The Skeletal System
Five Major Functions
1.
2.
Gives shape and support to body
Protects your internal organs
1.
3.
4.
5.
Ex: ribs protect heart, skull protects brain
Major muscles are attached to bone
and help them move
Blood cells formed in center of bones
in soft tissue called red marrow
Major quantities of calcium and
phosphorus compounds are stored
Bone structure
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Bones can have different sizes, shapes,
Bone surface covered with periosteum
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Small blood vessels in periosteum carry
nutrients to bone
Two different bone tissues
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
Compact bone
Spongy bone
Compact Bone

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Directly under periosteum
Hard, strong layer that gives bones
strength
Framework containing calcium
phosphate
Living tissue of bone cells and blood
vessels that keeps bones from being
too rigid, brittle, or easily broken
Spongy Bone



Located towards end of long bones
Has many small, open spaces that make
bones lightweight
Inside cavities and spaces in spongy
bones, substance called marrow
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Some marrow yellow and composed of fat
cells
Red marrow produces red blood cells
Cartilage

Smooth, slippery, thick
layer of tissue that
covers the end of bones


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No blood vessels or
minerals
Flexible and important
in joints because it acts
as shock absorber
Makes movement easier
by reducing friction
Bone Formation

Before being born, baby skeleton made of
cartilage
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Bone cells called osteoblasts deposit calcium and
phosphorus in bones, making the tissue hard
At birth, we have >300 bones, but as we develop,
bones fuse and only have 206
Bone tissue always being formed
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Osteoblasts build bone
Osteoclast breaks down bone
Joints

Any place where two or more bones
come together
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Bones kept far enough apart by cartilage
Classified as immovable or movable
Ligaments tough band of tissue that
holds bones in place at joints
Immovable joints


Allows little or no movement
Joints of skull and pelvis are immovable
Movable Joints
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All movement requires movable joints
Several types
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Pivot
Ball and socket
Hinge
gliding
Pivot Joint

One bone rotates in a ring of another
bone that does not move

Ex: turning your head
Ball and Socket

Bone with rounded end that fits into a
cuplike cavity on another bone

Provides wider range of motion

Why your arms and legs can swing in almost
any direction
Hinge

Back and forth movement like hinges
on door

Ex: elbows, knees, fingers
Gliding Joint


One part of a bone slides over another
bone
Move in back and forth motion and are
used most in body

Ex: wrist, ankle
Joint Problems

Arthritis pain,
stiffness, and swelling
of joints


Osteoarthritis results
when cartilage breaks
down because of years of
use
Rheumatoid arthritis
ongoing condition in
which the body’s immune
system tries to destroy
its own tissues