17.2 The Skeletal System

Life Science, Ms. Wells

Functions of Skeletal System

• Provides all movement• Works with Muscles

– Skeletal System + Muscular System = Musculoskeletal System

Bone Shapes

• Long Bone = in arms & legs

• Short Bone– in feet & hands

Bones Shapes

• Irregular Bones = spinal column (vertebrae)

• Flat Bones = ribs, skull

Bones are Connective Tissue!

Bone Types• Compact Bone

– Solid layer– Outer layer– Very strong– Dense calcium

network

• Spongy Bone– Lightweight,

STRONG– Full of holes (for

blood vessels)– Middle layer

Calcium Network

Spongy Bone

Joints

• Function: allow for movement or to create a seal between 2 bones

• Definition: any place where 2 bones meet

Immovable Joints• NO

movement/motion• Example: Skull• Bones in skull are

fused together to seal brain inside

Slightly Movable Joints

• Can “give” a little, more flexible• But usually don’t move much• Example: Ribs

Freely Movable Joints

• Bones glide back & forth past each other

• Lots of motion• Many types

– Hinge– Pivot– Ball and Socket

Freely Movable: PIVOT Joint

• Motion: twist a door knob• Example: wrist

Freely Movable: HINGE Joint

• Motion: open and close only one way

• Example: knee, elbow

Freely Movable: BALL AND SOCKET

• Motion: throwing a baseball

• Example: shoulder, thigh bone to hips

Ligaments

• Connective tissue that holds bones together @ joints

• Stretchy

Osteoporosis• Osteo- = bone• -porosis = break

down, porous, holes• Loss of density in

bone• Calcium network

thins• Bones become brittle• Effects women more

than men

“Soft Spot” or Fontanelle• Immovable skull

joints are not entirely fused in infants

• Easier to squeeze big head out of mother

Cartilage

• Bones missing the CALCIUM network!

• Flexible, soft• Example: ears, nose, lining of

joints• All bones start out as cartilage• Add calcium to harden = OSSIFY

Cartilage & Joints• Cushions joints so

bones don’t grind• Arthritis =

cartilage covering bones in joints wears down which causes pain and limits movement

THE END!