U

Lungs

Foramen ovale

Left atrium

Left ventricle

Aortic arch

Aorta

Internal iliac arteries

Umbilical artery (carbon dioxide, wastes)

Heart, brain, upper limbs

Continued first powerful breath begins to expand the lungs, breathing eases.

A newborn's first breath is stimulated by increasing concentration of carbon dioxide, decreasing pH, low oxygen concentration, drop in body temperature, and mechanical stimulation during and after birth. Also, in response to the stress the fetus experiences during birth, blood concentrations of epinephrine and norepinephrine rise significantly (see chapter 13, p. 525). These hormones promote normal breathing by increasing the secretion of surfactant and dilating the airways.

For energy, the fetus primarily depends on glucose and fatty acids in the pregnant woman's blood. The new born, on the other hand, is suddenly without an external source of nutrients. The mother will not produce milk for two to three days, by which time the infant's gastrointestinal tract will be able to digest it. However, the mother's breasts secrete colostrum, a fluid rich in nutrients and antibodies, until the milk comes in—an adaptation to the state of the newborn's digestive physiology. The newborn has a high metabolic rate, and its liver, which is not fully mature, may be unable to supply enough glucose to support metabolism. Consequently, the newborn utilizes stored fat for energy.

A newborn's kidneys are usually unable to produce concentrated urine, so they excrete a dilute fluid. For

Pregnancy And Childbirth

Pregnancy And Childbirth

If Pregnancy Is Something That Frightens You, It's Time To Convert Your Fear Into Joy. Ready To Give Birth To A Child? Is The New Status Hitting Your State Of Mind? Are You Still Scared To Undergo All The Pain That Your Best Friend Underwent Just A Few Days Back? Not Convinced With The Answers Given By The Experts?

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