Make your own free website on Tripod.com

 

Osseous Tissue and Skeletal Structure

 


The Skeletal System: An Introduction

The skeletal system includes

      Bones of the skeleton

      Cartilages, ligaments and other connective tissues that stabilize and connect

 

Functions of the skeletal system

      Support

      Storage of minerals and lipids

      Blood cell production

      Protection

      Leverage


A Classification of Bones

Bone shapes

      Long

      Flat

      Short

      Irregular

      Sesamoid

      Sutural

 

Bone structure = two types of bone

      Compact bone (dense)

      Spongy bone (cancellous)

 

A typical long bone includes

      Diaphysis

      Epiphyses

      Metaphysis

      Articular cartilage

      Marrow cavity

    Filled with red or yellow marrow

 

Bone Histology

Osseous tissue

      Supporting tissue with a solid matrix

    Crystals of hydroxyapatite

      Minerals deposited in lamellae

      Covered by periosteum

 

Cells in bone:

      Osteocytes = mature bone cells

    In lacunae

    Connected by canaliculi

      Osteoblasts synthesize new matrix

    Osteogenesis

      Osteoclasts dissolve bone matrix

    Osteolysis

      Osteoprogenitor cells differentiate into osteoblasts

 

Compact bone and spongy bone

      Basic unit of compact bone is an osteon

    Osteocytes arranged around a central canal

    Perforating canals extend between adjacent osteons

      Spongy bone contains trabeculae

 

Bones and stress

      Compact bone located where stresses are limited in direction

      Spongy bone located where stresses are weaker or multi-directional

 

Bones are:

      Covered by periosteum

      Lined by endosteum

 

Bone development and growth

      Ossification = converting other tissue to bone

      Calcification = depositing calcium salts within tissues

 

Osseous Tissue and Skeletal Structure

Intramembranous ossification

      Begins with osteoblast differentiation

      Dermal bones produced

      Begins at ossification center

 

Figure 6.7 Intramembranous Ossification

Endochondral ossification

      Cartilage model gradually replaced by bone at metaphysis

    Increasing bone length

      Timing of epiphyseal closure differs

      Appositional growth increases bone diameter

Osseous Tissue and Skeletal Structure


The Dynamic Nature of Bone

continually changing

      Remodeling

      Exercise

      Hormone levels

    Growth hormone and thyroxine increase bone mass

    Calcitonin and PTH control blood calcium levels

 

The skeleton is a calcium reserve

      99% bodys calcium in the skeleton

      Calcium ion concentration maintained by bones GI tract and kidneys

      Calcitonin and PTH regulate blood calcium levels

    Calcitonin decreases blood calcium levels

    PTH increases blood calcium levels

 

Fracture repair

      Fracture hematoma

      External callus

 

Internal callus


Bone Markings (Surface Features)

Bone markings

      Are characteristic for each bone and each individual

      Markings include

    Elevations

    Projections

    Depressions

    Grooves and tunnels


Aging and the Skeletal System

Effects of aging include

      Osteopenia

      Osteoporosis