Skeletal Structure Skeletal Systems Skeletal Systems

Exo versus Endo Exoskeleton: (exo = outside) A hard outer layer found on many early animals. Used for protection and support - eg. Insects, spiders and crabs Endoskeleton: (endo = inside) A hard bone or cartilaginous structure found inside the body used for support. - eg. Mammals, birds, reptiles, amphibians

The vertebrate skeletal system Function: -Support -Protection (ribs cage in lungs and heart) -Produces red blood cells (bone marrow) -Assist muscular system (muscles anchor themselves on bones)

2 Parts of the Skeletal system Axial skeleton: The center of the body – Ribs and breast bone – Spinalcord and skull – Middle ear bones (ossicles) Appendicular skeleton:

2 Parts of the Skeletal system Axial skeleton: The center of the body – Ribs and breast bone – Spinalcord and skull – Middle ear bones (ossicles) Appendicular skeleton: The outer body – Arms and Legs – Hands and Feet – Pelvic and Pectoral Girdle

Diagram: Axial Skeleton: Grey Appendicular Skeleton: Purple

Two Types of Bone Compact Bone: Dense hard material. Makes up most of the longer bone Spongy Bone: Lighter less dense material. Smaller bones such as ribs are made of spongy bone.

Parts of the bone Periosteum: A thin covering over the bone that contains blood vessels, nerves and bone forming cells

Bone Development Formation of bone: 1) forms in cartilage: -Cartilage cells that form bone are called Osteoblast -Osteoblasts begin to form bone tissue inside the shaft of cartilage

Embryo bone development Ossification: Embryo bones are made of cartilage. As the embryo develops calcium and phosphate ions are deposited in the cartilage. At this point the cartilage cells begin to die off and the bone cells form canals within the structure

Bone formation Haversain Canals: The canals formed during ossification. Used by nerves and blood as pathways. Eventually the canals grow together forming bone marrow.

Structures in the Bone

Development of long bones Infant: Starts off as cartilage Child: Cartilage is converted into calcified cartilage Child-Adult: Calcified cartilage is replaced by bony tissue starting from the middle and moving towards the ends.

Long Bones Development of bone tissue in long bones:

Development of the bone Epiphyseal plates: aka growth plates. The ends of the long bone that still contain cartilage.

Development of the bone Epiphyseal plates: aka growth plates. The ends of the long bone that still contain cartilage. This tissue produces new cartilage cells but over time it is taken over by bone producing cells

Development of the bone Epiphyseal plates: aka growth plates. The ends of the long bone that still contain cartilage. This tissue produces new cartilage cells but over time it is taken over by bone producing cells Eventually (25 years) all the cartilage producing cells have all been replaced

Bone Development in Fibrous Connective Tissue Bone formation in connective tissue: Osteoblasts form spicules (bone splinters) These spicules join to form spongy bone If this process continues it forms compact bone

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