Skeletons Act As Anchorage And Levers for Muscles
Definition
Skeleton
A skeleton is a hard framework that protects the animal's body.
- There are two types of skeletons:
- Exoskeletons
- Endoskeletons
- Exoskeletons must be periodically shed and replaced during growth, a process called molting.
- During this time, the organism is temporarily vulnerable to predators and environmental stressors.
Exoskeletons
- Found in arthropods (e.g., insects, crustaceans).
- External structure made of chitin, providing protection and muscle attachment.
In a grasshopper, leg muscles attach to the exoskeleton, enabling powerful leaps.
Endoskeletons
- Found in vertebrates (e.g., humans, cheetahs).
- Internal framework of bones, which grows with the organism.
The long bones in a cheetah’s legs anchor muscles, allowing speeds of up to 80 km/h.
Skeletons as Anchorage Points for Muscles
- Origins and Insertions
- Origin: The fixed attachment point (bone does not move during contraction).
- Insertion: The movable attachment point (bone does move when the muscle contracts).
- Why Anchorage Matters
- Muscles only generate force by shortening.
- A rigid anchor (bone) ensures force is converted into movement rather than just muscle shortening in place.
The masseter muscle originates on the cheekbone and inserts on the jawbone, elevating the jaw for chewing.
To remember the difference: the "origin" stays stationary, while the "insertion" moves during contraction.
Skeletons as Levers
- Lever Basics
- A lever is a rigid structure (bone) that pivots around a fulcrum (joint).
- Effort (muscle force) acts against a load (resistance) to produce movement.
