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.