The Skeletal System
The Skeletal System
Reporter: Ronald L. Rubi
ELAINE N. MARIEBEIGHTH EDITION5
Copyright 2006 Pearson Education, Inc., publishing as Benjamin
CummingsPowerPoint Lecture Slide Presentation by Jerry L. Cook, Sam
Houston University
ESSENTIALSOF HUMANANATOMY& PHYSIOLOGYPART A
Divided into two divisionsAxial skeletonAppendicular
skeletonParts of the skeletal systemBones
(skeleton)JointsCartilagesLigaments
The Skeletal System
Functions of the BonesSupport of the bodyProtection of soft
organsMovement due to attached skeletal musclesStorage of minerals
and fatsBlood cell formation
The adult skeleton has 206 bonesTwo basic types of osseous
tissueCompact boneIs dense and looks smoothHomogenousSpongy
boneSmall needle-like pieces of boneMany open spaces
Classification of Bones
Classification of Bones on the Basis of Shape
Long bonesTypically longer than wideHave a shaft with heads at
both endsContain mostly compact boneExamples: Femur,
humerusClassification of Bones
Short bonesGenerally cube-shapeContain mostly spongy
boneExamples: Carpals, tarsals
Classification of Bones
Flat bonesThin and flattenedUsually curvedThin layers of compact
bone around a layer of spongy boneExamples: Skull, ribs,
sternum
Classification of Bones
Irregular bonesIrregular shapeDo not fit into other bone
classification categoriesExample: Vertebrae and hip
Classification of Bones
Gross Anatomy of a Long Bone
DiaphysisShaftComposed of compact boneEpiphysis Ends of the
boneComposed mostly of spongy bone
Structures of a Long BonePeriosteumOutside covering of the
diaphysisFibrous connective tissue membraneSharpeys fibersSecure
periosteum to underlying boneArteriesSupply bone cells with
nutrients
Articular cartilageCovers the external surface of the
epiphysesMade of hyaline cartilageDecreases friction at joint
surfaces
Structures of a Long Bone
Medullary cavityCavity of the shaftContains yellow marrow
(mostly fat) in adultsContains red marrow (for blood cell
formation) in infants
Structures of a Long Bone
Bone MarkingsSurface features of bonesSites of attachments for
muscles, tendons, and ligamentsPassages for nerves and blood
vesselsCategories of bone markingsProjections and processes grow
out from the bone surfaceDepressions or cavities indentations
Osteon (Haversian System)A unit of boneCentral (Haversian)
canalOpening in the center of an osteonCarries blood vessels and
nervesPerforating (Volkmans) canalCanal perpendicular to the
central canalCarries blood vessels and nervesMicroscopic Anatomy of
Bone
Microscopic Anatomy of Bone
Microscopic Anatomy of BoneLacunaeCavities containing bone cells
(osteocytes)Arranged in concentric ringsLamellaeRings around the
central canalSites of lacunae
Microscopic Anatomy of BoneCanaliculi Tiny canalsRadiate from
the central canal to lacunaeForm a transport system
Bone Formation, Growth and RemodelingIn embryos, the skeleton is
primarily hyaline cartilageDuring development, much of this
cartilage is replaced by boneCartilage remains in isolated
areasBridge of the noseParts of ribsJoints
Bone Formation, Growth and RemodelingOssification is the process
of bone formationIt involves two major phases:First, the hyaline
cartilage model is completely covered with bone matrix by bone
forming cells called osteoblasts.Then, the enclosed hyaline
cartilage model is digested away, opening up a medullar cavity
within the newly formed bone.
Long Bone Formationand Growth
How do bones widen?Osteoblasts in the periosteum add bone to the
external face of the diaphysis as osteoclasts in the endosteum
remove bone from the inner face of the diaphysis wall.Appositional
growth- The process by which the bones increase in diameter.
Formation and Growth of Long Bones
Bones are remodelled continually in response changes in two
factors:Calcium levels in the bloodThe pull of gravity and muscles
on the skeleton.
OsteocytesMature bone cellsOsteoblastsBone-forming
cellsOsteoclastsBone-destroying cellsBreak down bone matrix for
remodeling and release of calciumBone remodeling is a process by
both osteoblasts and osteoclastsTypes of Bone Cells
Is essential if bones are retain normal proportions and strength
during long-bone growth as the body increases in size and
weight.Bones become thicker and form large projections to increase
their strength in areas where bulky muscles are attached.Bone
Remodeling
A break in a boneTypes of bone fracturesClosed (simple)
fracture- break that does not penetrate the skin.Open (compound)
fracture- broken bone penetrates through the skinBone fractures are
treated by reduction or immobilizationRealignment of the boneBone
Fractures
Bone Fractures
Type of Bone Fractures
Hematoma (blood-filled swelling) is formed.Break is splinted by
fibrocartilage to form a callus.Fibrocartilage callus is replaced
by a bony callusBony callus is remodeled to form a permanent
patch.Repair of Bone Fractures
3. The bony callus formsAs the more osteoblasts and osteoclasts
migrate into the area and multiply, the fibrocartilage callus is
gradually replaced by one made of spongy bone the bony callus.4.
Bone remodeling occursOver the next few weeks or months, the bony
callus is remodeled in response to the mechanical stressed placed
on it and it forms a strong permanent patch at the fracture
sight.
Axial SkeletonForms the longitudinal axis of the bodyDivided
into three parts:SkullVertebral columnBony thorax
The SkullTwo sets of bonesCraniumFacial bonesBones are joined by
suturesOnly the mandible is attached by a freely movable joint.
CraniumThe boxlike cranium is composed of eight large flat
bones.Frontal Bone- forms the forehead, the bony projections under
the eyebrows and the superior part of each eyes orbit.Parietal
Bones- form most of the superior and lateral walls of the cranium.
They meet in the midline of the skull at the sagittal suture and
form the coronal suture, where they meet the frontal bone.
CraniumTemporal Bone- it lies inferior to the parietal bones;
they join them at the squamous sutures.Occipital Bone- the most
posterior part of the cranium. It forms the floor and black wall of
the skull.Sphenoid Bone- the butterfly-shaped sphenoid bone spans
the width of the skull and forms part of the floor of the cranial
cavity.
CraniumEthmoid Bone- is very irregularly shaped and lies
anterior to the sphenoid. It forms the roof of the nasal cavity and
part of the medial walls of the orbits.