1. Reproduction and Development in Humans
Chapter 25
Reproduction and
Development in Humans
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2. (I) Female Reproductive
System
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3. Gametogenesis The production of gametes (sex cells)
Males = spermatogenesis in the testes
Females = oogenesis in the ovaries
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4. (A) Ovaries The female gonads
Located within the lower portion of the body cavity
In the ovaries, each egg cell (ovum) is present in a tiny sac called a follicle
About once a month, a follicle matures and bursts. The egg is then released and travels into the oviduct (Fallopian tubules)
This is known as ovulation
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5. 4. Fertilization takes place within the Fallopian tubules (oviduct) forming a zygote
5. The zygote then travels down and into the uterus where it implants into the uterine lining and develops
6. When embryonic development of the baby is completed, the cervix dilates (opens) and the baby travels through the birth canal known as the vagina
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6. b) progesterone- maintains pregnancy
7. The ovaries also produce sex hormones known as estrogen and progesterone
a) estrogen- used for the development of secondary sex characteristics like mammary glands (breasts)
b) progesterone- maintains pregnancy
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8. (II) Menstrual Cycle Mature egg develops and is released
Begins at puberty and ends at menopause
Hormones involved:
FSH estrogen
LH progesterone
Stages involved in order:
follicle stage  ovulation  corpus luteum  menstruation
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9. 1. Follicle Stage
10-14 days
FSH is secreted by the pituitary gland which stimulates maturation of egg in the follicle
As the follicle develops, it releases estrogen which stimulates the uterine lining to thicken with blood
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10. Ovulation
Secretion of LH (lutenizing hormone) from the pituitary causes a mature egg to be released from the follicle and into the fallopian tubules (oviduct)
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11. 3. Corpus Luteum Stage 10-12 days
The burst follicle fills with cells forming the corpus luteum, which produces progesterone
Progesterone stimulates further thickening of the uterine lining
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12. 4. Menstruation
3-5 days
If the egg is not fertilized, progesterone secretion decreases and the lining of the uterus breaks down
The lining of the uterus is sloughed off and discharged from the body through the vagina as a result (period).
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14. (III) Fertilization and Implantation
Fertilization occurs in the fallopian tubules (oviduct)
If the egg is not fertilized within 24 hours after ovulation, it will deteriorate
After fertilization, the zygote undergoes cleavage and becomes an embryo
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16. 4. The embryo arrives in the uterus 5-10 days after fertilization
5. The embryo implants into the uterine wall and establishes pregnancy
6. Placenta- nourishes the embryo
7. Umbilical cord- attaches the embryo to the placenta
8. Amnion- embryo develops inside the amniotic sac which contains amniotic fluid that serves as a shock absorber
9. Gestation Period- length of pregnancy (approximately nine months)
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18.                                                                                                  
                                               
                                               
(IV) Multiple Births
1. Identical twins- Develops from one zygote separating into two during cleavage. One sperm and one egg is involved and therefore the babies will look identical and must be of same sex
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19. Identical twins do not have identical fingerprints
Identical twins do not have identical fingerprints. They are a product of their environment.
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20. (V) Multiple Births
Fraternal twins- Develop from two separate eggs, each fertilized by separate sperm cells. Therefore, the babies may not look identical and could be of different sex. Simply ciblings!
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21. (V) Multiple Births
Fertility drugs often cause production of more than one ovum during ovulation. Septuplets = 7 ova + 7 sperm (7 zygotes)
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22. (VI) Male Reproductive
System
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23. (A) Testes Are the male gonads Produce sperm
Sperm is produced in the seminiferous tubules and stored in the epididymis
Sperm then leaves the epididymis through the vas deferens and into the urethra (which is a tube inside the penis)
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24. 4. The penis is a structural adaptation for internal fertilization
5. Prostate Glands secrete a liquid into the urethra which combines with the sperm cells. This liquid serves as a transport medium for the sperm cells and is called semen
6. Testes also produce the male sex hormone called testosterone
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25. 8. Scrotum- sac in which the testes are located a) outside the body
7. Testosterone regulates the maturation of sperm and the development of secondary sex characteristics such as beard development and voice pitch
8. Scrotum- sac in which the testes are located
a) outside the body
b) keeps the temperature 1-2 degrees Celsius cooler than normal body temperature
c) this provides an optimum temperature for sperm production
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26. Seminal Vesicles- are glands at the base of the bladder and connected to the prostate gland that provide nutrients for the semen.
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27. The Penis
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