The Skeletal System

Structures and Functions

FUNCTIONS

• Support: Provides a framework for the body

Support for soft tissues and a point of attachment for muscles

Protection

• From injury by skeleton• Ex: skull protects brain• vertebrae protects spinal cord• Rib cage protects heart &

lungs• Pelvic bones protect

reproductive organs

Movement Facilitation

• Bones serve as levers to which muscles are attached, when muscles contract movable joints acting as fulcrums cause movement

Storage

• Calcium & Phosphorus: essential for many homeostatic balances

• Blood Cells: red marrow stores and produces RBC’s, some white blood cells, and platelets (hematopoesis)

• Energy: yellow marrow stores lipids for chemical energy

Hematopoiesis

• “heme” meaning “blood”

• “poiesis” meaning “to make”

• Done in the Red marrow.

Types of Bones

• Long Bones: ex: humerus

• Short: ex: carpals

• Flat: ex: frontal

• Irregular: ex: vertebrae

Structure of Long Bones

• Diaphysis: bone shaft• Medullary Canal: hollow area inside bone,

contains marrow• Epiphysis: ends of bone• Articular Cartilage: covers the epiphysis• Periosteum: fibrous covering, except at

joints• Endosteum: thin membrane lines the

medullary canal

Spongy vs. Compact

• Spongy: contains a network of needle like threads of bone tissue that is surrounded by marrow. This network is called “trabeculae”

• Compact: outer layer, hard and dense, contains “osteons” (Haversian Systems) which are concentric circles of hard bone tissue

Cartilage

• Made up of cells called “ chondrocytes”

• Lacks blood vessels, so nutrients must diffuse through the matrix of gel to reach the cells

Bone Formation & Growth

• In utero: skeletal tissue is made up of cartilage and fibrous material, so…

• Baby’s bones are cartilage until calcification occurs,.

• By birth, many of the long bones,skull bones, and bones of the hands and feet are calcified.

“Remodeling”

• Replacing of cartilage with calcified bone matrix.

• Osteoblasts: bone forming cells that do the work of remodeling.

• Osteoclasts: bone resorbing cells.

• Combined action of these 2 cells allows the sculpting of bones .

Divisions of Skeleton

• Axial Skeleton: bones of the center or axis of the body: ex: Cranium, Spine, Thoracic bones, Hyoid Bone

• There are a total of 80 Axial Skeletal Bones

Divisions of Skeleton

• Appendicular: Bones of the upper and lower extremities or appendages

• Ex: Humerus, radius, ulna, carpals etc. Femur, Tibia, Fibula, tarsals etc.

• There are a total of 126 appendicular bones

Skull

• Consists of:

• Cranium: 8 bones

• Face: 14 bones

• Ear: 6

• Sutures: immovable joints in the skull

Spine• Vertebral Column: series of vertebrae• 5 sections: Cervical, Thoracic,

Lumbar, Sacrum, Coccyx• Cervical: 7 vertebrae, 1st cervical

vertebrae is called the atlas, 2nd cervical vertebrae is called the axis.

• Thoracic: 12 vertebrae• Lumbar: 5 vertebrae• Sacrum & Coccyx: 1 of each

Appendicular Skeleton

• Humerus Radius Ulna

• Carpals Metacarpals Phlanges

• Ilium Ishium Symphysis Pubis

• Femur Patella Tibia

• Fibula Tarsals Metatarsals

• Phlanges

Conclusion

•

• Study Skeletal System…Know sections of long bones and label skeletal bones