Download - Today’s goals
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Today’s goals
1. Describe different types of fractures
2. Remember the Good times
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Bone Remodeling and Bone Repair
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Bone Fractures (Breaks)
• Bone fractures are classified by:– The position of the bone ends
after fracture– The completeness of the
break– The orientation of the bone to
the long axis– Whether or not the bones
ends penetrate the skin
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Types of Bone FracturesPosition of Ends
• Nondisplaced – bone ends retain their normal position
• Displaced – bone ends are out of normal alignment
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Types of Bone FracturesCompleteness
• Complete – bone is broken all the way through
• Incomplete – bone is not broken all the way through
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Types of Bone Fractures
Orientation• Transverse – the fracture is perpendicular
to the long axis of the bone• Linear – the fracture is parallel to the long
axis of the bone
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Types of Fractures
Relation to skin• Compound (open) – bone ends penetrate
the skin• Simple (closed) – bone ends do not
penetrate the skin
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Common Types of Fractures• Comminuted – bone fragments into three
or more pieces; common in the elderly• Spiral – ragged break when bone is
excessively twisted; common sports injury• Depressed – broken bone portion pressed
inward; typical skull fracture
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Common Types of Fractures• Compression – bone is crushed; common
in porous bones• Epiphyseal – epiphysis separates from
diaphysis along epiphyseal line; occurs where cartilage cells are dying
• Greenstick – incomplete fracture where one side of the bone breaks and the other side bends; common in children
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Fractures A break in a bone
• Can be classified by causeCAUSE– Traumatic break due to injury– Pathological break due to disease
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Types of Fractures
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Compressed
• Bone is crushed• Common in osteoporotic bones subjected to
trauma, such as in a fall
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Epiphyseal Fracture
• Epiphysis separates from diaphysis at the epiphyseal plate
• Occurs when cartilage cells are dying & calcification is occurring
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Depressed
• Broken bone portion pressed inward• Typical of skull fracture
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Greenstick Fracture
• Incomplete break• Only breaks on 1 side• Like a twig on a tree• More common in kids
whose bones are more
flexible
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Fissured Fracture
• Incomplete longitudinal break
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Comminuted Fracture
• Complete break & results in 3 or more fragments• Common in the aged, where bones are more brittle
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Transverse Fracture
• Complete break, horizontally
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Oblique Fracture
• Complete break at an angle
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Spiral Fracture
• Complete break caused by a twisting motion• Most frequent break in athletes
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Stages in the Healing of a Bone Fracture
• Hematoma formation– Torn blood vessels
hemorrhage– A mass of clotted
blood (hematoma) forms at the fracture site
– Site becomes swollen, painful, and inflamed Figure 6.13.1
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Stages in the Healing of a Bone Fracture
– Osteoblasts migrate to the fracture and begin reconstructing the bone
– Osteoblasts begin forming spongy bone
Figure 6.13.2
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Stages in the Healing of a Bone Fracture
• Bone formation– New bone
trabeculae appear – Bone formation
begins 3-4 weeks after injury, and continues until firm 2-3 months later
Figure 6.13.3
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Stages in the Healing of a Bone Fracture
• Compact bone is laid down to reconstruct shaft walls
Figure 6.13.4
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Other Skeletal Conditions
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Scoliosis
• Abnormal curve of the spine
• May cause the head to appear off center
• One hip or shoulder to be higher than the opposite side
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Lordosis
• Exaggerated lumbar curvature
• A.K.A. “swayback” • Due to factors like
being overweight, pregnancy, or muscle conditions
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Kyphosis
• Exaggerated curvature of the thoracic vertebrae
• A.K.A. “Hunchback”• Often seen in older
adults• Possibly due to
osteoporosis or poor posture
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Common Types of Fractures
Table 6.2.1
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Common Types of Fractures
Table 6.2.2
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Common Types of Fractures
Table 6.2.3
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Bone Remodeling
• Remodeling units – adjacent osteoblasts and osteoclasts deposit and resorb bone at periosteal and endosteal surfaces
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Goal Today:
• Talk basics of Bone Remodeling (Deposition) and Breakdown (Resorbtion)
• Describe 2 Mechanisms for bone remodeling
• Hormonal– Calcitonin – Parathyroid Hormone
• Mechanical
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Bone Deposition• Occurs where bone is injured or added
strength is needed• Requires a diet rich in protein, vitamins C,
D, and A, calcium, phosphorus, magnesium, and manganese
• Alkaline phosphatase is essential for mineralization of bone
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Bone Deposition
• Sites of new matrix deposition are revealed by the:– Osteoid seam – unmineralized band of bone
matrix– Calcification front – abrupt transition zone
between the osteoid seam and the older mineralized bone
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Bone Resorption
• Accomplished by osteoclasts• Resorption bays – grooves formed by
osteoclasts as they break down bone matrix
• Resorption involves osteoclast secretion of:– Lysosomal enzymes that digest organic matrix– Acids that convert calcium salts into soluble
forms
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Importance of Ionic Calcium in the Body
• Calcium is necessary for:– Transmission of nerve impulses– Muscle contraction– Blood coagulation– Secretion by glands and nerve cells– Cell division
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Control of Remodeling
• Two control loops regulate bone remodeling– Hormonal mechanism maintains calcium
homeostasis in the blood– Mechanical and gravitational forces acting on
the skeleton
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Hormonal Mechanism
• Ca2+ levels go UP (and they stay there)• trigger the thyroid to release calcitonin
•Calcitonin stimulates calcium salt deposit in bone
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Bone Resorption
• Falling blood Ca2+ levels signal the parathyroid glands to release– Parathyroid Hormone = PTH
• PTH signals osteoclasts to degrade bone matrix and release Ca2+ into the blood
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Hormonal Control of Blood Ca
Figure 6.11
PTH;calcitoninsecreted
Calcitoninstimulatescalcium saltdepositin bone
Parathyroidglands releaseparathyroidhormone (PTH)
Thyroidgland
Thyroidgland
Parathyroidglands
Osteoclastsdegrade bonematrix and releaseCa2+ into blood
Falling bloodCa2+ levels
Rising bloodCa2+ levels
Calcium homeostasis of blood: 9–11 mg/100 ml
PTH
Imbalance
Imbalance
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Response to Mechanical Stress
• Trabeculae form along lines of stress• Large, bony projections occur where
heavy, active muscles attach
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Response to Mechanical Stress
• Wolff’s law – a bone grows or remodels in response to the forces or demands placed upon it
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Observations supporting Wolff’s law include
• Long bones are thickest midway along the shaft (where bending stress is greatest)
• Curved bones are thickest where they are most likely to buckle
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Response to Mechanical Stress
Figure 6.12