Inc. External Callus Spongy About 1 month Figure 6-17 Types of Fractures and Steps in Repair Swelling Remodeling 3-5 years External callus Osteoblasts and osteocytes remodel Internal callus © 2012 Pearson Education, Inc. External Callus Spongy Fractures • Fracture Classification: • Position of ends • • Completeness • • Nondisplaced vs. displaced Complete vs. incomplete Skin penetration • Open (compound) vs. closed (simple) © 2012 Pearson Education, Inc. Figure 6-17 Types of Fractures and Steps in Repair Displaced fracture Across long axis Transverse fracture disaligned © 2012 Pearson Education, Inc. Figure 6-17 Types of Fractures and Steps in Repair Compression fracture Vertebrae, from fall © 2012 Pearson Education, Inc. Spiral fractur e Twisting, from fall Figure 6-17 Types of Fractures and Steps in Repair Epiphyseal fracture Multiple bony fragments Comminuated fracture Where calcification is happening © 2012 Pearson Education, Inc. Distal radius (ulna) From catching as u fall One side, incomplete break © 2012 Pearson Education, Inc. Ankle, both bones Pott’s fracture ra Greenstick f Colles fracture cture Figure 6-17 Types of Fractures and Steps in Repair
