KS3 Biology - Human Reproductive Systems — Transcript

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1. 0:07In this video, we'll learn about human
2. 0:08reproductive systems.
3. 0:10We'll cover what gametes are,
4. 0:12the main parts of the male reproductive
5. 0:14system,
6. 0:15and the main parts of the female
7. 0:16reproductive system as well.
8. 0:21Let's begin with what gametes are.
9. 0:24Gametes, which are also known as sex
10. 0:26cells, are specialized cells used for
11. 0:28reproduction, and the main role of the
12. 0:30male and female reproductive systems is
13. 0:33to produce these gametes.
14. 0:35In the male reproductive system, the
15. 0:37gametes are called sperm cells, and in
16. 0:39the female reproductive system, the
17. 0:41gametes are egg cells, or ova.
18. 0:44Now, when a sperm and egg cell fuse
19. 0:45together during a process called
20. 0:47fertilization, they form a cell called a
21. 0:49zygote, which has the potential to
22. 0:51develop into a whole new baby human.
23. 0:54Let's look at some adaptations of
24. 0:55gametes that increase the chances of
25. 0:57fertilization.
26. 0:59Starting with sperm cells, these gametes
27. 1:01have a tail, which is sometimes called a
28. 1:03flagellum, that allows them to swim out
29. 1:06of the male reproductive system and
30. 1:08through the female reproductive system
31. 1:09towards an egg cell so that they can
32. 1:11fertilize it.
33. 1:13They also have lots of mitochondria that
34. 1:15release the energy they need for this
35. 1:16journey.
36. 1:18Moving on to egg cells, these gametes
37. 1:20are much larger than sperm cells, and
38. 1:22they contain lots of nutrients to
39. 1:23support the early stages of development
40. 1:25if fertilization happens.
41. 1:31Next, let's take a look at the main
42. 1:32parts of the male reproductive system by
43. 1:35following the journey of a sperm cell
44. 1:36through the body.
45. 1:38Starting with the testes, these produce
46. 1:40sperm cells, and most male reproductive
47. 1:42systems have two testes.
48. 1:45They're held in the scrotum, which is a
49. 1:47sack of skin that hangs outside of the
50. 1:48body and keeps the testes cooler than
51. 1:50the body's internal temperature. This is
52. 1:52important for producing healthy sperm.
53. 1:55After being produced, sperm cells travel
54. 1:57along tube called the sperm duct or the
55. 2:00vas deferens.
56. 2:01Along the way, glands like the prostate
57. 2:04gland add fluids to the sperm cells to
58. 2:06create semen,
59. 2:07which is a fluid that provides sperm
60. 2:09with nutrients and also helps them swim.
61. 2:12This semen and the sperm cells within it
62. 2:14then travel along the urethra, which is
63. 2:16a tube that runs through the penis.
64. 2:19The penis itself has lots of blood
65. 2:20vessels, so it grows in size when more
66. 2:22blood flows to it, which makes it easier
67. 2:24to deliver semen into the vagina in the
68. 2:26female reproductive system.
69. 2:28It's also got an opening at its tip, so
70. 2:30the urethra can transport semen out of
71. 2:32the male reproductive system and
72. 2:34potentially into the female vagina
73. 2:35during a process called ejaculation.
74. 2:38In males, the urethra can carry either
75. 2:40urine or semen, but not at the same
76. 2:43time.
77. 2:44Females also have a urethra, but it only
78. 2:46carries urine.
79. 2:48It's also worth noting that the bladder,
80. 2:50which stores urine before it travels
81. 2:51along the urethra, is not involved in
82. 2:53the reproductive system.
83. 2:59Finally, let's take a look at the main
84. 3:00parts of the female reproductive system
85. 3:02by following the journey of an egg cell
86. 3:04instead.
87. 3:06If we start with the ovaries, these
88. 3:07produce egg cells, and most female
89. 3:09reproductive systems have two ovaries.
90. 3:12Generally, one egg cell is released from
91. 3:14one of the ovaries per month in a
92. 3:16process called ovulation.
93. 3:18This egg cell then travels into one of
94. 3:20the two fallopian tubes, which are also
95. 3:22known as oviducts,
96. 3:24and are usually where fertilization
97. 3:26happens.
98. 3:27Let's pause on the journey of the egg
99. 3:29cell for a moment so we can see how
100. 3:30sperm cells reach the fallopian tubes to
101. 3:32potentially fertilize this egg cell.
102. 3:35The vagina is where sperm cells first
103. 3:37enter the female reproductive system,
104. 3:40and then they move up through the
105. 3:41cervix, which is the spongy tissue at
106. 3:43the base of the uterus.
107. 3:45If the sperm cells make it through the
108. 3:46uterus, they might then enter the
109. 3:48fallopian tubes and fertilize an egg if
110. 3:50they happen to be there at the same
111. 3:51time.
112. 3:54If the egg cell is fertilized, it then
113. 3:56travels to the uterus and implants
114. 3:57itself in the uterine lining,
115. 3:59which is just the scientific name for
116. 4:01the wall of the uterus.
117. 4:03The uterus itself is where the
118. 4:04fertilized egg cell can develop into a
119. 4:06baby,
120. 4:07and the uterine lining is really rich in
121. 4:09blood vessels in order to supply the
122. 4:10nutrients needed to support the baby's
123. 4:12development.
124. 4:13It's also really muscular, so it can
125. 4:15push out the fully developed baby when
126. 4:17it's ready to be born.
127. 4:19More often, though, the egg cell isn't
128. 4:21fertilized, and so it doesn't implant
129. 4:23into the uterus.
130. 4:25Instead, the egg cell moves out of the
131. 4:26uterus via the cervix and exits the body
132. 4:29through the vagina along with the
133. 4:30uterine lining.
134. 4:32This process, where the unfertilized egg
135. 4:34cell and uterine lining leave the body
136. 4:35through the vagina, is called
137. 4:36menstruation or a period, and it's
138. 4:39followed by the uterine lining
139. 4:40thickening again before the next
140. 4:42ovulation occurs.
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