Bones and Bone Tissue

Chapter 06

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See separate PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes and animations.

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6.1 Functions of the Skeletal System

• Support. Bone is hard and rigid; cartilage is flexible yet strong. Cartilage in nose, external ear, thoracic cage and trachea. Ligaments- bone to bone • Protection. Skull around brain; ribs, sternum, vertebrae protect organs of thoracic cavity • Movement. Produced by muscles on bones, via tendons. Ligaments allow some movement between bones but prevent excessive movement • Storage. Ca and P. Stored then released as needed. Adipose tissue stored in marrow cavities • Blood cell production. Bone marrow that gives rise to blood cells and platelets 6-4 Components of Skeletal System • Bone • Cartilage: three types – Hyaline – Fibrocartilage – Elastic • Tendons and ligaments

6-5 Bone Cartilage

6-7 Tendons & Ligaments

Tendons of extensor digitorum muscle

Anterior cruciate ligament 6.2 Cartilage • Consists of specialized cells that produce matrix – Chondroblasts: form matrix – Chondrocytes: surrounded by matrix; are lacunae • Matrix. Collagen fibers for strength, proteoglycans for resiliency • Perichondrium. Double-layered C.T. sheath. Covers cartilage except at articulations – Inner. More delicate, has fewer fibers, contains chondroblasts – Outer. Blood vessels and nerves penetrate. No blood vessels in cartilage itself • Articular cartilage. Covers bones at joints; has no perichondrium • Growth – Appositional. New chondrocytes and new matrix at the periphery – Interstitial. Chondrocytes within the tissue divide and add more matrix between the cells.

Perichondrium Appositional growth (new cartilage is added to the surface of the Chondroblast cartilage by chondroblasts from the inner layer of the perichondrium) Lacuna Chondrocyte

Nucleus Interstitial growth (new cartilage is formed within the cartilage Chondrocytes that by chondrocytes that divide and produce have divided additional matrix) Matrix

LM 400x

6-10 •Chondrocytes Hyaline Cartilage •Lacunae

•Extracellular matrix •Nuclei of chondrocytes •Perichondrium Hyaline Cartilage High Magnification •Chondrocytes •Nuclei of chondrocytes

•Ground substance •Lacunae Fibrocartilage High Magnification Chondrocytes Lacunae

Collagen fibers Nuclei of chondrocytes Ground substance Fibrocartilage Low Magnification

Chondrocytes Collagen fibers

Ground substance Lacunae Nuclei of chondrocytes Elastic Cartilage Chondrocytes

Elastic fibers

Ground substance

Lacunae

Nuclei of chondrocytes

Perichondrium Elastic Cartilage High Magnification

Elastic fibers

Lacunae

Chondrocytes

Ground Nuclei of substance chondrocytes 6.3 Bone Histology • Bone matrix. Like reinforced concrete. Rebar is collagen fibers, cement is hydroxyapatite – Organic: collagen and proteoglycans

– Inorganic: hydroxyapatite. CaPO4 crystals • If mineral removed, bone is too bendable • If collagen removed, bone is too brittle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

(a) Without Without mineral collagen

(b) (c) a-c: © Trent Stephens Bone Cells • Osteoblasts – Formation of bone through Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ossification or osteogenesis. Bone surface Collagen produced by E.R. and golgi. Released by exocytosis. Osteoblast Connecting Precursors of hydroxyapetite (a) cell processes stored in vesicles, then released New bone by exocytosis. matrix – Ossification: formation of bone Osteocyte by osteoblasts. Osteoblasts (b) communicate through gap junctions. Cells surround themselves by matrix.

6-18 Bone Cells

• Osteocytes. Mature bone cells. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Stellate. Surrounded by matrix, New bone but can make small amounts of matrix matrix to maintain it. Osteocyte – Lacunae: spaces occupied by osteocyte cell body

– Canaliculi: canals occupied by (b) osteocyte cell processes – Nutrients diffuse through tiny Canaliculus amount of liquid surrounding cell Cell process Osteocyte and filling lacunae and canaliculi. Nucleus Then can transfer nutrients from one cell to the next through gap Lacuna junctions. Bone matrix (c) LM 1000x

6-19 Bone Cells • Osteoclasts. Resorption of bone – Ruffled border: where cell membrane borders bone and resorption is taking place. – H ions pumped across membrane, acid forms, eats away bone. – Release enzymes that digest the bone. – Derived from monocytes (which are formed from stem cells in red bone marrow) – Multinucleated and probably arise from fusion of a number of cells • Stem Cells. Mesenchyme (Osteochondral Progenitor Cells) become chondroblasts or osteoblasts. 6-20 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Nuclei

Osteoclast Acidic vesicles

Podosomes

+ H Ruffled pump border

Sealed Bone compartment

6-21 Woven and Lamellar Bone • Woven bone. Collagen fibers randomly oriented. – Formed • During fetal development • During fracture repair • Remodeling – Removing old bone and adding new – Woven bone is remodeled into lamellar bone • Lamellar bone – Mature bone in sheets called lamellae. Fibers are oriented in one direction in each layer, but in different directions in different layers for strength.

6-22 Spongy Bone Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Trabeculae

Compact bone Spongy bone

Spaces containing bone marrow and blood vessels (a) Trabeculae Lines of stress Osteoblast

Osteoclast

Osteocyte Trabecula

Canaliculus Lamellae © Robert Caladine/Visuals Unlimited (b) • Trabeculae: interconnecting rods or plates of bone. Like

scaffolding.

– Spaces filled with marrow. – Covered with endosteum.

– Oriented along stress lines 6-23 Spongy Bone

Marrow cavity Trabeculae Spongy Bone Low Magnification

Periosteum Marrow cavity Trabeculae Trabeculae of Spongy Bone Compact Bone

• Central or Haversian canals: parallel to long axis • Lamellae: concentric, circumferential, interstitial • Osteon or Haversian system: Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Osteon Osteon Circumferential central canal, contents, Concentric lamellae lamellae Interstitial Central canal lamellae Periosteum associated concentric lamellae Blood vessel within the periosteum Blood vessels within and osteocytes a perforating canal

Blood vessels within a central • Perforating or Volkmann’s (haversian) canal Canaliculi LM 400x Osteocytes in canal: perpendicular to long lacunae (b) (a) Canaliculi Lacunae Blood vessel connecting to a central canal axis. Both perforating and between osteons

a: © Trent Stephens central canals contain blood vessels. Direct flow of nutrients from vessels through cell processes of osteoblasts and from one cell to the next.

6-27 Compact Bone

• Osteons (Haversian systems) – Blood vessel-filled central canal (Haversian canal) – Concentric lamellae of bone surround central canal – Lacunae and canaliculi contain osteocytes and fluid • Circumferential lamellae on the periphery of a bone • Interstitial lamellae between osteons. Remnants of osteons replaced through remodeling

6-28 Osteon Interstitial lamellae Compact Bone

Cement line

Central Canal Osteocytes in lacuna Compact Bone Low Magnification Osteon Interstitial lamellae

Central canal Perforating canals Compact Bone High Magnification Osteon Interstitial lamella

Central canal Lamella

Osteocytes Lacunae Canaliculi Cement line Circulation in Bone

• Perforating canals: blood vessels from periosteum penetrate bone • Vessels of the central canal • Nutrients and wastes travel to and from osteocytes via – Interstitial fluid of lacunae and canaliculi – From osteocyte to osteocyte by gap junctions

• Long – Ex. Upper and lower limbs

Flat bone • Short (parietal bone from roof of skull) – Ex. Carpals and tarsals • Flat – Ex. Ribs, sternum, skull, scapulae • Irregular Irregular bone (sphenoid bone from skull) – Ex. Vertebrae, facial

Long bone Short bone (femur, or thighbone) (carpal, or wrist, bone) 6-33 Structure of a Long Bone

Articular cartilage Epiphysis • Diaphysis Epiphyseal plates in juveniles Epiphyseal lines – Shaft in adults Spongy bone

– Compact bone Compact bone

Medullary cavity (contains Diaphysis red marrow in juveniles and Diaphysis • Epiphysis yellow marrow in adults)

Periosteum

– End of the bone Endosteum

– Spongy bone Young bone (a) (b) Adult bone • Epiphyseal plate: growth plate – Hyaline cartilage; present until growth stops • Epiphyseal line: bone stops growing in length • Medullary cavity: In children medullary cavity is red marrow, gradually changes to yellow in limb bones and skull (except for epiphyses of long bones). Rest of skeleton is red. 6-34 Long Bone

Osteons including osteoblasts, osteoclasts and (haversian systems) Endosteum Inner osteochondral progenitor cells layer Periosteum Outer – Fibers of tendon become continuous layer with fibers of periosteum. Compact bone Central canals Spongy bone – Sharpey’s fibers: some periosteal With trabeculae fibers penetrate through the periosteum Connecting vessels Medullary cavity and into the bone. Strengthen (c) Adult bone attachment of tendon to bone. • Endosteum. Similar to periosteum, but more cellular. Lines all internal spaces including spaces in spongy bone. 6-36 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

TABLE 6.1 Gross Anatomy of a Long Bone

Part Description Part Description

Diaphysis Shaft of the bone Epiphyseal plate Area of hyaline cartilage between the diaphysis and epiphysis; cartilage growth followed by endochondral Epiphysis Part of the bone that develops from a center of ossification results in growth in bone length ossification distinct from the diaphysis Spongy bone Bone having many small spaces; found mainly in the Double-layered connective tissue membrane covering Periosteum epiphysis; arranged into trabeculae the outer surface of bone except where articular cartilage is present; ligaments and tendons attach Compact bone Dense bone with few internal spaces organized into to bone through the periosteum; blood vessels and osteons; forms the diaphysis and covers the spongy nerves from the periosteum supply the bone; the bone of the epiphyses periosteum is where bone grows in diameter Medullary cavity Large cavity within the diaphysis Endosteum Thin connective tissue membrane lining the inner Connective tissue in the spaces of spongy bone or in cavities of bone Red marrow the medullary cavity; the site of blood cell production Articular cartilage Thin layer of hyaline cartilage covering a bone where Fat stored within the medullary cavity or in the spaces it forms a joint (articulation) with another bone Yellow marrow of spongy bone

6-37 Structure of Flat, Short, and Irregular Bones • Flat Bones – No diaphyses, epiphyses Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. – Sandwich of spongy between compact bone • Short and Irregular Bone – Compact bone that surrounds spongy bone center; similar to structure of epiphyses of long Compact bone bones Spongy bone – No diaphyses and not elongated • Some flat and irregular bones of skull have sinuses lined by mucous membranes.

6-38 6.5 Bone Development

• Intramembranous ossification – Takes place in connective tissue membrane • Endochondral ossification – Takes place in cartilage • Both methods of ossification – Produce woven bone that is then remodeled – After remodeling, formation cannot be distinguished as one or other

6-39 Intramembranous Ossification

• Takes place in connective tissue membrane formed from embryonic mesenchyme • Forms many skull bones, part of mandible, diaphyses of clavicles • When remodeled, indistinguishable from endochondral bone. • Centers of ossification: locations in membrane where ossification begins • Fontanels: large membrane-covered spaces between developing skull bones; unossified

6-40 Intramembranous Ossification

Osteoblast

Osteocyte

Bone matrix of trabecula

LMLM 500x 500x LM 250x

1 A cross section of a newly formed trabecula shows 2 A lower magnification shows older bone than in step 1. the youngest bone in this series of Spongy bone has formed as a result of the photomicrographs. Osteocytes are surrounded by enlargement and interconnections of many trabeculae. bone matrix, and osteoblasts are forming a ring on the outer surface of the trabecula. As the osteoblasts lay down bone, the trabeculae increase in size.

Parietal Connective bone tissue Periosteum Ossification center Developing compact bone Superior part Frontal bone Red bone of occipital Ethmoid bone marrow bone Inferior part Nasal bone Trabeculae of occipital bone Maxilla LM 50x Zygomatic bone Temporal bone Mandible 3 A lower magnification than in step 2, with a Vertebrae Cartilage different stain that makes the bone appear of mandible blue, shows the oldest bone in this series. Styloid Sphenoid bone Within the spongy bone are trabeculae (blue) process and developing red bone marrow (pink). 12 weeks Beneath the periosteum is an outer layer of 6-41 developing compact bone.

(1): © Victor Eroschenko; (2): © Dr. Richard Kessel/Visuals Unlimited; (3): © Victor Eroschenko Endochondral Ossification

• Bones of the base of the skull, part of the mandible, epiphyses of the clavicles, and most of remaining bones of skeletal system • Cartilage formation begins at end of fourth week of development • Some ossification beginning at about week eight; some does not begin until 18-20 years of age

6-42 Endochondral Ossification

Uncalcified cartilage Uncalcified Calcified cartilage cartilage

Calcified Perichondrium cartilage Uncalcified Calcified cartilage Periosteum cartilage Calcified Bone collar Perichondrium Primary cartilage Blood vessel ossification Periosteum center Blood vessel Periosteum Bone collar Spongy bone Bone collar Blood vessel Open spaces Medullary to periosteum forming in bone cavity Cartilage Perichondrium Perichondrium

1 Chondroblasts 2 The perichondrium of the 3 A primary ossification center 4 The process of bone collar formation, produce a cartilage diaphysis becomes the forms as blood vessels and cartilage calcification, and spongy bone model that periosteum, and a bone collar is osteoblasts invade the calcified production continues. Calcified cartilage is surrounded by produced. Internally, the cartilage. The osteoblasts lay begins to form in the epiphyses. A perichondrium, except chondrocytes hypertrophy, and down bone matrix, forming medullary cavity begins to form in the where joints will form. calcified cartilage forms. spongy bone. center of the diaphysis.

6-43 Endochondral Ossification

Articular Articular cartilage cartilage Spongy Uncalcified Epiphysis bone cartilage Secondary Spongy Spongy ossification bone Blood vessel bone center Space in Calcified Epiphyseal bone cartilage line Blood vessel Epiphyseal Spongy bone plate Diaphysis Periosteum Bone collar Compact Compact bone bone Blood vessel Medullary Medullary Medullary cavity cavity cavity

7 In a mature bone, the epiphyseal plate 6 The original cartilage model is almost 5 Secondary ossification centers form has become the epiphyseal line, and all completely ossified. Unossified cartilage in the epiphyses of long bones. the cartilage in the epiphysis, except the becomes the epiphyseal plate and the articular cartilage, has become bone. articulazr cartilage.

6-44 6-45 6.6 Bone Growth • Growth in length occurs at the epiphyseal plate • Involves the formation of new cartilage by – Interstitial cartilage growth – Appositional growth on the surface of the cartilage • Closure of epiphyseal plate: epiphyseal plate is ossified becoming the epiphyseal line. Between 12 and 25 years of age • Articular cartilage: does not ossify, and persists through life • Appositional growth only – Interstitial growth cannot occur because matrix is solid – Occurs on old bone and/or on cartilage surface

6-46 Hand Xray: Phalanges Teenager

Epiphyseal plates

Metacarpals

Carpals

Sesamoid bones of thumb Radius Ulna Zones of the Epiphyseal Plate

1 New cartilage is produced on the epiphyseal side of the plate as the chondrocytes divide and form stacks 1 of cells.

2 Chondrocytes Mature and 2 enlarge.

3 Matrix is calcified, and chondrocytes die. 3 4 The cartilage on the diaphyseal side of the plate is 4 replaced by bone. LM400x

Femur

Patella

Epiphysis

Epiphyseal plate

Diaphysis

(a)

Length of bone increases.

1 New cartilage is Thickness of produced on 1 epiphyseal the epiphyseal side Plate remains of the plate as the unchanged. chondrocytes divide and form stacks of cells. Epiphyseal plate Chondrocytes 2 2 Chondrocytes divide and enlarge. Mature and Bone is enlarge. 3 added to diaphysis. 3 Matrix is calcified, Calcified cartilage and chondrocytes . is replaced by bone. die. Boneof diaphysis 4 The cartilage on 4 the diaphyseal side of the plate is (b) replaced by bone.

a: © Ed Reschke/Peter Arnold, Inc./Getty Images; b: © Bio-Photo Assocs/Photo Researchers, Inc. 6-49 Growth at Articular Cartilage

• Increases size of bones with no epiphyses: e.g., short bones • Chondrocytes near the surface of the articular cartilage similar to those in zone of resting cartilage

Osteoblast Ridge 1 Osteoblasts beneath the periosteum lay down bone (dark Groove brown) to form ridges separated by grooves. Blood vessels of the periosteum lie in the grooves.

Blood vessel

Periosteum

2 The groove is transformed into a tunnel when the bone Endosteum built on adjacent ridges meets. The Osteoblast periosteum of the groove becomes the endosteum of the Tunnel tunnel.

Concentric lamella

3 Appositional growth by osteoblasts from the endosteum results in the formation of a new concentric lamella.

4 The production of additional concentric lamellae fills in the tunnel and completes Osteon the formation of the osteon. 6-51 Factors Affecting Bone Growth • Size and shape of a bone determined genetically but can be modified and influenced by nutrition and hormones • Nutrition – Lack of calcium, protein and other nutrients during growth and development can cause bones to be small – Vitamin D • Necessary for absorption of calcium from intestines • Can be eaten or manufactured in the body • Rickets: lack of vitamin D during childhood • Osteomalacia: lack of vitamin D during adulthood leading to softening of bones – Vitamin C • Necessary for collagen synthesis by osteoblasts • Scurvy: deficiency of vitamin C • Lack of vitamin C also causes wounds not to heal, teeth to fall

out 6-52 Factors Affecting Bone Growth

• Hormones – Growth hormone from anterior pituitary. Stimulates interstitial cartilage growth and appositional bone growth – Thyroid hormone required for growth of all tissues – Sex hormones such as estrogen and testosterone • Cause growth at puberty, but also cause closure of the epiphyseal plates and the cessation of growth

6-53 Factors Affecting Bone Growth

6-54 6.7 Bone Remodeling

• Converts woven bone into lamellar bone • Caused by migration of Basic Multicellular Units – Groups of osteoclasts and osteoblasts that remodel bones • Involved in bone growth, changes in bone shape, adjustments in bone due to stress, bone repair, and Ca ion regulation • Relative thickness of bone changes as bone grows. Bone constantly removed by osteoclasts and new bone formed by osteoblasts. • Formation of new osteons in compact bone – Osteoclasts enter the osteon from blood in the central canal and internally remove lamellae. Osteoblasts replace bone – Osteoclasts remove bone from the exterior and the bone is rebuilt

6-55 6.7 Bone Remodeling

Articular cartilage Epiphyseal growth Growth in cartilage surrounding epiphysis

Cartilage replaced by bone Epiphyseal line Bone remodeled

Growth in length Cartilage growth in epiphyseal plate

Cartilage replaced by bone Bone remodeled Bone reabsorption

Growth in diameter Bone addition Bone reabsorption

Growing bone Adult bone 6-56 Mechanical Stress and Bone Strength

• Stress causes bone remodeling to: – Increase bone mass (density) – Align trabeculae with stress • Changes causes by: – Osteoblast activity • Increases with stress

6-57 6.8 Bone Repair 1. Hematoma formation. Localized mass of blood released from blood vessels but confined within an organ or space. Clot formation. 2. Callus formation. Callus: mass of tissue that forms at a fracture site and connects the broken ends of the bone. – Internal- blood vessels grow into clot in hematoma. • Macrophages clean up debris, osteoclasts break down dead tissue, fibroblasts produce collagen and granulation tissue. • Chondroblasts from osteochondral progenitor cells of periosteum and endosteum produce cartilage within the collagen. • Osteoblasts invade. New bone is formed. – External- collar around opposing ends. Periosteal osteochondral progenitor cells  osteoblasts and chondroblasts. Bone/cartilage collar stabilizes two pieces.

6-58 Bone Repair 3. Callus ossification. Callus replaced by woven, spongy bone 4. Bone remodeling. Replacement of spongy bone and damaged material by compact bone. Sculpting of site by osteoclasts

6-59 Bone Repair

Compact bone Medullary Woven cavity bone Periosteum External callus: Dead Hematoma Woven bone bone Cartilage Broken humerus

Internal callus: Compact Dead Fibers and bone at bone cartilage break site Woven bone

Hematoma formation Callus formation Callus ossification Bone remodeling 1 Blood released from 2 The internal callus forms 3 Woven, spongy bone 4 Compact bone replaces Callus around broken damaged blood vessels between the ends of the replaces the internal and woven bone, and part humerus (at arrow) forms a hematoma. bones, and the external external calluses. of the internal callus is callus forms a collar around removed, restoring the (a) the break. medullary cavity.

6-60 6.9 Calcium Homeostasis

• Bone is major storage site for calcium • The level of calcium in the blood depends upon movement of calcium into or out of bone. – Calcium enters bone when osteoblasts create new bone; calcium leaves bone when osteoclasts break down bone – Two hormones control blood calcium levels- parathyroid hormone and calcitonin.

Decreased Increased 5 blood Ca2+ 1 blood Ca2+

Posterior aspect of thyroid gland Parathyroid 1 Decreased blood Ca2+ stimulates PTH glands secretion from parathyroid glands. Kidney Thyroid gland 2 PTH stimulatesosteoclasts to break down bone and release Ca2+ into the blood.

3 In the kidneys, PTH increases Ca2+ reabsorption from the urine. PTH also 3 stimulates active Vitamin D formation. PTH Calcitonin 4 Vitamin D promotes Ca2+ absorption from the small intestine into the blood. 2 6 Increased blood Ca2+ stimulates calcitonin Stimulates Inhibits 5 Vitamin D secretion from the thyroid gland. osteoclasts osteoclasts 6 Calcitonin inhibits osteoclasts, which allows for Bone enhanced osteoblast uptake of Ca2+ from the Osteoclasts blood to deposit into bone. promote Ca2+ Ca2+ uptake from 4 bone. Osteoblasts promote Ca2+ deposition in bone. Small intestine

2+ Ca Blood 6-62 6.10 Effects of Aging on Skeletal System

• Bone matrix decreases. More brittle due to lack of collagen; but also less hydroxyapatite. • Bone mass decreases. Highest around 30. Men denser due to testosterone and greater weight. African Americans and Hispanics have higher bone masses than Caucasians and Asians. Rate of bone loss increases 10 fold after menopause. spongy bone lost first, then compact. • Increased bone fractures • Bone loss causes deformity, loss of height, pain, stiffness – Stooped posture – Loss of teeth

6-63 Bone Fractures • Open (compound)- bone break with open wound. Bone may be sticking out of wound. • Closed (simple)- Skin not perforated. • Incomplete- doesn’t extend across the bone. Complete- does • Greenstick: incomplete fracture that occurs on the convex side of the curve of a bone • Hairline: incomplete where two sections of bone do not separate. Common in skull fractures • Comminuted fractures: complete with break into more than two pieces

6-64 Bone Fractures

• Impacted fractures: one fragment is driven into the spongy portion of the other fragment. • Classified on basis of direction of fracture • Linear • Transverse • Spiral • Oblique • Dentate: rough, toothed, broken ends • Stellate radiating out from a central point.

6-65 Bone Fractures

Comminuted Impacted Linear Spiral

Incomplete Complete Oblique

Transverse

Diaphysis of femur

Fractured epiphyseal plate

Epiphysis of femur Joint cavity Epiphyseal plate Diaphysis of tibia 6-67 © J. M. Booher Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Diseases and Disorders TABLE 6.3

Condition Description

Tumors May be malignant or benign and cause a range of bone defects Growth and Developmental Disorders Gigantism Abnormally small body size due to improper growth at the epiphyseal plates Dwarfsm Abnormally small body size due to improper growth at the epiphyseal plates Osteogenesis imperfecta Brittle bones that fracture easily due to insufficient or abnormal collagen Rickets Growth retardation due to nutritional deficiencies in minerals (Ca2+) or vitamin D; results in bones that are soft, weak, and easily broken Bacterial Infections Osteomyelitis Bone inflammation often due to a bacterial infection that may lead to complete destruction of the bone Tuberculosis Typically, a lung bacterium that can also affect bone Decalcification Osteomalacia Softening of adult bones due to calcium depletion; often caused by vitamin D deficiency Osteoporosis Reduction in overall quantity of bone tissue; see Systems Pathology

Go to www.mhhe.com/seeley10 for additional information on these pathologies.

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