Biology › Section O · Hormones, bones, and muscles › Topic O.4
Types of skeletal systems
A muscle can only pull, so every moving animal needs something firm for its muscles to pull against. Animals have solved that problem in three ways: a bag of pressurised fluid, a hard outer case, or a frame of living tissue inside the body.
In this topic
- Why animals need skeletons
- Hydrostatic skeletons: pressure in a closed bag
- Worked example: how an earthworm crawls
- Exoskeletons: armour with joints
- Endoskeletons: support from within
- The human skeleton and its five jobs
- The axial skeleton
- The appendicular skeleton
- Worked example: checking the count of 206
- From water to land
- Common mistakes to avoid
- Key takeaways
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