Appendicular Skeleton

Overview

The appendicular skeleton is a major division of the human skeletal system, primarily responsible for facilitating movement. It consists of the bones of the upper and lower limbs, as well as the pectoral and pelvic girdles that attach the limbs to the axial skeleton.

• Primary function: Aid in movement and locomotion.

• Includes: Bones of the upper limbs (arms) and lower limbs (legs).

• Pectoral girdle: 4 bones (2 clavicles, 2 scapulae).

• Pelvic girdle: 2 bones (hip bones, or coxal bones).

Pectoral Girdle

Structure and Function

The pectoral girdle connects the upper limbs to the trunk and provides a wide range of motion for the arms. It is composed of the clavicle and scapula.

• Consists of: Clavicle (collarbone) and scapula (shoulder blade).

• Does not articulate with the vertebral column.

• Sockets are shallow: This allows for greater mobility of the shoulder joint.

• Stabilized by: Dorsal (back), shoulder, and thoracic (chest) muscles.

Pectoral Girdle: Clavicle

Anatomy and Articulations

The clavicle is a long, slender bone that acts as a strut between the sternum and scapula, transferring mechanical force from the upper limb to the trunk.

• Transfers mechanical force: From upper limb to trunk.

• Sternoclavicular joint: Medial articulation with the manubrium of the sternum.

• Acromioclavicular joint: Lateral articulation with the acromion of the scapula.

Pectoral Girdle: Scapula

Surface Features

The scapula, or shoulder blade, is a flat, triangular bone with several important anatomical landmarks.

• Spine: Large posterior process for muscle attachment.

• Acromion: Flattened lateral portion of the spine; articulates with the clavicle.

• Coracoid process: Anterior projection, inferior to the clavicle; attachment site for muscles and ligaments.

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

Arm: Humerus

Structure and Articulations

The humerus is the longest and largest bone of the upper limb, forming the upper arm.

• Head: Articulates with the glenoid cavity of the scapula (glenohumeral joint).

• Deltoid tuberosity: Site of insertion for the deltoid muscle.

• Medial and lateral epicondyles: Origins for most forearm muscles.

Forearm: Radius and Ulna

Anatomy and Articulations

The radius and ulna are the two bones of the forearm, allowing for rotation and movement of the wrist and hand.

• Ulna: Longer bone, located medially (on the side of the little finger).

• Olecranon: Prominent process of the ulna that articulates with the humerus at the elbow.

• Radius: Shorter bone, located laterally (on the side of the thumb); disc-shaped head articulates with the ulna.

• Interosseous membrane: Fibrous sheet joining the shafts of the radius and ulna, providing stability and muscle attachment.

Additional info:

• The appendicular skeleton is essential for voluntary movement and interaction with the environment.

• Joints formed by these bones (shoulder, elbow, wrist) are synovial, allowing for a wide range of motion.