The human fertilization process and the period of development of the embryo

You might hear your doctor talk about different phases of pregnancy with specific medical terms like embryo and zygote.

The human fertilization process and the period of development of the embryo

The gender may sometimes be seen The average fetus at 14 weeks is 3. Fetal Age 13 weeks Fetal movement may be sensed now called quickening. Some mothers don't feel the fetus moving until about 25 weeks.

The average fetus at 15 weeks is 6. Hearing is beginning to form [12].


The pseudoglandular stage of lung development ends at about 17 weeks. Gestational Age 18 weeks 4. Fetal Age 16 weeks The ears are standing out, and the fetus is beginning to respond to sound. Fetal Age 17 weeks The ears, nose and lips are now recognizable. Fetal Age 19 weeks The fetus is now able to suck and grasp, and may have bouts of hiccups.

Some women may begin feeling Braxton Hicks contractions at this time. Fetal Age 21 weeks The fetus is having rapid eye movements during sleep.

The canalicular period of lung development is ending. If the fetus is a boy, his testicles are descending. Fetal Age 37 to 39 weeks The fetus is now full term. Outcomes are based on specific characteristics in a specific setting: The ultrasound femur length as a predictor of fetal length.

Hadlock FP, et al. Computer-assisted analysis of multiple fetal growth parameters. Definition of term pregnancy. American College of Obstetricians and Gynecologists.

Age terminology during the perinatal period. Hay DL, Lopata A. Chorionic gonadotropin secretion by human embryos in vitro. J Clin Endocrinol Metab. Lohstroh P, et al. Daily immunoactive and bioactive human chorionic gonadotropin profiles in periimplantation urine samples.

Epub Mar 8 9. The effect of embryonic and fetal exposure to x-ray, microwaves, and ultrasound: Development of fetal hearing. Ultrasonographic assessment of gestational age with the distal femoral and proximal tibial ossification centers in the third trimester.

The human fertilization process and the period of development of the embryo

Determination of gestational age by ultrasound. J Obstet Gynaecol Can. Proximal humeral ossification center of the fetus: Curr Top Dev Biol.

Abdominal ultrasound examination of the first-trimester fetus. Am J Obstet Gynecol Diagnostic criteria for nonviable pregnancy early in the first trimester. N Engl J Med ; Closure of the cerebellar vermis: Bennett GL Agenesis of the corpus callosum:The Fetal Period The fetal period is characterized by two processes.

The first is rapid growth (increase in size and cell number) and the second is continued tissue and organ differentiation (specialization of cells to perform distinct functions).

This page shows some key events of human development during the embryonic period of the first eight weeks (weeks 1 - 8) following fertilization.

Timeline human development - Embryology

This period is also considered the organogenic period, when most organs within the embryo have begun to form. Stage 1 embryos have the potential to develop into all of the subsequent stages of a human 1 starts at the beginning of fertilization, when an oocyte is penetrated by a sperm, and ends with the intermingling of the paternal (male) and maternal (female) chromosomes on the spindle at metaphase of the first mitotic division of the single cell.

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Fertilization The process of development begins with the fusion of gametes: egg (ovum) and motile sperm swims to the egg, pierces its cell membrane and enters the cell. Fertilization is the fusion of the nuclei of the egg and sperm, and the single cell that results from this fusion is called the fertilized egg or zygote (see Figure 2).

The human fertilization process and the period of development of the embryo

Human embryogenesis refers to the development and formation of the human is characterised by the process of cell division and cellular differentiation of the embryo that occurs during the early stages of biological terms, human development entails growth from a one-celled zygote to an adult human being.

Fertilisation occurs when the sperm cell successfully enters .

The First Week | Prenatal Overview