0:00:03.150,0:00:06.570 NARRATOR: The human body[br]is a complex network 0:00:06.570,0:00:11.580 of cells, tissues,[br]and organs that 0:00:11.580,0:00:17.370 together make life possible. 0:00:17.370,0:00:21.510 10 major systems are responsible[br]for the body's functions-- 0:00:21.510,0:00:28.260 skeletal, muscular,[br]cardiovascular, nervous, 0:00:28.260,0:00:34.300 endocrine, lymphatic,[br]respiratory, digestive, 0:00:34.300,0:00:37.640 urinary, reproductive. 0:00:37.640,0:00:41.340 The skeletal, muscular,[br]cardiovascular, 0:00:41.340,0:00:43.350 and nervous systems[br]in particular 0:00:43.350,0:00:48.570 create an infrastructure that[br]facilitates the other systems. 0:00:48.570,0:00:53.130 The adult skeletal system is[br]a framework of over 200 bones. 0:00:53.130,0:00:55.890 They hold the body[br]together, give it shape, 0:00:55.890,0:00:58.960 and protect its[br]organs and tissues. 0:00:58.960,0:01:01.200 The skeleton also[br]provides anchor points 0:01:01.200,0:01:03.420 for the muscular[br]system, which includes 0:01:03.420,0:01:05.310 three types of muscles-- 0:01:05.310,0:01:08.250 skeletal, smooth, and cardiac. 0:01:08.250,0:01:11.400 They are found throughout the[br]body and facilitate movement. 0:01:11.400,0:01:14.820 Nestled within these muscles[br]is the cardiovascular system, 0:01:14.820,0:01:17.980 a pipeline that includes[br]the heart, blood vessels, 0:01:17.980,0:01:19.680 and the blood itself. 0:01:19.680,0:01:21.930 Also called the[br]circulatory system, 0:01:21.930,0:01:23.880 the cardiovascular[br]system delivers 0:01:23.880,0:01:26.640 oxygen, white blood[br]cells, hormones, 0:01:26.640,0:01:29.370 and nutrients[br]throughout the body. 0:01:29.370,0:01:33.000 Lastly, the nervous system[br]is a communication network 0:01:33.000,0:01:35.160 of nerve cells[br]that the body uses 0:01:35.160,0:01:39.240 to transmit information and[br]coordinate bodily functions. 0:01:39.240,0:01:41.310 It's comprised of[br]the brain, the hub 0:01:41.310,0:01:45.210 of sensory and intellectual[br]activity, the spinal cord, 0:01:45.210,0:01:49.380 and the many cranial and spinal[br]nerves that emanate from them. 0:01:49.380,0:01:53.700 This infrastructure, created[br]by neurons, blood, muscles, 0:01:53.700,0:01:56.430 and bones allows[br]three other systems 0:01:56.430,0:01:59.760 to regulate the body's[br]environment-- the endocrine, 0:01:59.760,0:02:02.970 lymphatic, and urinary systems. 0:02:02.970,0:02:05.610 The endocrine system[br]is a series of glands 0:02:05.610,0:02:08.910 that use information carried[br]by the nervous system 0:02:08.910,0:02:12.120 to help regulate the[br]body's processes. 0:02:12.120,0:02:14.100 Thanks to this[br]neural connection, 0:02:14.100,0:02:16.530 endocrine glands,[br]such as the thyroid, 0:02:16.530,0:02:18.480 are aware of the[br]amount of hormones 0:02:18.480,0:02:20.970 and other chemicals[br]they need to produce. 0:02:20.970,0:02:23.730 These chemicals are then[br]distributed throughout the body 0:02:23.730,0:02:26.700 by way of the[br]cardiovascular system. 0:02:26.700,0:02:28.950 The cardiovascular[br]and nervous systems 0:02:28.950,0:02:32.100 are also utilized by[br]the lymphatic system-- 0:02:32.100,0:02:34.200 a collection of lymph[br]nodes and vessels 0:02:34.200,0:02:36.840 that help regulate[br]the body's defenses. 0:02:36.840,0:02:40.080 Also called the immune[br]system, the lymphatic system 0:02:40.080,0:02:42.990 uses neural pathways[br]to transmit information 0:02:42.990,0:02:45.090 about affected[br]areas of the body, 0:02:45.090,0:02:48.090 and then sends out healing[br]agents, like white blood cells, 0:02:48.090,0:02:50.610 via the bloodstream. 0:02:50.610,0:02:54.240 Another key regulatory[br]system is the urinary system, 0:02:54.240,0:02:58.830 which includes the kidneys,[br]ureters, bladder, and urethra. 0:02:58.830,0:03:01.980 The urinary, or renal[br]system, maintains 0:03:01.980,0:03:04.800 the body's electrolyte[br]levels and filters waste 0:03:04.800,0:03:06.060 from the blood. 0:03:06.060,0:03:08.460 This waste is sent[br]through the blood vessels, 0:03:08.460,0:03:12.660 into the kidneys, and[br]then expelled as urine. 0:03:12.660,0:03:15.900 All of these systems[br]require energy to function, 0:03:15.900,0:03:21.570 and that's where the respiratory[br]and digestive systems come in. 0:03:21.570,0:03:25.470 The respiratory system is a[br]group of passageways and organs 0:03:25.470,0:03:29.310 that extracts life-giving[br]oxygen from the air we breathe. 0:03:29.310,0:03:31.800 Air enters the body[br]through nasal cavities, 0:03:31.800,0:03:35.890 travels down the throat, and is[br]then transported to the lungs. 0:03:35.890,0:03:37.800 The lungs extract[br]oxygen for the body 0:03:37.800,0:03:40.950 to use, and then expel a[br]carbon dioxide byproduct 0:03:40.950,0:03:42.390 when we exhale. 0:03:42.390,0:03:45.660 Energy can also come[br]in the form of food. 0:03:45.660,0:03:49.050 The digestive system is an[br]approximately 30-foot series 0:03:49.050,0:03:52.120 of organs that convert[br]food into fuel. 0:03:52.120,0:03:54.480 Food enters the system[br]through the mouth, 0:03:54.480,0:03:56.910 then moves into the[br]esophagus, the stomach, 0:03:56.910,0:03:58.440 and the intestines. 0:03:58.440,0:04:00.840 Nutrients are absorbed[br]into the body, 0:04:00.840,0:04:03.960 while solid waste is expelled[br]through the anal canal, 0:04:03.960,0:04:07.170 the end of the digestive tract. 0:04:07.170,0:04:09.870 No matter the role,[br]size, or shape 0:04:09.870,0:04:12.000 of any of the[br]body's systems, each 0:04:12.000,0:04:15.180 began with the[br]reproductive system. 0:04:15.180,0:04:18.480 This system is responsible[br]for creating life. 0:04:18.480,0:04:21.870 The primary organs involved[br]differ between the sexes, 0:04:21.870,0:04:25.360 with ovaries, fallopian[br]tubes, the uterus, and vagina 0:04:25.360,0:04:29.790 found in women, and testes and[br]a sperm channel found in men. 0:04:29.790,0:04:33.840 Together, fertilization may[br]occur, organ systems form, 0:04:33.840,0:04:37.110 and then a child is born. 0:04:37.110,0:04:40.830 Humans are[br]complicated organisms. 0:04:40.830,0:04:44.460 But when our 10 major[br]organ systems are healthy, 0:04:44.460,0:04:46.080 they ensure our well-being. 0:04:46.080,0:04:50.030 [MUSIC PLAYING]