The kidney is not one large filter. Each kidney is made up of about a million filtering units called nephrons. Each nephron filters a small amount of blood. The nephron includes a filter, called the glomerulus, and a tubule. The nephrons work through a two-step process.
Generally speaking, first babies tend to engage from about 34 weeks to 36 weeks. However, some babies only engage once labour starts. Try not to worry, though. Even if your baby hasn't engaged by the time labour starts, in most cases, it's not a problem.
The egg only lives 24-36 hours or so if not fertilized. You can ovulate on day 14 if you had sex4- 5 days before you could get pregnant from that sperm. You can also get pregnant the day after ovulation. So you have 6-7 days where if you have sex during ovulation time it is POSIBLE to get pregnant.