Biology 3201 Unit 2 – Reproduction & Development. Chapter 15 Continuance of Human Life Ms. K. Morris 2010-2011. Section 15.1 : The Human Reproductive System p. 486-499. The Human Male Reproductive System. Male Sexual Structures
Continuance of Human Life
Ms. K. Morris 2010-2011
(1) Follicle Stimulating Hormone (FSH)- stimulates spermatogenesis from the anterior pituitary.
(2) Inhibin- released by the seminiferous tubules and forms a negative feedback loop with FSH. It acts on the hypothalamus to slow the production of releasing factors that control the release of FSH. Interaction of inhibin and FSH controls the rate of formation of sperm.
(3) Luteinizing hormone (LH)- also from anterior pituitary, stimulates the interstitial cells of the testes that surround the seminiferous tubules to produce male sex hormones.
(4) Testosterone - the major androgen (male sex hormone) and is responsible for the development of male secondary characteristics
Some doctors prescribe hormone replacement therapy in the form of low levels of estrogen and progesterone
Potential side effects of estrogen replacement:
Potential side effects of combined estrogen and progesterone replacement:
(diseases spread through sexual contact )
1. AIDS and HIV
Three Stages of AIDS:
- caused by bacteria
Stage one: chancre sores appear at infection site
Stage two : rash appears (usually on palms or soles of feet but may appear anywhere on skin) this stage is extremely infectious
Stage three: infection affects cardiovascular and nervous system and may develop blindness, mental illness, and heart disease
(i) Blocked Oviducts – often caused by PID (pelvic inflammatory disease) which is often caused by STI’s.
(ii) Failure to Ovulate – caused by hormonal imbalances that occur for a variety of reasons, including being underweight or overweight.
(iii) Endometriosis – a painful condition in which the endometrium grows outside the uterus.
(iv) Damaged Egg – which may be caused by environmental factors, such as exposure to chemicals.
(v) Obstruction in the Vas Deferens or Epididymis – which may be caused by complications arising from STI’s or from varicose veins in the testicles.
(vi) Low Sperm Count – caused by numerous factors, including overhead testicles, smoking, and alcohol intake.
(vii) Abnormal Sperm – caused by factors including overheated testicles, exposure to toxins, and infections, such as STI’s.
Technological solutions to human infertility:
(p. 501, Table 15.1)
(ii) In Vitro Fertilization (IVF) – Fertilization takes place outside the body, in a laboratory procedure. The fertilized oocytes are implanted in the uterus. Used by: a woman who has damaged or blocked oviducts.
(iii) In Vitro Maturation (IVM) – Primary follicles are removed from the uterus and induced to mature into secondary oocytes. IVM is used to produce numerous oocytes for in vitro fertilization. Used by: a woman who will undergo in vitro fertilization.
(iv) Surrogate Motherhood – A fertilized oocyte from an infertile couple (obtained by IVF) is placed in the uterus of a surrogate mother. Alternatively, a surrogate mother undergoes AI, using sperm from the male of the infertile couple. Used by: a woman who cannot bring a child to term, or a couple who is infertile due to unknown factors or factors that cannot be overcome by other technologies.
(v) Superovulation (using fertility drugs) – Used to produce multiple eggs for in vitro fertilization, to increase the chance of pregnancy. FSH (follicle stimulating hormone) injections stimulate the development of multiple follicles. Cont’….
…HCG (human chorionic gonadotrophin) stimulates ovulation. Used by: a woman who is undergoing in vitro fertilization, or a woman who does not ovulate regularly, frequently, or at all, to increase her chances of pregnancy.
(vi) Embryo Storage (Cryopreservation) – Oocytes, semen, and even embryos are preserved by freezing. Used by: a male or female cancer patient, who may become infertile or sterile due to radiation therapy, or a sperm bank that supplies semen for AI.
Evaluate the design of birth control technologies and the way they function. Include: (p. 502)
1. Male Condom – about 85% effective. A latex sheath that fits over the erect penis. It traps the sperm. Risk is a reaction to latex.
2. Female Condom – about 85% effective. A polyurethane pouch that is inserted into the vagina. It prevents the sperm from contacting the vagina and cervix. No known risks.
3. Diaphragm – about 90% effective. A large latex cup that fits over the cervix and prevents sperm from entering. It is usually used with spermicidal jelly or foam. Sperm is blocked at the cervix. Risks are reaction to latex.
4. Cervical Cap – almost 85% effective. Must be used with the jelly. A latex cap is attached to the cervix by suction. Sperm is blocked, and killed by the spermicide, at the cervix. Risks are reaction to latex.
5. Spermicidal Jellies & Foams – about 75% effective. These products are inserted into the vagina before intercourse. They are often used with a condom or diaphragm. A large percent of sperm are killed. Risk is reaction to spermicide.
6. IUD (interutine device) – over 90% effective. An IUD is a plastic coil or armature that is inserted into the uterus. It lasts about 5 years. Implantation (of the egg) is prevented. Risk is PID (pelvic inflammatory disease).
7. Birth Control Pill – close to 100% effective (if used correctly). A daily hormone medication taken orally. FSH and LH are not released. Risks include blood clots (especially in smokers), and hormonal side effects.
8. Morning After Pill – close to 100% effective (if taken properly). It can be taken up to 3 days after possible fertilization but the sooner it is taken the higher the success rate. Contains high doses of estrogen and progesterone. Prevents or delays the release of oocyte from ovary and if fertilization occurred it stops embryo from implanting in the endometrium. Side effects: nausea and vomiting.
9. Norplant (implant) – over 90% effective. Hormones are implanted under the skin. FSH and LH are not released. Risks are hormonal side effects.
10. Depo-Provera (needle) - 99% effective. A woman is given one hormone injection every three months. FSH and LH are not released. Risks are hormonal side effects.
11. Tubal Ligation – close to 100% effective. The oviducts are cut and tied. The eggs do not reach the oviduct or uterus. Risks are that it is permanent, irreversible, and sterility.
12. Vasectomy – close to 100% effective. The sperm ducts are cut and tied. There is no sperm in the ejaculate. Risks are that it is permanent, irreversible, and sterility.
13. Rhythm Method – about 70% effective. The date of ovulation is determined by record keeping and temperature measurements. Intercourse is avoided at the most fertile times. No risks.
14. Abstinence - 100% effective. The woman must refrain from sexual intercourse. Sperm does not contact the vagina. No risks.
Assess the effects of birth control technology on the population demographics of developed and underdeveloped countries & debate the merits of funding solutions to human fertility problems versus human population control. (Read p. 503-505)
Drop is birth rate is possible with improved contraception, but yet some countries remain in stage 2. Why?
Explain the processes of fertilization and development in human reproduction. Trace the journey of sperm and egg from their origin until fertilization and implantation.
- Describe the following basic stages of embryonic development. (p. 508)
Development (fertilization, cleavage, blastulation, gastrulation, neurulation, organogenesis)
Cleavage converts a single-celled zygote into a multi-celled embryo by mitosis.
Organ formation occurs in the next stage of the development of the embryo.
Travels of a Young Zygote
Identify chemical control hormones associated with implantation, birth and lactation. Include:
The First Trimester (Weeks 1-12)
The Second Trimester (Weeks 13-24)
The Third Trimester (Weeks 25-38)
Birth (p. 512-513)
1) Dilation - dilation of the cervix. Membranes of the amniotic fluid rupture, lubricating the vagina.
2)Expulsion - Strong uterine contractions of a minute in duration separated by two to three minute intervals propel the fetus down the birth canal.
3) Placental –The placenta (or afterbirth) in expelled through the vagina.
Describe the functions of primary membranes during the embryonic development of animals:
Development of the fetus can be compared to a chick embryo:
1. Chorion is the layer located just inside the shell. It surrounds the embryo and other membranes. It controls the exchange of gases.
2. Allantois is a sac‑like structure that grows out of the digestive tract of the embryo. It exchanges gases and collects the waste material of the embryo.
3. Amnion is a sac that surrounds the embryo. It is filled with fluid and keeps the embryo moist. It also cushions the embryo for protection.
4. Yolk sac holds the yolk. The yolk is food for the embryo. The embryo consumes all of the yolk before hatching.
Placenta - a blood vessel-rich organ which is present only during pregnancy.
Umbilical Cord - it is a lifeline, connecting the developing embryo and fetus to the placenta.
1. Cigarette Smoke - may constrict fetus’s blood vessels preventing the fetus from getting enough oxygen.
2. Alcohol - can affect the fetus’s brain, CNS, and physical development.
4 techniques used to monitor various stages of embryonic or fetal development: