Pl. IX · Sustinens fibrosus — fibrocartilage

The plate

The specimen, drawn

Pl. IX

Cartilage and tendon doing one job together. Thick collagenA structural protein in the dermis that provides strength and elasticity. bundles for the pull, chondrocytes for the squeeze.

Habitat & range

Where it lives

Body map

Fibrocartilage turns up wherever the load is crushing and the tissue still has to resist a pull.

Range

• The twenty-three intervertebral discs, as the annulus fibrosus.
• The pubic symphysisCartilaginous joint connecting the two pubic bones at the midline..
• The menisci of the knee.
• The glenoid labrum of the shoulder and the acetabular labrum of the hip.
• Where some large tendons insert into bone.

Collection record

• Add your slide numbers here.

Niche

What it does for a living

Taking compression without splitting. A disc is squeezed every second you are upright and pulled sideways every time you bend, so it needs the crush resistanceThe opposition to airflow in the respiratory tract, influenced by airway diameter. of cartilageA flexible connective tissue found in joints, the ear, nose, and rib cage. Cartilage can be of three and the tensile strength of tendon at once. Fibrocartilage has no perichondrium, is the strongest of the three cartilages, and — being the compromise — is slow to heal like both its parents.

field collected specimen

How to know it on sight

• Thick pink collagen bundles, clearly visible, sweeping across the field.
• ChondrocytesMature cartilage cells housed in lacunae. in lacunae squeezed into rows between the bundles, in single file.
• No perichondrium anywhere.
• Looks like dense regular tissue that has grown cartilage cellsThe basic structural and functional units of life., which is roughly what it is.

People keep calling her by the wrong name

Look-alikes

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

Hyaline cartilage

Hyaline matrix shows no fibres. If you can see bundles between the lacunae, it is fibrocartilage.

Dense regular connective tissue

Both are parallel bundles. The difference is the cells: fibroblasts are flat dark lines, chondrocytes sit in round lacunae.

Examine it yourself

The virtual slide

Find a row of chondrocytes and follow it. Then find the collagen bundles on either side of that row and notice they are running the same way — the cells have been lined up by the pull.

Virtual slide courtesy of Histology Guide.

Field notes

Why this organism

A coconut is built to be dropped from the top of a palm onto sand, repeatedly, without splitting, and the part doing that work is the husk: coarse fibre, packed thick, running every way at once around the thing it is protecting. Nobody eats the husk and nobody notices it. An intervertebral disc is a husk with a vertebra above and below it, and you will go your whole life without thinking about it unless one day one of them fails.