A student writes: "The blood of the mother flows through the umbilical cord into the foetus." Is…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A student writes: "The blood of the mother flows through the umbilical cord into the foetus."
- Is this correct? Give the right account.
- Which part of the placenta belongs to the embryo, and which part to the mother?
- Name two things that the placenta removes from the foetus.
- Why can a new born baby have some antibodies of its mother?
Need a reminder? The key ideaShow
The placenta forms from the chorionic villi of the trophoblast and the tissue of the uterus. It passes oxygen and nutrients to the embryo and takes carbon dioxide and waste away. The placenta makes hCG, hPL, oestrogens and progestogens. The ovary secretes relaxin in the later phase of pregnancy. hCG, hPL and relaxin are made only in pregnancy. The blood of the mother and the blood of the embryo do not mix.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) No. The two bloods do not mix. The cord carries the blood of the foetus to and from the placenta, and the exchange happens across a thin barrier.
Step 2. (b) The chorionic villi belong to the embryo, because they grow out of the trophoblast. The uterine tissue and the blood spaces around the villi belong to the mother.
Step 3. (c) Carbon dioxide and the wastes made by the foetus.
Step 4. (d) The antibodies of the mother can pass across the placenta to the foetus.
Answer: (a) no, the bloods stay apart; (b) villi belong to the embryo, the uterine tissue to the mother; (c) carbon dioxide and wastes; (d) antibodies cross the placenta.
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