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    Related Topics

    From Musculoskeletal System

    Metacarpals (5 bones)
    5 bones forming the palm of the hand.
    Thoracic Cage
    Ribs and sternum forming the protective cage for the heart and lungs.
    Acetabulum
    The acetabulum is the pelvic socket that connects with the femoral head to form the hip joint, vital for stability, movement, and weight-bearing.
    Quadriceps Tendon
    Tendon that connects the quadriceps to the patella.
    Rotator Cuff Tendons
    Tendons of the rotator cuff muscles.
    Ball-and-Socket Joints
    e.g., shoulder, hip
    Patellar Tendon
    Tendon connecting the patella to the tibia.
    Syndesmoses
    Fibrous joints where bones are connected by ligaments.
    Inferior Nasal Conchae
    Bones inside the nasal cavity that filter and humidify air.
    Coccygeus
    Pelvic floor muscle supporting the coccyx.
    Mandible
    Lower jawbone that houses the teeth.
    Obliques (External and Internal)
    Muscles responsible for torso rotation.
    Lumbar Vertebrae (L1 - L5)
    Vertebrae in the lower back (L1-L5).
    Biceps Tendon
    Tendon that attaches the biceps muscle to the bone.
    Sphenoid Bone
    Bone forming part of the base of the skull and sides of the orbits.
    Abductor Digiti Minimi Muscle
    The abductor digiti minimi muscle is a hypothenar muscle that abducts and flexes the little finger, aiding grip and precision in hand movements.
    Acromioclavicular Joint
    The acromioclavicular joint connects the clavicle and scapula at the top of the shoulder, enabling smooth scapular motion and stability during arm movements.
    Levator Ani
    Pelvic floor muscle responsible for lifting the anus.
    Adductors
    Muscles that bring the thighs toward the midline.
    Vomer Bone
    Bone forming the nasal septum.
    Synchondroses
    Cartilaginous joints where bones are connected by hyaline cartilage.
    Diaphragm
    Primary muscle for breathing.
    Tibialis Anterior
    Muscle that dorsiflexes and inverts the foot.
    Gomphoses
    Fibrous joints where a peg fits into a socket (e.g., teeth in jaw).
    Maxillae
    Upper jaw bones that house the teeth and form part of the orbit.

    Coccyx

    Reviewed by our medical team

    Tailbone, the remnant of the tail in humans.

    1. Overview

    The coccyx, commonly known as the tailbone, is the terminal portion of the vertebral column. It is a small, triangular bony structure composed of 3 to 5 fused vertebrae, usually four. The coccyx is considered a vestigial structure, the remnant of a tail in humans, but it still plays important roles in posture, muscle attachment, and weight-bearing when sitting. Despite its small size, injury or dysfunction of the coccyx can lead to significant pain and discomfort.

    2. Location

    The coccyx is located at the inferior end of the vertebral column:

    • Superiorly: Articulates with the sacrum at the sacrococcygeal joint.

    • Inferiorly: Ends in an apex that may be slightly curved or pointed.

    • Posteriorly: Lies just beneath the skin at the base of the spine.

    In seated posture, it is positioned anterior to the gluteal cleft and can be palpated externally.

    3. Structure

    The coccyx is typically made up of four small fused vertebrae (Co1–Co4), though variation exists:

    • Co1: The largest and most prominent segment, often retains rudimentary transverse processes and may articulate with the sacrum.

    • Co2–Co4: Progressively smaller; lack true pedicles, laminae, and spinous processes.

    • Sacrococcygeal joint: A fibrocartilaginous joint (sometimes synovial) between the sacrum and coccyx; may become fused with age.

    • Ligamentous support: Includes the anterior and posterior sacrococcygeal ligaments and the intercornual ligament connecting the sacral and coccygeal cornua.

    4. Function

    The coccyx serves several biomechanical and support functions:

    • Supports weight in sitting: Helps bear body weight when seated, especially when leaning backward.

    • Muscle and ligament attachment: Serves as an anchor for several pelvic floor muscles and ligaments.

    • Shock absorption: Acts as a slight buffer or flex point during falls or sudden seating pressure.

    5. Physiological role(s)

    Despite being vestigial, the coccyx plays important physiological roles:

    • Pelvic floor support: Provides attachment for muscles such as the levator ani, coccygeus, and external anal sphincter, which support pelvic organs and control continence.

    • Postural balance: Contributes to distribution of pressure and posture during sitting and dynamic movement.

    • Parturition (childbirth): May move slightly backward to increase the pelvic outlet during vaginal delivery.

    6. Clinical Significance

    The coccyx can be a source of clinical concern, especially in cases of trauma or dysfunction:

    • Coccydynia (tailbone pain):

      • Pain in the coccygeal region, often from falls, prolonged sitting, childbirth, or idiopathic causes.

      • May involve inflammation, dislocation, or spasm of surrounding muscles (e.g., coccygeus, levator ani).

    • Fracture or dislocation:

      • Results from direct trauma (e.g., falling onto a hard surface); can be very painful and slow to heal.

    • Hyper- or hypomobility:

      • Excessive or restricted movement at the sacrococcygeal joint may cause chronic pain or functional limitations.

    • Surgical consideration:

      • In rare, refractory cases of coccydynia, coccygectomy (surgical removal of the coccyx) may be considered.

    • Referred pain:

      • Pelvic floor dysfunction or nerve entrapment in the region may mimic coccygeal pain and require differential diagnosis.

    Did you know? Sesamoid bones are bones that form within tendons, like the patella.