Logo

    Related Topics

    From Musculoskeletal System

    Ribs (12 Pairs)
    12 pairs of bones that form the sides of the thoracic cage.
    Lumbar Vertebrae (L1 - L5)
    Vertebrae in the lower back (L1-L5).
    Anterior Longitudinal Ligament
    Spinal ligament running along the front of the vertebral column.
    Ischium
    Part of the pelvis that supports weight while sitting.
    Hyoid Bone
    U-shaped bone in the neck that supports the tongue.
    Scapula
    Shoulder blade providing attachment for muscles of the upper limb.
    Sternum
    Breastbone located in the center of the chest.
    Pelvic Floor Muscles
    Muscles that support pelvic organs.
    Nasal Bones
    Bones forming the bridge of the nose.
    Coccygeus
    Pelvic floor muscle supporting the coccyx.
    Coccyx
    Tailbone, the remnant of the tail in humans.
    Levator Ani
    Pelvic floor muscle responsible for lifting the anus.
    Ulna
    Forearm bone on the pinky side.
    Sacrum
    Triangular bone at the base of the spine.
    Glenohumeral Ligaments
    Shoulder ligaments that stabilize the shoulder joint.
    Synchondroses
    Cartilaginous joints where bones are connected by hyaline cartilage.
    Maxillae
    Upper jaw bones that house the teeth and form part of the orbit.
    Biceps Brachii
    Muscle responsible for elbow flexion.
    Iliolumbar Ligament
    Ligament connecting the ilium and lumbar vertebrae.
    Coracoacromial Ligament
    Ligament that connects the acromion to the coracoid process.
    Pectoralis Major
    Chest muscle responsible for shoulder movement.
    Obliques (External and Internal)
    Muscles responsible for torso rotation.
    Facial Bones
    Bones forming the structure of the face.
    Phalanges (14 bones)
    14 bones forming the toes.
    Ball-and-Socket Joints
    e.g., shoulder, hip

    Cranial Bones

    Reviewed by our medical team

    Bones of the skull that protect the brain.

    1. Overview

    The cranial bones are a group of eight bones that collectively form the neurocranium, which encases and protects the brain. These bones also contribute to the formation of the cranial cavity, provide attachment sites for head and neck muscles, and house structures such as the meninges, cranial nerves, and blood vessels. Unlike facial bones, cranial bones primarily function in protection rather than movement or facial expression.

    2. Location

    Cranial bones are located in the superior and posterior portion of the skull, forming the cranial vault and cranial base:

    • Superiorly and laterally: Parietal and frontal bones form the dome-like roof of the skull.

    • Posteriorly: Occipital bone forms the back and base of the skull.

    • Anteriorly: Frontal bone forms the forehead and part of the orbital cavity.

    • Inferiorly: Sphenoid and ethmoid bones contribute to the cranial base and nasal cavities.

    • Laterally: Temporal bones house the structures of the ears and form part of the cranial base and sides.

    3. Structure

    The human skull contains eight cranial bones:

    • Frontal bone (1): Forms the forehead, superior part of the orbit, and anterior cranial fossa.

    • Parietal bones (2): Form the sides and roof of the cranial vault.

    • Temporal bones (2): Contain the external auditory canal and form part of the middle and posterior cranial fossae.

    • Occipital bone (1): Forms the posterior skull and contains the foramen magnum for passage of the spinal cord.

    • Sphenoid bone (1): A butterfly-shaped bone forming the central base of the skull; articulates with all other cranial bones.

    • Ethmoid bone (1): Located between the orbits; forms part of the nasal cavity and medial orbital walls.

    These bones are joined together by sutures (immovable fibrous joints), such as the sagittal, coronal, lambdoid, and squamous sutures.

    4. Function

    The cranial bones serve several essential functions:

    • Protection: Encase and safeguard the brain from mechanical injury.

    • Support: Provide structural support to the head and anchor soft tissues such as the meninges.

    • Attachment sites: Serve as origins for muscles involved in chewing, head movement, and facial expressions.

    • Pathway housing: Contain foramina, canals, and fissures that allow passage of cranial nerves and blood vessels.

    5. Physiological role(s)

    Beyond mechanical protection, cranial bones play critical physiological roles:

    • Brain homeostasis: Protects neural tissue from temperature extremes, mechanical impact, and infectious agents.

    • Hematopoiesis: In infants and children, the diploë (spongy bone between outer and inner compact bone) may contain red bone marrow involved in blood cell production.

    • Growth and development: Fontanelles and sutures allow for skull expansion during brain growth in infancy and early childhood.

    • Sensory integration: Houses structures for vision, hearing, smell, and balance (e.g., optic canal, petrous part of temporal bone).

    6. Clinical Significance

    Cranial bones are involved in a variety of clinical and developmental conditions:

    • Fractures:

      • Common in trauma; basilar skull fractures may cause cerebrospinal fluid (CSF) leaks, raccoon eyes, or Battle’s sign.

    • Craniostenosis (Craniosynostosis):

      • Premature fusion of one or more cranial sutures, leading to abnormal head shape and possibly increased intracranial pressure.

    • Hydrocephalus:

      • Excess CSF can cause separation of sutures and bulging fontanelles in infants; treated with shunting procedures.

    • Paget’s disease of bone:

      • Can cause thickening of cranial bones, leading to nerve compression and symptoms like hearing loss.

    • Tumors:

      • Metastatic lesions, meningiomas, or multiple myeloma may involve cranial bones, requiring imaging and biopsy.

    • Surgical relevance:

      • Understanding cranial bone anatomy is essential for neurosurgery, craniotomy, and procedures involving sinuses and orbital decompression.

    Did you know? The femur is the longest and strongest bone in the human body.