Concise Summary of the Skeletal System

Skeletal System Overview

• The skeletal system serves as the framework for physical support and locomotion in organisms.

• Types of skeletal systems: Hydrostatic, Exoskeleton, Endoskeleton (e.g., in rats and vertebrates).

Functions of the Skeletal System

• Provides shape and support to the body.

• Protects internal organs.

• Serves as attachment points for muscles.

• Main site for blood cell formation (hematopoiesis) in red marrow.

• Acts as a storage organ for calcium and phosphorus.

Bone Classification

• 206 bones in the adult human skeleton classified into five categories by shape:

  • Long: e.g., Femur, tibia, support and movement.

  • Short: e.g., Carpals, stability and support.

  • Flat: e.g., Sternum, points of attachment for muscles and protectors of organs.

  • Irregular: e.g., Vertebrae, complex shapes for support and protection.

Bone Cells

• Osteogenic cells: Stem cells in bone.

• Osteoblasts: Form bone matrix.

• Osteocytes: Maintain bone tissue.

• Osteoclasts: Resorb bone.

Anatomy of Long Bones

• Consist of two main regions:

  • Diaphysis (shaft): Contains the medullary cavity filled with yellow marrow.

  • Epiphysis (ends): Contains spongy bone and red marrow.

• Growth occurs at the epiphyseal plate until adulthood when it becomes the epiphyseal line.

Axial vs. Appendicular Skeleton

• Axial Skeleton: Includes skull, vertebral column, ribs, and sternum.

• Appendicular Skeleton: Comprises the girdles and limbs.

Specific Bones of Interest

• Skull:

  • Made up of cranial and facial bones, including maxilla and mandible.

• Vertebral Column:

  • Comprises cervical (7), thoracic (12), lumbar (5), sacral (5 fused), and caudal (variable).

• Rib Cage:

  • 12 pairs of ribs protecting the thoracic organs; classified into true, false, and floating ribs.

Joint Types

• Synovial Joints: Include hinge, ball-and-socket, pivot, gliding, saddle, planar.

• Immovable Joints (Sutures): Found between skull bones, allowing for limited motion and stability in the cranium.