Bones of the Shoulder (Pectoral) Girdle

Clavicle and Scapula

The shoulder girdle consists of the clavicle and scapula, which connect the upper limb to the axial skeleton and provide attachment points for muscles.

• Clavicle: S-shaped bone that acts as a strut between the sternum and scapula.

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

Key Points

• Glenoid cavity: Shallow socket for the head of the humerus, forming the shoulder joint.

• Acromion: Extension of the scapular spine, articulates with the clavicle.

• Coracoid process: Provides attachment for muscles and ligaments.

Bones of the Upper Extremity

Humerus, Ulna, Radius, Carpals, Metacarpals, and Phalanges

The upper extremity includes the humerus (arm), ulna and radius (forearm), carpals (wrist), metacarpals (hand), and phalanges (fingers).

Key Points

• Olecranon process: Prominent projection of the ulna, forms the elbow.

• Carpals: Eight small bones forming the wrist; scaphoid is one of the most commonly fractured.

• Phalanges: Each finger has three phalanges (proximal, middle, distal), except the thumb, which has two.

Bones of the Pelvic Girdle

Hip Bone (Innominate Bone): Ilium, Ischium, Pubis

The pelvic girdle supports the weight of the upper body and protects pelvic organs. It consists of the ilium, ischium, and pubis, which fuse to form the hip bone.

Key Points

• Acetabulum: Deep socket for the head of the femur, forming the hip joint.

• Ischial tuberosity: Supports body weight when sitting.

• Greater and lesser sciatic notches: Passageways for nerves and blood vessels.

• Pelvic differences: Male pelvis is generally narrower and deeper; female pelvis is wider for childbirth.

Bones of the Lower Extremity

Femur, Patella, Tibia, Fibula, Tarsals, Metatarsals, Phalanges

The lower extremity includes the femur (thigh), patella (kneecap), tibia and fibula (leg), tarsals (ankle), metatarsals (foot), and phalanges (toes).

Key Points

• Femur: Longest and strongest bone in the body.

• Patella: Protects the knee joint and improves leverage of thigh muscles.

• Tibia: Main weight-bearing bone of the leg.

• Fibula: Provides lateral stability to the ankle.

• Talus and calcaneus: Key bones of the ankle and heel.

Knee Joint Structures

Ligaments and Menisci

The knee joint is a complex hinge joint stabilized by ligaments and cushioned by menisci.

• Lateral meniscus: Cartilaginous disc on the outer side of the knee.

• Medial meniscus: Cartilaginous disc on the inner side of the knee.

• Medial (tibial) collateral ligament: Connects femur to tibia on the inner side.

• Posterior cruciate ligament: Prevents posterior displacement of tibia.

• Lateral (fibular) collateral ligament: Connects femur to fibula on the outer side.

• Anterior cruciate ligament: Prevents anterior displacement of tibia.

• Patellar (quadriceps) tendon: Connects quadriceps muscle to tibia via patella.

• Patellar ligament: Connects patella to tibia.

Shoulder Joint Structures

Ligaments, Bursa, and Labrum

The shoulder joint is a ball-and-socket joint with a wide range of motion, stabilized by ligaments, bursa, and the glenoid labrum.

• Tendon of biceps brachii: Passes through the shoulder joint capsule.

• Joint capsule: Encloses the joint, providing stability.

• Glenoid labrum: Fibrocartilaginous rim that deepens the glenoid cavity.

• Coracoacromial ligament: Connects coracoid process to acromion.

• Subacromial/subdeltoid bursa: Reduces friction between acromion and rotator cuff tendons.

• Acromioclavicular ligament: Connects acromion to clavicle.

• Coracoclavicular ligament: Connects coracoid process to clavicle.

• Coracoacromial arch: Formed by coracoid process, acromion, and coracoacromial ligament.

Classification of Joints

Types of Synovial Joints

Joints are classified by the number of axes of movement and the shapes of their articulating surfaces.

• Uniaxial joint: Movement in one plane (e.g., elbow, knee).

• Biaxial joint: Movement in two planes (e.g., metacarpophalangeal joint).

• Triaxial joint: Movement in three planes (e.g., shoulder, hip).

• Ball and socket joint: Spherical head fits into a cup-like socket, allowing multiaxial movement (e.g., hip, shoulder).

• Hinge joint: Allows flexion and extension (e.g., knee, elbow, interphalangeal joints).

Key Points

• Hinge joints: Knee, elbow, interphalangeal joints.

• Ball and socket joints: Hip, shoulder.

Additional info:

• Understanding bone landmarks is essential for identifying muscle attachments and joint articulations.

• Joint classification helps predict movement and stability characteristics.