The sphenoid bone, part 1
A bone can be influenced by any bone that articulates with it. For example, the scapula is influenced in its alignment and articulations by the humerus. Taking this a step further, the humerus is influenced in its alignment and articulations by the ulna and the radius. Which means that the scapula can be influenced by the ulnar and the radial position because of how they affect the humerus. This gets complicated and a systemic dysfunction could be mapped out by following the misalignment of one bone. Yet, many of these bones only articulate with one or two other bones. They are in a constant tug a war trying to find balance in the joints they help to create.
The sphenoid is unusual in that it articulates directly, or is attached to through ligaments, a substantial number of bones. The sphenoid will affect all of these bones, and all of these bones will affect the sphenoid. The sphenoid sits in the cranial base and is one of 7 bones in the eye orbit.
Following is a list of bones it articulates with and the joints it helps to create.
Occiput bone Sphenobasilar joint
Frontal bone Sphenofrontal suture
Temporal bones Sphenosquamosal sutures
Parietal bones Sphenoparietal sutures
Ethmoid bone Sphenoethmoid suture
Vomer bone Sphenovomerine suture
Zygomatic bones Sphenomalar sutures
Palatine bones Sphenopalatine sutures
Maxillary bones Sphenomaxillary sutures
It is important to note that the sphenomaxillary sutures do not exist in all people. Some people have this articulation and some do not. In addition to articulations with all of these bones, the sphenoid bone may also be affected by or affect the mandible. This is due to the sphenomandibular ligament, which attaches to both bones, and to the lateral and medial pterygoid muscles. Both the lateral and medial pterygoid muscles have originations on the lateral pterygoid plate of the sphenoid bone, and insertions on the mandible.
In addition to the bones that can affect or will be affected by the sphenoid, within the sella turcica of the sphenoid bone sits the pituitary. This means that a shift in the alignment of the sphenoid, which, as we have seen, is affected by the alignment of many other bones, can cause problems in the communication between the pituitary and the hypothalamus.
A quick review: The pituitary is called the master gland. It sends out messages to all components of the endocrine system to produce or stop producing a variety of hormones. However, the pituitary takes its instruction from the hypothalamus, which regularly monitors the hormone levels in the bloodstream. The pituitary and hypothalamus communicate through the hypophyseal stalk (also called the infundibulum stalk), a bridge traveling between the two. In other words, the hypophyseal stalk travels from the hypothalamus within the brain to the pituitary gland, which sits in the sella turcica of the sphenoid bone.
In part 2 of this article, we will track what can shift the sphenoid and the possibilities for what is affected by said shift. For now, it is amazing to think that this one bone can affect and be affected by so many other structures.