The head of spermatozoa contains a nucleus but no acrosome . the nuclear fossa developes well . during the process of spermtogenesis , within the nucleus the chromatin condenses step by step into wads , among which are loose chromatin fibers 成熟精子头部无顶体，主要为核占据，精子形成过程中，细胞核中的染色质浓缩成致密的团块状，团块状的染色质之间分布着松散的纤维状染色质。
Paraduodenal fossae originate as congenital peritoneal anomalies owing to failure of mesenteric fusion with the parietal peritoneum and an associated abnormal rotation during imprisonment of the small intestine beneath the developing colon ( 1 ? 3 , 22 , 27 ? 33 ) 十二指肠旁隐窝的产生是由于先天性的腹膜异常，即肠系膜与壁层腹膜融合失败，同时小肠在局限于整条结肠中间位置的发育过程中旋转异常。
This is the first study on the microsurgical anatomy of the erssma . . the part 1 of this study stressed on the craniotomy device of the retrosigmoid aproach to improve the operating skills . part 2 aimed at the safety and feasibility of the erssma . part 3 deal with the microanatomy of the rssma and it ' s effectiveness of it ' s exposure to the middle fossa and the superior clivus 扩大乙状奏后经内耳孔上人路显槽外科解剖学系列研究中文柄耍本题第一部分对乙状窦后入路的骨瓣设计进行改良研究，以改进乙状窦后入路的开颅技术；第二部分研究扩大乙状窦后经内耳孔上入路的安全性和可行性。
