Appendicular Skeleton

The Appendicular Skeleton

Overview

• Composed of bones that make up the upper and lower extremities.

• Includes bones forming the pectoral and pelvic girdles.

Pectoral Girdle

• Functions to attach upper extremities to the axial skeleton.

• Main bones include:

  • Clavicles:

    • Articulate with scapula and sternum.

    • S-shaped bones with notable features:

      • Medial sternal end: articulates with the manubrium of the sternum (sternoclavicular joint).

      • Lateral acromial end: articulates with the acromion of scapula (acromioclavicular joint).

  • Scapulae:

    • Flat, triangular bone located on the posterior surface of the thorax.

    • Key landmarks:

      • Body: main part.

      • Spine: bony ridge on posterior surface.

      • Acromion: lateral, flat end of the spine (high point of the shoulder).

      • Coracoid process: projection of the body for muscle attachment.

      • Glenoid cavity: articulation with the head of the humerus, forming the glenohumeral joint (shoulder joint).

Upper Extremities

• Each upper limb consists of 30 bones, including:

  • Humerus:

    • Proximal end:

      • Head: articulates with the glenoid cavity.

      • Greater and lesser tubercles: projections distal to the anatomical neck.

    • Body: shaft of the bone.

    • Distal end:

      • Medial and lateral epicondyles: attachment sites for forearm muscles.

      • Capitulum: articulates with the radius.

      • Trochlea: articulates with the ulna.

      • Olecranon fossa: accommodates the olecranon process of the ulna.

  • Forearm:

    • Composed of radius and ulna, articulating with humerus at the elbow.

    • Radius:

      • Lateral bone, with key features such as the radial head and tuberosity.

    • Ulna:

      • Medial bone, containing the trochlear notch, coronoid process, olecranon process, and styloid process.

  • Wrist:

    • Composed of 8 carpals arranged in two rows.

  • Metacarpals:

    • 5 long bones in palm, articulating with carpals and finger bones.

  • Fingers:

    • Composed of phalanges - 14 in each hand.

Pelvic Girdle

• Attaches lower extremities to the axial skeleton.

• Made of two coxal bones, which articulate with each other and the sacrum.

• Composition of Coxal Bones:

  • Formed by the fusion of ilium, ischium, and pubis.

  • Articulate with the acetabulum for leg attachment and the sacrum posteriorly.

Male vs. Female Pelvic Structures

• Male:

  • Narrower pelvic arch (less than 90 degrees).

  • Larger acetabulum and heavier structure.

  • Longer, narrower sacrum.

• Female:

  • Wider pelvic arch (greater than 90 degrees) for childbirth.

  • Smaller acetabulum and lighter structure.

  • Wider and shorter sacrum.

Lower Extremities

• 30 bones per limb, totaling 60 bones:

  • Femur:

    • Proximal end: contains head, greater and lesser trochanter.

    • Neck: narrow area (common fracture site).

    • Distal end: epicondyles, condyles for knee joint articulation.

  • Tibia:

    • Medial bone supporting body weight; features include condyles for knee joint articulation and tibial tuberosity.

  • Fibula:

    • Lateral bone with a head articulating with the tibia; contains a lateral malleolus at the ankle.

  • Tarsals (ankle and heel): 7 short bones (talus, calcaneus, navicular, etc.).

  • Metatarsals and Phalanges: similar structure to metacarpals and fingers; total of 14 phalanges in each foot.

Foot Arches

• Comprised of ligaments and tendons forming two arches:

  • Longitudinal Arch and Transverse Arch.

• Functions: distribute body weight, act as a spring, support the body, and provide leverage for walking.

Disorders Related to Foot Structure

• Flat foot: decreased longitudinal arch.

• Club foot: increased longitudinal arch.

• Bunion: deformity of the big toe.