Skeletal System

main functions

1. scaffold to support body weight

2. protects vital organs

3. produces blood cells (RBC, WBC, platelets)

4. stores minerals and nutrients

5. point of muscle attachment for movement

206 bones in adult human body

5 different types of bones that are classified on their shape

• long

• short

• irregular

• sesamoid

• flat

Axial skeleton

• bones found along the central axis of your body

• cranium (ossicles, hyoid), vertebral column, ribs, sternum

Appendicular skeleton

• bones found in the appendages or limbs

• pelvic girdle and leg bones, pectoral girdle, arm bones

bone is a type of connective tissue as it has cells and a non-cellular matrix (made of calcium, phosphate)

Long Bone

external macrostructure

• bones that are longer then they are wide

• they act as levers to move the body, contain bone marrow

1. diaphysis (long, narrow shaft)

2. epiphyses (short rounded ends)

3. cartilage (at the ends of the epiphyses where another bone would present to reduce friction)

4. periosteum (except where cartilage is found)

internal macrostructure

• diaphysis contains

• compact bone with a hollow medullary cavity that is filled with yellow bone marrow which stores fat

• epiphyses contain:

• a thin layer of compact bone at the edge with spongy or cancellous bone inside which contains red bone marrow which produces blood cells

Compact Bone Microstructure

• made of repeating units of osteons or Haversian systems

• they run parallel to the length of the bone for maximum strength/ support

each osteon contains

• central canal (for blood vessels, lymphatics, nerves

• concentric layers of matrix called lamellae

• gaps called lacunae between the matrix and house osteocytes (bone cell)

• canals called canaliculi to connect to lacunae so projections from osteocytes can extend into the canal to exchange materials with each other