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Bone TissueBone TissueDr. Gary MumaughDr. Gary Mumaugh

Function of BonesFunction of Bones SupportSupport – form the framework that supports the body and cradles soft organs – form the framework that supports the body and cradles soft organs ProtectionProtection – provide a protective case for the brain, spinal cord, and vital organs – provide a protective case for the brain, spinal cord, and vital organs MovementMovement – provide levers for muscles – provide levers for muscles Mineral storage Mineral storage – reservoir for minerals, especially calcium and phosphorus– reservoir for minerals, especially calcium and phosphorus Blood cell formationBlood cell formation – hematopoiesis occurs within the marrow cavities of bones– hematopoiesis occurs within the marrow cavities of bones

Gross Anatomy of BoneGross Anatomy of Bone

Classification of BonesClassification of Bones Axial skeleton Axial skeleton – bones of the skull, vertebral column, and rib cage– bones of the skull, vertebral column, and rib cage Appendicular skeletonAppendicular skeleton – bones of the upper and lower limbs, shoulder, and hip– bones of the upper and lower limbs, shoulder, and hip

Shape of BonesShape of Bones Long bonesLong bones Short bonesShort bones Flat bonesFlat bones Irregular bonesIrregular bones

Long BonesLong Bones

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Long bones – longer than they are wide Long bones – longer than they are wide Humerus, radius, ulnaHumerus, radius, ulna Femur, tibia, fibulaFemur, tibia, fibula

Structure of Long BonesStructure of Long Bones DiaphysisDiaphysis

o Tubular shaft that forms the axis of long bones EpiphysesEpiphyses

oo Expanded ends of long bonesoo Joint surface is covered with articular (hyaline) cartilageoo Epiphyseal line separates the diaphysis from the epiphyses

Short BonesShort Bones Short bonesShort bones

oo Bones of the wrist and ankleoo Bones that form within tendons

(e.g., patella)

Flat BonesFlat Bones

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Flat bones – thin, flattened, and a bit curved (e.g., sternum, and most skull bones)Flat bones – thin, flattened, and a bit curved (e.g., sternum, and most skull bones)

Irregular BonesIrregular Bones Irregular bones – bones with complicated shapes (e.g., vertebrae and hip bones)Irregular bones – bones with complicated shapes (e.g., vertebrae and hip bones)

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Bone MembranesBone Membranes Periosteum – double-layered protective membranePeriosteum – double-layered protective membrane

o Outer fibrous layer is dense regular connective tissueo Richly supplied with nerve fibers, blood, and lymphatic vessels, which enter

the bone via nutrient foramina Endosteum – delicate membrane covering internal surfaces of boneEndosteum – delicate membrane covering internal surfaces of bone

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Bone MarrowBone Marrow bone marrow – general term for soft tissuebone marrow – general term for soft tissue

that occupies the marrow cavity of a longthat occupies the marrow cavity of a long bone and small spaces amid thebone and small spaces amid the trabeculae of spongy bonetrabeculae of spongy bone

red marrow red marrow oo in nearly every bone in a childin nearly every bone in a childoo hemopoietic tissue - produceshemopoietic tissue - produces

blood cells blood cells oo in adults, found in skull, vertebrae,in adults, found in skull, vertebrae,

ribs, sternum, part of pelvic girdle,ribs, sternum, part of pelvic girdle, and proximal heads of humerus andand proximal heads of humerus and femurfemur

yellow marrow found in adultsyellow marrow found in adultsoo most red marrow turns into fatty yellow marrowmost red marrow turns into fatty yellow marrowoo no longer produces bloodno longer produces blood

Bone DevelopmentBone Development ossification or osteogenesis – theossification or osteogenesis – the

formation of boneformation of bone in the human fetus and infant,in the human fetus and infant,

bone develops by two methods:bone develops by two methods:oo intramembranous ossificationintramembranous ossificationoo endochondral ossification endochondral ossification

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Bone Growth and RemodelingBone Growth and Remodeling ossification continues throughout life with the growth and remodeling of bonesossification continues throughout life with the growth and remodeling of bones bones grow in two directions: length and widthbones grow in two directions: length and width bone elongation bone elongation

oo epiphyseal plate – a region of transition from cartilage to boneepiphyseal plate – a region of transition from cartilage to bone functions as growth zone where the bones elongatefunctions as growth zone where the bones elongate consists of typical hyaline cartilage in the middleconsists of typical hyaline cartilage in the middle with a transition zone on each side where cartilage is being replaced with a transition zone on each side where cartilage is being replaced

by boneby bone

Factors Affecting Bone GrowthFactors Affecting Bone Growth HeredityHeredity NutritionNutrition

o Calcium, phosphorus, protein, Vitamin D, A, C HormonesHormones Exercise or “stress”Exercise or “stress”

Without bones becoming weight bearing, they lose calcium

Hormonal Regulation of Bone Growth During YouthHormonal Regulation of Bone Growth During Youth During infancy and childhood, epiphyseal plate activity is stimulated by growth During infancy and childhood, epiphyseal plate activity is stimulated by growth

hormonehormone During puberty, testosterone and estrogens: During puberty, testosterone and estrogens:

oo IInitially promote adolescent growth spurtsoo Cause masculinization and feminization of specific parts of the skeletonoo Later induce epiphyseal plate closure, ending longitudinal bone growth

Importance of Ionic Calcium in the BodyImportance of Ionic Calcium in the Body Calcium is necessary for:Calcium is necessary for:

oo Transmission of nerve impulsesoo Muscle contractionoo Blood coagulationoo Secretion by glands and

nerve cellsoo Cell division

Response to Mechanical StressResponse to Mechanical Stress Wolff’s law – a bone grows orWolff’s law – a bone grows or

remodels in response to the forcesremodels in response to the forces or demands placed upon itor demands placed upon it

Observations supporting Wolff’s lawObservations supporting Wolff’s law includeinclude

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oo Long bones are thickest midway along the shaft (where bending stress is greatest)

oo Curved bones are thickest where they are most likely to buckleBone Fractures (Breaks)Bone Fractures (Breaks) Bone fractures are classified by:Bone fractures are classified by:

oo The position of the bone ends after fractureoo The completeness of the breakoo The orientation of the bone to the long axisoo Whether or not the bones ends penetrate the skin

Types of Bone FracturesTypes of Bone Fracturesoo Compound (open) – bone ends penetrate the skinCompound (open) – bone ends penetrate the skinoo Simple (closed) – bone ends do not penetrate the skinSimple (closed) – bone ends do not penetrate the skinoo Greenstick – incomplete fracture where one side of the bone breaks and the Greenstick – incomplete fracture where one side of the bone breaks and the

other side bends; common in childrenother side bends; common in childrenoo Comminuted – bone fragments into three or more pieces; common in the Comminuted – bone fragments into three or more pieces; common in the

elderlyelderlyoo Compression – bone is crushed; common in porous bonesCompression – bone is crushed; common in porous bones

Stages in the Healing of a Bone FractureStages in the Healing of a Bone Fracture Hematoma formationHematoma formation A A

oo Torn blood vessels hemorrhageoo A mass of clotted blood (hematoma) forms at the fracture siteoo Site becomes swollen, painful, and inflamed

Fibrocartilaginous callus formsFibrocartilaginous callus forms BB Bony callus formationBony callus formation CC

oo Bone callus begins 3-4 weeks after injury, and continues until firm union is formed 2-3 months later

Bone remodelingBone remodeling DDoo Excess material on the bone shaft exterior and in the medullary canal is

removedoo Compact bone is laid down to reconstruct shaft walls

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Homeostatic ImbalancesHomeostatic Imbalances OsteomalaciaOsteomalacia

oo Bones are inadequately mineralized causing softened, weakened bonesoo Main symptom is pain when weight is put on the affected boneoo Caused by insufficient calcium in the diet, or by vitamin D deficiency

RicketsRicketsoo Bones of children are inadequately mineralized causing softened, weakened

bonesoo Bowed legs and deformities of the pelvis, skull, and rib cage are commonoo Caused by insufficient calcium in the diet, or by vitamin D deficiency

OsteopeniaOsteopeniaoo Normal bone demineralization seen after 35-40 years old

OsteoporosisOsteoporosisoo Spongy bone of the spine is most

vulnerableoo Occurs most often in

postmenopausal womenoo Bones become so fragile that

sneezing or stepping off a curb can cause fractures

oo Osteoporosis TreatmentOsteoporosis Treatment Calcium and vitamin DCalcium and vitamin D

supplementssupplements 1200 mg. of calcium

per day Increased weight-Increased weight-

bearing exercisebearing exercise Hormone (estrogen)Hormone (estrogen)

replacement therapy (HRT) slows bone lossreplacement therapy (HRT) slows bone loss Natural progesterone cream prompts new bone growthNatural progesterone cream prompts new bone growth

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