Histology of Bone and Cartilage Dr. Sama ul Haque

Understand the histology of bone. Understand the histology of cartilage. Objectives

Composition of Bones Collagen: chief organic constituent (protein) Inorganic Calcium Salts: Vitamin D essential for absorption

A Chemical Analysis of Bone

Cells Osteoblasts: bone building, bone repairing cells in the periosteum and synthesize new matrix (Osteogenesis) Osteocytes: osteoblast embedded within the bone matrix (mature bone cells) Osteoclasts: cells that cause absorption of bone or dissolve bone matrix (Osteolysis)

Periosteum Dense, fibrous membrane covering bone Contains blood vessels Essential for bone cell survival and bone formation Endosteum

Histological or Microscopically Compact bone (dense) Basic unit of compact bone is an osteon. Osteocytes within lacunae arranged in concentric circles called lamellae. This surround a central canal; complex is called Haversian system. Weight Bearing.

Histological or Microscopically Spongy bone (cancellous) Contains trabeculae Found at ends of Long Bones, Ribs, Sternum, Hips, Vertebrae, Cranium Web-Like Arrangement Low Stress Areas Where Weight of Bone Would Be a Problem.

Compact and Spongy Bone

Osteoblasts and Osteocytes

Lacunae and Canaliculi Communication

Periosteum and Endosteum

Mature Bone (Compact)

Mature Bone (Spongy)

Osteon Lacunae (L) Canaliculi (C) Osteocytes (O)

Cartilage  Type of Dense connective tissue ( Cells and fibers)  Perichondrium ( Fibro-vasculo-cellular membrane)  Cells = Characterized by Rigid with flexibility and Resilience.  Avascular  Nerves and lymphatics are absent  Cells (Chondroblasts and chondrocytes)  Matrix => Connective tissue fibers (Collagen, Elastin)

Hyaline Cartilage  Hyaline (Glass)  Commonest form  Bluish white, translucent and homogenous in appearance with collagen fibers. Sites: => Articular cartilage => Costal cartilage => Tracheal cartilage  Ossifies to form bone in young age

Hyaline Cartilage and Perichondrium

Elastic Cartilage  Yellow; Elastin fibers  More elastic than hyaline  Sites: => Pinna of the ear => Epiglottis => Auditory tube  Never o ssifies

Elastic Cartilage

Fibro-cartilage  White, Opaque with collagen fibers  Sites => Intervertebral disc => Intra articular disc => Menisci  Ossifies in old age

Collagen (c) Fibrocartilage

Cartilages

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