Skeletal System: Organization and Major Bones

Concept: Parts of the Skeleton

Skeletal Organization

The human skeleton is a complex structure that provides support, protection, and movement for the body. It consists of 206 bones and is organized into two main parts: the axial skeleton and the appendicular skeleton.

• Axial Skeleton: Includes the skull, vertebral column, and thoracic cage (ribs and sternum). It supports the body’s structure and protects internal organs.

• Appendicular Skeleton: Includes the limbs and the pectoral & pelvic girdles. It provides body movement.

Example: The axial skeleton contains the skull, ribs, and vertebrae, while the appendicular skeleton includes the shoulder blades, arms, and legs.

Classification Table: Axial vs. Appendicular Skeleton

Axial Skeleton	Appendicular Skeleton
Skull, vertebral column, ribs, sternum	Shoulder girdle, upper limbs, pelvic girdle, lower limbs
Supports and protects organs	Enables movement
Example: Spine, head	Example: Finger bones, femur

Major Bones of the Axial Skeleton

Skull

• Upper Jaw: Maxilla

• Lower Jaw: Mandible

• Cranium: Protects the brain

Thoracic Cage

• Ribs: Protects thoracic organs

• Breastbone: Sternum

Spinal Column

• Vertebrae: Individual bones forming the spine

• Sacrum: Base of the spine

• Coccyx: Tailbone

Example: The anatomical name for the tailbone is coccyx; for the breastbone, it is sternum.

Major Bones of the Appendicular Skeleton

Pectoral Girdle

• Clavicle: Collarbone

• Scapula: Shoulder blade

Upper Limbs

• Arm: Humerus

• Forearm: Radius & Ulna

• Hand: Carpals (wrist), Metacarpals (palm), Phalanges (fingers)

Pelvic Girdle

• Hip bone: Os coxae

Lower Limbs

• Thigh: Femur

• Leg: Tibia (shin), Fibula (side of leg)

• Foot: Tarsals (ankle), Metatarsals (foot), Phalanges (toes)

Example: The anatomical name for the thighbone is femur; for the shinbone, it is tibia.

Classification Table: Major Bones of the Appendicular Skeleton

Region	Main Bones
Pectoral Girdle	Clavicle, Scapula
Upper Limb	Humerus, Radius, Ulna, Carpals, Metacarpals, Phalanges
Pelvic Girdle	Os coxae
Lower Limb	Femur, Tibia, Fibula, Tarsals, Metatarsals, Phalanges

Key Terms and Definitions

• Axial Skeleton: The central part of the skeleton, including the skull, vertebral column, and thoracic cage.

• Appendicular Skeleton: The limbs and girdles attached to the axial skeleton.

• Clavicle: The collarbone, part of the pectoral girdle.

• Femur: The thighbone, the longest bone in the body.

• Phalanges: Bones of the fingers and toes.

Additional info: The skeleton not only provides structure and movement but also serves as a reservoir for minerals and is involved in blood cell production (hematopoiesis).