Human Body Systems
Skeletal System
Chapter 17-1: The Skeletal System
1. The skeletal system is all of the bones in
the human body.
 At birth the skeleton contains about 350
bones. The adult skeleton has only 206
bones.
 Of these 29 are in the skull, 26 in the
backbone, 25 in the sternum & ribs, 64 in the
shoulders, arms and hands and 62 in the
pelvis, legs and feet.
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Types of bones
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Bones are classified by shape and size.
Shape/Size
Example
Long
Femur
Short
Carpals
Flat
Sternum
Irregular
Pelvis
Bone structure
2. Bone is made of layers of living tissue.
 The membrane that covers the bone is called
the periosteum.
 Large bones are hollow and are filled with
bone marrow. Bone marrow produces red
and white blood cells.
 A smooth thick layer of tissue called cartilage
separates the bones from each other and
reduces friction.
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A ligament is a band of tissue that holds
bones together at the joints.
 3. Two types of bone
 A. Compact bone is the hard strong layer of
bone.
 B. Spongy bone is found at the ends of long
bones and has open spaces in it to make it
lightweight.
 4. Two types of joints
 Immovable joints allow little or no
movement. Ex – Skull bones.
 Movable joints allow the body a wide range
of movement.
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Types of movable joints
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5. Four types of movable joints
A. Pivot: one joint rotates in a ring of another joint.
Ex – Head/neck joint
B. Ball and Socket: One bone has a rounded end
that fits into a cup-like cavity in another. Ex –
Shoulder and hip joints
C. Hinge: Back and forth movement like the hinge
of a door. Ex – knees and elbows
D. Gliding: One part of a bone slides over another
bone. This is the most common joint in the body.
Ex – wrists and ankles
Functions of the skeletal system
6. The five main functions of the skeletal
system.
 A. Shape and support the body.
 B. Protects the internal organs.
 C. Gives muscles a place to attach.
 D. Produces blood cells (marrow)
 E. Stores minerals (calcium and phosphorus)
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Bone cells
7. Two types of bone cells.
 A. Osteoclasts – cells that break (cut) down
bone.
 B. Osteoblasts – cells that build bone up.
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