[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:06.83,0:00:08.01,Default,,0000,0000,0000,,It's a hot day,
Dialogue: 0,0:00:08.01,0:00:10.37,Default,,0000,0000,0000,,and you've just downed \Nseveral glasses of water,
Dialogue: 0,0:00:10.37,0:00:12.29,Default,,0000,0000,0000,,one after the other.
Dialogue: 0,0:00:12.29,0:00:16.18,Default,,0000,0000,0000,,Behind the sudden urge that follows\Nare two bean-shaped organs
Dialogue: 0,0:00:16.18,0:00:19.72,Default,,0000,0000,0000,,that work as fine-tuned internal sensors.
Dialogue: 0,0:00:19.72,0:00:22.10,Default,,0000,0000,0000,,They balance the amount of fluid\Nin your body,
Dialogue: 0,0:00:22.10,0:00:24.11,Default,,0000,0000,0000,,detect waste in your blood,
Dialogue: 0,0:00:24.11,0:00:26.77,Default,,0000,0000,0000,,and know when to release \Nthe vitamins, minerals,
Dialogue: 0,0:00:26.77,0:00:29.45,Default,,0000,0000,0000,,and hormones you need to stay alive.
Dialogue: 0,0:00:29.45,0:00:31.64,Default,,0000,0000,0000,,Say hello to your kidneys.
Dialogue: 0,0:00:31.64,0:00:35.94,Default,,0000,0000,0000,,The main role of these organs\Nis to dispose of waste products
Dialogue: 0,0:00:35.94,0:00:38.67,Default,,0000,0000,0000,,and to turn them into urine.
Dialogue: 0,0:00:38.67,0:00:41.56,Default,,0000,0000,0000,,The body's eight liters of blood\Npass through the kidneys
Dialogue: 0,0:00:41.56,0:00:44.88,Default,,0000,0000,0000,,between 20 and 25 times each day,
Dialogue: 0,0:00:44.88,0:00:51.85,Default,,0000,0000,0000,,meaning that together, these organs filter\Nabout 180 liters every 24 hours.
Dialogue: 0,0:00:51.85,0:00:54.68,Default,,0000,0000,0000,,The ingredients in your blood\Nare constantly changing
Dialogue: 0,0:00:54.68,0:00:56.82,Default,,0000,0000,0000,,as you ingest food and drink,
Dialogue: 0,0:00:56.82,0:01:00.48,Default,,0000,0000,0000,,which explains why \Nthe kidneys need to be on permanent duty.
Dialogue: 0,0:01:00.48,0:01:04.46,Default,,0000,0000,0000,,Blood enters each kidney through arteries\Nthat branch and brach,
Dialogue: 0,0:01:04.46,0:01:09.61,Default,,0000,0000,0000,,until they form tiny vessels that entwine\Nwith special internal modules,
Dialogue: 0,0:01:09.61,0:01:11.48,Default,,0000,0000,0000,,called nephrons.
Dialogue: 0,0:01:11.48,0:01:12.80,Default,,0000,0000,0000,,In each kidney,
Dialogue: 0,0:01:12.80,0:01:17.53,Default,,0000,0000,0000,,1 million of these nephrons form \Na powerful array of filters and sensors
Dialogue: 0,0:01:17.53,0:01:20.54,Default,,0000,0000,0000,,that carefully sift through the blood.
Dialogue: 0,0:01:20.54,0:01:22.47,Default,,0000,0000,0000,,This is where we see just how refined
Dialogue: 0,0:01:22.47,0:01:25.97,Default,,0000,0000,0000,,and accurate this internal \Nsensing system is.
Dialogue: 0,0:01:25.97,0:01:30.98,Default,,0000,0000,0000,,To filter the blood, each nephron\Nuses two powerful pieces of equipment:
Dialogue: 0,0:01:30.98,0:01:37.60,Default,,0000,0000,0000,,a blob-like structure called a glomerulus,\Nand a long, stringy, straw-like tubule.
Dialogue: 0,0:01:37.60,0:01:41.42,Default,,0000,0000,0000,,The glomerulus works like a sieve,\Nallowing only certain ingredients,
Dialogue: 0,0:01:41.42,0:01:45.25,Default,,0000,0000,0000,,such as vitamins and minerals,\Nto pass into the tubule.
Dialogue: 0,0:01:45.25,0:01:47.44,Default,,0000,0000,0000,,Then, this vessel's job is to detect
Dialogue: 0,0:01:47.44,0:01:51.36,Default,,0000,0000,0000,,whether any of those ingredients \Nare needed in the body.
Dialogue: 0,0:01:51.36,0:01:54.86,Default,,0000,0000,0000,,If so, they're reabsorbed in amounts\Nthat the body needs,
Dialogue: 0,0:01:54.86,0:01:57.78,Default,,0000,0000,0000,,so they can circulate in the blood again.
Dialogue: 0,0:01:57.78,0:02:00.45,Default,,0000,0000,0000,,But the blood doesn't only \Ncarry useful ingredients.
Dialogue: 0,0:02:00.45,0:02:02.96,Default,,0000,0000,0000,,It contains waste products, too.
Dialogue: 0,0:02:02.96,0:02:05.78,Default,,0000,0000,0000,,And the nephrons have to figure out \Nwhat to do with them.
Dialogue: 0,0:02:05.78,0:02:09.12,Default,,0000,0000,0000,,The tubules sense compounds \Nthe body doesn't need,
Dialogue: 0,0:02:09.12,0:02:12.46,Default,,0000,0000,0000,,like urea, left over from \Nthe breakdown of proteins,
Dialogue: 0,0:02:12.46,0:02:15.52,Default,,0000,0000,0000,,and redirects them as urine \Nout of the kidneys
Dialogue: 0,0:02:15.52,0:02:19.12,Default,,0000,0000,0000,,and through two long sewers,\Ncalled ureters.
Dialogue: 0,0:02:19.12,0:02:23.32,Default,,0000,0000,0000,,The tubes empty their contents\Ninto the bladder to be discharged,
Dialogue: 0,0:02:23.32,0:02:26.54,Default,,0000,0000,0000,,ridding your body of that waste\Nonce and for all.
Dialogue: 0,0:02:26.54,0:02:28.85,Default,,0000,0000,0000,,There's water in that urine, too.
Dialogue: 0,0:02:28.85,0:02:31.70,Default,,0000,0000,0000,,If the kidney detects too much of it\Nin your blood,
Dialogue: 0,0:02:31.70,0:02:34.98,Default,,0000,0000,0000,,for instance, when you've chugged\Nseveral glasses at once,
Dialogue: 0,0:02:34.98,0:02:38.97,Default,,0000,0000,0000,,it sends the extra liquid\Nto the bladder to be removed.
Dialogue: 0,0:02:38.97,0:02:41.51,Default,,0000,0000,0000,,On the other hand,\Nlow water levels in the blood
Dialogue: 0,0:02:41.51,0:02:44.69,Default,,0000,0000,0000,,prompt the kidney to release some\Nback into the blood stream,
Dialogue: 0,0:02:44.69,0:02:48.28,Default,,0000,0000,0000,,meaning that less water \Nmakes it into the urine.
Dialogue: 0,0:02:48.28,0:02:52.04,Default,,0000,0000,0000,,This is why urine appears yellower\Nwhen you're less hydrated.
Dialogue: 0,0:02:52.04,0:02:56.48,Default,,0000,0000,0000,,By controlling water, your kidneys\Nstabilize the body's fluid levels.
Dialogue: 0,0:02:56.48,0:03:00.95,Default,,0000,0000,0000,,But this fine balancing act\Nisn't the kidney's only skill.
Dialogue: 0,0:03:00.95,0:03:03.97,Default,,0000,0000,0000,,These organs have the power \Nto activate vitamin D
Dialogue: 0,0:03:03.97,0:03:08.57,Default,,0000,0000,0000,,to secrete a hormone called renin\Nthat raises blood pressure,
Dialogue: 0,0:03:08.57,0:03:11.26,Default,,0000,0000,0000,,and another hormone \Ncalled erythropoietin,
Dialogue: 0,0:03:11.26,0:03:14.67,Default,,0000,0000,0000,,which increases red blood cell production.
Dialogue: 0,0:03:14.67,0:03:19.35,Default,,0000,0000,0000,,Without the kidneys, our bodily fluids \Nwould spiral out of control.
Dialogue: 0,0:03:19.35,0:03:24.24,Default,,0000,0000,0000,,Every time we ate, our blood would receive\Nanother load of unsifted ingredients.
Dialogue: 0,0:03:24.24,0:03:29.74,Default,,0000,0000,0000,,Soon, the build up of waste would overload\Nour systems and we'd expire.
Dialogue: 0,0:03:29.74,0:03:32.96,Default,,0000,0000,0000,,So each kidney not only \Nkeeps things running smoothly.
Dialogue: 0,0:03:32.96,0:03:34.98,Default,,0000,0000,0000,,It also keeps us alive.
Dialogue: 0,0:03:34.98,0:03:38.64,Default,,0000,0000,0000,,Lucky then that we have two \Nof these magical beans.