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Reproduction and Development Reproductive Systems Human Development The Reproductive Systems Male Female Sexually Transmitted Infections Hormonal Regulation The Male Reproductive System • The functions of the male reproductive system include: 1. To produce male gametes (spermatogenesis) 2. To produce hormones (testosterone) 3. To maintain primary and secondary male sexual characteristics The Female Reproductive System • The functions of the female reproductive system include: 1. To produce female gametes (oogenesis) 2. To produce hormones (estrogen and progesterone) 3. To maintain primary and secondary female sexual characteristics 4. To maintain and deliver a developing fetus Sexually Transmitted Infections • An STI is an infection that is transmitted only or mainly by sexual contact • STI’s are caused by 1. Bacteria (gonorrhea, syphilis, chlamydia) 2. Viruses (HIV/AIDS, hepatitis B, genital herpes, HPV) 3. Parasites (pubic lice) Hormonal Regulation • The male reproductive system is influenced by a negative feedback loop and involves the following hormones: 1. GnRH: stimulates the release of FSH and LH from the anterior pituitary gland 2. FSH: stimulates spermatogenesis by the seminiferous tubules of the testes 3. LH: stimulates testosterone production by the interstitial cells of the testes Hormonal Regulation 4. 5. Inhibin: inhibits FSH production by the anterior pituitary gland Testosterone: stimulates the development of the male reproductive system and secondary sex characteristics Hormonal Regulation • The female reproductive system is influenced by a negative feedback loop and involves the following hormones: 1. GnRH: stimulates the release of FSH and LH from the anterior pituitary gland 2. FSH: stimulates estrogen production and oogenesis by the follicles of the ovaries 3. LH: stimulates ovulation and progesterone production by the corpus luteum of the ovaries Hormonal Regulation 4. 5. Estrogen: stimulates the development of the female reproductive system and secondary sex characteristics Progesterone: Causes uterine thickening and prevents uterine contractions * Hormones of the female reproductive system are secreted according to a 28 day cycle from puberty to menopause Human Development Fertilization and Embryonic Development Fetal Development and Birth Reproductive Technology Fertilization and Embryonic Development • • • • The embryonic period of human development takes place from fertilization until 8 weeks The fetal period of development is from 8 weeks until full term (40 weeks) Fertilization is the joining of male and female gametes to form a zygote The gender of the zygote is determined by the X and Y chromosomes of the egg and sperm Fertilization and Embryonic Development • • • • The first cell divisions of the zygote is called cleavage Cleavage results in the formation of the blastocyst The blastocyst implants in the endometrium within 5 days of fertilization The implanted blastocyst begins secreting the hormone human chorionic gonadotropin (hCG) Fertilization and Embryonic Development • 1. 2. 3. • • The blastocyst undergoes gastrulation to make three tissues (differentiation*) Endoderm Ectoderm Mesoderm The extra-embryonic membranes develop The process of neurulation and organogenesis occur Fetal Development and Birth • Fetal development and human pregnancy is divided into three trimesters First Trimester (1-12 weeks) 1. – – – – – Embryonic development completes The embryo becomes a fetus The placenta grows from the chorion External reproductive organs are distinguishable Teratogens are most harmful Fetal Development and Birth 2. Second Trimester (13-24 weeks) – – – – – Fetal organs continue to grow and develop Fetal skeleton begins to form bones Mother begins to feel movement Fetus is covered in fine hair and mucus If the fetus is born prematurely he/she is unlikely to survive Fetal Development and Birth 3. Third Trimester (25-38 weeks) – – – – Fetal organs continue to grow and develop Testes descend in the male fetus Fat layer forms and hair is lost Digestive and respiratory systems complete development Fetal Development and Birth • The birthing process is called parturition and occurs due to hormonal changes • The events of parturition are commonly called labour • Labour occurs in three stages 1. Dilation (2 -20 hours): Uterine contractions cause the cervix to dilate and the amnion ruptures Fetal Development and Birth 2. Expulsion (30 min-2 hours): forceful contractions push the baby through the cervix and the birth canal (a Csection may be necessary) 3. Placental: the placenta and umbilical cord are expelled about 30 minutes after the birth of the baby Fetal Development and Birth • • • Lactation is the production of breast milk by the mother The hormone prolactin is secreted from the anterior pituitary gland and stimulates lactation Expressing milk is due to the hormone oxytocin Reproductive Technology • Categories of reproductive technologies include: 1. Conception Control • Preventing fertilization using physical barriers, spermicidal chemicals, surgery, NFP or hormones 2. Birth Control • Preventing birth by inhibiting implantation or clinical abortion Reproductive Technology 3. Diagnostic • Detecting fetal abnormalities before birth using ultrasound, amniocentesis , chorionic villus sampling and fetal surgery 4. Fertility • Increasing the likelihood of ovulation, fertilization or implantation using techniques including artificial insemination, invitro fertilization, and fertility drugs