Human Anatomy
Bone and Cartilage Histology
Bone and cartilage histology for MBBS: cartilage types, osteon structure, bone cells and ossification, mapped to NMC codes AN71.1 and AN71.2.
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Bone and Cartilage Histology
Bone and cartilage histology for MBBS: cartilage types, osteon structure, bone cells and ossification, mapped to NMC codes AN71.1 and AN71.2.
This chapter describes the histology of the three types of cartilage and of compact and spongy bone. It covers the bone cells, the osteon and the two modes of ossification that build the skeleton.
High-yield: Bone and Cartilage Histology
- Bone and cartilage are specialised connective tissues with a firm matrix, giving support and protection.
- Cartilage is avascular and receives nutrition by diffusion through its matrix from the surrounding perichondrium.
- Hyaline cartilage is the commonest type and covers articular surfaces and forms the costal cartilages and airway rings.
- Elastic cartilage contains elastic fibres and forms the pinna of the ear, the epiglottis and parts of the larynx.
- Fibrocartilage has abundant collagen bundles and forms the intervertebral discs, pubic symphysis and menisci.
- Chondrocytes lie in spaces called lacunae within the cartilage matrix.
- Bone matrix is mineralised with hydroxyapatite crystals, which give the tissue its hardness.
- The structural unit of compact bone is the osteon or Haversian system, a set of concentric lamellae around a central canal.
- The Haversian canal carries blood vessels and is linked to neighbouring canals by transverse Volkmann's canals.
- Osteocytes occupy lacunae and communicate through fine channels called canaliculi.
- Osteoblasts lay down new bone matrix while osteoclasts, which are multinucleate, resorb bone.
- Compact bone forms the dense outer shell and spongy or cancellous bone forms the inner trabecular network.
- Intramembranous ossification forms flat bones such as those of the skull directly within mesenchyme.
- Endochondral ossification replaces a hyaline cartilage model and forms most long bones.
- The epiphyseal growth plate allows long bones to elongate until it fuses at the end of growth.
Cartilage types and bone structure
- **Hyaline cartilage:** Commonest. Articular surfaces, costal cartilage, airway rings; a model for long bone development.
- **Elastic cartilage:** Elastic fibres. Pinna of the ear, epiglottis and parts of the larynx.
- **Fibrocartilage:** Abundant collagen. Intervertebral discs, pubic symphysis and menisci.
- **Osteon:** Concentric lamellae around a Haversian canal; osteocytes in lacunae linked by canaliculi.
NMC competencies in this chapter
- **AN71.1:** Identification and classification of bone with structure-function correlation
- **AN71.2:** Identification and types of cartilage with structure-function correlation
Frequently Asked Questions
What are the three types of cartilage?
Hyaline cartilage on joint surfaces and in the airways, elastic cartilage in the ear and epiglottis, and fibrocartilage in the intervertebral discs, pubic symphysis and menisci.
What is an osteon?
It is the structural unit of compact bone, made of concentric lamellae surrounding a central Haversian canal that carries blood vessels. Osteocytes sit in lacunae between the lamellae.
What do osteoblasts and osteoclasts do?
Osteoblasts synthesise and deposit new bone matrix, while osteoclasts are large multinucleate cells that resorb bone. Their balance controls bone remodelling.
How do intramembranous and endochondral ossification differ?
Intramembranous ossification forms bone directly within mesenchyme, as in the flat bones of the skull. Endochondral ossification replaces a hyaline cartilage model and forms most long bones.
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