Human Growth and Development

Journey of Life

Life begins at conception and ends at death. In between, life does not develop - it is simply there. "What does develop," says Sir William Liley, the New Zealand scientist who is internationally recognized as the "father" of the science of fetology, "is the morphological structure, the earthly home of life, the physiological performance of that structure, behavioral traits and personality." These are some of the milestones of the first nine months of life: Conception: Father's sperm penetrates mother's egg cell. Within the hour, genetic instructions from both parents interact to establish the design and inheritance of a new and unique individual - at this stage no bigger than a grain of sugar.

Thirty Hours :A few hours after the nuclei has fused, the fertilized ovum divides for the first time, with a powerful force.


Two Days :The division continue; four visible cells and perharps eight all together are on their way through the Fallopian Tube's thicket of cilia to uterus.


Four Days :Surrounded by its transparent wall, the zona pellucida , the blastocyst now glides in the uterus.


Eight Days :The blastocyst has landed! Like a raspberry on a cake, it sinks slightly into its foundation.


Three Weeks :The human embryo is barely 2 mm. (.08 inch) long. The genes have begun to concentrate development in the three germ (cell) layers from which all the body's organs are to merge.


Four Weeks :The basic human design is beginning to merge. The embryo shows the clear rudiments of brain and backbone.


Five Weeks :The embryo is five weeks old and appears like a bright dot in its membrane sac. The yolk sac, visible in the foreground , is the embryo's blood cell factory.


Six Weeks :The cells are seething with life, the heart is beating, blood is being pumped through the umbilical cord and the whole embryo is in constant motion.


Eight Weeks :Weightless, the embryo lies suspended in the amniotic fluid. This fluid with the salinity of the primeval sea protect the embryo's delicate organs and tissues against impacts and pressures


Four Months :Now the facial features are being modeled : the forehead is growing with the thread like blood vessel fully visible under the transparent skin.


Four and a Half Months :The body system are being tested. It moves and waves its arms. A finger touching its lips precipitates a slight sucking reflex.


Five Months :The fetus stretches, grasps and turns. All these movements are necessary for the development of fine motor ability.


7 months:Permanent eye teeth are present. Eyelids open and close, and eyes look around. Hands grip strongly. Mother's voice can be heard and recognized. The baby begins to accumulate some fat.


Thirty Five Weeks :Weight increases by 1kg (just over 2 lb) and the baby's quarters begin to get cramped


9 months:Labour begins (triggered by the child) and birth occurs, usually 255-275 days after conception. Of the 45 generations of cell divisions between conception and adulthood, 41 have taken place. The remaining four will occur during the rest of childhood and adolescence. The milestones listed above have been documented by scientific research. Slight variations of hours or days, may exist and future research using more sensitive methods may show that some of these milestones occur earlier than is now realized.