The physiology of the mammalian urinary outflow tract
The physiology of the mammalian urinary outflow tract
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DOI：
10.1111/j.1469-445x.1999.tb00084.x
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发表时间：
1999-01-01
影响因子：
2.7
通讯作者：
Brading, AF
中科院分区：
文献类型：
--
作者：
Brading, AF
哺乳动物膀胱的尿流是通过尿路发生的。这个流出道是一个复杂的结构，由横纹肌、平滑肌和血管尿路上皮组成。它由躯体和自主神经控制，具有多种功能：在膀胱充盈过程中产生持续的张力，防止尿漏；当腹部压力上升时，产生瞬间反射增加的压力，防止管腔开放；在排尿前经历松弛，并在排尿期间产生尿道口和缩短。尿路压力曲线显示峰值压力大于或等于100 cmH(2)O。最外层的外衣是横纹肌，即横纹肌或外括约肌。纤维主要是圆形取向的。这种程度在不同物种和不同性别之间有所不同。在人类女性中，它延伸到尿路的长度，主要由缓慢的痉挛纤维组成。在男性，括约肌从膜性尿道处延伸到前列腺基底部，并具有几乎相同数量的慢速和快速性痉挛纤维。在两性中，后缘可能缺乏横纹肌，并由环状取向的平滑肌肉填充。在膀胱充盈过程中，通过躯体神经的慢收缩纤维的活动可能是连续的。外环和内纵向的肌条都能产生持久的色调，尤其是从高压区切开的时候。这种张力是肌源性的，可以在没有动作电位的情况下实现，但依赖于通过L型钙通道的钙内流。两层均接受交感、副交感兴奋性神经支配和氮能抑制性神经支配。正常的尿路压力需要血液流向尿路上皮(固有层)。横纹肌和平滑肌肉都被认为对人体静息的尿路压力有贡献，但平滑肌肉在排尿过程中的确切作用尚不清楚。
Urinary outflow from the mammalian bladder occurs through the urethra. This outflow tract is a complicated structure composed of striated and smooth muscle and vascular urothelium. It is controlled by somatic and autonomic nerves and has several functions: it generates sustained tone to prevent urinary leakage during bladder filling; it generates transient reflex increases in pressure to prevent opening of the lumen when abdominal pressure rises; it undergoes relaxation preceding micturition and can generate urethral opening and shortening during micturition. A urethral pressure profile shows a peak pressure of greater than or equal to 100 cmH(2)O. The outermost coat is striated muscle, the striated or external sphincter. The fibres are predominantly circularly oriented. The extent varies in different species and between sexes. In the human female it extends the length of the urethra, and is composed mainly of slow twitch fibres. In the male, the sphincter extends from the membranous urethra over the base of the prostate and has nearly equal numbers of slow and fast twitch fibres. In both sexes, the posterior border may be deficient in striated muscle, and filled by circularly oriented smooth muscle. Activity in the slow twitch fibres through somatic nerves may be continuous during bladder filling. Outer circular and inner longitudinal smooth muscle is present Strips from either layer will generate sustained tone particularly if dissected from the high pressure zone. This tone is myogenic, and may be achieved in the absence of action potentials, but relies on influx of calcium through L-type calcium channels. Both layers receive sympathetic and parasympathetic excitatory innervation and nitrergic inhibitory innervation. Normal urethral pressure requires blood flow to the urothelium (lamina propria). Striated and smooth muscles are both thought to contribute to the resting urethral pressure in the human, The precise role of the smooth muscles during micturition is as yet unresolved.