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La biología del desarrollo prenatal


8 a 12 semanas


THE BIOLOGY OF PRENATAL DEVELOPMENT

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El período fetal (8 semanas hasta el nacimiento)

Capítulo 37   9 semanas: deglute, suspira y se despereza

The fetal period continues until birth.

By 9 weeks, thumb sucking begins and the fetus can swallow amniotic fluid.

The fetus can also grasp an object, move the head forward and back, open and close the jaw, move the tongue, sigh, and stretch.

Nerve receptors in the face, the palms of the hands, and the soles of the feet can sense light touch.

"In response to a light touch on the sole of the foot," the fetus will bend the hip and knee and may curl the toes.

The eyelids are now completely closed.

In the larynx, the appearance of vocal ligaments signals the onset of vocal cord development.

In female fetuses, the uterus is identifiable and immature reproductive cells, called oogonia, are replicating within the ovary.

External genitalia begin to distinguish themselves as either male or female.

Capítulo 38   10 semanas: pone lo ojos en blanco y bosteza, aparecen las uñas y huellas digitales

A burst of growth between 9 and 10 weeks increases body weight by over 75%.

By 10 weeks, stimulation of the upper eyelid causes a downward rolling of the eye.

The fetus yawns and often opens and closes the mouth.

Most fetuses suck the right thumb.

Sections of intestine within the umbilical cord are returning to the abdominal cavity.

Ossification is underway in most bones.

Fingernails and toenails begin to develop.

Unique fingerprints appear 10 weeks after fertilization. These patterns can be used for identification throughout life.

Capítulo 39   11 semanas: absorbe glucosa y agua

By 11 weeks the nose and lips are completely formed. As with every other body part, their appearance will change at each stage of the human life cycle.

The intestine starts to absorb glucose and water swallowed by the fetus.

Though sex is determined at fertilization, external genitalia can now be distinguished as male or female.
8 a 12 semanas