You are watching: What is the longest stage of prenatal development?
A single sperm cell penetrates the outer coating that the egg cell and also fuses to form one fertilized cell.
The ectoderm (skin and also nervous systems), endoderm (digestive and respiratory systems), and mesoderm (muscle and skeletal systems).
Fertilized egg; divides and implants chin in the wall of the uterus; beginning a 2-week period of rapid cell department and creates into an embryo
Structure that permits oxygen and nutrients come pass right into fetus from mother"s bloodstream; permits waste to pass out
2nd stage of the prenatal development. Time: 2-8 weeks. (3rd mainly after conception) brain development (neural tube forms along neural key to mind vesicles to parts of brain). (4th week) Head, confront (eyes, nose, ears, and mouth), and neck develop. Heartbeat starts (blood vessel to heart->pulse). (5th week) buds for limbs type and grow. Major organs/digestive mechanism differentiating. Embryo weighs one gram and is one customs in length; has amniotic sac, placenta, and also umbilical cord.
the arising human biology from about 2 weeks after ~ fertilization through the 2nd month; organs begin to develop
The biggest dangers (viruses, drugs, or radiation) that can cause deformities in one embryo or fetus.
Part of the Fetal Stage. First trimester the pregnancy. Mind development continues (neurons come synapses). Arms and legs relocate (reflexive motions). Sex guts differentiate and develop rapidly. Digestive organs begin to function. Buds for teeth form. All organs and also muscles have formed.
Part the the Fetal Stage. 2nd trimester of pregnancy. Heartbeat grows stronger. Human body systems further developed. Challenge looks human. Lower body outgrows head. Bones room defined. First kick. Fetus covers v lanugo, special soft hair.
Part of the Fetal Stage. 2nd trimester the pregnancy. The fetus increases significantly in size. Fingernails and also toenails appear. Vernix caseosa (protective coating ) formed.
Part the the Fetal Stage. Second trimester the pregnancy. Eyebrows and also eyelids visible. Eyes fully formed. Lungs filled with amniotic fluid. Fetus start breathing and hearing things outside womb.
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Part that the Fetal Stage. Third trimester the pregnancy. Fetus qualified of life exterior the uterus (age threshold the viability has readjusted and is now taken into consideration 23-26 weeks instead of 27-28 weeks)
Part the the Fetal Stage. 3rd trimester the pregnancy. Fat is deposited for later use. Fingernails past fingertips. Lanugo is shed. Myelination of mind takes ar in the fetal stageVernix caseosa covers body. Turn head-down in ready for birth.