Chapter 7Chapter 7

Skeleton & Skeletal Skeleton & Skeletal StructureStructure

FunctionFunctionSupport – provide surfaces for

anchoring soft organs.Protection – skull, ribs,

vertebraeMovement – anchor muscles;

joints are pivot places, bones are levers

Storage – fat, minerals (Ca, P, K, Na, S, Mg, Cu,); 2/3 of bone weight

Hematopoiesis – red marrow makes RBC’s, WBC’s, platelets in adults; liver & spleen in infants

CLASSIFICATIONCLASSIFICATIONType of bone

tissue:

–Compact – dense & smooth

–Spongy (cancellous) – open spaces with “girders”

Compact

Spongy

Trabeculae – Trabeculae – “girders”“girders”

ShapeShape–Long bonesLong bones – (femur, humerus,

phalanges, etc.); compact; shaft w/2 ends; act as levers

–Short bonesShort bones – (carpals, tarsals); cube-like

»often embedded in joints to articulate tendons

»spongy w/compact on surface

»bones glide across one another in multiple directions

–Flat bonesFlat bones (cranium, ribs, shoulder)

» protect soft organs

»provide for large muscle attachment

»2 compact bone surfaces w/spongy in between

Structure of a Flat BoneStructure of a Flat Bone External and External and

internal surfaces internal surfaces composed of composed of compact bonecompact bone

Middle layer is Middle layer is spongy bone and spongy bone and bone marrowbone marrow

Skull fracture may Skull fracture may leave inner layer of leave inner layer of compact bone compact bone unharmedunharmed

–IrregularIrregular (bones of the inner skull, vertebrae, hip)

»varied for articulation with muscles, tendons, and ligaments

STRUCTURE (Gross)STRUCTURE (Gross)DiaphysisDiaphysis – – shaft

–cylinder of compact bone

–Covered with periosteum

Medullary cavityMedullary cavity – – center of bone–yellow marrow found

here (fat)–Lined with endosteum

Epiphysis – ends of long bones– spongy with red

marrow– covered by

compact bone and hyaline cartilage

– Epiphyseal disk (plate) – ends of long bones; covered in hyaline cartilage, points of growth; replaced by bone at time of growth = epiphyseal line

– Predictable growth rates

Endosteum – membrane lining the inside of shaft; contains:–Osteoblasts –

bone forming cells on the outside

–Osteoclasts – bone resorption cells on the inside

Periosteum – outer membrane on the diaphysis

Articular Cartilage – ends of articulating long bones; cushions and absorbs stress

Nutrient Formina – holes for blood vessels and nerves

Structure of a Structure of a Long BoneLong Bone

Compact and Compact and spongy bonespongy bone

Marrow cavityMarrow cavity Articular Articular

cartilagecartilage PeriosteumPeriosteum

                                   

STRUCTURE (Microscopic)STRUCTURE (Microscopic)Haversian system

(osteon) – structural unit of bone; consists of:–Hard bone matrix

arranged in rings (lamellae)

–Central canal (Haversian canal) through which vessels run

– Volkmann’s canals – perpendicular to Haversian canals; connects nerves and blood vessels to periosteum

– Osteocytes – spider-shaped; lie in lacunae

– Canaliculi – canals that link lacunae to each other and to Haversian canals

Blood Vessels of BoneBlood Vessels of Bone

Spongy – consists of trabeculae (fibers)–Irregularly arranged lamellae

and osteocytes–No osteon present

Spongy Bone Structure and StressSpongy Bone Structure and Stress

CHEMICAL COMPOSITIONCHEMICAL COMPOSITIONOrganic

–contributes to bone structure

–helps resist stretch and twist forces (tensile strength)

–1/3 of bone matrix is organic

–consists of: proteoglycans, glycoproteins, and collagen. Material is secreted by osteoblasts

Inorganic– 2/3 of bone weight

– contributes to bone hardness (compression strength)

– Mineral salts (Ca3PO4, CaOH2, CaCO3)

– Can resist 25,000 lb/in2 of compression and 15,000 lb/in2 of tension

– Lasts well past death

Low calcium = porous bones

Bone GrowthBone Growth Pts of skeleton begin to form within first Pts of skeleton begin to form within first

few weeks of prenatal developmentfew weeks of prenatal development

BONE GROWTHBONE GROWTHLongitudinal Growth (length)

–Chondroblasts slow their growth at the distal end of the epiphysis

–The chondroblasts are replaced by osteocytes

–Growth stops when the epiphyseal plates fuse with the bone; occurs in late adolescence

Appositional growth (diameter)– Thickness can continue with stress

from excessive muscle activity and/or body weight;

– accomplished through the antagonistic actions of osteoclasts and osteoblasts

Animation:Animation:Bone Growth in WidthBone Growth in Width

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Hormonal Regulation

–Human Growth Hormone – stimulates mitosis at epiphyseal plates

–Sex hormones – causes growth spurts; molds male and female skeletons»Girls grow faster than boys and reach full height earlier (estrogen stronger effect)

»Boys grow longer and taller

»Use of anabolic steroids causes growth plate to close prematurely

–Hypo- or hypersecretions – can cause “gigantism” or “dwarfism”

DwarfismDwarfism AchondroplasiaAchondroplasia

– long bones stop growing long bones stop growing in childhoodin childhood

» normal torso, short normal torso, short limbslimbs

– spontaneous mutation spontaneous mutation during DNA replicationduring DNA replication

– failure of cartilage failure of cartilage growthgrowth

Pituitary Pituitary

– lack of growth hormonelack of growth hormone

– normal proportions with normal proportions with short statureshort stature

REMODELINGREMODELING Occurs at the tissue level, not at the

cellular level as in other systems Deposition and Resorption results in

remodeling Unequal by area – for example the

femur is replaced every 5-6 months

Deposition –occurs at an area of

stress or breakage–Osteoblasts put bone

material down on the outside surface of the bone

–Dental braces reposition teeth and remodel bone through pressure variances

–Abnormal calcification Abnormal calcification (ectopic) may occur in (ectopic) may occur in lungs, brain, eyes, muscles, lungs, brain, eyes, muscles, tendons or arteries tendons or arteries (arteriosclerosis)(arteriosclerosis)

Resorption – Osteoclasts absorb bone material from the inside of the bone

Control

–Hormonal through a negative feedback mechanism

–PTH (parathyroid hormone) is released when calcium levels in the blood are low

–This causes osteoclast activity to increase

–When Ca+ levels rise, osteoclast activity ceases

–Calcitonin is released when Ca+ levels are high; this inhibits bone resorption and stimulates osteoblasts to put bone material down on the outside of the bone.

–When Ca+ levels fall, calcitonin release is stopped

–This mechanism balances Ca+ levels in the blood.

–Calcium needed in neurons, Calcium needed in neurons, muscle contraction, blood clotting muscle contraction, blood clotting and exocytosisand exocytosis» ~1100g in adult skeleton~1100g in adult skeleton»plasma concentration is ~ 10 plasma concentration is ~ 10 mg/dL mg/dL

Hormonal Control of Calcium BalanceHormonal Control of Calcium Balance

PTH and calcitonin maintain normal PTH and calcitonin maintain normal blood calcium concentration.blood calcium concentration.

Ca+ is absorbed from food in the intestines in the presence of activated Vitamin D.

Abnormal softness Abnormal softness (rickets) in children (rickets) in children and (osteomalacia) in and (osteomalacia) in adults without adults without vitamin Dvitamin D

Mechanical/gravity/stress causes remodeling

–Wolff’s law »bone grows or remodels in response to forces or stress

»stress causes minute electrical currents to be produced in the bone

»currents accelerate osteoblast activity

»thus the use of exercise for those with osteoporosis.

–Hormones determine whether or when remodeling occurs

–Mechanical stress determines where remodeling occurs.

REPAIRREPAIRRequired when trauma, pathology has

occurredFracture – treated by “reduction”

–Closed reduction – manipulation of ends of bones outside the skin to align ends

–Open reduction – requires surgery and wires/pins

–Traction – risks long-term confinement

Types of Bone FracturesTypes of Bone Fractures

FracturesFractures

Phases of Repair1. Hematoma formation – blood clot; cells die (hours)

2. Callus formation – forms soft tissue then a callus; capillaries grow, phagocytes eat up callus (days)

3. Bony Callus formation – from the migration of osteoblast and osteoclasts to site of injury (6-8 weeks)

4. Remodeling – callus completely removed – (months)

Healing of Fractures Healing of Fractures

Fractures and Their RepairsFractures and Their Repairs

PATHOLOGYPATHOLOGY OsteoporosisOsteoporosis

– disease in which resorption outpaces disease in which resorption outpaces deposition deposition

– Results in porous, light bonesResults in porous, light bones– Risk of hip, wrist, vertebral fracturesRisk of hip, wrist, vertebral fractures– Complications with pneumonia and Complications with pneumonia and

blood clotsblood clots

–Postmenopausal white women Postmenopausal white women at greater risk (30% loss by at greater risk (30% loss by age 70)age 70)

–Black women rarely suffer Black women rarely suffer symptomssymptoms

–caused by a number of factorscaused by a number of factors» decrease in estrogen levels decrease in estrogen levels (estrogen inhibits resorption)(estrogen inhibits resorption)

»low bone stress (lack of exercise)low bone stress (lack of exercise)»inadequate Ca+ and protein inadequate Ca+ and protein consumptionconsumption

»abnormal Vit. D synthesis, abnormal Vit. D synthesis, malabsorption of Ca+malabsorption of Ca+

–TreatmentTreatment

»EEstrogenstrogen R Replacementeplacement T Therapyherapy – slows – slows resorption, but may increase resorption, but may increase cancer risks, stroke, heart cancer risks, stroke, heart diseasedisease

»PTH (Fosamax, Boniva)PTH (Fosamax, Boniva)

»Prevention – exercise, Prevention – exercise, calcium intakecalcium intake

Animation: OsteoporosisAnimation: Osteoporosis

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Osteomalacia–Soft bones–Inadequate

mineralization–Little Ca+

absorption–Called “Ricketts” in

children – usually due to malnutrition

Paget’s Disease

–Excessive absorption and deposition in inappropriate places

–Causes deformities due to the high rate of spongy/compact bone

–Skull, spine, femur and pelvis are common sites

–May be an autoimmune disease with viral triggers

Paget’s Paget’s DiseaseDisease

Chapter 9Chapter 9JointsJoints

Joints are Joints are designed to designed to

secure bones secure bones and, in many and, in many cases, provide cases, provide

movementmovement

ClassificationClassificationStructural:Structural:

–Fibrous Fibrous – – »bones joined by bones joined by fibrous tissue (ligament)fibrous tissue (ligament)

»having no joint cavityhaving no joint cavity»most provide no movementmost provide no movement»Ex: bones of skull, tibia with Ex: bones of skull, tibia with fibula.fibula.

–CartilaginousCartilaginous – – »joints united by joints united by cartilage;cartilage;

»having no joint cavity;having no joint cavity;»provides provides minimal minimal movement;movement;

»Ex: ribs and Ex: ribs and sternum, sternum, pubis of pubis of pelvispelvis

– SynovialSynovial – –

»articulating bones are separated by articulating bones are separated by a fluid filled joint cavitya fluid filled joint cavity

»surrounded by surrounded by a sac (bursa)a sac (bursa)

» freely moveablefreely moveable»stability stability

influenced by influenced by articular articular surfaces, surfaces, ligaments and ligaments and muscle tone.muscle tone.

FunctionalFunctional

–SynarthrosisSynarthrosis – immovable – immovable–Amphiarthrosis Amphiarthrosis

– slightly – slightly moveablemoveable

–DiarthrosisDiarthrosis – – freely movablefreely movable

Types of Synovial Joints Types of Synovial Joints (structural plan)(structural plan)

PlanePlane – intercarpal, intertarsal, – intercarpal, intertarsal, vertebrae – slipping or sliding in vertebrae – slipping or sliding in all directionsall directions

HingeHinge – elbow, knee, – elbow, knee, interphalangeal, one plane interphalangeal, one plane of motion, round end fits in of motion, round end fits in concave surfaceconcave surface

PivotPivot – atlas an axis with head – atlas an axis with head to indicate “no”to indicate “no”

CondyloidCondyloid – radiocarpal, – radiocarpal, metacarpophalangeal, metacarpophalangeal, (“knuckle”), (“knuckle”), atlantooccipitalatlantooccipital

SaddleSaddle – thumb – more – thumb – more freedom of movementfreedom of movement

Ball-and-socketBall-and-socket – shoulder – shoulder and hip and hip

Types of Synovial Movements Types of Synovial Movements (functional)(functional)

GlidingGliding – plane joint – plane jointFlexionFlexion – bending that – bending that

decreases joint angle and decreases joint angle and brings bones together brings bones together (“dorsiflexion” of the foot(“dorsiflexion” of the foot

ExtensionExtension – opposite of – opposite of flexion (“plantarflexion” of flexion (“plantarflexion” of the foot, hyperextension of the the foot, hyperextension of the head)head)

AbductionAbduction – move away, arm or leg – move away, arm or leg laterally or up, spreading fingerslaterally or up, spreading fingers

AdductionAdduction – opposite of abduction, – opposite of abduction, move towardsmove towards

CircumductionCircumduction – flexion, – flexion, extension, and abduction extension, and abduction together in a cone shape together in a cone shape movement (thumb movement)movement (thumb movement)

RotationRotation – turning of bone around – turning of bone around its own axis (arm or leg)its own axis (arm or leg)

SupinationSupination – radius around ulna – radius around ulna (palms up)(palms up)

PronationPronation – – opposite of opposite of supination supination (palms down)(palms down)

InversionInversion – sole of foot turned – sole of foot turned mediallymedially

EversionEversion – opposite of – opposite of inversion, sole of foot faces inversion, sole of foot faces laterallylaterally

ProtractionProtraction – jutting your jaw – jutting your jaw or squaring your shouldersor squaring your shoulders

RetractionRetraction – opposite of – opposite of protractionprotraction

ElevationElevation – shrug your – shrug your shouldersshoulders

DepressionDepression – dropping your – dropping your jawjaw

ArthritisArthritis (osteoarthritis, rheumatoid) – (osteoarthritis, rheumatoid) – – a wearing down of bone surfaces in a a wearing down of bone surfaces in a

joint cavityjoint cavity

Pathologies

– Causes extreme pain, swelling, and Causes extreme pain, swelling, and deformitydeformity

GoutGout – – – accumulation of uric acid crystals accumulation of uric acid crystals

in the joints (usually in the feet)in the joints (usually in the feet)

Bursitis/tendonitisBursitis/tendonitis – – – inflammation of the bursa sac and/or inflammation of the bursa sac and/or

associated tendonsassociated tendons

–requires rest and/or anti-requires rest and/or anti-inflammatoriesinflammatories

Infected bursitis

DislocationDislocation – separation of – separation of bones within a joint cavitybones within a joint cavity

Sprain/strainSprain/strain – – tendons/ligamentstendons/ligaments

Kyphosis – humped curvature of the spine

Scoliosis – lateral curvature of the spine

Lordosis – “Sway back”