Question

The pectoral and pelvic girdles and the bones of limb form (a) Axial skeleton (b) Appendicular skeleton (c) Visceral skeleton (d) Outer skeleton

Short answer

The pectoral and pelvic girdles and the bones of the limbs form the Appendicular Skeleton.

Step-by-step solution

- Understanding the Terminologies

The axial skeleton includes the bones located along the central axis of the body, including the skull, vertebral column, and rib cage. On the other hand, the appendicular skeleton primarily includes bones of appendages (arms and legs), and girdles (pectoral and pelvic). The visceral skeleton refers to the bones that form certain soft organs, which is not applicable in this case. The term 'outer skeleton' does not apply in this context.

- Analyzing the Given Body Parts

The exercise mentions the pectoral and pelvic girdles and the bones of the limbs, which are parts of the appendages and they are attached around the central axis of the body.

- Conclusion

Based on definitions and the body parts provided, it is clear that the pectoral and pelvic girdles and the bones of the limbs form the Appendicular skeleton.

Key concepts

Axial skeleton

The axial skeleton forms the central core of the human body, often likened to the trunk of a tree. It consists of 80 bones spread across several key areas:

• Skull: Protects the brain and forms the structure of the face.
• Vertebral Column: Offers support to the body, protects the spinal cord, and enables flexible movement.
• Rib Cage: Shields vital organs such as the heart and lungs.

This skeleton is fundamental to our upright posture and protects the crucial organs of our head, neck, and torso. Without the axial skeleton, maintaining structural integrity and balance would be impossible, and the body's internal organs would lack their crucial protective barriers.

Pectoral girdle

The pectoral girdle is crucial as it connects the upper limbs to the axial skeleton. It consists primarily of two types of bones:

• Clavicles (Collarbones): These long, slender bones maintain the position of the shoulder blades and are positioned horizontally across the front of the upper chest.
• Scapulae (Shoulder Blades): These triangular, flat bones provide attachment for several muscles and facilitate arm movements.

The pectoral girdle is designed for flexibility rather than stability, which is why our arms have such a wide range of motion. This structural design allows for activities such as lifting, throwing, and rotating the arms.

Pelvic girdle

The pelvic girdle is a ring-like bony structure located in the lower part of the body, providing attachment for the lower limbs to the axial skeleton. It performs several vital functions:

• Support for Body Weight: It helps bear the weight of the upper body when sitting and standing.
• Movement Facilitation: It allows for leg movements, such as walking and running.
• Protection of Pelvic Organs: It shelters organs such as the intestines, bladder, and reproductive organs.

Formed by the fusion of the hip bones on each side, along with the sacrum and coccyx at the back, the pelvic girdle is essential for balance and stability. The robust structure provides a strong architecture for support and movement, essential for daily activities and locomotion.