BIO 202 Lecture Notes - Lecture 3: Neurotransmitter, Coagulation, Extracellular Fluid
Bones and Skeletal Tissues
Bone Development
-Ossification (osteogenesis)
oProcess of bone tissue formation
oFormation of bony skeleton
Begins in 2nd month of development
oPostnatal bone growth
Until early adulthood
oBone remodeling and repair
Lifelong
- 2 types of ossification
oEndochondral ossification
Bone forms by replacing hyaline cartilage
Bones called cartilage (endochondral) bones
Forms most of skeleton
Forms most all bones inferior to base of skull
Except clavicles
Begins late in 2nd month of development
Uses hyaline cartilage models
Requires breakdown of hyaline cartilage prior to ossification
of shaft
Blood vessel infiltration of perichondrium converts it to periosteum
underlying cells change to osteoblasts
Bone collar forms around diaphysis of cartilage model
Central cartilage in diaphysis calcifies, then develops cavities
Periosteal bud invades cavities formation of spongy bone
Diaphysis elongates & medullary cavity forms
Epiphyses ossify
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oIntramembranous ossification
Bone develops from fibrous membrane
Bones called membrane bones
Forms flat bones, e.g. clavicles and cranial bones
Forms frontal, parietal, occipital, temporal bones, and clavicles
Begins within fibrous connective tissue membranes formed by mesenchymal
cells
Ossification centers appear
Osteoid is secreted
Woven bone and periosteum form
Lamellar bone replaces woven bone & red marrow appears
Postnatal Bone Growth
oInterstitial (longitudinal) growth
Increase in length of long bones
oAppositional growth
Increase in bone thickness
Growth in Length of Long Bones
- Interstitial growth
- Requires presence of epiphyseal cartilage
- Epiphyseal plate maintains constant thickness
oRate of cartilage growth on one side balanced by bone replacement on other
- Concurrent remodeling of epiphyseal ends to maintain proportion
- Result of five zones within cartilage
oResting (quiescent) zone
oProliferation (growth) zone
oHypertrophic zone
oCalcification zone
oOssification (osteogenic) zone
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- Resting (quiescent) zone
oCartilage on epiphyseal side of epiphyseal plate
oRelatively inactive
- Proliferation (growth) zone
oCartilage on diaphysis side of epiphyseal plate
oRapidly divide pushing epiphysis away from diaphysis lengthening
- Hypertrophic zone
oOlder chondrocytes closer to diaphysis and their lacunae enlarge and erode
interconnecting spaces
- Calcification zone
oSurrounding cartilage matrix calcifies, chondrocytes die and deteriorate
- Ossification zone
oChondrocyte deterioration leaves long spicules of calcified cartilage at epiphysis-
diaphysis junction
oSpicules eroded by osteoclasts
oCovered with new bone by osteoblasts
oUltimately replaced with spongy bone
oNear end of adolescence chondroblasts divide less often
oEpiphyseal plate thins then is replaced by bone
oEpiphyseal plate closure
Bone lengthening ceases
Requires presence of cartilage
Bone of epiphysis and diaphysis fuses
Females – about 18 years
Males – about 21 years
Growth in Width
- Appositional Growth
- Allows lengthening bone to widen
- Occurs throughout life
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Document Summary
Ossification (osteogenesis: process of bone tissue formation, formation of bony skeleton. Begins in 2nd month of development: postnatal bone growth. Until early adulthood: bone remodeling and repair. Forms most all bones inferior to base of skull. Requires breakdown of hyaline cartilage prior to ossification of shaft. Blood vessel infiltration of perichondrium converts it to periosteum underlying cells change to osteoblasts. Bone collar forms around diaphysis of cartilage model. Central cartilage in diaphysis calcifies, then develops cavities. Periosteal bud invades cavities formation of spongy bone. Forms flat bones, e. g. clavicles and cranial bones. Forms frontal, parietal, occipital, temporal bones, and clavicles. Begins within fibrous connective tissue membranes formed by mesenchymal cells. Lamellar bone replaces woven bone & red marrow appears. Increase in length of long bones: appositional growth. Epiphyseal plate maintains constant thickness: rate of cartilage growth on one side balanced by bone replacement on other. Concurrent remodeling of epiphyseal ends to maintain proportion.
