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    From Musculoskeletal System

    Acromioclavicular Ligament
    Ligament that connects the acromion to the clavicle.
    Ilium
    Uppermost and largest part of the hip bone.
    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.
    Sacrum
    Triangular bone at the base of the spine.
    Ulna
    Forearm bone on the pinky side.
    Hyoid Bone
    U-shaped bone in the neck that supports the tongue.
    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.
    Frontal Bone
    Bone forming the forehead and upper part of the orbits.
    Hinge Joints
    e.g., elbow, knee
    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.
    Femur
    Thigh bone, the longest and strongest bone in the body.
    Cranial Bones
    Bones of the skull that protect the brain.
    Clavicle
    Collarbone connecting the arm to the body.
    Palatine Bones
    Bones forming part of the hard palate and nasal cavity.
    Gastrocnemius
    Calf muscle responsible for plantarflexion of the foot.
    Ellipsoidal (Condyloid) Joints
    e.g., wrist
    Cervical Vertebrae (C1 - C7)
    Vertebrae in the neck region (C1-C7).
    Gluteus Maximus
    Largest muscle in the buttocks responsible for hip extension.
    Radius
    Forearm bone on the thumb side.
    Diaphragm
    Primary muscle for breathing.
    Occipital Bone
    Bone forming the back and base of the skull.
    Hamstrings
    Biceps Femoris, Semitendinosus, Semimembranosus.
    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.
    Latissimus Dorsi
    Back muscle responsible for arm adduction and extension.
    Medial Collateral Ligament (MCL)
    Knee ligament that stabilizes the inner knee.

    Parietal Bones

    Reviewed by our medical team

    Bones forming the sides and roof of the skull.

    1. Overview

    The parietal bones are a pair of large, curved, quadrilateral bones forming a significant portion of the superior and lateral walls of the cranium. These bones are essential components of the neurocranium, enclosing and protecting the brain, particularly the parietal lobes. The right and left parietal bones meet at the top of the skull and contribute to its overall strength and structure.

    2. Location

    The parietal bones are located on the upper lateral sides of the skull:

    • Superiorly: Meet each other at the sagittal suture.

    • Anteriorly: Articulate with the frontal bone at the coronal suture.

    • Posteriorly: Articulate with the occipital bone at the lambdoid suture.

    • Inferiorly: Articulate with the temporal and sphenoid bones at the squamosal and sphenoparietal sutures, respectively.

    3. Structure

    Each parietal bone is thin, flat, and curved, contributing to the cranial vault:

    • External surface: Convex and smooth, provides attachment for the temporalis muscle; marked by parietal eminence (a rounded prominence).

    • Internal surface: Concave and grooved for meningeal vessels, especially the middle meningeal artery.

    • Four borders: Frontal (anterior), occipital (posterior), temporal (inferior), and sagittal (medial).

    • Four angles: Frontal, sphenoidal, occipital, and mastoid angles, which connect with corresponding bones.

    The bone consists of two layers of compact bone (inner and outer tables) with cancellous bone (diploë) in between, providing strength and lightness.

    4. Function

    The parietal bones serve several crucial roles in cranial protection and form:

    • Protect the brain: Enclose the parietal lobes of the brain, shielding them from external trauma.

    • Structural support: Contribute to the cranial vault, maintaining the shape and strength of the skull.

    • Muscle attachment: Provide surfaces for temporalis and other muscles of mastication and facial expression.

    • Formation of sutures: Interlock with surrounding bones to form immovable joints that stabilize the skull.

    5. Physiological role(s)

    Although passive in terms of direct physiological processes, the parietal bones support vital functions by:

    • Enabling cerebral protection: Encase brain tissue, especially the parietal lobes responsible for sensory perception and spatial orientation.

    • Assisting thermoregulation: The scalp and underlying skull dissipate heat produced by brain metabolism.

    • Providing pathways: Grooves on the inner surface house vessels like the middle meningeal artery, essential for cranial perfusion.

    6. Clinical Significance

    Parietal bones are involved in several clinical and surgical conditions:

    • Skull fractures:

      • Parietal bones are commonly fractured in head trauma due to their exposure; may result in epidural hematomas if the middle meningeal artery is torn.

    • Craniotomy procedures:

      • Parietal regions are often accessed surgically to reach underlying brain tissue during tumor resections or hemorrhage evacuation.

    • Hydrocephalus and cranial expansion:

      • In pediatric patients, parietal bones may expand or bulge in conditions like hydrocephalus or craniosynostosis.

    • Parietal foramina anomalies:

      • Small openings near the sagittal suture may transmit emissary veins; enlarged foramina can be associated with syndromes like cleidocranial dysostosis.

    • Decompression surgery:

      • Increased intracranial pressure may require removal of a parietal bone flap (decompressive craniectomy).

    Did you know? The largest muscle in the body is the gluteus maximus, responsible for hip extension.