Histology Photomicrographs

• Epithelial tissue
• Connective tissue proper
• Skin
• Cartilage and bone
  • Hyaline cartilage
  • Compact bone
  • Spongy bone
  • Epiphyseal plate
• Skeletal muscle, smooth muscle
• Nervous system
• Cardiovascular system
• Lymphatic system
• Respiratory system
• Digestive system
• Urinary system
• Reproductive system
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Cartilage and bone: Spongy bone 

Spongy bone is the tissue that makes up the interior of bones; compact bone is the tissue that forms the surface of bones. In long bones, spongy bone forms the interior of the epiphyses; the diaphysis (shaft) consists of compact bone surrounding the central marrow cavity.

Spongy bone is a network of irregularly-shaped sheets and spikes of bone (trabeculae). The trabeculae are only a few cell layers thick. The spaces between the trabeculae contain red or yellow marrow, depending on a person's age and on which bone it is.

The marrow in these images is red marrow. Red marrow contains blood stem cells and blood cells in all stages of development. These cells are supported by a reticular connective tissue framework. In yellow marrow one would see abundant adipocytes instead of
blood-forming cells.

The arrow labeled o points to an osteocyte in its lacuna. Canaliculi (not visible here) connect the lacunae of osteocytes to each other and to the marrow spaces between the trabeculae.

There are no blood vessels within the matrix of spongy bone, but blood vessels are nearby in the marrow spaces. Exchange of nutrients, gases, etc. occurs between capillaries in the marrow and the interstitial fluid of the marrow. The interstitial fluid extends into the canaliculi and thereby supplies the osteocytes.