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The Skeletal System

Chapter 7a

Skeletal System

• Introduction• Functions of the skeleton• Framework of bones• The skeleton through life

Functions of the Skeleton

• Support• Protection• Movement• Storage areas

– Minerals– Lipids

• Hemopoiesis– Red marrow

Histology of Bones

• Bone = osseous tissue (connective tissue)• Intercellular substance

– Calcium phosphate crystals– Collagenous fibers

Human Anatomy, 3rd editionPrentice Hall, © 2001

Anatomy of a Long Bone• Diaphysis – shaft• Epiphysis – extremity

of bone• Articular cartilage –

covers epiphysis• Periosteum –

covering around surface of bone

• Medullary cavity –marrow cavity in diaphysis

• Endosteum – lines medullary cavity

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The Periosteum

• Two layers– Outer layer

• Fibrous connective tissue

– Inner layer• Osteoblasts

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The Endosteum

• Single layer– Osteoclasts– Osteoblasts

Human Anatomy, 3rd editionPrentice Hall, © 2001

Structure of Bone Tissue

• Pores– Living cells– Channels for blood vessels– Decrease weight of bone

• Degree of porosity– Spongy bone– Compact bone

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Compact Bone

• Haversian system(Osteon)– Haversian canals– Lacunae– Canaliculi

Human Anatomy, 3rd editionPrentice Hall, © 2001

Spongy Bone• Composed of trabeculae• Penetrated by blood vessels from periosteum

Ossification

• Embryo skeleton– Begins as cartilage & membrane– Bone formation begins about 6 weeks after

fertilization

Ossification

• 1st stage – embryonic cells migrate into future bone sites– Become chondroblasts or– Become osteoblasts

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Endochondral Ossification• Occurs within a hyaline cartilage model• Occurs in most bones of the body• Periosteum forms at about week 8• Calcification begins in center of diaphysis

– Primary ossification center• Secondary ossification centers at

epiphyses• Medullary cavity forms

Endochondral Ossification

Endochondral Ossification Fetus. 10 weeks

Fetus, 16 weeks Remaining Cartilage• Articular cartilage• Epiphyseal plate

– Bone grows in length

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Homeostasis

• Remodeling– Different rates in body– Balance between osteoclasts and osteoblasts

• Factors affecting bone growth– Calcium & phosphorus in diet– Vitamins A, C, & D– Hormones

Fracture Repair

• Hematoma formation• Formation of fibrocartilagenous callus• Formation of bony callus• Remodeling of bony callus

Fracture Repair Disorders• Vitamin deficiencies

– Scurvy– Rickets

• Osteoporosis

Scurvy

http://www.pathguy.com/lectures/nejm_scurvy.gif

Scurvy Blood Vessels

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Rickets

http://bioe.eng.utoledo.edu/adms_staffs/akkus/2003_WEB_PROJECTS/hormone/vitamin_d.htm

Osteoporosis

Human Anatomy, 3rd editionPrentice Hall, © 2001

Organization of the Skeletal SystemAxial skeleton

SkullVertebral columnThoracic cage

Appendicular skeletonPectoral girdleUpper limbsPelvic girdleLower limbs

Human Anatomy, 3rd editionPrentice Hall, © 2001

The Human Skeleton

Human Anatomy, 3rd editionPrentice Hall, © 2001

Skull

– Cranium• Protects brain

– Facial bones• Protect sense organs

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Vertebral Column– Vertebrae

• Cervical• Thoracic• Lumbar• Sacral

– Sacrum– Coccyx– Function

• Protect spinal cord and nerves

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Human Anatomy, 3rd editionPrentice Hall, © 2001

Intervertebral Discs

• Vertebrae– Separated by

intervertebral discs

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The Atlas and Axis

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A Typical Vertebra

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The Sacrum and Coccyx• Sacrum

– Several fused vertebrae

• Coccyx– Rudimentary tailbone

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Thoracic Cage– Ribs (12 pairs)

• Articulate with vertebrae

– Sternum(breastbone)

– Function• Protect underlying

organs

Human Anatomy, 3rd editionPrentice Hall, © 2001

Pectoral Girdle– Scapula (shoulder

blade)– Clavicle (collar bone)– Attached to posterior

ribs and sternum– Function

• Connects bones of arms to axial skeleton

• Aids in arm movements

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Human Anatomy, 3rd editionPrentice Hall, © 2001

Upper Limbs– Humerus– Radius– Ulna– Carpals– Metacarpals– Phalanges

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The Radius and Ulna

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Bones of the Wrist and Hand

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Pelvic Girdle

– Coxal (hip) bones• Ileum• Ischium• Pubis

– Attached to sacrum and coccyx

– Function• Connect bones of

legs to axial skeleton

Human Anatomy, 3rd editionPrentice Hall, © 2001

The Pelvic Girdle

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Lower Limbs– Femur– Tibia– Fibula– Patella– Tarsals– Metatarsals– Phalanges

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The Femur

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Bones of the Lower Leg

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The Patella

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Bones of the Foot