The Skeletal System

Do NowWhat is the job of the frame/walls of a building?Why do you think we have bones?What do you think would happen if we didn’t have bones?

When a baby is born, not all of the bones in their skull have fused together so they have soft spots.

Bone Formation Cartilage breaks down over time to get replaced by bone– Osteoblasts are bone-forming cells that deposit calcium and phosphorus to make bones. At birth, your skeleton is 300 + separate bones - as you age they fuse. As adults, you only have 206.

What is the Skeletal System?• The framework of

bones and other tissues that supports the body

Bones• The BONES are the organs of the body.• Made up of tissues. Tissue DescriptionCompact Bone The hard, dense outer layer of boneSpongy Bone Hard, but has many “holes” in itMarrow Soft tissue with the spongy bone, makes blood cells

Compact Bone Compact bone is directly under the periosteum - it is living tissue!Provides strength to bonesMade of calcium phosphate depositsContains bone cells and blood vessels

Spongy Bone Spongy bone is near the ends of longer bones.Contains lots of small spaces to make bones lighter. Cavities in spongy bone are filled with marrow. Marrow can be yellow and be made of fat cells, or red and produce red blood cells.

Cartilage Cartilage is a thick tissue layer covering the ends of bones. Cartilage is slippery and thick to be a shock absorber and to reduce friction when bones rub together.

Bones and Cartilage

Functions of the Skeletal System• Shape and Support• Movement• Protection• Production• Storage

Shape and Support Skeleton determines shape of your body just like the frame determines the shape of a building

Movement• Bones form joints, which is a place where two bones come together• Joints allow bones to move in different ways

JointsA joint is any place where two or more bones come together.Cartilage always holds healthy bones apart.Ligaments hold healthy bones in place. A ligament is a thick band of tissue.

You have immovable and movable joints.Immovable joints don’t allow movement (duh). Ex: Bones in the skull.Movable joints DO allow movement. There are different types: pivot, ball and socket, hinge, and gliding. They allow different types of movement.

ProtectionSkull protects your brainRib cage protects heart, lungs, and other organs in the center of your body

Production Bones produce blood cells. The long bones in your arms and legs can be thought of as factories that make certain blood cells.

Storage• Bones store minerals until body needs them– These minerals include calcium and phosphorus, which are in many foods we eat

Care of the System