Skeletal System Anatomy and Bone Classifications

Overview of the Skeletal System

  • The skeletal system is a complex structure supporting the body, facilitating movement, and protecting vital organs.

Bone Classifications

  • Types of Bones:

    • Flat Bone: Example - Sternum

    • Long Bone: Example - Humerus

    • Short Bone: Example - Trapezoid (wrist bone)

    • Irregular Bone: Example - Vertebra

    • Sesamoid Bone: Example - Patella

Bone Structure

  • Compact Bone:

    • Resists stress from weight and movement.

    • Components:

    • Arranged into osteons or Haversian systems.

    • Each osteon includes:

      • Central canal (Haversian canal)

      • Concentric lamellae

      • Lacunae

      • Osteocytes

      • Canaliculi

  • Spongy Bone:

    • Lacks osteons

    • Consists of trabeculae (lattice of thin columns):

    • Makes bones lighter

    • Supports and protects the red bone marrow

    • Features lamellae arranged in a lattice pattern

Divisions of the Skeletal System

  • The human skeleton has 206 named bones, divided into two principal divisions:

    • Axial Skeleton:

    • Bones around the longitudinal axis of the body:

      • Skull bones

      • Auditory ossicles (ear bones)

      • Hyoid bone

      • Ribs and sternum

      • Vertebral column

    • Appendicular Skeleton:

    • Upper and lower limbs (extremities) and girdles connecting them to the axial skeleton:

      • Pectoral girdle (shoulder)

      • Pelvic girdle

Anatomy of Long Bones

  • Long bone (e.g., Humerus) consists of:

    • Articular Cartilage: Covers ends

    • Compact Bone: Dense outer layer

    • Diaphysis: Shaft of the bone

    • Distal Epiphysis: End of the bone farthest from the body

    • Proximal Epiphysis: End of the bone nearest to the body

    • Medullary Cavity: Central cavity containing marrow

    • Metaphysis: Growth plate area

    • Spongy Bone: Inner structure aiding in reduce weight

Axial Skeleton Details

  • Skull Anatomy:

    • Major bones include:

    • Ethmoid

    • Frontal

    • Lacrimal

    • Mandible

    • Maxilla

    • Nasal

    • Sphenoid

    • Zygomatic

  • Vertebral Column:

    • Composed of different sections:

    • Cervical vertebrae (7)

    • Thoracic vertebrae (12)

    • Lumbar vertebrae (5)

    • Sacrum (1)

    • Coccyx (1)

Appendicular Skeleton Details

  • Pectoral Girdle:

    • Includes Clavicle and Scapula

    • Articulates with upper limb (Humerus)

  • Upper Limb Components:

    • Carpals, Humerus, Metacarpals, Phalanges, Radius, and Ulna

  • Pelvic Girdle:

    • Includes components like Hip bones, Sacrum, and Coccyx

  • Lower Limb:

    • Consists of Femur, Patella, Tibia, Fibula, Metatarsals, Phalanges, and Tarsals

Important Notes

  • Bone types and structures are vital for understanding functionality and disease implications in the skeletal system.

  • Mastering the key components of each bone type and division will aid in recalling anatomical and physiological concepts from the skeletal system.