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    Diaphragm
    Primary muscle for breathing.
    Gastrocnemius
    Calf muscle responsible for plantarflexion of the foot.
    Gluteus Maximus
    Largest muscle in the buttocks responsible for hip extension.
    Buccinator
    Muscle that helps with chewing and blowing air out.
    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.
    Frontal Bone
    Bone forming the forehead and upper part of the orbits.
    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.
    Palatine Bones
    Bones forming part of the hard palate and nasal cavity.
    Ilium
    Uppermost and largest part of the hip bone.
    Parietal Bones
    Bones forming the sides and roof of the skull.
    Patella
    Knee cap, protecting the knee joint.
    Soleus
    Calf muscle responsible for plantarflexion of the foot.
    Ischium
    Part of the pelvis that supports weight while sitting.
    Vertebral Column
    Spinal column consisting of vertebrae.
    Ulna
    Forearm bone on the pinky side.
    Radius
    Forearm bone on the thumb side.
    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.
    Facial Bones
    Bones forming the structure of the face.
    Zygomatic Bones
    Cheekbones that form part of the orbit.
    Skull
    Bony structure of the head that encases the brain.
    Lumbar Vertebrae (L1 - L5)
    Vertebrae in the lower back (L1-L5).
    Maxillae
    Upper jaw bones that house the teeth and form part of the orbit.
    Hyoid Bone
    U-shaped bone in the neck that supports the tongue.
    Fibula
    Smaller bone in the lower leg, located alongside the tibia.
    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.

    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 wrist has 8 bones, while the ankle has 7.