The human elbow is a complex joint composed of three bones and various other structures. Here's a breakdown of its key parts:
Bones of the Elbow
The elbow joint is primarily formed by the articulation of three bones:
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Humerus: This is the bone of the upper arm. The distal (lower) end of the humerus forms the upper portion of the elbow joint. Specific features include:
- Trochlea: Articulates with the ulna.
- Capitulum: Articulates with the radius.
- Epicondyles (Medial and Lateral): Bony prominences on either side of the humerus that serve as attachment points for muscles and ligaments.
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Ulna: This is one of the two bones in the forearm, located on the pinky finger side. The proximal (upper) end of the ulna forms a major part of the elbow joint. Key features include:
- Olecranon: The bony prominence at the back of the elbow that fits into the olecranon fossa of the humerus.
- Coronoid Process: A bony projection that fits into the coronoid fossa of the humerus.
- Trochlear Notch (Semilunar Notch): Articulates with the trochlea of the humerus.
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Radius: This is the second bone in the forearm, located on the thumb side. The head of the radius articulates with the capitulum of the humerus, allowing for rotation of the forearm.
Ligaments
Ligaments are strong bands of tissue that connect bones and provide stability to the elbow joint. The main ligaments include:
- Ulnar Collateral Ligament (UCL): Located on the medial (inner) side of the elbow, providing resistance to valgus (outward) stress.
- Radial Collateral Ligament (RCL): Located on the lateral (outer) side of the elbow, providing resistance to varus (inward) stress.
- Annular Ligament: Wraps around the head of the radius, holding it in place against the ulna.
Muscles and Tendons
Several muscles cross the elbow joint, allowing for flexion, extension, pronation, and supination of the forearm. Key muscles and their tendons include:
- Biceps Brachii: Flexes the elbow and supinates the forearm.
- Brachialis: A powerful elbow flexor.
- Triceps Brachii: Extends the elbow.
- Brachioradialis: Flexes the elbow and assists with pronation and supination.
- Pronator Teres and Pronator Quadratus: Pronate the forearm.
- Supinator: Supinates the forearm.
Other Structures
- Joint Capsule: A fibrous envelope that surrounds the elbow joint, enclosing the joint space and containing synovial fluid.
- Synovial Membrane: Lines the joint capsule and produces synovial fluid, which lubricates the joint and reduces friction.
- Nerves: Several nerves pass near the elbow, including the ulnar nerve, median nerve, and radial nerve, which control sensation and muscle function in the forearm and hand.
- Blood Vessels: Blood vessels supply the elbow joint with nutrients and oxygen.
In summary, the elbow is a complex joint comprised of the humerus, ulna, and radius bones, supported by ligaments, muscles, tendons, a joint capsule, and other vital structures that enable a wide range of arm movements.
