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    From Musculoskeletal System

    Phalanges (14 bones)
    14 bones forming the toes.
    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.
    Inferior Nasal Conchae
    Bones inside the nasal cavity that filter and humidify air.
    Ulna
    Forearm bone on the pinky side.
    Cervical Vertebrae (C1 - C7)
    Vertebrae in the neck region (C1-C7).
    Facial Bones
    Bones forming the structure of the face.
    Scapula
    Shoulder blade providing attachment for muscles of the upper limb.
    Buccinator
    Muscle that helps with chewing and blowing air out.
    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.
    Clavicle
    Collarbone connecting the arm to the body.
    Maxillae
    Upper jaw bones that house the teeth and form part of the orbit.
    Brachioradialis
    Muscle responsible for forearm flexion.
    Ligamentum Flavum
    Spinal ligament connecting the laminae of adjacent vertebrae.
    Deltoid
    Shoulder muscle responsible for arm abduction.
    Hinge Joints
    e.g., elbow, knee
    Wormian Bones
    Sutural bones in the skull.
    Sacroiliac Ligaments
    Ligaments connecting the sacrum to the iliac bones.
    Masseter
    Muscle that elevates the mandible.
    Triceps Brachii
    Muscle responsible for elbow extension.
    Nasal Bones
    Bones forming the bridge of the nose.
    Latissimus Dorsi
    Back muscle responsible for arm adduction and extension.
    Tarsals (7 bones)
    7 ankle bones.
    Sartorius
    Longest muscle in the body responsible for hip flexion.
    Mandible
    Lower jawbone that houses the teeth.
    Posterior Cruciate Ligament (PCL)
    Knee ligament that stabilizes the joint.

    Symphyses

    Reviewed by our medical team

    Cartilaginous joints where bones are connected by fibrocartilage.

    1. Overview

    A symphysis is a type of cartilaginous joint where two bones are joined together by a pad of fibrocartilage. These joints are amphiarthrotic, meaning they allow limited movement while maintaining strong structural integrity. Symphyses are found in the axial skeleton and serve important roles in absorbing shock and providing stability to the body’s midline.

    2. Location

    Symphyses are located along the midline of the body, primarily in the axial skeleton. Major examples include:

    • Pubic symphysis: Between the two pubic bones of the pelvis.

    • Intervertebral discs: Between the vertebral bodies from C2 to the sacrum.

    • Manubriosternal joint: Between the manubrium and the body of the sternum (may ossify with age).

    3. Structure

    Symphyses are composed of:

    • Articulating bones: Covered with a thin layer of hyaline cartilage.

    • Fibrocartilaginous disc: A strong, compressible pad of fibrocartilage situated between the bones.

    • No synovial cavity: Unlike synovial joints, symphyses do not contain a joint capsule or synovial fluid.

    • Limited vascularity: Fibrocartilage has a poor blood supply, especially in central areas.

    Despite their simplicity, symphyses are durable and adaptable, with a structure optimized for both stability and resilience.

    4. Function

    Symphyses serve key mechanical and supportive functions:

    • Shock absorption: The fibrocartilage discs cushion forces transmitted between bones, especially during weight-bearing activities.

    • Limited movement: Allow slight movement for flexibility, such as vertebral bending or expansion of the pelvis during childbirth.

    • Joint stability: Provide firm articulation in regions where strength and minimal mobility are required.

    5. Physiological role(s)

    Symphyses play roles beyond mechanical function:

    • Spinal flexibility: Intervertebral symphyses allow bending, twisting, and compression of the vertebral column while protecting the spinal cord.

    • Pelvic expansion: The pubic symphysis loosens under the influence of hormones like relaxin during pregnancy, allowing safe passage during childbirth.

    • Height maintenance: Intervertebral discs contribute to overall height and slightly compress throughout the day with activity.

    6. Clinical Significance

    Symphyses are involved in several clinical conditions:

    • Degenerative disc disease:

      • Intervertebral discs may lose hydration and elasticity with age, leading to pain, reduced flexibility, and nerve compression.

    • Herniated disc:

      • Protrusion of the nucleus pulposus through the annulus fibrosus in intervertebral symphyses, potentially compressing spinal nerves.

    • Symphysis pubis dysfunction (SPD):

      • Common during pregnancy due to increased ligament laxity; causes pain in the pubic area and difficulty with walking or climbing stairs.

    • Ankylosis:

      • Fusion of the symphysis, either due to age (e.g., manubriosternal joint) or disease (e.g., ankylosing spondylitis).

    • Inflammatory conditions:

      • Symphysitis or inflammation of a symphysis joint can cause localized pain, such as osteitis pubis seen in athletes or post-surgery patients.

    Did you know? The smallest bone in the human body is the stapes (in the ear), measuring just 0.1 inches.