Section 8-11: The Pectoral (Shoulder) Girdle and Upper Limb Bones

Overview of the Pectoral Girdle

The pectoral girdle consists of the clavicle and scapula, connecting the upper limb to the axial skeleton. It allows for a wide range of motion and supports the arm.

• Articulation: The only direct articulation between the pectoral girdle and the axial skeleton is at the sternoclavicular joint, where the clavicle meets the sternum.

• Acromioclavicular Joint: The clavicle also articulates with the acromion of the scapula at the acromioclavicular joint.

• Glenohumeral Joint: The scapula articulates with the head of the humerus at the glenohumeral joint, forming the shoulder joint.

Key Terms:

• Manubrium: The upper part of the sternum, articulates with the clavicle.

• Acromion: The lateral extension of the scapula, articulates with the clavicle.

• Coracoid Process: A projection on the scapula for muscle attachment.

• Glenoid Cavity: The socket in the scapula for the head of the humerus.

Examples: The clavicle is commonly fractured in falls on the shoulder due to its subcutaneous position.

Adaptations for Free Movement

The bones of the upper limb are adapted for mobility, allowing for complex movements such as lifting, throwing, and rotation.

• Metaphysis: The region between the diaphysis and epiphysis of a long bone; in the humerus, the surgical neck corresponds to the metaphysis.

• Surgical Neck: Common site for fractures in the humerus.

• Tuberosity: A rough projection for muscle attachment, such as the deltoid tuberosity on the humerus.

• Epicondyles: Medial and lateral projections at the distal end of the humerus for ligament and muscle attachment.

Additional info: The radial tuberosity is the site of biceps brachii attachment, allowing for forearm flexion.

Key Joints and Landmarks

• Pivot Joint: The proximal radioulnar joint allows for rotation of the forearm (pronation and supination).

• Radial Notch: Found on the ulna, articulates with the head of the radius.

• Styloid Process: Found at the distal ends of the radius and ulna, serves as attachment for ligaments of the wrist.

• Pollex: The anatomical term for the thumb.

Section 8-12: The Pelvic Girdle and Lower Limb Bones

Overview of the Pelvic Girdle

The pelvic girdle consists of the two hip bones (os coxae), sacrum, and coccyx, forming a strong basin for supporting the weight of the upper body and protecting pelvic organs.

• Acetabulum: The deep socket in the hip bone for the head of the femur.

• Pubic Symphysis: A cartilaginous joint uniting the left and right pubic bones.

• Sacroiliac Joint: The joint between the sacrum and ilium.

• Obturator Foramen: A large opening in the hip bone for nerves and blood vessels.

Additional info: The pelvis is classified as male or female based on features such as the pelvic inlet, outlet, and pubic angle.

Key Structures and Functions

• Ischial Tuberosity: The part of the pelvis you sit on; attachment for hamstring muscles.

• Pelvic Outlet: The lower opening of the pelvis, important in childbirth.

• Pelvic Inlet: The upper opening of the pelvis.

Section 8-14: Bones of the Lower Limb Adapted for Movement and Support

Overview of the Lower Limb Bones

The bones of the lower limb are specialized for weight-bearing and locomotion, including the femur, patella, tibia, fibula, tarsals, metatarsals, and phalanges.

• Femur: The longest and strongest bone in the body.

• Patella: The kneecap, a sesamoid bone formed within the tendon of the quadriceps femoris muscle.

• Tibia: The main weight-bearing bone of the lower leg.

• Fibula: The lateral bone of the lower leg, not weight-bearing.

• Malleolus: The medial and lateral projections at the ankle (medial malleolus of tibia, lateral malleolus of fibula).

• Tarsals: Seven bones forming the ankle and heel, including the talus and calcaneus.

• Metatarsals and Phalanges: Bones of the foot and toes.

Additional info: The arch of the foot is formed by the arrangement of tarsal and metatarsal bones, providing shock absorption and support.

Key Landmarks and Joints

• Tibial Tuberosity: Attachment for the patellar ligament.

• Talus: The bone that articulates with the tibia and fibula at the ankle joint.

• Calcaneus: The heel bone, largest tarsal bone.

Section 8-15: Sex Differences in the Human Skeleton

Overview of Sex Differences

Sexual dimorphism in the human skeleton is most evident in the pelvis, which is adapted for childbirth in females.

• General Appearance: Male skeletons are generally larger and more robust.

• Pelvic Inlet: Wider and more circular in females; narrower in males.

• Pelvic Outlet: Larger in females to facilitate childbirth.

• Pubic Angle: Greater in females (usually >90°) than in males.

Key Formulas and Equations

• Bone Strength:

• Joint Classification:

Summary Table: Major Bones and Landmarks