The Skeletal System

What are the basic components of bone tissue?

Cells in a hard extracellular matrix made of inorganic salts and collagenous fibers.

Osteoclasts

Cells that break down and absorb bone tissue for remodeling.

Osteoblasts

Cells that secrete the matrix of bone tissue.

Osteocytes

Principle bone cells that maintain the condition of bone.

Function of the skeletal system - Framework and support

Adds shape and structure to the body.

Function of the skeletal system - Body movement

Bones work as levers with skeletal muscles attached.

Function of the skeletal system - Protection

Skull protects the brain; rib cage protects heart and lungs.

Function of the skeletal system - Formation of blood cells

Red marrow produces blood cells within spongy bone.

Function of the skeletal system - Mineral salt storage

Bones absorb and release inorganic salts as needed.

Axial skeleton components

Skull, hyoid, vertebral column, rib cage.

Appendicular skeleton components

Shoulder girdle, upper appendages, pelvic girdle, lower appendages.

Fossa

A pit or depression.

Foramen

A hole.

Meatus

A tube-like passageway.

Sinus

A cavity within a bone.

Suture

An interlocking joint between bones.

Osteon

A ring structure formed by concentric layers of bone matrix.

Spongy bone

Interior bone with branching structures called trabeculae.

Compact bone

Tightly packed exterior bone providing strength.

Medullary cavity

The hollow chamber in the diaphysis containing yellow bone marrow.

Epiphysis

Widened ends of bone containing red marrow.

Periosteum

Dense connective tissue membrane enclosing bone.

Articular cartilage

Cartilage that covers the epiphysis for smooth joint motion.

Homeostasis of bone tissue

Balanced remodeling between osteoclasts and osteoblasts.

Role of osteoclasts in remodeling

Resorb old or damaged bone tissue.

Role of osteoblasts in remodeling

Replace resorbed tissue with new bone.

Bone healing process - Step 1

Blood escapes from ruptured vessels forming a hematoma.

Bone healing process - Step 2

Inflammation occurs, and phagocytes and fibroblasts invade the area.

Bone healing process - Step 3

Fibroblasts create a soft callus of fibrocartilage.

Class of joints - Fibrous joints

Generally immovable, connected by dense connective tissue.

Class of joints - Cartilaginous joints

Slightly movable, connected by cartilage.

Class of joints - Synovial joints

Freely movable, covered by articular cartilage.

Ball and socket joint

Allows movement in three planes, like hip and shoulder.

Hinge joint

Allows movement in one plane, like between phalanges.

Pivot joint

One bone rotates in a cusp of another, like radius and ulna.

Flexion

Decreasing the angle between parts.

Extension

Increasing the angle or straightening.

Abduction

Drawing away from the body’s midline.

Adduction

Moving toward the body’s midline.

Pronation

Rotation of the forearm with the palm facing down.

Supination

Rotation of the forearm with the palm facing up.

Protraction

Moving a part forward.

Retraction

Moving a part backward.