Question

Chapter 28: The Reproductive Systems and Development

Critical Thinking Questions

1. Assume that a 30-year-old male is able to produce sufficient spermatozoa, but because of an obstruction in his duct system, the spermatozoa cannot be discharged through the urethra. If each duct in the system had to be examined to locate the obstruction, explain the sequence in which the ducts would have to be examined, starting with the urethra and termination in the seminiferous tubules.

2. Make a flowchart explaining the hormonal relationships that exist among the pituitary gland, ovarian cycle, and uterine (menstrual) cycle.

3. Jan has a history of miscarriage in the first trimester. Her physician thinks that her problem might be hormonal. What hormones could be implicated in failing to maintain the pregnancy during the first trimester?

4. Doris wants to have her child born on a particular day. She asks her physician if he can induce labor on that day. Is this procedure possible? If so, what will the physician have to do? Are there any negative consequences to having labor induced?

5. Based on your knowledge of the reproductive system, describe some possible methods of birth control that would impair ovulation, fertilization or implantation.

Answer 1

1. Sperms are stored in the epididymis. From here they travel through the vas deferens up the spermatic cord to the prostate behind the bladder. The vas deferens joins with the seminal vesicle to form the ejaculatory duct, which passes through the prostate and empties into the urethra.

The sequence of examination would be urethra, ejaculatory duct, vas deferens, epididymis and finally seminiferous tubules.

2. The anterior pituitary gland releases the FSH and LH hormones. The release of these hormones is governed by the gonadotrophin-releasing hormone. FSH and LH stimulate the maturation of ovarian follicles. The ovarian follicles produce estradiol which acts on the endometrium. When ovulation occurs, the corpus luteum produces progesterone. This causes the proliferation of endometrium and makes it ready for pregnancy in case fertilization occurs. If pregnancy occurs, the high levels of circulating estrogen and progesterone have inhibitory feedback on the pituitary gland. This inhibits the secretion of FSH and LH.

3. Hormones like Thyroxine and Progesterone are linked to miscarriages in the first trimester. Women with hypothyroidism have low levels of Thyroxine. This is associated with a higher risk of miscarriage. Progesterone causes the endometrium to thicken. The thick lining will helps create an ideal supportive environment in the uterus for a fertilized egg/embryo. Low levels of progesterone may lead to inadequate development of the endometrium. This may also cause a miscarriage.

4. This procedure is possible. The physician will first have to assess the gestational age of the fetus. A physical examination will reveal the presentation of the fetus (cephalic or breech). The engagement of the head can also be determined. Fetal heart rate monitoring will also reveal the status of the fetus. An Ultrasound scan will help assess the extent of the maturity of the fetus. If 38 weeks of gestation have passed, the physician can induce labor by cervical priming with dinoprostone. Labour can be induced through oxytocin infusion. If the patient wants analgesia, an epidural catheter can be inserted for labor analgesia.  The negative consequences of having labor induced include - the risk of premature delivery, postpartum hemorrhage, and perineal tears. Induction of labor may also cause placental abruption and uterine rupture.

5. Methods of contraception

Impair ovulation: Oral contraceptive pills, Depot medroxyprogesterone acetate

Prevent fertilization -  Barrier methods like condoms, diaphragms, sponges, and cervical caps that prevent the sperm from entering the uterine cavity

Prevent Implantation: Intrauterine contraceptive devices (Copper T, Mirena, etc)