Interesting Facts About Cranial Bones
The human skull is a bony structure that acts as a protective cavity that houses the brain, and helps to support the face. The skull is composed of three different parts: The neurocranium or cranial bones, sutures, and viscerocranium or facial bones. It is of utmost importance to understand the anatomy of the cranial bones, as oftentimes they may be misaligned and contribute to cognitive and functional disorders.
What Causes The Cranial Bones To Be Misaligned?
- The birth process- due to pressure being exerted onto the skull bones, especially if the head is pressed up against the pelvis, or use of forceps during the birthing process.
- A fall when learning how to walk or rolling off the bed onto the floor when young
- A blow to the head or head injuries
- Habitual poor sleeping posture (7)
Therefore, having knowledge in the anatomy of the cranial bones is key in order to be able to better help our patients.
The Cranial Bones
The cranial bones are made up of eight different bones, and they include:
- The single sphenoid bone
- The paired temporal bones
- The single frontal bone
- The single occipital bone
- The paired parietal bones
- The single ethmoid bone
The single sphenoid bone joins pretty much every other bone in the skull. It contains the sphenoid sinuses and sella turcica, which seats the pituitary gland. The pituitary gland plays a major role in our bodies. It is a small, bean-shaped gland that influences almost every single body part. It produces hormones that help in regulating many important functions like your blood pressure and growth to name a few; as it senses the body’s needs and sends signals to different organs and glands throughout the body in order to help regulate their function and maintain homeostasis.
The sphenoid bone also contains the medial and lateral pterygoid plates. The medial pterygoid plates help to form the posterior lateral walls of the nasal cavity, while the lateral pterygoid plates act as an attachment site for important muscles of mastication. The greater wing of the sphenoid bone, is a bony projection off the sphenoid bone, which forms the anterior floor of the middle cranial fossa.
Hail to the sphenoid bone! The sphenoid bone is the MOST IMPORTANT cranial bone of all. In the event that this cranial bone is misaligned several issues may present such as:
- Sinus problems
- Brain fog
- Neck and lower back problems (6)
The paired temporal bones help to form the lateral sides of the skull. It articulates with the zygomatic, parietal, sphenoid and occipital bones. The temporal bones are divided into three different regions: the squamous, tympanic, and petrous regions. The squamous region forms the zygomatic process of the temporal bone, which is part of the zygomatic arch. The tympanic region of the temporal bone forms most of the acoustic meatus, and the petrous region of the temporal bone contains the mastoid process, which serves as an area for the sternocleidomastoid muscle attachment.
Misalignment of the temporal bone can contribute to:
- Hearing and balance disturbances
- Ringing in the ears
The single frontal bone forms the forehead, and contains the frontal sinuses; which are small paired, air-filled cavities located just behind your eyes in the brow region, that produce a thin mucus that drains through your nasal passages. (4)
The frontal bone articulates with the cranial and facial bones. It also helps to form the fibrous connective tissue joint that helps to separate the paired parietal bones from the frontal bone during its articulation with the paired parietal bones. The frontal bone also aids in forming the supraorbital margin of the orbit, which contains the supraorbital foramen. The supraorbital foramen acts as a passageway for the supraorbital nerve, which helps provide sensory innervation to the ipsilateral forehead.
Misalignment of this bone can contribute to:
- Sinus congestion
- Loss of smell
- Frontal headaches
The Occipital Bone
The single occipital bone makes up the most posterior portion of the skull, articulating with the parietal, temporal, and sphenoid cranial bones. This bone is also responsible for forming the foramen magnum, which acts as a large opening allowing for the passage of the spinal cord as it exits the skull.
Both the occipital bone and the petrous part of the temporal bone make up the jugular foramen, which acts as a passageway for essential structures to pass through such as, the glossopharyngeal, vagus, and accessory nerves.
The occipital condyles, which are two large protuberances that are located on the underside of the occipital bone, beside the foramen magnum form a movable articulation with the atlas of the spine. The atlas, also known as C1, is the most superior first cervical vertebrae of the spine.
Misalignment of this bone can contribute to:
- Instability of your cervical spine
- Interference of the flow of your cerebral spinal fluid
The paired parietal bones make up a large part of the sides of the cranium. They articulate to form the coronal, sagittal, squamosal, and lambdoidal sutures.
Misalignment of these bones can contribute to:
- Attention span issues
- Visual problems
The single ethmoid bone runs straight through the midsagittal plane, and is located just anterior to the sphenoid bone. The ethmoid bone articulates with several bones: the sphenoid bone, the lacrimal bones, the frontal bone, maxilla, as well as adjoining the vomer at its inferior and posterior borders.(2)
The ethmoid bone forms the base of the cranium and the orbits of the eye. It contains the ethmoid sinuses, which are hollow spaces located in the bones around the nose; and have a mucus lining which helps prevent the nasal cavity from becoming dry. Inflammation in this area can increase pressure and lead to pain in the areas surrounding the nose and in between the eyes; this is known as ethmoid sinusitis.
The ethmoid bone is made up of two unpaired plates known as the vertical perpendicular plate and the horizontal cribriform plate. The vertical perpendicular plate is seen within the structure of the nasal cavity, aiding the nasal septal cartilage and vomer in forming the nasal septum. A vertical midline continuation of the perpendicular plate superiorly into the cranial cavity is the wedge-shaped crista galli, which serves as an attachment for layers covering the brain. (2)
The horizontal cribriform plate is located between the anterior cranial fossa and the nasal cavity. It supports the olfactory bulb and allows for passage of the olfactory nerves.
The superior and middle nasal conchae make up the perpendicular plate of the ethmoid bone, while increasing surface area of respiratory epithelium. The inferior nasal concha on the other hand, sits on the nasal septum and helps separate the nasal cavity into two bilaterally symmetrical cavities.
The ethmoid bone plays a very important role in forming the midface region. It is a significant component of the upper nasal cavity and the nasal septum, and constitutes the medial orbit wall.
- The ethmoid bone articulates with 13 bones.
- Contributes to your sense of smell
It is of utmost importance for dental and medical professionals to be well versed in the cranial bones and their functions, as any type of misalignment can compromise the space between the skull and the brain. This can further compress the blood supply and flow of the cerebral spinal fluid to the brain, contributing to cognitive and functional disorders, as well as headaches. (7)
To learn more about cranial bones, check out our YouTube video:
- “skull”. Merriam-Webster Dictionary. Archived from the original on 17 February 2015.
- Fehrenbach, Margaret J., and Susan W. Herring. Illustrated Anatomy of the Head and Neck. Elsevier, 2017.
- “Ethmoid Sinusitis: Causes, Symptoms, and Treatment.” Medical News Today, MediLexicon International, www.medicalnewstoday.com/articles/327517.
- Team, The Healthline Editorial. “Frontal Sinusitis: Causes, Symptoms, and Diagnosis.” Healthline, Healthline Media, 10 July 1980, www.healthline.com/health/frontal-sinusitis.
- You and Your Hormones, www.yourhormones.info/glands/pituitary-gland/#:~:text=The%20pituitary%20gland%20is%20called,and%20maintain%20an%20appropriate%20environment.
- “Fixing Cranial Misalignments.” Healing Partnership, www.healingpartnership.com/conditions-we-treat/fixing-cranial-misalignments/.
- “Technique FYI: Cranial Adjusting Turner Style.” Chiropractic + Naturopathic Doctor, 13 Dec. 2019, www.cndoctor.ca/technique-fyi-cranial-adjusting-turner-style-1136/#:~:text=When%20the%20bones%20in%20the,disorders%20as%20well%20as%20headaches.
- OpenStax, Lumen Learning &. “Anatomy and Physiology I.” The Skull | Anatomy and Physiology I, courses.lumenlearning.com/suny-ap1/chapter/the-skull/.
- Darby, Michele. Mosby’s Comprehensive Review of Dental Hygiene 6th edition. Elsevier, 2006.
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