Anatomy of the Pectoral Girdle and Upper Limb Bones

Pectoral Girdle

Scapula

The scapula, or shoulder blade, is a flat, triangular bone that forms the posterior part of the pectoral girdle. It provides attachment points for several muscles and articulates with the clavicle and humerus.

• Acromion: The lateral end of the spine of the scapula that articulates with the acromial end of the clavicle.

• Coracoid process: Projects above the glenoid cavity as a hooklike process; serves as an attachment for the biceps brachii muscle.

• Glenoid cavity: A shallow socket that articulates with the head of the humerus, forming the shoulder joint.

• Spine: A prominent ridge on the posterior surface, easily felt through the skin.

Clavicle

The clavicle, or collarbone, is a slender, S-shaped bone that serves as a strut between the scapula and the sternum.

• Acromial end: The flattened lateral end that articulates with the acromion of the scapula.

• Sternal end: The triangular medial end that articulates with the sternum.

Example:

The pectoral girdle allows for a wide range of motion at the shoulder, essential for activities such as throwing or lifting.

Upper Limb

Humerus

The humerus is the long bone of the upper arm, extending from the shoulder to the elbow. It articulates proximally with the scapula and distally with the radius and ulna.

• Greater tubercle: Large lateral prominence; site of attachment for rotator cuff muscles.

• Lesser tubercle: Small medial prominence; also a site of muscle attachment.

• Surgical neck: The constricted area below the tubercles; common site of fractures.

• Deltoid tuberosity: Roughened area about midway down the shaft; attachment for the deltoid muscle.

• Shaft: The elongated, cylindrical portion of the bone.

• Lateral epicondyle: Small condyle proximal to the capitulum.

• Medial epicondyle: Rough condyle proximal to the trochlea.

• Radial fossa: Small lateral depression; receives the head of the radius during flexion.

• Coronoid fossa: Small medial anterior depression; receives the coronoid process of the ulna during flexion.

• Olecranon fossa: Large distal posterior depression; accommodates the olecranon of the ulna during extension.

• Capitulum: Rounded lateral condyle that articulates with the radius.

• Trochlea: A flared medial condyle that articulates with the ulna.

Example:

The humerus is commonly fractured at the surgical neck, especially in elderly individuals.

Radius

The radius is one of the two bones of the forearm, located on the lateral (thumb) side. It is involved in the movement of the wrist and rotation of the forearm.

• Head: The proximal end that articulates with the capitulum of the humerus.

• Radial tuberosity: A medial prominence just below the head; site of attachment for the biceps brachii muscle.

• Styloid process: Distal prominence; site of attachment for wrist ligaments.

Example:

The radius rotates over the ulna during pronation and supination of the forearm.

Ulna

The ulna is the medial bone of the forearm, located on the side of the little finger. It forms the major portion of the elbow joint with the humerus.

• Olecranon process: Prominent projection on the proximal posterior ulna; fits into the olecranon fossa of the humerus during extension.

• Trochlear notch: Deep notch that separates the olecranon and coronoid processes; articulates with the trochlea of the humerus.

• Coronoid process: Shaped like a point on a crown; articulates with the trochlea of the humerus during flexion.

• Styloid process: Distal pointed projection; located medial to the head of the ulna.

• Radial notch: Small proximal lateral notch that articulates with the head of the radius.

Example:

The olecranon process forms the bony tip of the elbow, which can be felt when the arm is flexed.

Comparative Table: Key Features of Upper Limb Bones

Bone	Key Features	Articulations
Scapula	Acromion, Coracoid process, Glenoid cavity, Spine	Clavicle, Humerus
Clavicle	Acromial end, Sternal end	Scapula, Sternum
Humerus	Greater/Lesser tubercle, Deltoid tuberosity, Capitulum, Trochlea	Scapula, Radius, Ulna
Radius	Head, Radial tuberosity, Styloid process	Humerus, Ulna, Carpal bones
Ulna	Olecranon process, Trochlear notch, Coronoid process, Styloid process	Humerus, Radius, Carpal bones

Additional info: The pectoral girdle and upper limb bones are essential for the wide range of motion and dexterity of the human arm. Their articulations and surface features provide attachment points for muscles and ligaments, enabling complex movements.