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    Related Topics

    From Musculoskeletal System

    Ball-and-Socket Joints
    e.g., shoulder, hip
    Gomphoses
    Fibrous joints where a peg fits into a socket (e.g., teeth in jaw).
    Palatine Bones
    Bones forming part of the hard palate and nasal cavity.
    Diaphragm
    Primary muscle for breathing.
    Facial Bones
    Bones forming the structure of the face.
    Vertebral Column
    Spinal column consisting of vertebrae.
    Frontal Bone
    Bone forming the forehead and upper part of the orbits.
    Hinge Joints
    e.g., elbow, knee
    Pubis
    Part of the pelvis that joins with the opposite side to form the pubic symphysis.
    Deltoid
    Shoulder muscle responsible for arm abduction.
    Thoracic Cage
    Ribs and sternum forming the protective cage for the heart and lungs.
    Hamstrings
    Biceps Femoris, Semitendinosus, Semimembranosus.
    Coccyx
    Tailbone, the remnant of the tail in humans.
    Ischium
    Part of the pelvis that supports weight while sitting.
    Ilium
    Uppermost and largest part of the hip bone.
    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.
    Brachioradialis
    Muscle responsible for forearm flexion.
    Vomer Bone
    Bone forming the nasal septum.
    Quadriceps
    Rectus Femoris, Vastus Medialis, Vastus Lateralis, Vastus Intermedius.
    Symphyses
    Cartilaginous joints where bones are connected by fibrocartilage.
    Achilles Tendon
    Tendon connecting the calf muscle to the heel bone.
    Quadriceps Tendon
    Tendon that connects the quadriceps to the patella.
    Pelvic Floor Muscles
    Muscles that support pelvic organs.
    Carpals (8 bones)
    8 wrist bones.
    Iliolumbar Ligament
    Ligament connecting the ilium and lumbar vertebrae.

    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 smallest bone in the human body is the stapes (in the ear), measuring just 0.1 inches.