Bone Structure All bones are similar in their structure, the way they develop, and the functions they perform

Generality Human skeleton consists of 206 bones Human skeleton consists of 206 bones We are actually born with about 300 bones, but some fuse together We are actually born with about 300 bones, but some fuse together These bones support your body and allow you to move These bones support your body and allow you to move

Functions of Bones Even though our bones provide body shape, they also perform important body functions Even though our bones provide body shape, they also perform important body functions 1. Support 2. Protection 3. Movement 4. Storage 5. Blood cell formation

1. Support Form the internal framework Form the internal framework Cradles soft organs Cradles soft organs Bones of legs act as pillars to support trunk Bones of legs act as pillars to support trunk Rib cage supports thoracic wall Rib cage supports thoracic wall

2. Protection Protect soft body organs Protect soft body organs Example: Fused bones of skull provide enclosure for brain Example: Fused bones of skull provide enclosure for brain Example: Vertebrae surrounds spinal cord Example: Vertebrae surrounds spinal cord What is another example? What is another example?

3. Movement Skeletal muscles attach to bones by tendons Skeletal muscles attach to bones by tendons Bones are used as levers to move the body Bones are used as levers to move the body As a result we can walk, swim, throw, and breathe As a result we can walk, swim, throw, and breathe

4. Storage Bones store many important minerals including calcium and phosphorus Bones store many important minerals including calcium and phosphorus Most of body’s calcium is deposited in bone as calcium salts Most of body’s calcium is deposited in bone as calcium salts - “Deposits” and “withdrawls” of calcium go on all the time Bones store fat within the internal cavities Bones store fat within the internal cavities

5. Blood Cell Formation Blood cell formation occurs within the marrow cavities of certain bones Blood cell formation occurs within the marrow cavities of certain bones Hematopoieses Hematopoieses Makes red and white blood cells Makes red and white blood cells

Skeletal structure Bone is composed of a variety of tissues Bone is composed of a variety of tissues Bone tissue, cartilage, fibrous connective tissue, blood, nerve tissue Bone tissue, cartilage, fibrous connective tissue, blood, nerve tissue Bone contains very active, living tissues Bone contains very active, living tissues

Parts of a Long Bone Epiphysis- at each end of the bone, forms a joint with another bone Epiphysis- at each end of the bone, forms a joint with another bone Articular cartilage- hyaline cartilage on the outer surface of the epiphysis Articular cartilage- hyaline cartilage on the outer surface of the epiphysis Diaphysis- shaft of the bone Diaphysis- shaft of the bone

Parts of a Long Bone Periosteum- tough, vascular covering of fibrous tissue Periosteum- tough, vascular covering of fibrous tissue Fibers are continuous with ligaments and tendons Fibers are continuous with ligaments and tendons Formation and repair of bone tissue Formation and repair of bone tissue

Parts of a Long Bone Compact bone- tightly packed tissue forming the wall of the diaphysis Compact bone- tightly packed tissue forming the wall of the diaphysis Solid, strong, resistant to bending Solid, strong, resistant to bending

Parts of a Long Bone Spongy bone- epiphyses composed mainly of spongy bone Spongy bone- epiphyses composed mainly of spongy bone Consists of many branching bony plates Consists of many branching bony plates Irregular spaces occur between these plates, help reduce weight Irregular spaces occur between these plates, help reduce weight Provides bone strength, highly developed where it is subject to forces of compression Provides bone strength, highly developed where it is subject to forces of compression

Medullary cavity Hollow chamber within diaphysis that connects to spaces of spongy bone Hollow chamber within diaphysis that connects to spaces of spongy bone Filled with specialized soft connective tissue, marrow Filled with specialized soft connective tissue, marrow Red marrow- produces red blood cells Red marrow- produces red blood cells Yellow marrow- fat storage Yellow marrow- fat storage

Bone Marrow 2 kinds 2 kinds 1. Red marrow- formation of red blood cells, white blood cells, platelets - hemoglobin within red blood cells 2. Yellow marrow- replaces red marrow with increasing age - fat storage tissue, inactive in blood cell production