Appendicular Skeleton: Structure, Components, and Functional Anatomy

Appendicular Skeleton

Overview of the Appendicular Skeleton

The appendicular skeleton consists of the bones of the limbs and the girdles that attach them to the axial skeleton. It is essential for movement and manipulation of the environment.

• Main Divisions: Pectoral (shoulder) girdle, upper limbs, pelvic (hip) girdle, and lower limbs.

• Function: Provides support, facilitates movement, and serves as attachment points for muscles.

• Comparison: Unlike the axial skeleton, the appendicular skeleton is more involved in locomotion and manipulation rather than protection of vital organs.

Example: The humerus (upper arm bone) is part of the appendicular skeleton and is crucial for arm movement.

Major Bones of the Appendicular Skeleton

Region	Bones	Number
Pectoral Girdle	Clavicle, Scapula	2 each
Upper Limb	Humerus, Radius, Ulna, Carpals, Metacarpals, Phalanges	1, 1, 1, 8, 5, 14 per limb
Pelvic Girdle	Hip bones (Ilium, Ischium, Pubis)	2 (each side)
Lower Limb	Femur, Patella, Tibia, Fibula, Tarsals, Metatarsals, Phalanges	1, 1, 1, 1, 7, 5, 14 per limb

Pectoral Girdle

Structure and Function

The pectoral girdle connects the upper limb to the trunk and provides attachment points for muscles that move the shoulder and arm.

• Bones: Clavicle (collarbone) and scapula (shoulder blade).

• Function: Allows for a wide range of motion at the shoulder joint.

• Muscle Attachment: The girdle has ridges and processes for muscle attachment, contributing to the mobility and stability of the shoulder.

Example: The clavicle acts as a strut to keep the scapula in position, allowing the arm to hang freely.

Scapula

Key Landmarks and Anatomy

The scapula is a flat, triangular bone located on the posterior side of the ribcage. It serves as a major attachment site for muscles and forms part of the shoulder joint.

• Borders: Superior, medial (vertebral), and lateral (axillary) borders.

• Spine of Scapula: A prominent ridge dividing the posterior surface into the supraspinous and infraspinous fossae.

• Fossae: Supraspinous fossa (above the spine), infraspinous fossa (below the spine), and subscapular fossa (anterior surface).

• Processes: Acromion (articulates with clavicle), coracoid process (muscle attachment).

• Glenoid Cavity: Shallow socket that articulates with the head of the humerus to form the shoulder joint.

Example: The infraspinous fossa provides attachment for the infraspinatus muscle, a rotator cuff muscle.

Scapular Borders and Surfaces

• Superior Border: Shortest and thinnest border, located at the top of the scapula.

• Medial Border: Closest to the vertebral column; provides attachment for several muscles.

• Lateral Border: Thickest border, located near the armpit (axilla); ends at the glenoid cavity.

• Posterior View: The spine is visible, dividing the bone into two distinct fossae.

Example: The acromion process extends laterally from the spine and forms the highest point of the shoulder.

Additional info:

• The appendicular skeleton is essential for movement and interaction with the environment, while the axial skeleton primarily provides protection and support.

• Understanding the landmarks of the scapula is crucial for identifying muscle attachments and understanding shoulder mechanics.