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    From Musculoskeletal System

    Levator Ani
    Pelvic floor muscle responsible for lifting the anus.
    Anterior Scalene Muscle
    The anterior scalene muscle is a deep neck muscle that elevates the first rib during inspiration and aids in neck flexion and stability, located between key neurovascular structures.
    Hyoid Bone
    U-shaped bone in the neck that supports the tongue.
    Ellipsoidal (Condyloid) Joints
    e.g., wrist
    Humerus
    Upper arm bone connecting the shoulder to the elbow.
    Lacrimal Bones
    Bones forming part of the eye socket and housing the tear ducts.
    Gomphoses
    Fibrous joints where a peg fits into a socket (e.g., teeth in jaw).
    Masseter
    Muscle that elevates the mandible.
    Inferior Nasal Conchae
    Bones inside the nasal cavity that filter and humidify air.
    Extensor Tendons
    Tendons that help extend the fingers and toes.
    Patella
    Knee cap, protecting the knee joint.
    Rotator Cuff Muscles
    Supraspinatus, Infraspinatus, Teres Minor, Subscapularis.
    Annular Ligament
    The annular ligament is a strong fibrous band encircling the head of the radius, stabilizing the proximal radioulnar joint and allowing smooth rotation of the forearm.
    Wormian Bones
    Sutural bones in the skull.
    Tibialis Anterior
    Muscle that dorsiflexes and inverts the foot.
    Thoracic Cage
    Ribs and sternum forming the protective cage for the heart and lungs.
    Posterior Longitudinal Ligament
    Spinal ligament running along the back of the vertebral column.
    Ilium
    Uppermost and largest part of the hip bone.
    Gastrocnemius
    Calf muscle responsible for plantarflexion of the foot.
    Palatine Bones
    Bones forming part of the hard palate and nasal cavity.
    Ligamentum Flavum
    Spinal ligament connecting the laminae of adjacent vertebrae.
    Achilles Tendon
    Tendon connecting the calf muscle to the heel bone.
    Scapula
    Shoulder blade providing attachment for muscles of the upper limb.
    Femur
    Thigh bone, the longest and strongest bone in the body.
    Lumbar Vertebrae (L1 - L5)
    Vertebrae in the lower back (L1-L5).

    Synchondroses

    Reviewed by our medical team

    Cartilaginous joints where bones are connected by hyaline cartilage.

    1. Overview

    Synchondroses are a type of cartilaginous joint where two bones are joined by hyaline cartilage. These joints are typically immovable (synarthroses) and are primarily found during growth and development stages. Some synchondroses are temporary and fuse over time, while others persist throughout life, serving structural and functional roles in the axial skeleton.

    2. Location

    Synchondroses occur in various regions, particularly in growing bones and parts of the thoracic and cranial base. Common examples include:

    • Epiphyseal plates (growth plates): Between the epiphysis and diaphysis of long bones during development.

    • First sternocostal joint: Between the first rib and the manubrium of the sternum (permanent synchondrosis).

    • Spheno-occipital synchondrosis: Between the sphenoid and occipital bones in the cranial base (fuses in adolescence).

    • Intra-pelvic synchondroses (in infants): Found temporarily between parts of developing hip bones.

    3. Structure

    Synchondroses are structurally simple yet biomechanically significant:

    • Connecting tissue: Hyaline cartilage unites the two bones.

    • Bone surfaces: Covered by smooth cartilage without a synovial cavity.

    • No joint capsule: Unlike synovial joints, synchondroses lack a surrounding fibrous capsule.

    • Vascularity: Limited blood supply in the cartilage; most nourishment comes via diffusion.

    In growing bones, synchondroses are often part of the growth mechanism and later undergo ossification (endochondral fusion).

    4. Function

    Synchondroses provide both temporary and permanent mechanical functions:

    • Allow bone growth: Epiphyseal plates enable longitudinal growth in long bones during childhood and adolescence.

    • Provide stability: In permanent synchondroses like the first sternocostal joint, they ensure rigid yet slightly flexible connections.

    • Transmit forces: Act as force-transmitting interfaces between adjacent skeletal elements (e.g., ribs and sternum).

    5. Physiological role(s)

    Synchondroses support critical physiological functions:

    • Facilitate development: Essential in endochondral ossification during skeletal growth.

    • Maintain thoracic shape: Provide slight flexibility to the upper rib cage for breathing while maintaining stability.

    • Cranial base formation: Contribute to the alignment and shape of the skull during early development.

    6. Clinical Significance

    Though less commonly injured, synchondroses are involved in several clinical scenarios:

    • Growth plate fractures:

      • In children and adolescents, trauma can damage epiphyseal synchondroses (Salter-Harris fractures), potentially affecting bone growth.

    • Premature closure:

      • Early fusion of epiphyseal plates can lead to limb length discrepancies or skeletal deformities.

    • Spheno-occipital fusion issues:

      • Abnormal fusion may contribute to craniofacial anomalies or interfere with cranial base development.

    • Costochondritis (rarely involving first rib synchondrosis):

      • Inflammation near the first sternocostal synchondrosis may cause localized chest pain, though most costochondritis affects synovial joints of other ribs.

    • Ossification and aging:

      • Many synchondroses ossify with age, reducing thoracic flexibility and contributing to skeletal rigidity in elderly individuals.

    Did you know? The sternum is connected to the ribs by cartilage.