Exercises: The reproductive systems

Name the two types of human gametes, state in which organs each is produced, and cite one observable difference between them.

In the image of the female reproductive system, four structures have been marked with numbers. Write the name of the marked structures and state in which of them egg cells (ova) are formed.

In the cross-sectional image of the male reproductive system, four structures have been marked with numbers. Write the name of the marked structures and describe the path sperm cells travel from where they are formed in the testes until they leave the body, naming the structures they pass through.

Explain where fertilisation usually takes place in the female reproductive system and what path the zygote takes afterwards until it becomes implanted in the place where it will develop.

The testes are located outside the abdominal cavity, in the scrotum, because sperm production requires a temperature slightly lower than that inside the body. Reason what might happen to sperm production if the testes were always kept at internal body temperature.

In addition to producing gametes, the ovaries and testes produce sex hormones. Explain what type of organs ovaries and testes are, therefore, and state two changes that these hormones cause during puberty.

A classmate holds two mistaken ideas: "After a vasectomy, a man can no longer ejaculate semen and loses his male characteristics because he has no testosterone," and "a woman with tubal ligation stops having periods because the egg does not reach the uterus."

1. a) Reasonably refute the statement about the man: explain where most of the volume of ejaculated semen comes from and clarify why a vasectomy does not prevent testosterone from reaching the blood or alter its effects.
2. b) Refute the statement about the woman: explain why she continues to have a menstrual cycle and ovulate normally despite having her fallopian tubes severed.

Look at the compared characteristics of the two human gametes:

• Sperm cell: length of about 0.05 mm, no nutrient reserves, motile via flagellum, continuous production of about 100 million per day.

• Egg cell: diameter of about 0.15 mm (a volume hundreds of times greater), non-motile, loaded with nutrient reserves, maturation of 1 every 28 days.

1. a) Justify why the sperm cell requires such a light design and such a massive production, relating it to the physical obstacles and the journey it faces within the female reproductive system.
2. b) Explain why it would be biologically unfeasible and detrimental for a woman to mature millions of egg cells at once, taking into account the energy cost of producing reserves and the type of mammalian gestation.

A woman goes to the emergency department with acute abdominal pain at 7 weeks of pregnancy. The ultrasound confirms that the embryo is not in the uterus, but has implanted in the wall of one of the Fallopian tubes (tubal ectopic pregnancy).

1. a) Knowing that the embryo normally takes between 5 and 7 days to travel from the site of fertilization to the uterus propelled by cilia and muscular contractions, deduce what functional or anatomical failure in the tube could have caused it to become trapped there.
2. b) Compare the structure and distensibility of the uterine myometrium with the thin muscular layer of the Fallopian tube. Based on this comparison, justify why this pregnancy is non-viable and represents a surgical emergency due to the risk of rupture and severe hemorrhage.