# 13.6: Human Skeletal System

Difficulty Level: At Grade Created by: CK-12
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Practice Human Skeletal System

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The skeletal system consists of all the bones of the body. How important are your bones?

Try to imagine what you would look like without them. You would be a soft, wobbly pile of skin, muscles, and internal organs, so you might look something like a very large slug. Not that you would be able to see yourself—folds of skin would droop down over your eyes and block your vision because of your lack of skull bones. You could push the skin out of the way, if you could only move your arms, but you need bones for that as well!

### The Skeleton

The human skeleton is an internal framework that, in adults, consists of 206 bones, most of which are shown in Figure below. Learn more about bones in the animation “Bones Narrated”: http://medtropolis.com/virtual-body/

In addition to bones, the skeleton also consists of cartilage and ligaments:

• Cartilage is a type of dense connective tissue, made of tough protein fibers, that provides a smooth surface for the movement of bones at joints.
• A ligament is a band of fibrous connective tissue that holds bones together and keeps them in place.

The human skeleton consists of bones, cartilage, and ligaments.

The skeleton supports the body and gives it shape. It has several other functions as well, including:

1. protecting internal organs
2. providing attachment surfaces for muscles
3. producing blood cells
4. storing minerals
5. maintaining mineral homeostasis.

Maintaining mineral homeostasis is a very important function of the skeleton, because just the right levels of calcium and other minerals are needed in the blood for normal functioning of the body. When mineral levels in the blood are too high, bones absorb some of the minerals and store them as mineral salts, which is why bones are so hard. When blood levels of minerals are too low, bones release some of the minerals back into the blood, thus restoring homeostasis.

### Summary

• The adult human skeleton includes 206 bones and other tissues.
• The skeleton supports the body, protects internal organs, produces blood cells, and maintains mineral homeostasis.

### Practice I

Use this resource to answer the questions that follow.

• http://www.hippocampus.org/Biology \begin{align*}\rightarrow\end{align*} Biology for AP* \begin{align*}\rightarrow\end{align*} Search: Skeletons: Overview
1. What are the roles of the skeleton?
2. Describe the three types of skeletons.

### Review

1. What is cartilage? What is its role in the skeletal system?

2. List three functions of the human skeleton.

3. Explain how bones maintain mineral homeostasis in the body.

### Notes/Highlights Having trouble? Report an issue.

Color Highlighted Text Notes

### Vocabulary Language: English Spanish

TermDefinition
bone Hard tissue in most vertebrates that consists of a collagen matrix, or framework, filled in with minerals such a calcium.
cartilage Dense connective tissue that provides a smooth surface for the movement of bones at joints; involved in endochondral ossification.
ligament Band of fibrous connective tissue that holds bones together.
mineral homeostasis Having the proper levels of minerals in the blood for normal functioning of the body.

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