The pituitary gland is located in the saddle and is ovoid in shape, weighing 600-700 mg, with a normal volume of about 1100 mm3. The pituitary gland is usually divided into two parts: the pituitary gland and the pituitary gland, both of which also include the funnel and the pituitary stalk. The median bulge is the lower posterior part of the funiculus, which is an important part of the vascular connection between the hypothalamus and the adenopituitary gland. The pituitary gland is separated from the cranial cavity by a saddle septum between the dura mater and the cranial cavity, with a small hole of variable size in the center of the saddle septum, usually 2-3 mm, through which the pituitary stalk is connected to the hypothalamus. The arachnoid membrane that surrounds the pituitary stalk mostly does not enter the saddle. Hu satellite, Department of Neurosurgery, The First Affiliated Hospital of Nanjing Medical University The pituitary gland secretes six hormones with significant physiological activity, namely, prolactin (PRL), growth hormone (GH), adrenocorticotropic hormone (ACTH), thyroid stimulating hormone (TSH), follicle stimulating hormone (FSH), and luteinizing hormone (LH). It is widely believed that the pituitary gland, including the median eminence, funicular stem and posterior pituitary lobe, develops from the base of the mesencephalon downward. The funnel extends from the gray node between the optic cross and the papillary body, gradually becoming thinner and continuing as the funnel stem, which merges with the union to form the pituitary stalk. The pituitary gland is composed of glial cells and nerve fibers, which have no secretory function. Anti-diuretic hormone (ADH) (containing two hormonal components: pressin and oxytocin) is secreted by nerve cells in the supraoptic and paraventricular nuclei of the hypothalamus, along the pituitary bundle of the hypothalamus. It is transported to the pituitary gland as granules along with their respective neurohormones and is stored. The distance from the lateral pituitary wall to the cavernous sinus segment of the internal carotid artery is 1-3 mm, and the venous sinuses within the cavernous sinuses often grow into the pterygoid saddle in varying degrees of size, which is often encountered during surgery when pituitary tumors are very small. The two cavernous sinuses are connected to each other by two transverse anastomosing sinuses DD anterior and posterior intercavernous sinuses. When the pituitary tumor is large, most of these interstitial sinuses are occluded. About 14% of the cavernous sinus segments of the internal carotid artery are deviated medially, and it has been reported that hemorrhage during transsphenoidal surgery is due to injury to the internal carotid artery or laceration of its branches. In most cases, there should be an intact dural septum between the pituitary gland and the cavernous sinus, but there are cases where the pituitary tumor penetrates the lateral dura into the cavernous sinus, which is a form of invasive pituitary tumor. The relationship between the optic cross and the pterygoid saddle is very important for the difficulty of revealing the pituitary fossa through the frontal approach. The optic cross is located above the saddle septum in 70% (normal position), above the anterior saddle septum in 15% (anterior type) and above the posterior saddle septum in 15% (posterior type). The space between the anterior optic cross and the saddle node is extremely small, usually less than 3 mm. this location has no effect on the pathophyseal approach, but transcranial surgery limits access to the pituitary gland. MRI of special conditions can show the relationship between the tumor and the optic cross. The pituitary gland is located in a saddle of variable size, with an anterior-posterior diameter of 7-16 mm, a deep diameter of 7-14 mm, and a wide diameter of 8-23 mm. The anterior part of the saddle is the saddle node, and the posterior part is the dorsal part of the saddle and the bed prominence after upward extension. The pneumatization of the anterior and inferior pterygoid sinus can be divided into pterygoid saddle type (86%), anterior saddle type (11%), and meconium type (3%). In the former case, the pneumatization of the pterygoid sinus is the most complete. In adults, pituitary tumors with a mesenteric pterygoid sinus are most commonly seen in pituitary ACTH tumors. Most of the pterygoid sinuses have bony partitions, and some of them do not have bony partitions. The partitions are mostly longitudinal or irregular, and sometimes there are multiple partitions. Pneumatization and segregation of the pterygoid sinus are helpful in determining intraoperative anatomy during transsphenoidal surgery.