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.
Počinje sa malo neugode i uskoro postaje pritisak koji je nemoguće ignorirati. Na kraju, samo na to možete misliti, i iz čistog očaja, idete u lov na toalet dok ne bude "ahh." Ljudi bi trebali mokriti bar četiri do šest puta dnevno, ali ponekad, pritisak modernog života nas tjera da trpimo i zadržavamo. Koliko je ova navika loša, i koliko dugo to naša tijela mogu izdržati? Odgovori leže u karakteristikama mjehura, ovalne vrećice koja se nalazi u zdjelici. Drugi organi okružuju ovu strukturu koja zajedno čini cijeli mokraćni sustav. Dva bubrega, dva mokraćovoda, dva sfinktera mokraćne cijevi, i mokraćna cijev. Stalno kapajući iz bubrega je žućkasta tekućina znana kao mokraća. Bubrezi rade mokraću iz mješavine vode i otpadnih tvari u tijelu, usmjeravajući neželjenu tekućinu u dvije mišićne cijevi, mokraćovode. One ih nose dolje u šuplji organ, znan kao mokraćni mjehur. Mišićni zid ovog organa načinjen je od tkiva nazvanog detruzor koji se opušta kako se mjehur puni dozvoljavajući da se napuše poput balona. Kada se mjehur napuni, detruzor se skuplja. Unutarnji sfinkter mokraćne cijevi se automatski otvara, i mokraća se ispušta. Krećući se prema dolje, tekućina ulazi u mokraćnu cijev i staje na vanjskom sfinkteru mokraćne cijevi. Ovo radi kao slavina. Kada želite odgoditi mokrenje držite sfinkter zatvoren. Kada ga želite otpustiti, to možete svojevoljno učiniti. Ali kako osjećate da je mjehur pun tako da znate kada piškiti? U slojevima detruzora su milijuni receptora rastezanja koji se aktiviraju kako se puni mjehur. Oni šalju signale živcima do sakralne regije u vašoj leđnoj moždini. Refleksni signal putuje do vašeg mjehura, tjerajući detruzore da se malo skupe, i povećavajući pritisak mjehura tako da znate da se puni. U isto vrijeme, unutarnji sfinkter mokraćne cijevi se otvara. Ovo se zove refleks mokrenja. Mozak mu se može suprostaviti ako nije vrijeme za mokrenje odašiljući drugi signlal za skupljanje vanjskog sfinktera mokraćne cijevi. S otprilike 150 do 200 mililitara mokraće u sebi, mišićni zid mjehura se dovoljno širi da osjetite da ima mokraće u njemu. S otprilike 400 do 500 mililitara pritisak postaje neugodan. Mjehur se može širiti do određene točke. Preko 1000 mililitara može i pući. Većina ljudi bi izgubila kontrolu prije nego se to dogodi, ali u rijetkim slučajevima, kao kada osoba ne osjeti da mora mokriti vrećica može pući tako da je potrebna operacija za popravak. Ali u normalnim okolnostima, vaša odluka da mokrite zaustavlja signal mozga vanjskom sfinkteru uzrokujući da se opusti i mjehuru da se isprazni. Vanjski sfinkter mokraćne cijevi je jedan od mišića dna zdjelice, i daje podršku mokraćnoj cijevi i vratu mjehura. Srećom imamo te miišiće jer izazivanjem pritiska kašljanjem, kihanjem, smijehom, ili skakanjem, mogli bi izazvati curenje iz mjehura. Umjesto toga, mišići zdjelice drže regiju zapečaćenom dok ne trebate ići. Ali ako predugo zadržavate, izbacujete mokraću prebrzo, ili mokrite bez potpore mišića, može kroz vrijeme oslabiti tu mišićnu praćku. To može dovesti preaktivnih zdjeličnih mišića, boli u mjehuru, hitnog mokrenja, ili inkontinencije. U interesu dugoročnog zdravlja, nije dobra navika zadržavati mokraću. Ali kratkoročno, barem, mozak i tijelo vas štite tako da možete birati kada ćete se olakšati.