Page 158 - 86 human physiology part-2

Development: Birth Through Death

Touch the foot in a The baby's toes will
stroking manner form
Babinski fan out and curl as 8 to 12 months Unknown
the toe toward the the foot twists in
heel

Neonatal

The neonatal period extends from birth to somewhere between 2 weeks and 1 month.

Immediately after the baby is born uterine contractions force blood, fluid, and the placenta from
the mother's body. The umbilical cord—the baby's lifeline to it's mother—is now severed. Without the
placenta to remove waste, carbon dioxide builds up in the baby's blood. This, along with other factors
including steps taken by medical personnel, stimulates the control centers in the brain which in turn
responds by triggering inhalation. Thus the newborn takes it's first breath. As the newborns lungs begin
to function, the bypass vessels of fetal circulation begin to close. The heart bypass, the foramen ovale,
normally closes slowly during the first year.

During this period the body goes through drastic physiological changes. The most critical need is
for the body to get enough oxygen as well as an adequate supply of blood. (The respiratory and heart
rate of a newborn is much faster than that of an adult.)

The newborn's appearance

A newborn's skin is oftentimes grayish to dusky blue in color. As soon as the newborn begins to
breathe, usually within a minute or two, the skin's color returns to its normal tones. Newborns are wet,
covered in streaks of blood, and coated with a white substance known as vernix caseosa, which is
hypothesized to act as an antibacterial barrier. The newborn may also have Mongolian spots, various
other birthmarks, or peeling skin, particularly at the wrists, hands, ankles, and feet.

A newborn's shoulders and hips are narrow, the abdomen protrudes slightly, and the arms and legs
are relatively short. The average weight of a full-term newborn is approximately 7 ½ pounds (3.2kg),
but can be anywhere from 5.5–10 pounds (2.7–4.6kg). The average total body length is 14–20 inches
(35.6–50.8cm), although premature newborns may be much smaller. The Apgar score is a measure of a
newborn's transition from the womb during the first ten minutes of life.

A newborn's head is very large in proportion to the rest of the body, and the cranium is enormous
relative to his or her face. While the adult human skull is about 1/8 of the total body length, the
newborn's is twice that. At birth, many regions of the newborn's skull have not yet been converted to
bone. These "soft spots" are known as fontanels; the two largest are the diamond-shaped anterior
fontanel, located at the top front portion of the head, and the smaller triangular-shaped posterior
fontanel, which lies at the back of the head.

During labor and birth, the infant's skull changes shape to fit through the birth canal, sometimes
causing the child to be born with a misshapen or elongated head. This will usually return to normal on
its own within a few days or weeks. Special exercises sometimes advised by physicians may assist the
process.

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