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    From Musculoskeletal System

    Soleus
    Calf muscle responsible for plantarflexion of the foot.
    Tibialis Anterior
    Muscle that dorsiflexes and inverts the foot.
    Obliques (External and Internal)
    Muscles responsible for torso rotation.
    Rectus Abdominis
    Abs muscle that flexes the trunk.
    Anterior Longitudinal Ligament
    Spinal ligament running along the front of the vertebral column.
    Patellar Tendon
    Tendon connecting the patella to the tibia.
    Sternocleidomastoid
    Muscle that rotates and flexes the neck.
    Ligamentum Flavum
    Spinal ligament connecting the laminae of adjacent vertebrae.
    Nasal Bones
    Bones forming the bridge of the nose.
    Ethmoid Bone
    Bone forming part of the nasal cavity and the orbit.
    Pubis
    Part of the pelvis that joins with the opposite side to form the pubic symphysis.
    Tarsals (7 bones)
    7 ankle bones.
    Sutures (in the skull)
    Fibrous joints between skull bones.
    Sternum
    Breastbone located in the center of the chest.
    Ulna
    Forearm bone on the pinky side.
    Extensor Tendons
    Tendons that help extend the fingers and toes.
    Sesamoid Bones
    e.g., patella, some found in hands/feet.
    Skull
    Bony structure of the head that encases the brain.
    Diaphragm
    Primary muscle for breathing.
    Sphenoid Bone
    Bone forming part of the base of the skull and sides of the orbits.
    Glenohumeral Ligaments
    Shoulder ligaments that stabilize the shoulder joint.
    Ellipsoidal (Condyloid) Joints
    e.g., wrist
    Inferior Nasal Conchae
    Bones inside the nasal cavity that filter and humidify air.
    Gastrocnemius
    Calf muscle responsible for plantarflexion of the foot.
    Zygomatic Bones
    Cheekbones that form part of the orbit.

    Wormian Bones

    Reviewed by our medical team

    Sutural bones in the skull.

    1. Overview

    Wormian bones, also called sutural bones, are extra bone pieces that occur within the sutures of the skull, most commonly within the lambdoid suture. These bones are irregular in size and shape and are considered normal anatomical variants. However, multiple or abnormally large Wormian bones may be associated with certain genetic or developmental disorders.

    2. Location

    Wormian bones are found within the cranial sutures, particularly:

    • Lambdoid suture: Between the parietal bones and the occipital bone — the most common location.

    • Coronal suture: Occasionally between the frontal and parietal bones.

    • Sagittal suture: Rare, but possible.

    • Fontanelles: Can also appear within fontanelles in infants, especially the posterior fontanelle.

    They are more prevalent in individuals of certain ethnic backgrounds and in some congenital conditions.

    3. Structure

    Wormian bones vary in number, size, and shape:

    • Composition: Composed of normal compact and cancellous bone tissue.

    • Shape: Usually small and irregular; can sometimes be large and resemble fractured bone fragments.

    • Number: Typically range from 1 to 10 in healthy individuals but may be more numerous in pathological states.

    • Borders: Surrounded by cranial sutures on all sides, unlike standard skull bones that are bordered by only a few sutures.

    4. Function

    Wormian bones themselves do not serve any independent physiological or mechanical function. However, they may have structural effects:

    • Suture accommodation: May represent a response to mechanical stress or abnormal suture growth.

    • Space fillers: May passively occupy gaps that arise during skull development or suture fusion.

    They are best understood as incidental findings rather than essential functional components.

    5. Physiological role(s)

    While they lack a direct physiological role, Wormian bones are sometimes indicative of underlying physiological or developmental processes:

    • Markers of skull development: Their presence may reflect irregularities in ossification or suture closure.

    • Variation in skull biomechanics: May form in response to abnormal tension or pressure at sutures during infancy.

    • Evolutionary and population variation: Common in some ethnic groups and can be used anthropologically to study populations.

    6. Clinical Significance

    The presence of Wormian bones is usually benign, but when excessive in number or unusually large, they can be associated with:

    • Osteogenesis imperfecta:

      • A brittle bone disease often associated with multiple Wormian bones, especially in the lambdoid region.

    • Cleidocranial dysplasia:

      • A condition involving delayed skull ossification and numerous sutural bones.

    • Hypothyroidism (cretinism):

      • May present with delayed cranial ossification and Wormian bones.

    • Down syndrome:

      • Wormian bones may occur more frequently in children with trisomy 21.

    • Diagnostic imaging:

      • May be seen on X-ray or CT scans and should not be confused with skull fractures or pathological lesions.

    • Forensic/anthropological relevance:

      • Useful in age estimation or identifying certain populations or genetic traits in skeletal remains.

    Did you know? Your hand has 5 metacarpal bones.