Copyright © 2010 Pearson Education, Inc.
Skeletal Cartilages
• Contain _____ blood vessels or nerves
• Dense connective tissue girdle of perichondrium contains blood vessels for nutrient delivery to cartilage
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Skeletal Cartilages
1. _________ cartilages
• Provide support, flexibility, and resilience
• Most abundant type
2. ___________ cartilages
• Similar to hyaline cartilages, but contain elastic fibers
3. _______________
• Collagen fibers—have great tensile strength
Copyright © 2010 Pearson Education, Inc. Figure 6.1
Axial skeleton
Appendicular skeleton
Hyaline cartilages
Elastic cartilages
Fibrocartilages
Cartilages
Bones of skeleton
EpiglottisLarynx
TracheaCricoidcartilage Lung
Respiratory tube cartilagesin neck and thorax
ThyroidcartilageCartilage in
external earCartilages innose
ArticularCartilageof a joint
Costalcartilage
Cartilage inIntervertebraldisc
Pubicsymphysis
Articular cartilageof a joint
Meniscus (padlikecartilage inknee joint)
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Growth of Cartilage
• ______________
• Cells secrete matrix against the external face of existing cartilage
• _________________
• Chondrocytes divide and secrete new matrix, expanding cartilage from within
• Calcification of cartilage occurs during
• Normal _____ growth
• Old age
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Bones of the Skeleton
• Two main groups, by location
• ____ skeleton (brown)
• _______________ skeleton (yellow)
Copyright © 2010 Pearson Education, Inc. Figure 6.1
Cartilage inexternal ear
Cartilages innose
ArticularCartilageof a joint
Costalcartilage
Cartilage inIntervertebraldisc
Pubicsymphysis
Articular cartilageof a joint
Meniscus (padlikecartilage inknee joint)
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Classification of Bones by Shape
• ____ bones
• Longer than they are wide
• ________ bones
• Cube-shaped bones (in wrist and ankle)
• Sesamoid bones (within tendons, e.g., patella)
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Classification of Bones by Shape
• _____ bones
• Thin, flat, slightly curved
• Irregular bones
• Complicated shapes
Copyright © 2010 Pearson Education, Inc. Figure 6.2
Copyright © 2010 Pearson Education, Inc.
Functions of Bones
• ____________
• For the body and soft organs
• ___________
• For brain, spinal cord, and vital organs
• _____________
• Levers for muscle action
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Functions of Bones
• ____________
• Minerals (calcium and phosphorus) and growth factors
• Blood cell formation (hematopoiesis) in marrow cavities
• Triglyceride (energy) storage in bone cavities
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Bone Markings
• Bulges, depressions, and holes serve as
• Sites of attachment for muscles, ligaments, and tendons
• Joint surfaces
• Conduits for blood vessels and nerves
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Bone Markings: Projections
• Sites of muscle and ligament attachment
• _________—rounded projection
• Crest—narrow, prominent ridge
• Trochanter—large, blunt, irregular surface
• Line—narrow ridge of bone
• _________—small rounded projection
• Epicondyle—raised area above a condyle
• Spine—sharp, slender projection
• _________—any bony prominence
Copyright © 2010 Pearson Education, Inc. Table 6.1
Copyright © 2010 Pearson Education, Inc.
Bone Markings: Projections
• Projections that help to form joints
• Head
• Bony expansion carried on a narrow neck
• _______
• Smooth, nearly flat articular surface
• Condyle
• Rounded articular projection
• Ramus
• Armlike bar
Copyright © 2010 Pearson Education, Inc. Table 6.1
Copyright © 2010 Pearson Education, Inc.
Bone Markings: Depressions and Openings
• _________
• Canal-like passageway
• Sinus
• Cavity within a bone
• Fossa
• Shallow, basinlike depression
• Groove
• Furrow
• ________
• Narrow, slitlike opening
• Foramen
• Round or oval opening through a bone
Copyright © 2010 Pearson Education, Inc. Table 6.1
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Bone Textures
• Compact bone
• Dense outer layer
• Spongy (___________) bone
• Honeycomb of trabeculae
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Structure of a Long Bone
• Diaphysis (______)
• Compact bone collar surrounds medullary (marrow) cavity
• Medullary cavity in adults contains fat (yellow marrow)
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Structure of a Long Bone
• _____________
• Expanded ends
• Spongy bone interior
• Epiphyseal line (remnant of growth plate)
• Articular (__________) cartilage on joint surfaces
Copyright © 2010 Pearson Education, Inc. Figure 6.3a-b
Proximalepiphysis
(b)
(a)
Epiphysealline
Articularcartilage
Periosteum
Spongy bone
Compact bone
Medullarycavity (linedby endosteum)
Compact bone
Diaphysis
Distalepiphysis
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Membranes of Bone
• ____________
• Outer fibrous layer
• Inner osteogenic layer
• Osteoblasts (bone-forming cells)
• Osteoclasts (bone-destroying cells)
• Osteogenic cells (stem cells)
• Nerve fibers, nutrient blood vessels, and lymphatic vessels enter the bone via nutrient foramina
• Secured to underlying bone by Sharpey’s fibers
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Membranes of Bone
• ___________
• Delicate membrane on internal surfaces of bone
• Also contains osteoblasts and osteoclasts
Copyright © 2010 Pearson Education, Inc. Figure 6.3c
(c)
Yellowbone marrow
Endosteum
Compact bone
Periosteum
Perforating(Sharpey’s) fibers
Nutrientarteries
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Structure of Short, Irregular, and Flat Bones
• Periosteum-covered compact bone on the outside
• Endosteum-covered spongy bone within
• Spongy bone called diploë in flat bones
• Bone marrow between the trabeculae
Copyright © 2010 Pearson Education, Inc. Figure 6.5
Compactbone
Trabeculae
Spongy bone(diploë)
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Location of Hematopoietic Tissue (Red Marrow)
• Red marrow cavities of adults
• Trabecular cavities of the heads of the femur and humerus
• Trabecular cavities of the diploë of flat bones
• Red marrow of newborn infants
• Medullary cavities and all spaces in spongy bone
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Microscopic Anatomy of Bone
• Cells of bones
• __________ (osteoprogenitor) cells
• Stem cells in periosteum and endosteum that give rise to osteoblasts
• ____________
• Bone-forming cells
Copyright © 2010 Pearson Education, Inc. Figure 6.4a-b
(a) Osteogenic cell (b) Osteoblast
Stem cell Matrix-synthesizingcell responsiblefor bone growth
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Microscopic Anatomy of Bone
• Cells of bone
• Osteocytes
• Mature bone cells
• _____________
• Cells that break down (resorb) bone matrix
Copyright © 2010 Pearson Education, Inc. Figure 6.4c-d
(c) Osteocyte
Mature bone cellthat maintains the
bone matrix
(d) Osteoclast
Bone-resorbing cell
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Microscopic Anatomy of Bone: Compact Bone
• ___________ system, or osteon—structural unit
• Lamellae
• Weight-bearing
• Column-like matrix tubes
• Central (Haversian) canal
• Contains blood vessels and nerves
Copyright © 2010 Pearson Education, Inc. Figure 6.6
Structuresin thecentralcanal
Artery withcapillaries
VeinNerve fiber
Lamellae
Collagenfibersrun indifferentdirections
Twistingforce
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Microscopic Anatomy of Bone: Compact Bone
• Perforating (Volkmann’s) canals
• At right angles to the central canal
• Connects blood vessels and nerves of the periosteum and central canal
• __________ —small cavities that contain osteocytes
• ___________ —hairlike canals that connect lacunae to each other and the central canal
Copyright © 2010 Pearson Education, Inc. Figure 6.7a-c
Endosteum lining bony canalsand covering trabeculae
Perforating (Volkmann’s) canal
Perforating (Sharpey’s) fibers
Periosteal blood vesselPeriosteum
Lacuna (withosteocyte)
(a)
(b) (c)
Lacunae
Lamellae
NerveVeinArtery
Canaliculi
Osteocytein a lacuna
Circumferentiallamellae
Osteon(Haversian system)
Central(Haversian) canal
Centralcanal
Interstitial lamellae
Lamellae
Compactbone
Spongy bone
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Microscopic Anatomy of Bone: Spongy Bone
• ___________
• Align along lines of stress
• No _____________
• Contain irregularly arranged lamellae, osteocytes, and canaliculi
• Capillaries in endosteum supply nutrients
Copyright © 2010 Pearson Education, Inc. Figure 6.3b
(b)
Lacunae
Lamellae
Nerve
Vein
Artery
Canaliculus
Osteocytein a lacuna
Centralcanal
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Chemical Composition of Bone: Organic
• Osteogenic cells, osteoblasts, osteocytes, osteoclasts
• Osteoid—organic bone matrix secreted by osteoblasts
• Ground substance (proteoglycans, glycoproteins)
• Collagen fibers
• Provide tensile strength and flexibility
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Chemical Composition of Bone: Inorganic
• Hydroxyapatites (mineral salts)
• 65% of bone by mass
• Mainly calcium phosphate crystals
• Responsible for hardness and resistance to compression
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Bone Development
• Osteogenesis (ossification)—bone tissue formation
• Stages
• Bone formation—begins in the 2nd month of development
• Postnatal bone growth—until early adulthood
• Bone remodeling and repair—lifelong
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Two Types of Ossification
1. _________________ ossification
• Membrane bone develops from fibrous membrane
• Forms flat bones, e.g. clavicles and cranial bones
2. _______________ ossification
• Cartilage (endochondral) bone forms by replacing hyaline cartilage
• Forms most of the rest of the skeleton
Copyright © 2010 Pearson Education, Inc. Figure 6.8, (1 of 4)
Mesenchymalcell
CollagenfiberOssificationcenter
Osteoid
Osteoblast
Ossification centers appear in the fibrousconnective tissue membrane.• Selected centrally located mesenchymal cells cluster
and differentiate into osteoblasts, forming anossification center.
1
Copyright © 2010 Pearson Education, Inc. Figure 6.8, (2 of 4)
Osteoid
Osteocyte
Newly calcifiedbone matrix
Osteoblast
Bone matrix (osteoid) is secreted within thefibrous membrane and calcifies.• Osteoblasts begin to secrete osteoid, which is calcified
within a few days.• Trapped osteoblasts become osteocytes.
2
Copyright © 2010 Pearson Education, Inc. Figure 6.8, (3 of 4)
Mesenchymecondensingto form theperiosteum
Blood vessel
Trabeculae ofwoven bone
Woven bone and periosteum form.• Accumulating osteoid is laid down between embryonic
blood vessels in a random manner. The result is a network(instead of lamellae) of trabeculae called woven bone.
• Vascularized mesenchyme condenses on the external faceof the woven bone and becomes the periosteum.
3
Copyright © 2010 Pearson Education, Inc. Figure 6.8, (4 of 4)
FibrousperiosteumOsteoblast
Plate ofcompact bone
Diploë (spongybone) cavitiescontain redmarrow
Lamellar bone replaces woven bone, just deep tothe periosteum. Red marrow appears.• Trabeculae just deep to the periosteum thicken, and are later
replaced with mature lamellar bone, forming compact boneplates.
• Spongy bone (diploë), consisting of distinct trabeculae, per-sists internally and its vascular tissue becomes red marrow.
4
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Endochondral Ossification
• Uses hyaline cartilage models
• Requires breakdown of hyaline cartilage prior to ossification
Copyright © 2010 Pearson Education, Inc. Figure 6.9
Bone collarforms aroundhyaline cartilagemodel.
Cartilage in thecenter of thediaphysis calcifiesand then developscavities.
The periostealbud inavades theinternal cavitiesand spongy bonebegins to form.
The diaphysis elongatesand a medullary cavityforms as ossificationcontinues. Secondaryossification centers appearin the epiphyses inpreparation for stage 5.
The epiphysesossify. Whencompleted, hyalinecartilage remains onlyin the epiphysealplates and articularcartilages.
Hyalinecartilage
Area ofdeterioratingcartilage matrix
Epiphysealblood vessel
Spongyboneformation
Epiphysealplatecartilage
Secondaryossificationcenter
Bloodvessel ofperiostealbud
Medullarycavity
Articularcartilage
Childhood toadolescence
BirthWeek 9 Month 3
Spongybone
BonecollarPrimaryossificationcenter
1 2 3 4 5
Copyright © 2010 Pearson Education, Inc. Figure 6.9, step 1
Bone collar forms aroundhyaline cartilage model.1
Hyaline cartilage
Week 9
Bone collar
Primaryossificationcenter
Copyright © 2010 Pearson Education, Inc. Figure 6.9, step 2
Cartilage in the centerof the diaphysis calcifiesand then develops cavities.
2
Area of deterioratingcartilage matrix
Copyright © 2010 Pearson Education, Inc. Figure 6.9, step 3
The periosteal bud inavadesthe internal cavities andspongy bone begins to form.
3
Spongyboneformation
Bloodvessel ofperiostealbud
Month 3
Copyright © 2010 Pearson Education, Inc. Figure 6.9, step 4
The diaphysis elongates and a medullary cavity formsas ossification continues. Secondary ossification centersappear in the epiphyses in preparation for stage 5.
4
Epiphysealblood vessel Secondary
ossificationcenter
Medullarycavity
Birth
Copyright © 2010 Pearson Education, Inc. Figure 6.9, step 5
The epiphyses ossify. When completed, hyaline cartilageremains only in the epiphyseal plates and articular cartilages.5
Epiphyseal platecartilage
Articular cartilage
Childhood to adolescence
Spongy bone
Copyright © 2010 Pearson Education, Inc. Figure 6.9
Bone collarforms aroundhyaline cartilagemodel.
Cartilage in thecenter of thediaphysis calcifiesand then developscavities.
The periostealbud inavades theinternal cavitiesand spongy bonebegins to form.
The diaphysis elongatesand a medullary cavityforms as ossificationcontinues. Secondaryossification centers appearin the epiphyses inpreparation for stage 5.
The epiphysesossify. Whencompleted, hyalinecartilage remains onlyin the epiphysealplates and articularcartilages.
Hyalinecartilage
Area ofdeterioratingcartilage matrix
Epiphysealblood vessel
Spongyboneformation
Epiphysealplatecartilage
Secondaryossificationcenter
Bloodvessel ofperiostealbud
Medullarycavity
Articularcartilage
Childhood toadolescence
BirthWeek 9 Month 3
Spongybone
BonecollarPrimaryossificationcenter
1 2 3 4 5
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Postnatal Bone Growth
• Interstitial growth:
• _____________ of long bones
• Appositional growth:
• __________ and ______________ of all bones by osteoblasts and osteoclasts on bone surfaces
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Growth in Length of Long Bones
• Epiphyseal plate cartilage organizes into four important functional zones:
• ____________ (growth)
• Hypertrophic
• _____________
• Ossification (osteogenic)
Copyright © 2010 Pearson Education, Inc. Figure 6.10
Calcified cartilagespicule
Osseous tissue(bone) coveringcartilage spicules
Resting zone
Osteoblast depositingbone matrix
Proliferation zoneCartilage cells undergo mitosis.
Hypertrophic zoneOlder cartilage cells enlarge.
Ossification zoneNew bone formation is occurring.
Calcification zoneMatrix becomes calcified; cartilage cells die; matrix begins deteriorating.
1
2
3
4
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Hormonal Regulation of Bone Growth
• Growth hormone stimulates epiphyseal plate activity
• Thyroid hormone modulates activity of growth hormone
• Testosterone and estrogens (at puberty)
• Promote adolescent growth spurts
• End growth by inducing epiphyseal plate closure
Copyright © 2010 Pearson Education, Inc. Figure 6.11
Bone growth Bone remodeling
Articular cartilage
Epiphyseal plate
Cartilagegrows here.
Cartilageis replacedby bone here.
Cartilagegrows here.
Bone isresorbed here.
Bone isresorbed here.
Bone is addedby appositionalgrowth here. Cartilage
is replacedby bone here.
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Bone Deposit
• 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
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Bone Deposit
• Sites of new matrix deposit are revealedby the
• Osteoid seam
• Unmineralized band of matrix
• Calcification front
• The abrupt transition zone between the osteoid seam and the older mineralized bone
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Bone Resorption
• Osteoclasts secrete
• Lysosomal enzymes (digest organic matrix)
• Acids (convert calcium salts into soluble forms)
• Dissolved matrix is transcytosed across osteoclast, enters interstitial fluid and then blood
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Control of Remodeling
•What controls continual remodeling of bone?
• Hormonal mechanisms that maintain calcium homeostasis in the blood
• Mechanical and gravitational forces
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Hormonal Control of Blood Ca2+
• Calcium is necessary for
• _____________ of nerve impulses
• Muscle contraction
• Blood ______________
• Secretion by glands and nerve cells
• Cell division
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Hormonal Control of Blood Ca2+
• Primarily controlled by parathyroid hormone (PTH)
Blood Ca2+ levels
Parathyroid glands release PTH
PTH ____________ osteoclasts to degrade bone matrix and release Ca2+
Blood Ca2+ levels
Copyright © 2010 Pearson Education, Inc. Figure 6.12
Osteoclastsdegrade bonematrix and release Ca2+
into blood.
Parathyroidglands
Thyroidgland
Parathyroidglands releaseparathyroidhormone (PTH).
StimulusFalling bloodCa2+ levels
PTH
Calcium homeostasis of blood: 9–11 mg/100 mlBALANCEBALANCE
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Hormonal Control of Blood Ca2+
• May be affected to a lesser extent by calcitonin
Blood Ca2+ levels
Parafollicular cells of thyroid release calcitonin
Osteoblasts deposit calcium salts
Blood Ca2+ levels
• Leptin has also been shown to influence bone density by inhibiting osteoblasts
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Response to Mechanical Stress
• Wolff’s law: A bone grows or remodels in response to forces or demands placed upon it
• Observations supporting Wolff’s law:
• Handedness (right or left handed) results in bone of one upper limb being thicker and stronger
• Curved bones are thickest where they are most likely to buckle
• Trabeculae form along lines of stress
• Large, bony projections occur where heavy, active muscles attach
Copyright © 2010 Pearson Education, Inc. Figure 6.13
Load here (body weight)
Head offemur
Compressionhere
Point ofno stress
Tensionhere
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Classification of Bone Fractures
• Bone fractures may be classified by four “either/or” classifications:
1. Position of bone ends after fracture:
• __________—ends retain normal position
• Displaced—ends out of normal alignment
2. Completeness of the break
• ________—broken all the way through
• _____________—not broken all the way through
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Classification of Bone Fractures
3. _____________ of the break to the long axis of the bone:
• Linear—parallel to long axis of the bone
• Transverse—perpendicular to long axis of the bone
4. Whether or not the bone ends penetrate the 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
• All __________ can be described in terms of
• Location
• External appearance
• Nature of the break
Copyright © 2010 Pearson Education, Inc. Table 6.2
Copyright © 2010 Pearson Education, Inc. Table 6.2
Copyright © 2010 Pearson Education, Inc. Table 6.2
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Stages in the Healing of a Bone Fracture
1. __________ forms
• Torn blood vessels hemorrhage
• Clot (hematoma) forms
• Site becomes swollen, painful, and inflamed
Copyright © 2010 Pearson Education, Inc. Figure 6.15, step 1
A hematoma forms.1
Hematoma
Copyright © 2010 Pearson Education, Inc.
Stages in the Healing of a Bone Fracture
2. Fibrocartilaginous callus forms
• Phagocytic cells clear debris
• __________ begin forming spongy bone within 1 week
• Fibroblasts secrete collagen fibers to connect bone ends
• Mass of repair tissue now called fibrocartilaginous callus
Copyright © 2010 Pearson Education, Inc. Figure 6.15, step 2
Fibrocartilaginouscallus forms.2
Externalcallus
Newbloodvessels
Spongybonetrabecula
Internalcallus(fibroustissue andcartilage)
Copyright © 2010 Pearson Education, Inc.
Stages in the Healing of a Bone Fracture
3. Bony ______ formation
• New trabeculae form a bony (hard) callus
• Bony callus formation continues until firm union is formed in ~2 months
Copyright © 2010 Pearson Education, Inc. Figure 6.15, step 3
Bony callus forms.3
Bonycallus ofspongybone
Copyright © 2010 Pearson Education, Inc.
Stages in the Healing of a Bone Fracture
4. Bone remodeling
• In response to mechanical stressors over several months
• Final structure resembles original
Copyright © 2010 Pearson Education, Inc. Figure 6.15, step 4
Bone remodelingoccurs.4
Healedfracture
Copyright © 2010 Pearson Education, Inc. Figure 6.15
Hematoma Externalcallus
Bonycallus ofspongyboneHealedfracture
Newbloodvessels
Spongybonetrabecula
Internalcallus(fibroustissue andcartilage)
A hematoma forms. Fibrocartilaginouscallus forms.
Bony callus forms. Boneremodelingoccurs.
1 2 3 4
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Homeostatic Imbalances
• ______________ and __________
• Calcium salts not deposited
• Rickets (childhood disease) causes bowed legs and other bone deformities
• Cause: vitamin D deficiency or insufficient dietary calcium
Copyright © 2010 Pearson Education, Inc.
Homeostatic Imbalances
• Osteoporosis
• Loss of ____ ____—bone resorption outpaces deposit
• Spongy bone of spine and neck of femur become most susceptible to fracture
• Risk factors
• Lack of estrogen, calcium or vitamin D; petite body form; immobility; low levels of TSH; diabetes mellitus
Copyright © 2010 Pearson Education, Inc. Figure 6.16
Copyright © 2010 Pearson Education, Inc.
Osteoporosis: Treatment and Prevention
• Calcium, vitamin D, and fluoride supplements
• Weight-bearing ________ throughout life
• _______ (estrogen) replacement therapy (HRT) slows bone loss
• Some drugs (Fosamax, SERMs, statins) increase bone mineral density
Copyright © 2010 Pearson Education, Inc.
Paget’s Disease
• Excessive and haphazard bone formation and breakdown, usually in spine, pelvis, femur, or skull
• Pagetic bone has very high ratio of spongy to compact bone and reduced mineralization
• Unknown cause (possibly viral)
• Treatment includes calcitonin and biphosphonates
Copyright © 2010 Pearson Education, Inc.
Developmental Aspects of Bones
• Embryonic skeleton ossifies predictably so fetal age easily determined from X rays or sonograms
• At birth, most long bones are well ossified (except epiphyses)
Copyright © 2010 Pearson Education, Inc. Figure 6.17
Parietal bone
Radius
Ulna
Humerus
Femur
Occipital bone
ClavicleScapula
Ribs
Vertebra
Ilium
Tibia
Frontal boneof skull
Mandible
Copyright © 2010 Pearson Education, Inc.
Developmental Aspects of Bones
• Nearly all bones completely ________ by age 25
• Bone mass decreases with age beginning in 4th decade
• Rate of loss determined by genetics and environmental factors
• In old age, bone resorption predominates