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 Protection (ex: skull/vertebral column) Movement (Leverage/force of motion) Support (ex: femur supports upper body) 4 Storage of minerals (calcium) and lipids (yellow marrow) 5 Blood cell production (in red bone marrow)

Classification of Bones Bones are identified by SHAPE Long bones Flat bones Sutural bones Irregular bones Short bones Sesamoid bones

Long Bones Are found in limbs, hands, feet, fingers, and toes 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