Bone Development

From Embryology
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Endochondral bone.jpg

Our adult skeleton forms from a larger number of developmental elements that are replaced and fuse. In development there are 2 separate signaling pathways for pattern formation and the formation of bone itself. Furthermore bone formation can be divided into 2 specific forms that occur in anatomically different regions. This practical class will describe the development and structure of bone and finish with a study of abnormalities associated with bone.

The image shown to the left shows a histological section through the developing lower limb at the level of a developing joint (knee), surrounding the developing bone are skeletal muscles and connective tissue of the limb.

For more development background see the Science Lecture - Musculoskeletal Development and notes on Bone Development.

New 2011 page - Bone Histology

Musculoskeletal Links: Introduction | mesoderm | somitogenesis | limb | cartilage | bone | bone timeline | bone marrow | shoulder | pelvis | axial skeleton | skull | joint | skeletal muscle | muscle timeline | tendon | diaphragm | Lecture - Musculoskeletal | Lecture Movie | musculoskeletal abnormalities | limb abnormalities | developmental hip dysplasia | cartilage histology | bone histology | Skeletal Muscle Histology | Category:Musculoskeletal
Historic Embryology - Musculoskeletal  
1853 Bone | 1885 Sphenoid | 1902 - Pubo-femoral Region | Spinal Column and Back | Body Segmentation | Cranium | Body Wall, Ribs, and Sternum | Limbs | 1901 - Limbs | 1902 - Arm Development | 1906 Human Embryo Ossification | 1906 Lower limb Nerves and Muscle | 1907 - Muscular System | Skeleton and Limbs | 1908 Vertebra | 1908 Cervical Vertebra | 1909 Mandible | 1910 - Skeleton and Connective Tissues | Muscular System | Coelom and Diaphragm | 1913 Clavicle | 1920 Clavicle | 1921 - External body form | Connective tissues and skeletal | Muscular | Diaphragm | 1929 Rat Somite | 1932 Pelvis | 1940 Synovial Joints | 1943 Human Embryonic, Fetal and Circumnatal Skeleton | 1947 Joints | 1949 Cartilage and Bone | 1957 Chondrification Hands and Feet | 1968 Knee


  • Understand the general microanatomy of bone
  • Understand bone cell types (location, structure, function)
  • Understand the histology of compact and spongy bone
  • Understand the 2 forms of developmental bone formation

Practical Audio 2009

Files below are Quicktime audio files recorded Wednesday 12 - 2 PM class (Podcast MP3 versions to follow).

Part 1 - Adult Bone Structure‎ | Part 2 - Bone Structure‎ | Part 3 - Developing Endochondral Ossification‎ | Part 4‎ - Developing Intramembranous Ossification

MH - Please note "perichondrium" instead of "periosteum" error somewhere in the above audio. Open in a separate tab to play the audio in the background.


Histology and Cell Biology: An Introduction to Pathology, A.L. Kierszenbaum, 2002 - Connective Tissue, Chapter 4 pp118-129; Osteogenesis, Chapter 5 pp131-145


UNSW Virtual Slidebox Virtual Slidebox Phase 1

Virtual Slidebox of Histology Decalcified rib, bone marrow | Developing bone | Paget's disease of bone

Bone Structure



  • Diaphysis - shaft
  • Epiphysis - expanded ends
  • Metaphysis - connecting region (between diaphysis and epiphysial line)
  • Medullary Cavity - (marrow) cavity within the bone.

More? Terms

Compact bone

  • (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.

Trabecular bone

  • (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.

Bone Growth

  • 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)

Bone Cells


Mouse osteoblast 01.jpg

  • 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)


Mouse osteoclast 01.jpg Osteoclast.jpg Bone remodeling cycle.jpg

  • 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

Bone Marrow

Hematopoietic and stromal cell differentiation
  • 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

Chondroblasts and Chondrocytes

  • immature and mature cartilage forming cells located at articular cartilage regions.
  • Interstitial growth - occurs mainly in immature cartilage. Chondroblasts in existing cartilage divide and form small groups of cells (isogenous groups) which produce matrix to become separated from each other by a thin partition of matrix.
  • Appositional growth - occurs also in mature cartilage. Mesenchymal cells surrounding the cartilage in the deep part of the perichondrium (or the chondrogenic layer) differentiate into chondroblasts.

Histology - Cartilage

Bone Matrix

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

Haversian Systems

Bone structure cartoon
  • 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

Endochondral ossification

Endochondral bone.jpg

Endochondral ossification slides: Developing bone | Bone, Developing (LS, Femur) Cat H&E

Blue Histology - endochondral | Dev Biology - endochondral ossification | endochondral ossification animation

Endochondral ossification.jpg Endochondral ossification 2.jpg

Ossification endochondral 1c.jpg Articular cartilage.jpg

Additional Histology Slides: developing Vertebra | Vertebra medium

Intramembranous Ossification

Intramembranous ossification slides: Head (Neonatal) Rat H& Van Gieson

Blue histology - intramembranous | intramembranous ossification animation

Ossification centre.jpg Intramembranous ossification centre.jpg

Human Fetal Head (12 week)

Fetal head medial.jpg Fetal head lateral.jpg


Fetal head section.jpg

Histology Stains

Alizarin Red

  • an anthraquinone derivative used to identify calcium in tissue sections
  • calcium forms an Alizarin Red S-calcium complex in a chelation process and the end product is also birefringent.
  • reaction can also identify magnesium, manganese, barium, strontium, and iron may interfere
    • these elements usually in too low concentration to interfere with the staining


  • acronym for hematoxylin and eosin stain
  • hematoxylin - basic dye which colors basophilic structures with blue-purple hue (nucleus, DNA, RNA)
  • eosin Y - acidic alcohol-based which colors eosinophilic structures bright pink (cytoplasm, extracellular matrix, protein)

H&Van Gieson

  • Van Gieson's Stain is a mixture of picric acid and acid fuchsin used for differential staining of collagen and other connective tissue.
    • Nuclei - stains brownish black to black
    • Collagen (fibrous connective tissue) - stains pink or deep red
    • Muscle, Cytoplasm, RBC and Fibrin - stains yellow

Links: Histology Stains

External Links

Other Textbooks



canaliculus - (plural, canaliculi) small channel in the bone matrix in which an osteocyte process lies and communicates with other osteocytes and the Haversian canal.

haematopoiesis (Greek, haima = "blood"; poiesis = "to make") the process of blood cell formation.

Haversian canal - the central canal of an osteon (Haversian system) in compact bone, within which blood vessels and nerves travel throughout the bone.

Haversian system - (osteon) the historic name for the functional unit of compact bone. Consists of a central canal (Haversian canal) surrounded by lamellar bone matrix within which osteocytes reside.

Howship's lacuna - (resorptive bay) the historic name for the shallow bay or cavity lying directly under an osteoclast. This is the site of bone matrix resorption.

lacuna - (Latin, lacuna = “ditch, gap” diminutive form of lacus = “lake”) lacunae is the plural, cavity in bone or cartilage for cell.

lamellar bone - the highly organized strong bone matrix deposited in concentric sheets with a low proportion of osteocytes. Many collagen fibers parallel to each other in the same layer.

osteon - (Haversian system) the functional unit of compact bone. Consists of a central canal (Haversian canal) surrounded by lamellar bone matrix within which osteocytes reside.

resorptive bay - (Howship's lacuna) the shallow bay or cavity lying directly under an osteoclast. This is the site of bone matrix resorption.

suture - in the skull a form of articulation where the contiguous margins of the bones are united by a thin layer of fibrous tissue.

woven bone - the first deposited weaker bone matrix with many osteocytes and a matrix disorganized structure. Replaced by lamellar bone. Seen in developing, healing and bone disease.

Glossary Links

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Cite this page: Hill, M.A. (2021, April 18) Embryology Bone Development. Retrieved from

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© Dr Mark Hill 2021, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G