Skeletal SystemSkeletal SystemMr. DiazMr. DiazVMHSVMHS

Lecture 1Lecture 1

The Skeletal SystemThe Skeletal System

►Parts of the skeletal systemParts of the skeletal system Bones (skeleton)Bones (skeleton) JointsJoints

►CartilagesCartilages LigamentsLigaments

►Divided into two divisionsDivided into two divisions Axial skeletonAxial skeleton Appendicular skeletonAppendicular skeleton

Functions of BonesFunctions of Bones

►Support of the bodySupport of the body►Protection of soft organsProtection of soft organs►Movement due to attached skeletal Movement due to attached skeletal

musclesmuscles►Storage of minerals and fatsStorage of minerals and fats►Blood cell formationBlood cell formation

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►HomogeneousHomogeneous

Spongy boneSpongy bone►Small needle-like Small needle-like

pieces of bonepieces of bone►Many open spacesMany open spaces

Figure 5.2b

Classification of Bones on the Classification of Bones on the Basis of ShapeBasis of Shape

Figure 5.1

Classification of BonesClassification of Bones

►Long bonesLong bones Typically longer than wideTypically longer than wide Have a shaft with heads at both endsHave a shaft with heads at both ends Contain mostly compact boneContain mostly compact bone

►Examples: Femur, humerusExamples: Femur, humerus

Classification of BonesClassification of Bones

►Short bonesShort bones Generally cube-shapeGenerally cube-shape Contain mostly spongy boneContain mostly spongy bone

►Examples: Carpals, tarsalsExamples: Carpals, tarsals

Classification of BonesClassification of Bones

►Flat bonesFlat bones Thin and flattenedThin and flattened Usually curvedUsually curved Thin layers of compact bone around a Thin layers of compact bone around a

layer of spongy bonelayer of spongy bone►Examples: Skull, ribs, sternumExamples: Skull, ribs, sternum

Classification of BonesClassification of Bones

► Irregular bonesIrregular bones Irregular shapeIrregular shape Do not fit into other bone classification Do not fit into other bone classification

categoriescategories►Example: Vertebrae and hipExample: Vertebrae and hip

Classification of Bones on the Classification of Bones on the Basis of ShapeBasis of Shape

Figure 5.1

Gross Anatomy of a Long Gross Anatomy of a Long BoneBone

►DiaphysisDiaphysis ShaftShaft Composed of Composed of

compact bonecompact bone

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

spongy bonespongy bone

Figure 5.2a

Structures of a Long BoneStructures of a Long Bone

► PeriosteumPeriosteum Outside covering of Outside covering of

the diaphysisthe diaphysis Fibrous connective Fibrous connective

tissue membranetissue membrane►Sharpey’s fibersSharpey’s fibers

Secure periosteum to Secure periosteum to underlying boneunderlying bone

►ArteriesArteries Supply bone cells with Supply bone cells with

nutrientsnutrients

Figure 5.2c

Structures of a Long BoneStructures of a Long Bone

►Articular cartilageArticular cartilage Covers the Covers the

external surface of external surface of the epiphysesthe epiphyses

Made of hyaline Made of hyaline cartilagecartilage

Decreases friction Decreases friction at joint surfacesat joint surfaces

Figure 5.2a

Structures of a Long BoneStructures of a Long Bone

►Medullary cavityMedullary cavity Cavity of the shaftCavity of the shaft Contains yellow Contains yellow

marrow (mostly fat) marrow (mostly fat) in adultsin adults

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

Figure 5.2a

Bone MarkingsBone Markings

►Surface features of bonesSurface features of bones►Sites of attachments for muscles, Sites of attachments for muscles,

tendons, and ligamentstendons, and ligaments►Passages for nerves and blood vesselsPassages for nerves and blood vessels►Categories of bone markingsCategories of bone markings

Projections and processes – grow out from Projections and processes – grow out from the bone surfacethe bone surface

Depressions or cavities – indentationsDepressions or cavities – indentations

►http://www.youtube.com/watch?v=Nc5IRj3OJhE

Microscopic Anatomy of BoneMicroscopic Anatomy of Bone

►Osteon (Haversian System)Osteon (Haversian System) A unit of boneA unit of bone

►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

Microscopic Anatomy of BoneMicroscopic Anatomy of Bone

Figure 5.3

Microscopic Anatomy of BoneMicroscopic Anatomy of Bone

► LacunaeLacunae Cavities containing Cavities containing

bone cells (osteocytes)bone cells (osteocytes) Arranged in concentric Arranged in concentric

ringsrings

► LamellaeLamellae Rings around the Rings around the

central canalcentral canal Sites of lacunaeSites of lacunae

Detail of Figure 5.3

Microscopic Anatomy of BoneMicroscopic Anatomy of Bone

►Canaliculi Canaliculi Tiny canalsTiny canals Radiate from the Radiate from the

central canal to central canal to lacunaelacunae

Form a transport Form a transport systemsystem

Detail of Figure 5.3

Changes in the Human Changes in the Human SkeletonSkeleton

► In embryos, the skeleton is primarily In embryos, the skeleton is primarily hyaline cartilagehyaline cartilage

►During development, much of this During development, much of this cartilage is replaced by bonecartilage is replaced by bone

►Cartilage remains in isolated areasCartilage remains in isolated areas Bridge of the noseBridge of the nose Parts of ribsParts of ribs JointsJoints

Bone GrowthBone Growth

►Epiphyseal plates allow for growth of Epiphyseal plates allow for growth of long bone during childhoodlong bone during childhood New cartilage is continuously formedNew cartilage is continuously formed Older cartilage becomes ossifiedOlder cartilage becomes ossified

►Cartilage is broken downCartilage is broken down►Bone replaces cartilageBone replaces cartilage

Bone GrowthBone Growth

►Bones are remodeled and lengthened Bones are remodeled and lengthened until growth stopsuntil growth stops Bones change shape somewhatBones change shape somewhat Bones grow in widthBones grow in width

Long Bone Formation and Long Bone Formation and GrowthGrowth

Figure 5.4a

Long Bone Formation and Long Bone Formation and GrowthGrowth

Figure 5.4b

Types of Bone CellsTypes of Bone Cells

►OsteocytesOsteocytes Mature bone cellsMature bone cells

►OsteoblastsOsteoblasts Bone-forming cellsBone-forming cells

►OsteoclastsOsteoclasts Bone-destroying cellsBone-destroying cells Break down bone matrix for remodeling and Break down bone matrix for remodeling and

release of calciumrelease of calcium► Bone remodeling is a process by both Bone remodeling is a process by both

osteoblasts and osteoclastsosteoblasts and osteoclasts