Introduction to the Skeletal System The Skeletal System

Introduction to the Skeletal System

The Skeletal System § Skeletal system includes: § bones of the skeleton § cartilages, ligaments, and connective tissues Main Functions of the Skeletal System 1 2 3 4 5 Protection (ex: skull/vertebral column) Movement (Leverage/force of motion) Support (ex: femur supports upper body) Storage of minerals (calcium) and lipids (yellow marrow) Blood cell production (in red bone marrow)

Classification of Bones § Bones are identified by SHAPE 1. 2. 3. 4. 5. 6. Long bones Flat bones Sutural bones Irregular bones Short bones Sesamoid bones

Long Bones § Are longer than they are wide § Are found in limbs, hands, feet, fingers, and toes

Flat Bones • Are thin (sometimes curved) • Are found in the skull, sternum, ribs, and scapula

Sutural Bones § Classified by LOCATION § Are found between the flat bones of the skull

Irregular Bones • Many different and complex shapes • Ex: ear bones/vertebrae

Short Bones § Are small and thick; cube-shaped § Ex: ankle & wrist bones

Sesamoid Bones • small and flat • Develop inside tendons near joints of knees, hands, and feet

Two Divisions of the Skeletal System Total Bones: 206 Axial § Total Bones: 80 § Includes the longitudinal axis of the body § Skull (29 Bones) § Vertebral Column (26 Bones) § Bony Thorax (25 Bones)

Two Divisions of the Skeletal System Appendicular § Total Bones: 126 § Upper Limbs (60 Bones) § Lower Limbs (60 Bones) § Pectoral Girdle (4 Bones) § Pelvic Girdle (2 Bones)

Long Bone Structure Diaphysis - the shaft A heavy wall of compact bone, or dense bone A central space called marrow cavity Epiphysis - wide part at each end of bones Mostly spongy bone Covered with compact bone Metaphysis - where diaphysis and epiphysis meet (PHYSIS = growth, dia = between, epi = on/upon, meta = middle)

Long Bone Structure Epiphyseal Line: where bone has stopped growing (plate = where bone is actively growing)

Long Bone Structure Articular Cartilage: Thin layer of hyaline cartilage at end of bones where bones connect

Long Bone Structure Periosteum: Covers bones; made up of tough fibrous membrane

Long Bone Structure MEDULLARY CAVITY: Space within diaphysis that contains bone marrow

Long Bone Structure Endosteum: Layer that lines the medullary cavity

Long Bone Structure Spongy Bone: cancellous bone that forms the epiphyses of long bones

Long Bone Structure Yellow Marrow: made up of lipids/fats

Flat Bones • Resembles a sandwich of spongy bone between 2 layers of compact bone The parietal bone & other flat bones of the cranium