Bone Development

Introduction

Macroscopic and microscopic bone structure in the adult and during development.

For more development background see Science Lecture - Musculoskeletal Development

Textbook

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

Slides

UNSW Virtual Slidebox Virtual Slidebox Phase 1

1. Compact Bone - Adult Bone , Adult (Ground, TS) Human Alizarin Red | Bone (Ground, LS) Human Alizarin Red
2. Compact Bone Rib Decalcified rib, bone marrow
3. Endochondral ossification Developing bone | Bone, Developing (LS, Femur) Cat H&E
4. Intramembranous ossification Head (Neonatal) Rat H& Van Gieson

Bone Structure

Compact bone

• 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.

Periosteum

Connective tissue covering surface of bone.

Endosteum

Connective tissue lining inner surface of bone.

Bone Cells

Osteocytes

• mature bone-forming cells embedded in bone matrix
• derive from osteogenic stem cells forming Osteoblasts
• line surface of bone, secrete organic matrix of bone (osteoid), converted into osteocytes when become embedded in matrix (which calcifies soon after deposition) (Google- osteoblast images)

Osteoclasts

• 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 secreted into this space by osteoclasts dissolves calcium phosphate crystals (give bone rigidity and strength) (Google- osteoclast images)
• do not mistake for megakaryocytes, found in bone marrow not associated with bone matrix.
  • megakaryocytes are also multi-niucleated and form platelets

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. (Google- bone matrix images)

Haversian Systems

Bone structure cartoon

• also called osteons
• Volkmann's canals - interconnect Haversian systems

Lamellae

• 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

Cells

• osteocytes and canaliculi

Endochondral ossification

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

Intramembranous ossification

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

H&E

• 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)

Links

• Original class notes
• UNSW Virtual Slidebox Virtual Slidebox Phase 1
• Virtual Slidebox of Histology (USA) Skeletal system
• Lecture - Musculoskeletal Development

Other Textbooks

• Anatomy of the Human Body (H. Gray, 1918.) historical anatomy text Osteology
• Molecular Biology of the Cell Bone Is Continually Remodeled by the Cells Within ItImage: Figure 22-52. Deposition of bone matrix by osteoblasts.Image: Figure 22-56. The development of a long bone.
• Molecular Cell Biology Mutations in Collagen Reveal Aspects of Its Structure and Biosynthesis
• The Cell- A Molecular Approach Steroid Hormones and the Steroid Receptor Superfamily
• Clinical Methods: The History, Physical, and Laboratory Examinations 100. Alkaline Phosphatase and Gamma Glutamyltransferase
• Endocrinology: An Integrated Approach by Nussey, S.S. and Whitehead, S.A. Endocrinology: Definition and causes of osteoporosis
• Developmental Biology 6th ed. by Gilbert, Scott F. Aging: The Biology of Senescence