The sella turcica is a saddle-shaped depression located deep within the base of the skull. This anatomical structure forms a protective housing for a major endocrine gland, shielding it from external forces and maintaining its position within the cranial cavity. Identifying the specific bone that contains this depression is key to understanding the complex neuroanatomy of the skull’s center. This bony enclosure contains an organ that regulates processes throughout the entire body.
The Sphenoid Bone and Skull Placement
The sella turcica is an integral part of the sphenoid bone, a single, unpaired bone situated at the center of the skull base. This bone connects the neurocranium, which surrounds the brain, with the facial skeleton. Its central location allows it to articulate with almost all other bones of the skull, including the frontal, parietal, temporal, and occipital bones. The sphenoid bone is divided into a central body, two greater wings, two lesser wings, and two pterygoid processes. The sella turcica is found specifically on the superior surface of the sphenoid bone’s body. This strategic placement in the midline of the skull’s floor ensures stability and protection.
Defining the Sella Turcica Structure
The Latin term sella turcica translates to “Turkish saddle,” a name derived from its appearance as a shallow depression. This structure is entirely formed by the sphenoid bone and belongs to the middle cranial fossa. The sella turcica consists of three distinct parts that define its boundaries.
Tuberculum Sellae
The anterior boundary is the tuberculum sellae, a slight elevation separating the depression from a groove in front of it.
Hypophyseal Fossa
The deepest part is the hypophyseal fossa, which serves as the seat of the saddle and contains the gland. The floor of this fossa is a thin plate of bone that overlies the sphenoidal air sinus below.
Dorsum Sellae
The posterior wall is a large, square plate of bone projecting upward, known as the dorsum sellae. This wall is terminated laterally by bony projections called the posterior clinoid processes, which provide attachment points for the protective covering of the brain. The bony enclosure created by these three elements provides a secure vault for the delicate organ housed within.
The Role of the Pituitary Gland
The primary function of the sella turcica is to provide a sheltered home for the pituitary gland, also known as the hypophysis. The gland rests securely within the hypophyseal fossa. This protection is important because the pituitary gland is often referred to as the “master gland” of the endocrine system. It regulates numerous other endocrine glands, including the thyroid, adrenal glands, and reproductive organs. It produces and releases hormones that control essential processes like growth, metabolism, and reproduction. The pituitary stalk connects the gland to the hypothalamus in the brain, passing through a small opening in the dural membrane that covers the sella turcica.
The anatomical relationship between the sella turcica and its contents has clinical relevance, especially in diagnostic imaging. Physicians frequently examine this area using MRI or CT scans to identify abnormalities. A common pathology is the development of a pituitary tumor, or adenoma, which can cause the sella turcica to expand or erode. Since the sella turcica is situated near the optic chiasm, an expanding tumor can press on the optic nerves, leading to visual disturbances.