Chapter 8: The Appendicular Skeleton – Structure and Function

The Appendicular Skeleton

Introduction to the Appendicular Skeleton

The appendicular skeleton is a major division of the human skeletal system. It is essential for movement and manipulation of objects, comprising all bones outside the axial skeleton. The appendicular skeleton includes the limbs and the supportive girdles that attach them to the axial skeleton.

• Function: Enables locomotion and interaction with the environment.

• Components:

  • Limbs: Upper and lower extremities.

  • Girdles: Pectoral (shoulder) and pelvic girdles.

Example: The appendicular skeleton allows humans to walk, grasp objects, and perform complex movements.

Overview of the Skeletal System

The human skeleton is divided into two main parts: the axial skeleton and the appendicular skeleton. The appendicular skeleton consists of 126 bones, while the axial skeleton contains 80 bones.

• Axial Skeleton: Skull, vertebral column, and thoracic cage.

• Appendicular Skeleton: Limbs and girdles.

Major Bones of the Appendicular Skeleton

Region	Main Bones	Number
Pectoral Girdle	Clavicle, Scapula	4
Upper Limbs	Humerus, Radius, Ulna, Carpals, Metacarpals, Phalanges	60
Pelvic Girdle	Hip bones (coxal bones)	2
Lower Limbs	Femur, Patella, Tibia, Fibula, Tarsals, Metatarsals, Phalanges	60

Additional info: The appendicular skeleton is crucial for voluntary movement and supports the body's weight during locomotion.

The Pectoral Girdle

Structure and Function

The pectoral girdle, also known as the shoulder girdle, connects the upper limbs to the trunk. It provides attachment points for muscles and supports arm movement.

• Components:

  • Two clavicles (collarbones)

  • Two scapulae (shoulder blades)

• Connection to Axial Skeleton: The pectoral girdle connects to the axial skeleton only at the manubrium of the sternum.

Example: The clavicle acts as a strut to keep the scapula in position, allowing for a wide range of shoulder movements.

Key Terms

• Clavicle: A long bone that serves as a strut between the shoulder blade and the sternum.

• Scapula: A flat, triangular bone located on the posterior side of the ribcage.

• Manubrium: The broad upper part of the sternum.

Additional info: The pectoral girdle is less stable than the pelvic girdle, allowing for greater mobility of the upper limbs.