It begins with a bit of discomfort and soon becomes a pressing sensation that's impossible to ignore. Finally, it's all you can think about, and out of sheer desperation, you go on a hunt for a bathroom until "ahh." Humans should urinate at least four to six times a day, but occasionally, the pressures of modern life forces us to clench and hold it in. How bad is this habit, and how long can our bodies withstand it? The answers lie in the workings of the bladder, an oval pouch that sits inside the pelvis. Surrounding this structure are several other organs that together make up the whole urinary system. Two kidneys, two ureters, two urethral sphincters, and a urethra. Constantly trickling down from the kidneys is the yellowish liquid known as urine. The kidneys make urine from a mix of water and the body's waste products, funneling the unwanted fluid into two muscular tubes called ureters. These carry it downward into the hollow organ known as the bladder. This organ's muscular wall is made of tissue called detrusor muscle which relaxes as the bladder fills allowing it to inflate like a balloon. As the bladder gets full, the detrusor contracts. The internal urethral sphincter automatically and involuntarily opens, and the urine is released. Whooshing downwards, the fluid enters the urethra and stops short at the external urethral sphincter. This works like a tap. When you want to delay urinating, you keep the sphincter closed. When you want to release it, you can voluntarily open the flood gates. But how do you sense your bladder's fullness so you know when to pee? Inside the layers of detrusor muscles are millions of stretch receptors that get triggered as the bladder fills. They send signals along your nerves to the sacral region in your spinal cord. A reflex signal travels back to your bladder, making the detrusor muscle contract slightly and increasing the bladder's pressure so you're aware that it's filling up. Simultaneously, the internal urethral sphincter opens. This is called the micturition reflex. The brain can counter it if it's not a good time to urinate by sending another signal to contract the external urethral sphincter. With about 150 to 200 milliliters of urine inside of it, the bladder's muscular wall is stretched enough for you to sense that there's urine within. At about 400 to 500 milliliters, the pressure becomes uncomfortable. The bladder can go on stretching, but only to a point. Above 1,000 milliliters, it may burst. Most people would lose bladder control before this happens, but in very rare cases, such as when as a person can't sense the need to urinate, the pouch can rupture painfully requiring surgery to fix. But under normal circumstances, your decision to urinate stops the brain's signal to the external urethral sphincter, causing it to relax and the bladder to empty. The external urethral sphincter is one of the muscles of the pelvic floor, and it provides support to the urethra and bladder neck. It's lucky we have these pelvic floor muscles because placing pressure on the system by coughing, sneezing, laughing, or jumping could cause bladder leakage. Instead, the pelvic floor muscles keep the region sealed until you're ready to go. But holding it in for too long, forcing out your urine too fast, or urinating without proper physical support may over time weaken or overwork that muscular sling. That can lead to an overactive pelvic floor, bladder pain, urgency, or urinary incontinence. So in the interest of long-term health, it's not a great habit to hold your pee. But in the short term, at least, your body and brain have got you covered, so you can conveniently choose your moment of sweet release.
刚开始还只是有点不舒服 但是很快就变成了不可忽视的尿意 最终,这变成你脑子里唯一想做的事情 而且纯粹出于绝望 你冲去厕所,直到“啊。” 人每天至少要排尿四到六次 偶尔情况下,都市生活的压力迫使我们只能憋着 这个习惯有多坏?我们身体能憋多久? 答案就在于膀胱的工作原理 骨盆里的一个椭圆囊 这个结构组织的旁边是几个其他的器官 合起来就组成了排尿系统 两个肾 两个输尿管 两个尿道括约肌 一个尿道 从肾脏连续流出来的黄色液体就是尿液 形成于肾脏里的尿液由身体里的水分和终末产物合成 废液通过漏斗般的口子流到两个叫着输尿管的肌管中 然后注入一个中空的器官,就是膀胱 这个器官壁是由一种叫做逼尿肌的组织构成的 当膀胱注入尿液时,它会像气球一样膨胀扩张 当膀胱涨满时,逼尿肌收缩 尿道内括约肌自然而然的张开 尿就排出来了 液体飞速的向下流进尿道 从膀胱经尿道排出体外 这个过程就像水龙头 当你想憋尿时,括约肌就会关上 当你想排尿时,你会无意识地打开这扇大门 但你怎样才能意识到你膀胱满了没有呢 所以你能知道你什么时候该尿尿了呢? 在逼尿肌里有千万层交织成网的牵张感受器 当膀胱尿量增加时,会牵拉这些感受器 它们通过神经发送信号到骨髓骶的中枢区域 一个反射信号再反射到膀胱 使括约肌轻微收缩 增加膀胱的压力,从而让使人知道膀胱已经满了 同时,括约肌内壁开始打开 这叫做排尿反射 大脑会判断现在是不是排尿的合适时机 通过发射另一个信号来控制尿道外括约肌 膀胱内尿量达到150到200毫升时, 膀胱壁扩张 能让人感觉到尿意 当有400到500毫升时,这种尿意使人感到不舒服 膀胱还是可以扩张,但是有一个极限点 尿液超过1000毫升时,膀胱可能会炸掉 多数人会在这种情况发生前就排尿 但是在极少数的情况下 例如当一个人感受不到要尿意时 膀胱会痛苦的破裂,需要手术来修复 但是在正常情况下 你要排尿的决定阻止了大脑向尿道外括约肌发出信号 使得它开始放松,膀胱排空 尿道外括约肌是一种盆底肌 它向尿道和膀胱颈提供支撑 能有这些盆底肌是幸运 因为像咳嗽 打喷嚏 大笑或者跳跃时对这个系统产生的压力 可能会时膀胱漏尿 相反的,盆底肌使这个区域封闭着 直到你准备好去排尿 但是憋着的时间太长 会导致你排尿的速度特别快 或者尿的时候没有合适的身体支撑 可能会使尿道括约肌痉挛或者逼尿肌无力 这可能会导致盆底肌松弛 膀胱痛 尿急 或者尿失禁 为了长期健康的考虑 憋尿不是好习惯 但是短期来说,至少你的身体和大脑都正常的情况下 你可以合理的来选择排尿的时间