1. The Mishnah discusses the Halachah in a case in which a woman gives birth to a placenta.
2. Rebbi Oshiya Ze'ira: Five things must be at least one Tefach for their respective Halachos to apply.
3. The spine of a Lulav must reach a Tefach higher than the top of the Hadasim.
4. Rebbi Oshiya (see #2) did not include cases in which there is a dispute about whether the size is a Tefach.
5. Rebbi was asked about a woman who miscarried a placenta and something that looked like a raven.
A BIT MORE
1. Tana Kama: It must be that the fetus somehow also came out and, therefore, the airspace of the house the woman was in when she gave birth is rendered Tamei. Rebbi Shimon: It is possible that the fetus was mixed into the blood from the birth and was nullified.
2. They are: A placenta (to cause the house in which it is born to be Tamei), a Shofar (to be large enough to blow on Rosh Hashanah), the spine of a Lulav (see below), the wall of a Sukah, and a hyssop branch.
3. The third wall of a Sukah is valid even if it is only one Tefach long.
4. There are several other cases in which one opinion maintains that something requires a Tefach in order for its Halachah to apply. For example, the Chachamim maintain that a small oven can become Tamei if it is at least the size of a Tefach.
5. Rebbi answered that there must have been a human fetus, since we do not assume that something that never has a placenta attached to it (a raven) is the reason why this placenta came out of the womb.