Chapter 5 – The Skeletal SystemChapter 5 – The Skeletal System

Support the bodySupport the body

Protect soft organsProtect soft organs

Allow movement due Allow movement due to attached skeletal to attached skeletal musclesmuscles

Store minerals and Store minerals and fatsfats

Blood cell formationBlood cell formation

The Skeletal SystemThe Skeletal System

Parts of the skeletal systemParts of the skeletal system– Bones (skeleton)Bones (skeleton)– JointsJoints– CartilagesCartilages– LigamentsLigaments

Two subdivisions of the skeletonTwo subdivisions of the skeleton– Axial skeletonAxial skeleton– Appendicular skeletonAppendicular skeleton

Bones of the Human BodyBones of the Human Body

The adult skeleton has 206 bonesThe adult skeleton has 206 bones

Two basic types of bone tissueTwo basic types of bone tissue– Compact boneCompact bone

– Spongy boneSpongy bone

Classification of Bones Based of ShapeClassification of Bones Based of Shape

Classification of BonesClassification of Bones

Long bonesLong bones– Typically longer than Typically longer than

they are widethey are wide– Have a shaft with Have a shaft with

heads at both endsheads at both ends– Contain mostly Contain mostly

compact bonecompact bone– ExampleExample::

FemurFemur

HumerusHumerus

Shaft

Classification of BonesClassification of Bones

Short bonesShort bones– Generally cube-shapeGenerally cube-shape– Contain mostly Contain mostly

spongy bonespongy bone– ExampleExample::

CarpalsCarpals

TarsalsTarsals

Classification of BonesClassification of Bones

Flat bonesFlat bones– Thin, flattened, and Thin, flattened, and

usually curvedusually curved– Two thin layers of Two thin layers of

compact bone compact bone surround a layer of surround a layer of spongy bonespongy bone

– ExampleExample: : SkullSkull

RibsRibs

SternumSternum

Classification of BonesClassification of Bones

Irregular bonesIrregular bones– Irregular shapeIrregular shape– Do not fit into other Do not fit into other

bone classification bone classification categoriescategories

– ExampleExample: : Vertebrae Vertebrae

Hip bonesHip bones

Anatomy of a Long BoneAnatomy of a Long Bone

DiaphysisDiaphysis– ShaftShaft– Composed of compact Composed of compact

bonebone

Epiphysis Epiphysis – Ends of the boneEnds of the bone– Composed mostly of Composed mostly of

spongy bonespongy bone

Anatomy of a Long BoneAnatomy of a Long Bone

PeriosteumPeriosteum– Outside covering of Outside covering of

the diaphysis (shaft)the diaphysis (shaft)– Fibrous connective Fibrous connective

tissue membranetissue membrane

Anatomy of a Long BoneAnatomy of a Long Bone

Articular cartilageArticular cartilage– Covers the external surface of the epiphysesCovers the external surface of the epiphyses– Made of hyaline cartilageMade of hyaline cartilage– Decreases friction at joint surfacesDecreases friction at joint surfaces

Anatomy of a Long BoneAnatomy of a Long Bone

Epiphyseal plateEpiphyseal plate– Flat plate of hyaline cartilage seen in young, Flat plate of hyaline cartilage seen in young,

growing bone (a.k.a. = growth plate)growing bone (a.k.a. = growth plate)

Epiphyseal lineEpiphyseal line– Remnant of the epiphyseal plateRemnant of the epiphyseal plate– Seen in adult bonesSeen in adult bones

Anatomy of a Long BoneAnatomy of a Long Bone

Medullary cavity Medullary cavity – Cavity inside of the Cavity inside of the

shaftshaft– Contains yellow Contains yellow

marrow (mostly fat) in marrow (mostly fat) in adultsadults

– Contains red marrow Contains red marrow (for blood cell (for blood cell formation) in infantsformation) in infants

Bone MarkingsBone Markings

Surface features of bonesSurface features of bones– Sites of attachments for muscles, tendons, Sites of attachments for muscles, tendons,

and ligamentsand ligaments– Passages for nerves and blood vesselsPassages for nerves and blood vessels

Categories of bone markingsCategories of bone markings– Projections or processesProjections or processes — grow out from the — grow out from the

bone surfacebone surface– Depressions or cavitiesDepressions or cavities — indentations — indentations

Bone Surface MarkingsBone Surface Markingsprojections where muscles, tendons, ligaments attachprojections where muscles, tendons, ligaments attach

– tuberosity – tuberosity – large rounded projectionlarge rounded projection

– spinous process (or spine) – spinous process (or spine) – sharp,sharp, slender, pointed projectionslender, pointed projection

– trochanter – trochanter – very large, bluntvery large, blunt irregular shaped projectionirregular shaped projection

– crest – crest – narrow ridge of bonenarrow ridge of bone

Bone Surface MarkingsBone Surface Markings

Projections that help to form Projections that help to form jointsjoints– Head – Head – bony expansionbony expansion at the end of a long neckat the end of a long neck– Facet – Facet – smooth, almostsmooth, almost flat surfaceflat surface– Condyle – Condyle – rounded rounded

projectionprojection

– Ramus – Ramus – armlike arm of armlike arm of bonebone

Bone Surface MarkingsBone Surface MarkingsDepressions and openings for blood vessels Depressions and openings for blood vessels and nerves to pass throughand nerves to pass through– Foramen – Foramen – round orround or

oval opening in a boneoval opening in a bone– Meatus – Meatus – canal-likecanal-like

– Fossa – Fossa – shallow depressionshallow depression

mostly to form a jointmostly to form a joint

Microscopic Anatomy of BoneMicroscopic Anatomy of Bone

Osteon (Haversian system)Osteon (Haversian system)– A unit of bone containing central canal and A unit of bone containing central canal and

matrix ringsmatrix rings

Central (Haversian) canalCentral (Haversian) canal– Opening in the center of an osteonOpening in the center of an osteon– Carries blood vessels and nervesCarries blood vessels and nerves

Perforating (Volkman’s) canalPerforating (Volkman’s) canal– Canal perpendicular to the central canalCanal perpendicular to the central canal– Carries blood vessels and nervesCarries blood vessels and nerves

Microscopic Anatomy of BoneMicroscopic Anatomy of Bone

Figure 5.3a

Microscopic Anatomy of BoneMicroscopic Anatomy of Bone

LacunaeLacunae– Cavities containing bone cells (osteocytes)Cavities containing bone cells (osteocytes)– Arranged in concentric ringsArranged in concentric rings

LamellaeLamellae– Rings around the central canalRings around the central canal– Sites of lacunaeSites of lacunae

Microscopic Anatomy of BoneMicroscopic Anatomy of Bone

Figure 5.3b–c

Microscopic Anatomy of BoneMicroscopic Anatomy of Bone

Canaliculi Canaliculi – Tiny canalsTiny canals– Radiate from the central canal to lacunaeRadiate from the central canal to lacunae– Form a transport system connecting all bone Form a transport system connecting all bone

cells to a nutrient supplycells to a nutrient supply

Microscopic Anatomy of BoneMicroscopic Anatomy of Bone

Figure 5.3b

Types of Bone CellsTypes of Bone Cells

Osteocytes—mature bone cellsOsteocytes—mature bone cells

Osteoblasts—bone-forming cellsOsteoblasts—bone-forming cells

Osteoclasts—bone-destroying cellsOsteoclasts—bone-destroying cells– Break down bone matrix for remodeling and Break down bone matrix for remodeling and

release of calcium in response to parathyroid release of calcium in response to parathyroid hormonehormone

Bone remodeling is performed by both Bone remodeling is performed by both osteoblasts and osteoclastsosteoblasts and osteoclasts