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Appendicular Skeleton Features: Key Bones and Landmarks

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Appendicular Skeleton Features

The appendicular skeleton consists of the bones of the limbs and their girdles, which attach them to the axial skeleton. Understanding the key features and landmarks of these bones is essential for identifying and differentiating them, as well as for understanding their functions in movement and support.

Clavicle

The clavicle, or collarbone, is a slender, S-shaped bone that connects the upper limb to the trunk.

  • Sternal end: The medial, rounded end that articulates with the manubrium of the sternum.

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

Scapula

The scapula, or shoulder blade, is a flat, triangular bone located on the posterior thoracic wall.

  • Acromion: Lateral extension forming the highest point of the shoulder.

  • Coracoid process: Hook-like projection on the anterior surface.

  • Glenoid cavity: Shallow socket that articulates with the head of the humerus.

  • Spine: Prominent ridge running across the posterior surface.

Humerus

The humerus is the long bone of the upper arm, extending from the shoulder to the elbow.

  • Head: Rounded proximal end that fits into the glenoid cavity.

  • Olecranon fossa: Large depression on the posterior distal end for the ulna.

  • Medial epicondyle: Bony projection on the distal medial side.

  • Lateral epicondyle: Bony projection on the distal lateral side.

  • Trochlea: Spool-shaped structure on the distal end that articulates with the ulna.

Radius

The radius is one of the two forearm bones, located on the lateral (thumb) side.

  • Radial head: Proximal end that articulates with the humerus and ulna.

  • Styloid process: Distal projection on the lateral side of the wrist.

  • Radial tuberosity: Bony prominence below the neck for muscle attachment.

  • Ulnar notch: Distal medial indentation for articulation with the ulna.

Ulna

The ulna is the medial bone of the forearm, on the side of the little finger.

  • Olecranon process: Prominent projection at the proximal end, forming the elbow.

  • Styloid process: Distal projection on the medial side of the wrist.

  • Trochlear notch: Large, curved area that articulates with the trochlea of the humerus.

Carpals

The carpals are the eight small bones that make up the wrist. (Bones on lab 4 list.)

  • Arranged in two rows (proximal and distal) and allow for wrist movement.

Pelvic Girdle

The pelvic girdle consists of two hip bones, each formed by the fusion of three bones: ilium, pubis, and ischium.

  • Ilium: Superior, flared portion; includes the iliac crest.

  • Pubis: Anterior portion; forms the pubic symphysis.

  • Ischium: Inferior, posterior portion; supports weight when sitting.

  • Landmarks: Iliac crest, anterior/posterior superior/inferior iliac spine, acetabulum (hip socket), pubic symphysis, obturator foramen, pubic arch.

  • Sexual dimorphism: Male vs. female pelvis differences (e.g., wider pubic arch in females).

Femur

The femur is the longest and strongest bone in the body, forming the thigh.

  • Head: Proximal, rounded end that fits into the acetabulum.

  • Neck: Narrow region just below the head.

  • Greater trochanter: Large lateral projection for muscle attachment.

  • Lateral and medial epicondyles: Distal projections for ligament attachment.

  • Patellar surface: Smooth area on the anterior distal end for the patella.

Tibia

The tibia is the larger, medial bone of the lower leg.

  • Anterior crest: Sharp ridge running down the anterior surface.

  • Tibial tuberosity: Bump on the anterior surface for patellar ligament attachment.

  • Medial malleolus: Distal projection forming the inner ankle.

Fibula

The fibula is the slender, lateral bone of the lower leg.

  • Head: Proximal end that articulates with the tibia.

  • Lateral malleolus: Distal projection forming the outer ankle.

Knee

The knee joint is a complex hinge joint involving several bones and ligaments.

  • Ligaments: ACL (anterior cruciate ligament), PCL (posterior cruciate ligament), MCL (medial collateral ligament), LCL (lateral collateral ligament).

  • Menisci: Medial and lateral meniscus, fibrocartilage pads that cushion the joint.

  • Patellar ligament: Connects the patella to the tibial tuberosity.

Shoulder

The shoulder joint is a ball-and-socket joint with a wide range of motion.

  • Glenoid cavity: Shallow socket of the scapula.

  • Rotator cuff: Group of muscles and tendons stabilizing the joint.

  • Specific muscles: (Refer to lab 6 for details.)

Hip

The hip joint is a deep ball-and-socket joint providing stability and support for body weight.

  • Iliofemoral ligament: Strong ligament reinforcing the anterior joint capsule.

  • Pubofemoral ligament: Supports the joint inferiorly and anteriorly.

  • Acetabulum: Deep socket in the pelvis for the femoral head.

Additional info:

  • Students should be able to differentiate left and right for each bone by examining the orientation of key landmarks (e.g., the direction of the head, position of the malleoli, etc.).

  • Sexual dimorphism in the pelvis is important for forensic and clinical applications.

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