Human fertilization - Wikipedia
For a conception an egg cell and many sperm are needed. When the Such great numbers are necessary because most sperm do not reach the ovum. Also, for. However, for a pregnancy to develop it must first meet sperm from the male whilst it is still held The sperm then begin their long journey towards the egg. At 8 cells the embryo continues to keep dividing to make more cells, but now the cells . Fertilization: Sperm meets egg. The mature egg is fertilized when it is joined with a sperm cell. This usually happens after a penis* has ejaculated semen inside.
Also unlike sperm, the meiotic division to create eggs, oogenesis, only makes one viable egg. The egg is covered in a thick outer coating known as the zona pellucida, a layer of carbohydrate-covered proteins that surrounds the plasma membrane. The zona pellucida helps protect the egg and is responsible for mediating the initial meeting of sperm and egg.
Embryology - The human egg cell and sperm
Cortical granules filled with enzymes line the inside of the cell membrane, and will help make sure that only one sperm can fertilize the egg. The setting Egg and sperm travel in opposite directions to meet in most often the fallopian tubes.
During ovulation, ovaries release an egg into one of the fallopian tubes, and the egg proceeds down the tube toward the uterus, which is being prepared for possible implantation. Part of this preparation involves elevated levels of estrogen and luteinizing hormone LH.
LH triggers the ovaries to release the egg, while higher blood estrogen levels stimulate the vaginal membrane to secrete glycogen, which is then metabolized to lactate. This lowers vaginal pH to as low as 3. However, this environment can also be toxic to sperm, though the semen a basic fluid can buffer the vaginal acidity to preserve sperm cells.
Only about 1 in 1 million sperm that are ejaculated into the vagina will reach the site of fertilization. Estrogen also relaxes the cervix, causes cervical mucus to become watery and more alkaline, and stimulates uterine contractions — all of which help sperm penetrate and navigate the female reproductive system. Relaxing the cervix allows sperm to pass from the vagina into the uterus and reduces a potential physical barrier.
Cervical mucus may prevent sperm from passing into the uterus, but during ovulation when the egg is released from the ovaries, the mucus gets thinner and lower in pH. The nucleus is outspread, the chromosomes are unwound not folded up. The cell is internally active and mobile.
The sperm cells have hardly any cytoplasm and are concentrated in their nuclear DNA. They have a crystalline structure. These cells are internally structured and rigid. In contrast, the ovum is externally not active.
After her release, she is passively moved by the fluid-flow in the oviduct uterine tubewhile the sperm cells are active, using their tails to swim against the stream of fluid in the oviduct. They are externally active and mobile. The ovum is internally mobile and externally passive, this is a polarity. The sperm shows the opposite: Egg cell and sperm have a polarity and are opposite to each other, we see a double polarity.
Biological Steps to Becoming Pregnant | SexInfo Online
Metabolism An egg cell is a metabolically active cell; substances are absorbed and released. An egg cell lives only 12 to 24 hours in her own environment and cannot be preserved. The egg cell can easily be destroyed. She is an active cell and open to the environment.
Sperm cells do not absorb or release substances. There is no interaction with the environment. They are not easy to destroy. They are closed off from the environment and metabolically passive. The open and vulnerable state of the egg cell is polar to the closed and robust state of the sperm cells. Since several years an ovum can be frozen by vitrification, a process whereby water is removed and replaced by a concentrated liquid, leaving no freezing crystals, which can damage the chromosomes.
Egg meets sperm
Number For a conception one ovum and millions of sperm are required. The one ovum is worth as much as all those millions of sperm. A man with less than million sperm in an ejaculation is barren. Such great numbers are necessary because most sperm do not reach the ovum. Also, for a conception more than one spermatozoon is necessary.
See the page Conception. The ovum is alone and the sperm are with millions. One sperm cell is nothing, one ovum determines everything. The ideal time of fertilization is around ovulation when the egg is in the fallopian tube. Male Fertility After traveling through the vaginal canal, the strongest sperm make it to the cervix.
From here, the sperm must travel through the uterus and into one of the fallopian tubes. Since the human body functions to procreate, the egg that is released monthly from the ovaries waits for sperm cells in the fallopian tube for about a day. Additionally, sperm can survive in the female reproductive track for up to 5 days. This union of egg and sperm creates a zygote fertilized egg and this new zygote cell has a core of 46 chromosomes 23 from the sperm and 23 from the egg.
Embryonic Development This new zygote cell begins to divide rapidly over the next few hours through a process called mitosis, and this expanded bundle of cells is now called an embryo.
Sperm Meets Egg: Weeks 1 to 3 of Pregnancy
If the fertilizing sperm has a Y chromosome, the embryo will develop into a male baby, while a fertilizing sperm with an X chromosome will develop into a female baby. Implantation By the time the fertilized egg reaches the uterus, it is a cluster of about cells, and it forms a blastocyst.
Simultaneously, the lining of the uterus gets thicker, and the cervix is closed off with a mucus plug that will stay in place until the end of the pregnancy term. Around the time of implantation, some females may notice spotting light bleedingwhich should only last about 48 hours. This irregularity is called an ectopic pregnancy and it can be very dangerous. In these cases, the female will either need to take medication to stop the embryo from growing, or have surgery to prevent the fallopian tube from rupturing.
Detection Naturally, about half of all fertilized eggs are lost before a female even knows that she is pregnant.