When a young woman reaches puberty, she starts to ovulate. This is when a mature egg or ovum is released from one of the ovaries. The ovaries are the two female reproductive organs found in the pelvis. If the egg is fertilized by a sperm as it travels down the fallopian tube, then pregnancy occurs.
The fertilized egg attaches to the lining of the uterus. The placenta then develops. The placenta transfers nutrition and oxygen to the fetus from mother. This process is called implantation. As cells from the blastocyst take in nourishment, another stage of development begins. In the embryonic stage, the inner cells form a flattened circular shape called the embryonic disk, which will develop into a baby.
The outer cells become thin membranes that form around the baby. The cells multiply thousands of times and move to new positions to eventually become the embryo EM-bree-oh.
After about 8 weeks, the embryo is about the size of a raspberry, but almost all of its parts — the brain and nerves, the heart and blood, the stomach and intestines, and the muscles and skin — have formed. During the fetal stage, which lasts from 9 weeks after fertilization to birth, development continues as cells multiply, move, and change.
It gets oxygen and nourishment from the mother's blood via the placenta pluh-SEN-tuh. This disk-like structure sticks to the inner lining of the uterus and connects to the fetus via the umbilical um-BIL-ih-kul cord. The amniotic fluid and membrane cushion the fetus against bumps and jolts to the mother's body. Pregnancy lasts an average of days — about 9 months. When the baby is ready for birth, its head presses on the cervix, which begins to relax and widen to get ready for the baby to pass into and through the vagina.
Mucus has formed a plug in the cervix, which now loosesn. It and amniotic fluid come out through the vagina when the mother's water breaks. When the contractions of labor begin, the walls of the uterus contract as they are stimulated by the pituitary hormone oxytocin ahk-see-TOE-sin.
The contractions cause the cervix to widen and begin to open. After several hours of this widening, the cervix is dilated opened enough for the baby to come through. The baby is pushed out of the uterus, through the cervix, and along the birth canal. The baby's head usually comes first. The umbilical cord comes out with the baby.
It's clamped and cut close to the navel after the baby is delivered. The last stage of the birth process involves the delivery of the placenta, which at that point is called the afterbirth.
After it has separated from the inner lining of the uterus, contractions of the uterus push it out, along with its membranes and fluids. Reviewed by: Larissa Hirsch, MD. Larger text size Large text size Regular text size. What Is Reproduction? Sucking reflex is developing. Fat is forming under the skin. Ridges form in the hands and feet that later will be fingerprints and footprints. Skin is wrinkled and reddish from visible blood vessels.
Lungs are fully formed but not yet ready to function outside the uterus. Loud sounds can make your fetus respond with a startled movement and pull in the arms and legs. Eyelids can open and close.
Nervous system is developing. Skin begins to look smoother as more fat is added. The fetus can stretch, kick, and make grasping motions. Eyes can sense changes in light. Bone marrow is forming red blood cells. Head may have some hair. Lanugo begins to disappear. Bones harden but the skull remains soft and flexible. Fingernails have grown to the end of the fingers. Limbs begin to look chubby. The fetus may turn into a head-down position for birth. Circulatory system is done developing.
Musculoskeletal system also is done developing. Lungs, brain, and nervous system are finishing their development. Fat continues to be added all over to keep the baby warm after birth. Fertilization: A multistep process that joins the egg and the sperm. Genitals: The sexual or reproductive organs. Oxygen: An element that we breathe in to sustain life. Sperm: A cell made in the male testicles that can fertilize a female egg. Article continues below Advertisement. If you have further questions, contact your ob-gyn.
Don't have an ob-gyn? Search for doctors near you. The wider, upper part of the uterus is called the corpus or fundus. This is the inner lining. It is shed during your period. This is the thick middle muscle layer of the corpus or fundus. This expands during pregnancy to hold the growing baby. It contracts during labor to push the baby out. This is the smooth outer layer.
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