Unit 5: The Skeletal Unit 5: The Skeletal SystemSystem

Ch. 7Ch. 7

General OrganizationGeneral Organization206 bones*206 bones*

Axial Skeleton – down Axial Skeleton – down the centerthe center

Skull Skull Cranium – 8Cranium – 8 Facial – 14Facial – 14 Middle Ear - 6Middle Ear - 6

Vertebral ColumnVertebral Column Cervical – 7Cervical – 7 Thoracic – 12Thoracic – 12 Lumbar – 5Lumbar – 5 Sacrum, CoccyxSacrum, Coccyx

Thoracic Cage Thoracic Cage 12 pairs12 pairs

7 true ribs7 true ribs 5 False 5 False

RibsRibs 2 2

floatinfloatingg ribs ribs

Appendicular Skeleton – the appendagesAppendicular Skeleton – the appendages Pectoral GirdlePectoral Girdle

Scapula – 2Scapula – 2 Clavicle – 2Clavicle – 2

Upper LimbsUpper Limbs Humerus – 2Humerus – 2 Radius – 2Radius – 2 Ulna – 2Ulna – 2 Carpals – 16Carpals – 16 Metacarpals – 10Metacarpals – 10 Phalanges – 28Phalanges – 28

Pelvic GirdlePelvic Girdle Coxal – 2Coxal – 2

Lower LimbsLower Limbs Femur – 2Femur – 2 Patella – 2Patella – 2 Tibia – 2Tibia – 2 Fibula – 2Fibula – 2 Tarsals – 14Tarsals – 14 Metatarsal 10Metatarsal 10 Phalanges - 28Phalanges - 28

Types of BonesTypes of Bones Long – cartoon boneLong – cartoon bone

Expanded endsExpanded ends Longer than wideLonger than wide Humerus, femur, finger bones Humerus, femur, finger bones

Short – boxy or cube-likeShort – boxy or cube-like Carpals, tarsalsCarpals, tarsals

Flat – platelikeFlat – platelike Ribs, scapula, sternumRibs, scapula, sternum

Irregular – variety of shapesIrregular – variety of shapes Vertebrae, many facial bonesVertebrae, many facial bones

Sesamoid – found in joints for stabilitySesamoid – found in joints for stability Patella (knee cap)Patella (knee cap)

Wormian (sutural) – extra bones in skull where Wormian (sutural) – extra bones in skull where cranial bones meetcranial bones meet

Bone Structure:Bone Structure: Macroscopic Structure – Long boneMacroscopic Structure – Long bone

Epiphyses – expanded endsEpiphyses – expanded ends Articular Cartilge – hyaline; protection in jointsArticular Cartilge – hyaline; protection in joints

Diaphysis – shaftDiaphysis – shaft Medullary Cavity – hollow portion containing marrowMedullary Cavity – hollow portion containing marrow Periosteum – outer coveringPeriosteum – outer covering Endosteum – inner coveringEndosteum – inner covering

Types of boneTypes of bone Compact – dense for strengthCompact – dense for strength

outerouter OsteonsOsteons

Spongy – light, airySpongy – light, airy innerinner Reduce weightReduce weight TrabeculaeTrabeculae

Bone Structure:Bone Structure: Microscopic – CompactMicroscopic – Compact

Osteon – Repeating unitOsteon – Repeating unit BullseyeBullseye

Osteonic (Haversion Canal)Osteonic (Haversion Canal) CentralCentral Blood vessels, nervesBlood vessels, nerves

Lamellae – concentric circles of matrixLamellae – concentric circles of matrix Osteocytes – mature bone cellsOsteocytes – mature bone cells

LacunaeLacunae CanaliculiCanaliculi

Transverse (perforating/ Volkmann’s) CanalTransverse (perforating/ Volkmann’s) Canal Connects osteonic canalsConnects osteonic canals

Bone Structure:Bone Structure:

Spongy - cancellousSpongy - cancellous Trabeculae – bony platesTrabeculae – bony plates

Osteocytes found hereOsteocytes found here

Bone Growth and Bone Growth and DevelopmentDevelopment

Skeletal Formation AnimationSkeletal Formation Animation OssificationOssification – formation of bone – formation of bone

OsteoblastOsteoblast – deposit solid mineral matrix – deposit solid mineral matrix Turn into Turn into osteoclastsosteoclasts – mature bone cells – mature bone cells

Endochondral Bone FormationEndochondral Bone Formation Most common; arise from hyaline cartilageMost common; arise from hyaline cartilage Periosteum forms; deposit bone underneath – Periosteum forms; deposit bone underneath –

outside of bone firstoutside of bone first Primary ossification center – center of Primary ossification center – center of

diaphysisdiaphysis Ossification moves towards endsOssification moves towards ends

Secondary Ossification Center – EpiphysesSecondary Ossification Center – Epiphyses Mainly spongy bone developsMainly spongy bone develops

Bone Growth and Bone Growth and DevelopmentDevelopment

Epiphyseal Disk – growth plateEpiphyseal Disk – growth plate Area between the two ossification centers that Area between the two ossification centers that

remains cartilageremains cartilage Does not ossifiy until adulthoodDoes not ossifiy until adulthood 4 layers of cells 4 layers of cells

Cartilage cells continue to divide, mature, ossify and dieCartilage cells continue to divide, mature, ossify and die Move toward ends of boneMove toward ends of bone

Intramembranous Ossification – bone Intramembranous Ossification – bone formation between two sheets of connective formation between two sheets of connective tissuetissue Generally in flat bones of skullGenerally in flat bones of skull

Factors Affecting Bone GrowthFactors Affecting Bone Growth Diet – what you eatDiet – what you eat

Minerals such as calcium, phosphatesMinerals such as calcium, phosphates Vitamin D – needed for proper absorption of calciumVitamin D – needed for proper absorption of calcium

Rickets/ osteomalacia – lack of vit. D; soft bonesRickets/ osteomalacia – lack of vit. D; soft bones Dehydrocholesterol – inactive form; activated by sunlight in the Dehydrocholesterol – inactive form; activated by sunlight in the

skinskin Vitamin A & CVitamin A & C

Vit. A – bone resorptionVit. A – bone resorption Lack causes retardation in developmentLack causes retardation in development

Vit. C – collagen synthesisVit. C – collagen synthesis Hormones – chemical messengers from glandsHormones – chemical messengers from glands

Human Growth Hormone – pituitary; stimulates growth of Human Growth Hormone – pituitary; stimulates growth of epiphyseal diskepiphyseal disk

Dwarfism, gigantism, achondroplasia, acromegalyDwarfism, gigantism, achondroplasia, acromegaly Thyroid hormone – thyroid; replace cartilage with boneThyroid hormone – thyroid; replace cartilage with bone Male and Female Sex HormonesMale and Female Sex Hormones

Physical Stress – exercisePhysical Stress – exercise Tug of tendons cause bones to thicken and strengthenTug of tendons cause bones to thicken and strengthen

Skeletal Functions:Skeletal Functions: Support and ProtectionSupport and Protection Body Movement – lever actionsBody Movement – lever actions

11stst class – EF, F, RF class – EF, F, RF TricepsTriceps

22ndnd class – F, RF, EF class – F, RF, EF MandibleMandible

33rdrd Class – F, EF, RF Class – F, EF, RF BicepBicep

Blood Cell Formation – HematopoiesisBlood Cell Formation – Hematopoiesis Marrow – hematopoietic tissueMarrow – hematopoietic tissue

Found in medullary cavity of long bones (young); Found in medullary cavity of long bones (young); spongy bone spaces (older)spongy bone spaces (older)

Red – blood cell formationRed – blood cell formation Yellow – fat storageYellow – fat storage

Can be converted back and forth as neededCan be converted back and forth as needed

Skeletal Functions:Skeletal Functions: Hemocytoblast – blood stem cellHemocytoblast – blood stem cell

Erythrocyte – red blood cellErythrocyte – red blood cell Leukocyte – white blood cellLeukocyte – white blood cell Thrombocyte – plateletThrombocyte – platelet

Inorganic Salt StorageInorganic Salt Storage Electrolytes needed for a variety of Electrolytes needed for a variety of

physiological functionsphysiological functions CaCa++++ needed for nerve impulse conduction, skeletal needed for nerve impulse conduction, skeletal

muscle contractionmuscle contraction Negative FeedbackNegative Feedback

Blood Ca levels too high: Thyroid releases Calcitonin Blood Ca levels too high: Thyroid releases Calcitonin osteoblast activity; deposit calcium in bone osteoblast activity; deposit calcium in bone

Blood Ca levels too low: Parathyroid release Blood Ca levels too low: Parathyroid release parathyroid hormone parathyroid hormone Osteoclast activity; dissolve Osteoclast activity; dissolve bone, release minerals into bloodbone, release minerals into blood