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Cortical white matter increases from childhood (~9 years) to adolescence (~14 years), most notably in the frontal and parietal cortices. [8] Cortical grey matter development peaks at ~12 years of age in the frontal and parietal cortices, and 14–16 years in the temporal lobes (with the superior temporal cortex being last to mature), peaking at about roughly the same age in both sexes ...
The fetus reaches a length of 20 cm (8 in). Lanugo covers the entire body. Eyebrows and eyelashes appear. Nails appear on fingers and toes. The fetus is more active with increased muscle development. "Quickening" usually occurs (the mother and others can feel the fetus moving). The fetal heartbeat can be heard with a stethoscope.
Human embryonic development covers the first eight weeks of development, which have 23 stages, called Carnegie stages. At the beginning of the ninth week, the embryo is termed a fetus (spelled "foetus" in British English). In comparison to the embryo, the fetus has more recognizable external features and a more complete set of developing organs.
The development of the nervous system in humans, or neural development, or neurodevelopment involves the studies of embryology, developmental biology, and neuroscience. These describe the cellular and molecular mechanisms by which the complex nervous system forms in humans, develops during prenatal development , and continues to develop ...
HIV can be transmitted from an infected mother to the neonate in three circumstances: across the placenta during pregnancy (in utero), at birth due to fetal contact with infected maternal genital secretions and blood, or postnatally through the breast milk. [8] This type of viral transmission is also known of as vertical transmission.
Bogaert's hypothesis argues that "the target of the immune response may be male specific molecules on the surface of male fetal brain cells (e.g., including those in the anterior hypothalamus). Anti-male antibodies might bind to these molecules and thus interfere with their role in normal sexual differentiation, leading some later born males to ...
A fetus is a stage in the human development considered to begin nine weeks after fertilization. [4] [5] In biological terms, however, prenatal development is a continuum, with many defining features distinguishing an embryo from a fetus. A fetus is also characterized by the presence of all the major body organs, though they will not yet be ...
Once the fetus is sufficiently developed, chemical signals begin the process of birth, which begins with the fetus being pushed out of the birthing canal. The newborn, which is called an infant in humans, should typically begin respiration on its own shortly after birth. Not long after, the placenta eventually falls off on its own.