The human skeleton is made up of two main parts: the axial skeleton and the appendicular skeleton. It's important to understand how these two parts differ, especially when studying medical anatomy.

1. Composition

• Axial Skeleton: This part has 80 bones. It includes:

  • Skull: 22 bones (these are the bones in your head).
  • Vertebral Column: 26 bones (these make up your spine). They are divided into:
    • Cervical (7 bones in your neck)
    • Thoracic (12 bones in your upper back)
    • Lumbar (5 bones in your lower back)
    • Sacrum (1 bone)
    • Coccyx (1 tailbone)
  • Rib Cage: 24 ribs (which are 12 pairs) plus the sternum (1 breastbone).

• Appendicular Skeleton: This part has 126 bones. It includes the arms and legs and the bones that connect them to the axial skeleton. These bones are divided into:

  • Upper Limbs: 60 bones (30 bones in each arm). Some of these are:
    • Humerus (2)
    • Ulna (2)
    • Radius (2)
    • Carpals (16: 8 in each wrist)
    • Metacarpals (10: 5 in each hand)
    • Phalanges (28: 14 in each hand)
  • Lower Limbs: 60 bones (30 bones in each leg). These include:
    • Femur (2)
    • Patella (2)
    • Tibia (2)
    • Fibula (2)
    • Tarsals (14: 7 in each ankle)
    • Metatarsals (10: 5 in each foot)
    • Phalanges (28: 14 in each foot)
  • Pelvic Girdle: 2 bones (the hip bones, which are made up of ilium, ischium, and pubis).

2. Functions

• Axial Skeleton: This part helps support your body and protects important organs like the brain and spinal cord. It also helps you maintain good posture and balance.

• Appendicular Skeleton: This part is important for moving around and interacting with things around you. It allows your arms and legs to move freely so you can walk, run, and handle objects.

3. Anatomical Position

• Axial Skeleton: Always stays in the center of your body. It forms the core that your limbs are attached to.

• Appendicular Skeleton: This includes all the limbs and the bones that connect them to the central part, allowing them to move at joints.

4. Lifespan Changes

As we grow, our skeletons change. When we are born, we have about 270 bones because some bones have not yet fused together. As we grow, these bones eventually come together, and adults usually end up with 206 bones.

In summary, the axial skeleton is all about support and protection, while the appendicular skeleton is vital for movement and flexibility. Knowing the differences between these parts is key when studying human anatomy, especially for medical purposes.