The corpus callosum（CC）represents the major commissure between the two cerebral hemispheres；it extends from the frontal lobe anteriorly to above the quadrigeminal plate and into the quadrigeminal cistern posteriorly. Under normal condition the corpus callosum is present with all its components，going front to back: rostrum, genu, body and splenium. The leaves of the septum pellucidum enclose the space of the cavum septi pellucidi（CSP）, which is located under the CC.
CC位于大脑半球纵裂的底部，是大脑半球中最大的连合纤维，连接左右两侧大脑半球的横行神经纤维束，其神经纤维在两半球中间形成弧形板。
胼胝体嘴、膝部很小，嘴部后下方是前连合，干部（也叫体部）下方是透明隔腔和穹隆柱（穹窿柱下方是三脑室），压部厚而短，后下方是小脑蚓部（呈桔子瓣状）。胼胝体在妊娠8-20周形成，由膝后部–体前部–体后部–膝前部–压部–嘴部的顺序发育。也有文章说胼胝体从12周开始发育，先发育嘴膝部，再发育体部和压部，总体意思就是从前往后逐渐发育，大概19周发育完整。个人支持后者的“单向发育学说”，即胼胝体首先发育形成喙部，然后向后上方形成膝部、体部，最后形成压部。
CC主要功能是将一侧大脑皮层的活动向另一侧传送，联合两侧大脑半球，负责沟通两半球的信息传导。
The CC appears as hypoechoic midline structure at US. Recently the possibility to visualize some portions of CC in axial planes has been described. The anterior complex, a group of anatomical structures visible on the routine transventricular imaging plane, allows to visualize a cross section through the genu of the CC. Although technically more difficult, slicing cranially from the transventricular plane, the posterior complex may be depicted showing a cross section through the splenium of the CC.
However, the ultimate proof of the presence of the CC has been proven only by median/mid-sagittal plane of the fetal brain. Although some indirect signs of the absence of the CC could be identifiable in axial scans, the direct evaluation of CC in all its components requires a median/midsagittal plane. In addition, it is worth mentioning that the depiction of an apparently normal corpus callosum is not necessarily a guarantee that it will remain normal, since this does not exclude the possibility of subtle callosal developmental congenital anomalies or callosal pathologies that may develop later in pregnancy or even after delivery due to brain insults such as ischemia or infection.
