The Testicular Descent in Human: Origin, Development and Fate of the Gubernaculum Hunteri, Processus Vaginalis Peritonei, and Gonadal Ligaments
The Testicular Descent in Human: Origin, Development and Fate of the Gubernaculum Hunteri, Processus Vaginalis Peritonei, and Gonadal Ligaments
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人类睾丸下降：亨特氏管、腹膜阴道突和性腺韧带的起源、发育和命运
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发表时间：
2000
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通讯作者：
Jacob Mi
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作者：
Barteczko Kj;Jacob Mi
睾丸下降必须分为睾丸和附睾从腹部本身转出和生殖器官的内腹下降。这两个事件都与韧带的发育和重组密切相关，并取决于韧带的发育和重组，主要是Hunteri引带。这些看似明确的事件是有争议的描述，因为第一次描述的引带，和其他物种的结果和细节与来自人类的数据混杂在一起，从而给更多的混乱比清晰的性腺发育的这一重要步骤。在这里，我们集中在人类胚胎，按时间顺序研究连续切片，扫描电子显微镜，三维重建，显微解剖和免疫组织化学。第一个需要回答的问题是，生殖腺是否存在真实的内在遗传。我们通过显示生殖腺、中肾、颅中肾韧带和横膈原基与脊椎节段的关系来证明这种内部下降。在某些椎体节段中未观察到可能模拟性腺下降的爆炸样增加。内降与性腺（卵巢或睾丸）的生长、中肾的退化、降横隔或横隔原基以及颅中肾间韧带的发育相结合。这条韧带总是插入内侧的边界之间的性腺和中肾的密切关系，腹部口的苗勒管，一个地区，包虫病经常发生。与睾丸相反，卵巢很早就到达了S2/3（骨盆终线水平）的位置--20 - 25 mm CRL，但卵巢是横向的。内降过程中，颅侧性腺韧带的长度没有明显增加。它不含血管。在两性退化时，它将被卵巢血管形成的皱襞所取代，即成人所知的卵巢悬韧带。第二点是要调查的起源，发展，结构和命运的引带Hunteri以及处理迷走腹膜。它们的排列和组成对睾丸下降至关重要。我们区分了五个阶段的发展和分化。阶段I表征阶段14 CC（5-7 mm CRL）胚胎的引带的早期发育。它起源于腹股沟圆锥，连接脐动脉外侧的腹壁和中肾襞的尾部。正是在这个早期阶段，腹股沟内环的定位被定义。在第二阶段，20-23 CC期（21-30 mm CRL），可以区分引带的三个部分-腹部，间质和皮下。腹膜迷走突的背侧层与引带的腹侧紧密相连。引带在生殖导管交叉处向头侧插入生殖导管间质。在它的对面，但在一定距离处，韧带连接睾丸的尾极和生殖导管的背侧间充质。在雌性胚胎中，卵巢韧带的analge表现为U形，双重腹膜褶皱。II期再分为IIa期（32-55 mm CRL），其特征为引带长度和体积的巨大增加以及腹膜迷走突的扩大。在第三阶段，性腺位置和引带结构的性别特异性差异，可以观察到的第一次。睾丸体积增大，靠近生殖导管的间充质。睾丸的尾极与两个导管重叠。我们还将这一阶段细分为IIIa期（约100 mm CRL），其中男性胎儿发生两个非常重要的事件：1，引带肿胀，2，睾丸滑过生殖管。这种滑动是由苗勒管的退化和T
Testicular descent has to be divided into the turn-out of the testis and epididymis from the abdomen proper and an inner abdominal descent of genital organs. Both events are closely related to and depend on the development and reorganisation of ligaments, mainly the gubernaculum Hunteri. These seemingly unambiguous events are controversially described since the first description of the gubernaculum, and results and specifics of other species were intermingled with data from humans, thus giving more confusion than lucidity in this important step of gonadal development. Here, we concentrate on human embryos, chronologically investigated by serial sections, scanning electron microscopy, three-dimensional reconstructions, microdissection and immunohistochemistry. The first question to be answered was whether a real inner descent of gonads occurs. We demonstrated this inner descent by showing the relations of the gonads, mesonephros, cranial mesonephric ligament and the anlage of the diaphragm with the vertebral segments. No explosion-like increase in certain vertebral segments was observed which might simulate a gonadal descent. The inner descent is coupled with the growth of the gonad (ovary or testis), the involution of mesonephros, the descending septum transversum or the anlage of the diaphragm, and the intercalated cranial mesonephric ligament. This ligament always inserts medially at the border between the gonad and mesonephros in close relationship to the abdominal ostium of the mullerian duct, a region where hydatides often occur. In contrast to the testes, the ovaries arrive very early--20-25 mm CRL--at their definitive position of S2/3 (level of linea terminalis pelvis), yet, are transversally oriented. The cranial gonadal ligament does not exhibit notable increase in length during inner descent. It does not contain blood vessels. While regressing in both sexes, it will be replaced by the plica formed by the ovarian vessels, that is the suspensorium ligament of the ovary as known in adults. The second point to be investigated was the origin, development, structure and fate of the gubernaculum Hunteri as well as the processus vaginalis peritonei. Their arrangement and composition is crucial for testicular descent. We discriminated five phases of their development and differentiation. Phase I characterises the early development of the gubernaculum of stage 14 CC (5-7 mm CRL) embryos. It arises as conus inguinalis and connects the abdominal wall lateral to the umbilical artery with the caudal part of the mesonephric fold. It is in this early stage that the localisation of the inner inguinal ring is defined. In phase II, stage 20-23 CC (21-30 mm CRL), three parts of the gubernaculum--abdominal, interstitial and subcutaneous--can be distinguished. The processus vaginalis peritonei appears with its dorsal layer firmly adhering to the ventral side of the gubernaculum. The gubernaculum inserts cranially into the mesenchyme of the genital ducts at their crossing-over. Opposite to it, but at some distance, a ligament connects the caudal pole of the testis with the dorsal mesenchyme of the genital ducts. In female embryos, the analge of the ovarian ligament appears as a U-shaped, double peritoneal fold. Phase II is subdivided in phase IIa (32-55 mm CRL), characterised by an enormous increase in length and volume of the gubernaculum and also an enlargement of the processus vaginalis peritonei. In phase III, sex-specific differences in gonadal position and gubernacular structure can be observed for the first time. Testes increase in volume and come close to the mesenchyme of the genital ducts. The caudal pole of the testis overlaps both ducts. We also subdivide this phase into phase IIIa (about 100 mm CRL) where two very important events occur in male foetuses: 1, the swelling of the gubernaculum, and 2, the gliding of the testis across the genital ducts. This gliding is permitted by both, the regression of the mullerian duct and t