Skeletal

Functions of the Skeletal System

Support, Protect, Movement, Storage, Blood cell production.

Components of the Skeletal System

Bones, hyaline cartilage, tendons (muscle to bone), ligaments (bone to bone).

Bone Matrix Composition

35% organic (collagen, proteoglycans) and 65% inorganic (calcium phosphate - hydroxyapatite).

Osteoblasts

Bone-forming cells that produce collagen and proteoglycans and are responsible for ossification.

Osteocytes

Mature bone cells that maintain the bone matrix and account for 90-95% of bone cells.

Osteoclasts

Bone-destroying cells involved in bone resorption and remodeling.

Bone Types

Spongy bone (less matrix, more space) and compact bone (more matrix, less space).

Diaphysis

The center portion of a long bone composed of compact bone surrounding the medullary cavity.

Epiphyseal Plate

Location where growth in bone length occurs, becomes the epiphyseal line when ossified.

Intramembranous Ossification

Bone formation that starts within embryonic connective tissue membranes, forming skull bones.

Endochondral Ossification

Bone formation that starts with a cartilage model, occurring primarily in long bones.

Appositional Growth

Growth in bone width, where new bone is added to the outer edge.

Interstitial Growth

Growth in bone length occurring at the epiphyseal plate.

Bone Remodeling

A process involving the removal of existing bone by osteoclasts and deposition of new bone by osteoblasts.

Bone Repair Steps

1. Hematoma forms, 2. Callus forms, 3. Woven spongy bone replaces callus, 4. Compact bone replaces spongy bone.

Parathyroid Hormone (PTH)

Secreted when blood calcium levels are low, increases osteoclast activity and calcium reabsorption.

Calcitonin

Secreted when blood calcium levels are high, inhibits osteoclast activity and reduces calcium in blood.

Axial Skeleton Composition

Includes 80 bones, a segment of the skeleton which contains the vertebral column and the skull.

Vertebral Column

Central axis of the skeleton, typically consisting of 26 individual bones in adults.

Classification of Joints (Structural)

Fibrous, cartilaginous, synovial based on connective tissue type and joint capsule presence.

Classification of Joints (Functional)

Synarthroses (non-movable), amphiarthroses (slightly movable), diarthroses (freely movable).