11.4d Pregnancy & Birth
01/04/2013 § 1 Comment
Okay, so this has been a weird unit – weird because there’s a woah amount of material to cover and this is just high school stuff. The final blogpost for unit 9 will briefly cover pregnancy, childbirth, and … the placenta.
Note to classmates: I find it’s a lot easier to understand what’s going on with the study guide, as opposed to the course companion, but maybe that’s just me. The study guide is just more straight to the point and clear about what it’s trying to say.
After fertilization, which was covered in the previous blogpost, the fetus has to develop. At 8 weeks, the embryo that took form after the fusion of the egg and sperm (the production of fertilization) starts to develop what will become its bones and is then known as a fetus. The way the fetus gets the materials and nutrients it needs to live are through maternal and fetal blood via the placenta and the umbilical cord.
The last structure we’ll have to know will then be the placenta. The placenta is composed of placental villi, inter-villous spaces, umbilical veins and umbilical arteries. The entire structure of a placenta exchanges material between maternal and fetal blood at the surface of villi with the use of active transport. (Honestly, just expect further detail during the lecture in class.)
Also important to note is that estrogen and progesterone are of course necessary throughout pregnancy to develop the uterus lining. And, after the embryo implants into the uterus wall (the endometrium!), another hormone is secreted: HCG, human chorionic gonadotrophin. HCG helps the growth of the corpus luteum and makes sure that the two hormones estrogen and progesterone are still secreted.
Finally, childbirth, which happens after nine agonizing months of pregnancy. Whoooooo. When the level of progesterone falls, pregnancy is just about done. Yet another hormone, oxytocin is secreted in order for the muscles in the uterus wall to contract. These contractions stimulate even further secretion of oxytocin – so the resulting cycle becomes an example of positive feedback, which is a control system specific to human physiology. So, while the uterus continues to contract (ow), the cervix becomes wider until the amniotic sac bursts and the fluid is released. I think that’s when the pregnant woman in the films suddenly reaches over to the nearest person and says, “…My water just broke.” Only after hours of contraction is the baby pushed out through the cervix and vagina.
And I bet that’s a lot of fun.
Essay Questions (Updated)
- Draw a labelled diagram of the adult female reproductive system. 4 marks
- Draw a labeled diagram of an adult male reproductive system. 6 marks
- Explain the processes involved in oogenesis in humans. 9 marks
- Draw the structure of a mature human egg. 4 marks
- Outline the roles of LH and FSH in the menstrual cycle, including the timing of their secretion during the cycle. 6 marks
- Outline the roles of progesterone and estrogen in the human menstrual cycle. 6 marks
- Outline the process of in vitro fertilization (IVF). 6 marks
- Discuss the ethical issues surrounding IVF. 6 marks
- Draw a labelled diagram of a mature sperm. 5 marks
- Outline the process of spermatogenesis in humans. 5 marks
- Outline the processes involved in semen production from the start of sperm formation (spermatogenesis) to ejaculation. 8 marks
- Compare the process of spermatogenesis and oogenesis. 7 marks
- Describe the process of fertilization in humans. 8 marks
- Outline the development of the early human embryo. 5 marks
- Outline the regulation of pregnancy by two named hormones. 4 marks
- State the role of the amniotic sac and the amniotic fluid. 2 marks
- Explain the function and structure of the placenta. 8 marks
- Outline the role of positive feedback in the process of birth in humans. 4 marks
*Despite the fact that these are all highlighted blue because we’ve learned them, I (and the rest of this class) need to study real hard because a lot of the essay questions are difficult on their own.
DATA BASED QUESTIONS
Page 283, electron micrograph of placenta
- a) Identify the structures that are visible in the upper part of the micrograph. Microvilli, inter-villous space, connective tissues.
- b) Explain the functions of these structures. The microvilli increase the surface area for the fetal blood to be charged with nutrients. The inter-villous space is where maternal blood flows through. The connective tissue are for inside the villus and are there as part of it’s structure.
2. In much of the area of the electron micrograph there are rounded structures, surrounded by a single membrane. These are parts of a system of tubules called the smooth endoplasmic reticulum (sER). Its function is the synthesis of lipids, including steroids. Suggest a function for the sER in the placenta. Smooth endoplasmic reticulum may not produce steroids during pregnancy but instead, estrogen, progesterone, HCG, and later, oxytocin, for childbirth.
3. Identify, with reasons, the structure in the lower left part of the micrograph. It is a fetal capillary mostly because it’s positioned close to the villus surface and seems to have thin walls (part of the capillary’s structure).
Chapter 26 Questions « Coming Soon »