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    Related Topics

    From Musculoskeletal System

    Maxillae
    Upper jaw bones that house the teeth and form part of the orbit.
    Lateral Collateral Ligament (LCL)
    Knee ligament that stabilizes the outer knee.
    Lumbar Vertebrae (L1 - L5)
    Vertebrae in the lower back (L1-L5).
    Extensor Tendons
    Tendons that help extend the fingers and toes.
    Cranial Bones
    Bones of the skull that protect the brain.
    Ribs (12 Pairs)
    12 pairs of bones that form the sides of the thoracic cage.
    Zygomatic Bones
    Cheekbones that form part of the orbit.
    Ligamentum Flavum
    Spinal ligament connecting the laminae of adjacent vertebrae.
    Rectus Abdominis
    Abs muscle that flexes the trunk.
    Temporal Bones
    Bones forming the lower sides of the skull and housing the ears.
    Nasal Bones
    Bones forming the bridge of the nose.
    Humerus
    Upper arm bone connecting the shoulder to the elbow.
    Inferior Nasal Conchae
    Bones inside the nasal cavity that filter and humidify air.
    Tibia
    Shin bone, the larger bone in the lower leg.
    Temporalis
    Muscle involved in closing the jaw.
    Hyoid Bone
    U-shaped bone in the neck that supports the tongue.
    Sesamoid Bones
    e.g., patella, some found in hands/feet.
    Quadriceps
    Rectus Femoris, Vastus Medialis, Vastus Lateralis, Vastus Intermedius.
    Interspinous Ligament
    Spinal ligament between adjacent vertebral spinous processes.
    Sternum
    Breastbone located in the center of the chest.
    Triceps Brachii
    Muscle responsible for elbow extension.
    Ethmoid Bone
    Bone forming part of the nasal cavity and the orbit.
    Metatarsals (5 bones)
    5 bones forming the mid-foot.
    Synchondroses
    Cartilaginous joints where bones are connected by hyaline cartilage.
    Masseter
    Muscle that elevates the mandible.

    Carpals (8 bones)

    Reviewed by our medical team

    8 wrist bones.

    1. Overview

    The carpal bones are a group of eight small, irregularly shaped bones that form the wrist (carpus) and connect the forearm to the hand. These bones are arranged in two rows—proximal and distal—and articulate with each other, the radius, and the metacarpals. The carpal bones contribute to the flexibility and strength of the wrist and serve as a stable yet mobile base for hand movement. They are vital for transmitting forces and allowing a wide range of motion while maintaining wrist stability.

    2. Location

    The carpal bones are located in the wrist region, situated between the distal end of the radius and ulna proximally, and the metacarpal bones distally. They are organized into:

    • Proximal row (lateral to medial): Scaphoid, Lunate, Triquetrum, Pisiform

    • Distal row (lateral to medial): Trapezium, Trapezoid, Capitate, Hamate

    The mnemonic “Some Lovers Try Positions That They Can’t Handle” helps recall the order from lateral (thumb side) to medial (pinky side).

    3. Structure

    Each carpal bone is composed of cortical bone externally and cancellous (spongy) bone internally. The structural characteristics include:

    • Scaphoid: Boat-shaped; largest bone of the proximal row; articulates with the radius.

    • Lunate: Crescent-shaped; centrally located; articulates with the radius and capitate.

    • Triquetrum: Pyramid-shaped; articulates with lunate and pisiform.

    • Pisiform: Pea-shaped sesamoid bone lying over the triquetrum; embedded in the tendon of flexor carpi ulnaris.

    • Trapezium: Saddle-shaped; articulates with the first metacarpal; key to thumb mobility.

    • Trapezoid: Wedge-shaped; articulates with the second metacarpal.

    • Capitate: Largest carpal bone; centrally located; articulates with the third metacarpal.

    • Hamate: Characterized by a hook-like projection (hamulus); articulates with the fourth and fifth metacarpals.

    4. Function

    The carpal bones work collectively to:

    • Allow wrist movement: Facilitate flexion, extension, radial deviation, and ulnar deviation of the wrist joint.

    • Transmit force: Distribute loads from the hand to the radius and ulna during grip and weight-bearing activities.

    • Enable thumb opposition: Especially through the trapezium, allowing fine manipulation.

    • Support tendons: Serve as pulleys and surfaces for tendon gliding, especially within the carpal tunnel.

    5. Physiological role(s)

    The carpal bones contribute to broader functional systems in the upper limb:

    • Dexterity: Provide a mobile yet stable platform for finger movement and tool use.

    • Muscle attachment: Serve as anchor points for muscles controlling the wrist and hand.

    • Ligamentous integrity: Connect with strong ligaments (e.g., scapholunate, radiocarpal) for wrist stability.

    • Neurovascular protection: The concavity formed by the carpal arch creates the carpal tunnel, through which the median nerve and tendons pass.

    6. Clinical Significance

    The carpal bones are frequently involved in fractures, dislocations, and compressive syndromes:

    • Scaphoid fracture:

      • Most commonly fractured carpal bone; typically due to a fall on an outstretched hand (FOOSH).

      • Prone to avascular necrosis due to poor blood supply, especially to the proximal pole.

    • Lunate dislocation:

      • Can compress the median nerve and lead to carpal instability or acute carpal tunnel syndrome.

    • Carpal tunnel syndrome:

      • Compression of the median nerve beneath the transverse carpal ligament, often caused by swelling or structural narrowing involving carpal bones.

    • Arthritis:

      • Osteoarthritis or rheumatoid arthritis can affect intercarpal joints, reducing wrist mobility and causing pain.

    • Kienböck’s disease:

      • Avascular necrosis of the lunate, leading to progressive collapse and wrist dysfunction.

    • Hook of hamate fracture:

      • Often seen in sports (e.g., golf, baseball); may compress the ulnar nerve and affect grip strength.

    Did you know? Your spinal cord is protected by the vertebral column.