 The Skeletal System

Parts of the skeletal system

Two subdivisions of the skeleton  Axial skeleton  Appendicular skeleton

Two subdivisions of the skeleton

 Adult skeleton approximately 206 bones  Axial: 80 bones  Appendicular: 126 bones

Two basic types of bone tissue  Compact bone  Homogeneous  Spongy bone  Many open spaces

Classification of Bones based on Shape

Anatomy of a Long Bone  Epiphysis

Anatomy of a Long Bone

 Diaphysis

Anatomy of a Long Bone  Periosteum  Sharpey ’ s fibers  Arteries

Anatomy of a Long Bone

 Articular cartilage  Covers surface of the epiphyses

Anatomy of a Long Bone  Epiphyseal plate  Epiphyseal line

Anatomy of a Long Bone

 Medullary cavity  Cavity inside of the shaft

Bone Markings  Are bones smooth surfaces?  Femur

 Are bones smooth surfaces?  Tibia

Bone Markings  Are bones smooth surfaces?  Mandible

Bone Markings  Are bones smooth surfaces?  Optical canal

Compact vs. Spongy bone

Microscopic Anatomy of Compact Bone  Osteocytes: mature bone cells  Lacunae:

Microscopic Anatomy of Compact Bone  Lamella:

Microscopic Anatomy of Compact Bone  Central (Haverersian) Canals:

Microscopic Anatomy of Compact Bone  Osteon (Haversian System):

Microscopic Anatomy of Compact Bone

 Canaliculi:  Hint: which way do central canals run?

Microscopic Anatomy of Compact Bone

 This eleaborate network of canals ensures bone cells are well nourished  What significance does this have?

 Perforating (Volkmann’s) canals:

Microscopic Anatomy of Compact Bone

Bone Formation, Growth, & Remodeling  Mostly hyaline cartilage  Replaced by bone

Bone Formation, Growth, & Remodeling Bone starting to replace cartilage Epiphyseal plate cartilage Articular cartilage Spongy bone In a childIn a fetusIn an embryo New bone forming Growth in bone width Growth in bone length Epiphyseal plate cartilage New bone forming Blood vessels Hyaline cartilage New center of bone growth Medullary cavity Bone collar Hyaline cartilage model (a)

Bone Formation, Growth, & Remodeling  Osteocytes—mature bone cells  Osteoblasts—bone-forming cells  Osteoclasts—bone-destroying cells

Growth & Remodeling  New cartilage is continuously formed  Older cartilage becomes ossified

Growth & Remodeling  Osteocytes can sense areas of stress  Enhances the process  Balance of calcium levels

Fractures

 Treated by Reduction:  Closed  Open