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.