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Pl. X · Sustinens osseus — compact bone

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2–3 minutes

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Pl. X · FAM. SUSTINENTIDAE

Sustinens osseus var. corallinus

captain concrete  ·  compact bone

The plate

The specimen, drawn

Pl. X

Hand-drawn field-guide plate. Title: Sustinens osseus, var. corallinus, Captain Concrete, Plate 10, family Sustinentidae. A drawing of a coral corallite seen end-on, a stony cup of concentric rings around a central hollow. Below, a schematic of compact bone showing osteons: five concentric lamellae ringing a central canal, with osteocytes in lacunae and fine canaliculi reaching between them. A circular inset at 400x shows one osteon.

Circles within circles. Each osteon is a cylinder of bone built around its own blood vessel, because nothing here can live by diffusion alone.

Habitat & range

Where it lives

Body map

A simple hand-drawn human body map, a female figure in outline with cross-hatched shading, used to show where compact bone is found. Numbered rust-coloured markers are placed on the figure and listed in a key below headed “where it lives”: the shaft of the femur; the shafts of the arm bones; the outer shell of the ribs; and a shell over every other bone.

Compact bone is the dense outer shell of every bone you have, and most of the shaft of the long ones.

Range

  • The shaft of the femur, where it is thickest.
  • The shafts of the humerus, radius and ulna.
  • The outer shell of the ribs, the skull and the pelvis.
  • A shell over the outside of every other bone, however small.
  • About eighty per cent of the skeleton by weight.

Collection record

  • Add your slide numbers here.

Niche

What it does for a living

Bearing weight and resisting bending. Bone matrix is collagen for tension plus hydroxyapatite for compression, and the result is stiff enough to stand on. Because the matrix is solid, nothing diffuses through it, so the tissue is built as osteons: concentric rings around a central canal carrying a vessel, with osteocytes trapped in lacunae and connected to each other by canaliculi fine enough to pass nutrients hand to hand.

field collected specimen

How to know it on sight

  • Osteons — concentric rings, like a tree trunk, each with a hole in the middle.
  • That hole is the central canal, and it carried a blood vessel.
  • Small dark lacunae between the rings, each one an osteocyte.
  • Fine canaliculi radiating from each lacuna, linking it to its neighbours.
High-magnification microscopic image of ground compact bone stained red. Circular osteons are centrally positioned within concentric lamellae. Whitish lacunae are irregularly distributed within the red matrix and surrounding the osteons. The overall composition highlights the organized structure of bone tissue.

Specimen 1

Microscopic ground compact bone. Image displays multiple osteons in light gray shades. The osteons appear as concentric rings surrounding dark oval-shaped central canals. Fine, radiating lines are observed extending outward from each ring. The overall composition fills the frame with a dense, irregular pattern.

Ground bone in grey. Pick one osteon and count its lamellae from the canal outwards.

People keep calling her by the wrong name

Look-alikes

Two plates. Read the line underneath each one before you decide.

Spongy bone

Histological slide depicts intramembranous ossification. Pink-stained bone matrix is interspersed with numerous small, ovoid lacunae containing osteocytes. Scattered light areas indicate active bone formation. The overall composition shows an irregular network of bone trabeculae characteristic of early bone development. Image captured via light microscope.
Dense irregular connective tissue. Pink-stained collagen fibers and cells in thin skin.

Spongy bone has struts and marrow spaces, not concentric rings. If you can see osteons, it is compact.

Hyaline cartilage

High magnification microscopic image of hyaline cartilage within the trachea. The dominant purple matrix contains chondrocytes, small cells appearing encapsulated in circular or oval lacunae that vary in darkness and internal detail. The overall composition is dense, showcasing fine cellular structure.
Micrograph of kidney tissue displaying tubular structures lined by simple cuboidal epithelium. The cells manifest as circular or elliptical forms with centrally positioned, round, blue-stained nuclei.

Both have cells in lacunae, but cartilage has no rings, no canals and no canaliculi.

Examine it yourself

The virtual slide

Zoom in on one osteon until the canaliculi appear as hairlines radiating from each lacuna. Then follow them outward and see that they connect one lacuna to the next, all the way to the canal.

Virtual slide courtesy of Histology Guide.

YOur missions

Field Notes for Future Missions

Mission 1: inside one osteon

Mission 2: quick check

Field notes

Why this organism

A coral corallite is a stony cup that one polyp builds around itself, laid down in rings from the middle outward, and a reef is made of millions of them cemented side by side. The animal lives in the hole in the middle; the rings are what it secreted while it was there. An osteon is the same object. Rings of mineral around a central space, built by the cells now trapped inside the rings, and the whole skeleton is built out of them packed together.

Next · Pl. XI

Sustinens osseus var. trabecularis

the lattice · spongy bone.

Continue to Pl. XI →

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