Vocabulary from the Sonlight Instructors Guide

Bone Marrow

Produces the cells that are in your blood

skeletal muscles

Bones to help you move. These are your voluntary muscles.

Smooth muscles

Control the movements necessary for your body's internal organs and blood vessels to function. Controlled by the brain, so movements they cause are involuntary.

cardiac muscle

A muscle found only in the heart. I controls how the blood is pumped throughout your body.


The process of skin cells hardening so that they form your hair, nails, and the outer layer of your skin.


the sum total of all bones in the body


All creatures with a vertebral column backbones.

Axial skeleton

The portion of the skeleton that supports and protects the head, neck, and trunk.

Appendicular skeleton

The portion of the skeleton that attaches to the axial skeleton and has the limbs attached to it.


Organisms from kingdom Animalia with no backbone.


A body covering, typically made of chitin, that provides support and protection.


Animals with exoskeletons, such as grasshoppers.


connective tissue that attaches the skeletal muscles to the skeleton.


A tough, flexible substance that allows joints to rub up against each other without damage.


Lubricates the joints so that their motion is smooth and easy.

Synovial fluid

Lubricates the joints so that their motion is smooth and easy.

Involuntary muscles

Muscles that cause involuntary movement, which is movement made without conscious thought.


The tendency of plants to grow so that they face the light.


The tendency for a plant to sense which way is "up" and to grow that way.


Outer layer of skin


The inner layer below the epidermis


Below the dermis and composed mostly of fat. It is not technically considered part of the skin


A close relationship between two or more species where at least one benefits.

Skin in other organisms

* Mammals - produce hair
* Birds - produce feathers
* Fish - produce scales
* Reptile - produce scales
* Amphibians - also breathe with their skin

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