Musculoskeletal System - Bone Development
The mesoderm forms nearly all the connective tissues of the musculoskeletal system, except within the head where neural crest also contributes connective tissues. Each tissue (cartilage, bone, and muscle) goes through many different mechanisms of differentiation.
The 2 key developmental processes are the initial "patterning" of bone location and then the overt "differentiation" of bone through the process of ossification.
Bone is formed through a lengthy process involving ossification of a cartilage formed from mesenchyme. Two main forms of ossification occur in different bones, intramembranous (eg skull) and endochondrial (eg limb long bones) ossification. Ossification continues postnatally, through puberty until mid 20s. Early ossification occurs at the ends of long bones.
The two major parts of the human skeleton are the axial (80 bones in skull, vertebra, ribs, sternum) and appendicular (126 bones in limbs, shoulders, pelvis) skeletons.
Musculoskeletal and limb abnormalities are one of the largest groups of congenital abnormalities.
- Musculoskeletal Links: Introduction | Mesoderm | Somitogenesis | Limb | Cartilage | Bone | Bone Timeline | Axial Skeleton | Skull | Joint | Muscle | Tendon | Diaphragm | Lecture - Musculoskeletal Development | Abnormalities | Limb Abnormalities | Cartilage Histology | Bone Histology | Skeletal Muscle Histology | Category:Musculoskeletal
Some Recent Findings
Adult Human Skeleton
- The Developing Human: Clinically Oriented Embryology (8th Edition) by Keith L. Moore and T.V.N Persaud - Moore & Persaud Chapter 15 the skeletal system
- Larsen’s Human Embryology by GC. Schoenwolf, SB. Bleyl, PR. Brauer and PH. Francis-West - Chapter 11 Limb Dev (bone not well covered in this textbook)
- Before we Are Born (5th ed.) Moore and Persaud Chapter 16,17: p379-397, 399-405
- Essentials of Human Embryology Larson Chapter 11 p207-228
- Identify the components of a somite and the adult derivatives of each component.
- Give examples of sites of (a) endochondral and (b) intramembranous ossification and to compare these two processes.
- Identify the general times (a) of formation of primary and (b) of formation of secondary ossification centres, and (c) of fusion of such centres with each other.
- Briefly summarise the development of the limbs.
- Describe the developmental abnormalities responsible for the following malformations: selected growth plate disorders; congenital dislocation of the hip; scoliosis; arthrogryposis; and limb reduction deformities.
Below is a very brief overview using simple figures of 3 aspects of early musculoskeletal development. More detailed overviews are shown on other notes pages Mesoderm and Somite, Vertebral Column, Limb in combination with serial sections and Carnegie images.
- Secondary ossification centres develop in the cartilage epiphysis of the long bones.
- No medulary cavity forms in a secondary ossification center.
- Appears late in fetal development.
- Used as a marker for term development if a secondary ossification centre present in either: head of femur, head of tibia, of head of humerus.
- The last secondary centre to appear is the clavical medial epiphysis, that does not develop until 18 or 20 years.
- Diaphysis - shaft
- Epiphysis - expanded ends
- Metaphysis - connecting region (between diaphysis and epiphysial line)
- Medullary Cavity - (marrow) cavity within the bone. Can also be identified as either red or yellow marrow.
- (dense) no spaces or hollows in the bone matrix visible to the eye.
- forms the thick-walled tube of the shaft (or diaphysis) of long bones, which surrounds the marrow cavity (or medullary cavity). A thin layer of compact bone also covers the epiphyses of long bones.
- (cancellous or spongy bone) consists of delicate bars (spicules) and sheets of bone, trabeculae
- branch and intersect to form a sponge-like network
- ends of long bones (or epiphyses) consist mainly of trabecular bone.
Connective tissue covering the surface of bone (except articular surfaces).
Connective tissue lining inner surface of bone.
- Appositional growth occurs at either the periosteum (outer surface), or the endosteum (inner surface).
- Osteoblasts secrete osteoid, a pre-bone material composed mainly of type I collagen that becomes mineralized.
- Early bone matrix deposited in development and during repair is woven rather than lamellar in appearance and structure.
- In development, there are 2 distinct types of bone formation (intramembranous and endochondral)
- derive from osteogenic stem cells the osteoprogenitor cells that differentiate to form pre-osteoblast then osteoblasts maturing to an osteocyte
- osteoprogenitor cells - "resting cell" line the inner and outer surfaces of bone
- mature bone-forming cells embedded in lacunae within the bone matrix
- osteoblasts and osteocytes - secrete organic matrix of bone (osteoid), converted into osteocytes when become embedded in matrix (which calcifies soon after deposition)
- bone-resorbing multinucleated macrophage-like cells
- origin- fusion of monocytes or macrophages, Blood macrophage precursor, Attach to bone matrix
- seal a small segment of extracellular space (between plasma membrane and bone surface), HCl and lysosomes secreted into this space by osteoclasts dissolves calcium phosphate crystals (give bone rigidity and strength)
- Resorptive bay - (Howship's lacuna) shallow bay lying directly under an osteoclast.
- do not mistake for megakaryocytes, found in bone marrow not associated with bone matrix.
- megakaryocytes are also multi-niucleated and form platelets
- red marrow - mainly haematopoietic (myeloid) tissue, newborn has all red marrow
- yellow marrow - mainly fat cells, found in diaphysis region of long bones
- stromal cells - all other support cells not involved in haematopoiesis
- Links: Blood Development
The bone matrix has 2 major components.
- Organic portion composed of mainly collagen Type 1 (about 95%) and amorphous ground substance.
- Inorganic portion (50% dry weight of the matrix) composed of hydroxyapatite crystals, calcium, phosphorus, bicarbonate, nitrate, Mg, K, Na.
- storage calcium and phosphate
- regulate blood calcium levels
- also called osteons
- Volkmann's canals - interconnect Haversian systems
- concentric - surrounding each Haversian System
- interstitial - bony plates that fill in between the haversian systems.
- circumferential - layers of bone that underlie the periosteum and endosteum
- osteocytes extending cytoplasmic processes into canaliculi
- Additional Histology images: low | medium | high
See also Bone Histology
- Links: Blue Histology - endochondral | Dev Biology - endochondral ossification | endochondral ossification animation
See also Bone Histology
Human Fetal Head (12 week)
The transcription factors Runx2 and Runx3 are essential for chondrocyte maturation, while Runx2 and Osterix are essential for osteoblast differentiation.
Osterix (OSX) encodes a transcription factor containing three Cys2-His2 zinc-finger DNA-binding domains at its C terminus that has been shown to be essential for bone formation.
Osteogenesis Imperfecta (OI, brittle bone disease) originally described as a collagen 1 gene mutation, but can have several different genetic causes and can be classified into eight different types (I-VIII).
- COL1A1 and COL1A2 mutations
- CRTAP and LEPRE1 mutations, in severe/lethal and recessively inherited osteogenesis imperfecta
- ↑ Antonella Galli, Dimitri Robay, Marco Osterwalder, Xiaozhong Bao, Jean-Denis Bénazet, Muhammad Tariq, Renato Paro, Susan Mackem, Rolf Zeller Distinct roles of Hand2 in initiating polarity and posterior Shh expression during the onset of mouse limb bud development. PLoS Genet.: 2010, 6(4);e1000901 PMID:20386744 | PMC2851570 | PLoS Genet.
- ↑ Jay R Shapiro, Paul D Sponsellor Osteogenesis imperfecta: questions and answers. Curr. Opin. Pediatr.: 2009, 21(6);709-16 PMID:19907330
Yingzi Yang Skeletal morphogenesis during embryonic development. Crit. Rev. Eukaryot. Gene Expr.: 2009, 19(3);197-218 PMID:19883365
E J Mackie, Y A Ahmed, L Tatarczuch, K-S Chen, M Mirams Endochondral ossification: how cartilage is converted into bone in the developing skeleton. Int. J. Biochem. Cell Biol.: 2008, 40(1);46-62 PMID:17659995
Search April 2010
- Musculoskeletal System Development - All (44637) Review (5065) Free Full Text (6601)
- Musculoskeletal Development - All (44637) Review (5065) Free Full Text (6601)
External Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name.
- Virtual Slidebox of Histology (USA) Skeletal system
- e-radiography Ossification
- UWA Blue Histology bone
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Cite this page:
Hill, M.A. (2013) Musculoskeletal System - Bone Development. Retrieved June 19, 2013, from http://php.med.unsw.edu.au/embryology/index.php?title=Musculoskeletal_System_-_Bone_Development
- Dr Mark Hill 2013, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G