skeletal system part 1
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The Skeletal System
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The Skeletal SystemParts of the skeletal system
Bones (skeleton)JointsCartilagesLigaments
Two subdivisions of the skeletonAxial skeletonAppendicular skeleton
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Functions of BonesSupport the bodyProtect soft organsAllow movement due to attached skeletal
musclesStore minerals and fatsBlood cell formation
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Bones of the Human BodyThe adult skeleton has 206 bonesTwo basic types of bone tissue
Compact boneHomogeneous
Spongy boneSmall needle-like
pieces of boneMany open spaces
Figure 5.2b
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Classification of Bones on the Basis of Shape
Figure 5.1
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Classification of BonesLong bones
Typically longer than they are wideHave a shaft with heads at both endsContain mostly compact boneExample:
FemurHumerus
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Classification of Bones
Figure 5.1a
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Classification of BonesShort bones
Generally cube-shapeContain mostly spongy boneExample:
CarpalsTarsals
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Classification of Bones
Figure 5.1b
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Classification of BonesFlat bones
Thin, flattened, and usually curvedTwo thin layers of compact bone surround a
layer of spongy boneExample:
SkullRibsSternum
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Classification of Bones
Figure 5.1c
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Classification of BonesIrregular bones
Irregular shapeDo not fit into other bone classification
categoriesExample:
Vertebrae Hip bones
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Classification of Bones
Figure 5.1d
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Anatomy of a Long BoneDiaphysis
ShaftComposed of compact bone
Epiphysis Ends of the boneComposed mostly of spongy bone
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Anatomy of a Long BonePeriosteum
Outside covering of the diaphysisFibrous connective tissue membrane
Sharpey’s fibersSecure periosteum to underlying bone
ArteriesSupply bone cells with nutrients
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Anatomy of a Long Bone
Figure 5.2c
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Anatomy of a Long BoneArticular cartilage
Covers the external surface of the epiphysesMade of hyaline cartilageDecreases friction at joint surfaces
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Anatomy of a Long BoneEpiphyseal plate
Flat plate of hyaline cartilage seen in young, growing bone
Epiphyseal lineRemnant of the epiphyseal plateSeen in adult bones
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Anatomy of a Long Bone
Figure 5.2a
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Anatomy of a Long BoneMedullary cavity
Cavity inside of the shaftContains yellow marrow (mostly fat) in adultsContains red marrow (for blood cell
formation) in infants
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Anatomy of a Long Bone
Figure 5.2a
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Bone MarkingsSurface features of bones
Sites of attachments for muscles, tendons, and ligaments
Passages for nerves and blood vesselsCategories of bone markings
Projections or processes—grow out from the bone surface
Depressions or cavities—indentations
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Bone Markings
Table 5.1 (1 of 2)
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Bone Markings
Table 5.1 (2 of 2)
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Microscopic Anatomy of BoneOsteon (Haversian system)
A unit of bone containing central canal and matrix rings
Central (Haversian) canalOpening in the center of an osteonCarries blood vessels and nerves
Perforating (Volkman’s) canalCanal perpendicular to the central canalCarries blood vessels and nerves
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Microscopic Anatomy of Bone
Figure 5.3a
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Microscopic Anatomy of BoneLacunae
Cavities containing bone cells (osteocytes)Arranged in concentric rings
LamellaeRings around the central canalSites of lacunae
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Microscopic Anatomy of Bone
Figure 5.3b–c
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Microscopic Anatomy of BoneCanaliculi
Tiny canalsRadiate from the central canal to lacunaeForm a transport system connecting all bone
cells to a nutrient supply
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Formation of the Human SkeletonIn embryos, the skeleton is primarily
hyaline cartilageDuring development, much of this cartilage
is replaced by boneCartilage remains in isolated areas
Bridge of the noseParts of ribsJoints
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Bone Growth (Ossification)Epiphyseal plates allow for lengthwise
growth of long bones during childhoodNew cartilage is continuously formedOlder cartilage becomes ossified
Cartilage is broken downEnclosed cartilage is digested away, opening up a
medullary cavityBone replaces cartilage through the action of
osteoblasts
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Bone Growth (Ossification)Bones are remodeled and lengthened until
growth stopsBones are remodeled in response to two
factorsBlood calcium levelsPull of gravity and muscles on the skeleton
Bones grow in width (called appositional growth)
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Long Bone Formation and Growth
Figure 5.4a
Bone startingto replacecartilage
Epiphysealplatecartilage
Articularcartilage
Spongybone
In a childIn a fetusIn an embryo
New boneforming
Growthin bonewidth
Growthin bonelength
Epiphysealplate cartilage
New boneforming
Bloodvessels
Hyalinecartilage
New center ofbone growth
Medullarycavity
Bone collarHyalinecartilagemodel
(a)
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Long Bone Formation and Growth
Figure 5.4b
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Types of Bone CellsOsteocytes—mature bone cellsOsteoblasts—bone-forming cellsOsteoclasts—bone-destroying cells
Break down bone matrix for remodeling and release of calcium in response to parathyroid hormone
Bone remodeling is performed by both osteoblasts and osteoclasts