ct_12. Lamellar membranous bone
(Decalcified bone specimen,
transverse section of tubular bone diaphysis, Schmorl’s stain)
1. Take a closer look at the multilayer structure of a tubular/cortical bone:
- outside, the tubular bones are covered with the periosteum, a connective tissue layer;
- external circumferential lamellae are stacked in parallel layers to the surface of the bone;
- osteons are the chief structural units of a cortical bone;
- internal circumferential lamellae are located around the marrow cavities.
2. Study the structure of the lamellar membranous bone in detail:
- the outer fibrous layer of the periosteum consists of dense connective tissue; the fibers are oriented parallel to the surface of the bone;
- the inner layer of the periosteum is composed of loose fibrous connective tissue containing flattened spindle-shaped osteogenic cells;
- osteons are roughly cylindrical structures with the central/osteonic canal in the middle containing blood vessels:
- around the canal there are from 3 to 25 concentrically arranged lamellae which appear dark and bright;
- between the lamellae there are cavities named bone lacunae containing osteocyte cell body;
- osteocyte processes are located in small tubes known as bone canaliculi;
- the spaces between adjacent osteons are filled with interstitial lamellae that often represent the remnants of older osteons.
3. Draw and point out:
(1 - an outer fibrous layer, 2 - an inner osteogenic layer),
II - external circumferential lamellae,
III - the osteon (3 - the central/osteonic canal, 4 - bone lamellae, 5 - bone lacunae, 6 - bone canaliculi, 7 - interstitial lamellae).
4. Define and write significant features of the lamellar membranous bone specimen.