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
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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
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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