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By the end of this section, you will be able to:
  • Discuss the importance of an infant’s first breath
  • Explain the closing of the cardiac shunts
  • Describe thermoregulation in the newborn
  • Summarize the importance of intestinal flora in the newborn

From a fetal perspective, the process of birth is a crisis. In the womb, the fetus was snuggled in a soft, warm, dark, and quiet world. The placenta provided nutrition and oxygen continuously. Suddenly, the contractions of labor and vaginal childbirth forcibly squeeze the fetus through the birth canal, limiting oxygenated blood flow during contractions and shifting the skull bones to accommodate the small space. After birth, the newborn’s system must make drastic adjustments to a world that is colder, brighter, and louder, and where he or she will experience hunger and thirst. The neonatal period (neo- = “new”; -natal = “birth”) spans the first to the thirtieth day of life outside of the uterus.

Respiratory adjustments

Although the fetus “practices” breathing by inhaling amniotic fluid in utero, there is no air in the uterus and thus no true opportunity to breathe. (There is also no need to breathe because the placenta supplies the fetus with all the oxygenated blood it needs.) During gestation, the partially collapsed lungs are filled with amniotic fluid and exhibit very little metabolic activity. Several factors stimulate newborns to take their first breath at birth. First, labor contractions temporarily constrict umbilical blood vessels, reducing oxygenated blood flow to the fetus and elevating carbon dioxide levels in the blood. High carbon dioxide levels cause acidosis and stimulate the respiratory center in the brain, triggering the newborn to take a breath.

The first breath typically is taken within 10 seconds of birth, after mucus is aspirated from the infant’s mouth and nose. The first breaths inflate the lungs to nearly full capacity and dramatically decrease lung pressure and resistance to blood flow, causing a major circulatory reconfiguration. Pulmonary alveoli open, and alveolar capillaries fill with blood. Amniotic fluid in the lungs drains or is absorbed, and the lungs immediately take over the task of the placenta, exchanging carbon dioxide for oxygen by the process of respiration.

Circulatory adjustments

The process of clamping and cutting the umbilical cord collapses the umbilical blood vessels. In the absence of medical assistance, this occlusion would occur naturally within 20 minutes of birth because the Wharton’s jelly within the umbilical cord would swell in response to the lower temperature outside of the mother’s body, and the blood vessels would constrict. Natural occlusion has occurred when the umbilical cord is no longer pulsating. For the most part, the collapsed vessels atrophy and become fibrotic remnants, existing in the mature circulatory system as ligaments of the abdominal wall and liver. The ductus venosus degenerates to become the ligamentum venosum beneath the liver. Only the proximal sections of the two umbilical arteries remain functional, taking on the role of supplying blood to the upper part of the bladder ( [link] ).

Questions & Answers

what is ventricular circulation
Maryam Reply
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Sale
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Sale
what factors that affect the rate diffusion
Gift Reply
sorry what are the common meaning of haemostatis
Juma Reply
what are the negatives feedback regulation of ADH
Nansi Reply
what is the the differences between DNA and RNA?
Mustapha
The major differences between the DNA and RNA are contain of double stranded and single stranded which the DNA contain duoble stranded and RNA contain single stranded.
Juma
what are the negatives feedback regulation of ADH before this we confused just verify long term of ADH firstly
Juma
How many genes consist of DNA?
Omaryare
omaryare muhyadiin when you talk about genes, is the material formed in a DNA genes have form like plasma have many genes round there
Juma
aldosterone, renin
Conan
to know the different structures of the body To know how the body works To know more about our body parts
Deitdre Reply
hi Deitdre you tock about knowledge or you ask the question
Juma
do you need any explanation when reading this book?
janet Reply
Its Good
Hashir
yes
Balogun
Yes
Mariam
yes
Sale
yes
Mustapha
if have many ability just do it!!
Juma
compare and contrast the operation of homeostasis
Dinelle Reply
what is the difference between an ionic, polar covalent and nonpolar covalent bond?
Dinelle
In summary, the bond has different in electronegativity.
Balogun
sorry help me to get the definition of hemostasis or the meaning
Juma
the definition of distal
Dinelle Reply
farthest away from the attachment point.
felix
Distal, is the farthest possition from the origin or midle point
Juma
exercise physiologist how ?
Noor Reply
hi noorr. when you talk about physiologist its a person who study physiology but exercise physiologist is what an exercise doing by physiologist in physiologican
Juma
can I get the questions of human physiology that is present in HSC 2nd semester
Rafiullah Reply
in my lerning the question com like for example ni eassy qustion must understand the the part of the body and how it work or mechanisms of each part learned
Juma
how can I memorize
mukhtaar Reply
which part of the body produces blood
aadil
give me answer
aadil
Red blood cells are formed in the red bone marrow ofbones. Stem cells in the red bone marrow called hemocytoblasts give rise to all of the formed element
mukhtaar
what is hemocytoblasts
Fatima
hemocytoblasts are stem cells in red bone marrow which give rise the all of formed elements
Khawaja
Discuss clonal theory in physiology and its application in measles infection in a 6yr child? Can anyone help me
Isaac Reply
Capillary permeability
what do you want to know about it?
Ramsin
Hello, I want to search about the topic, information and pictures
syncitium is the property of which of the following muscle
Shahab Reply
can I get the questions of human physiology that is present in HSC 2nd semester
Sai Reply
i now madam
irpa
ha can u please send me the PDF of questions
Sai
it's important to me to have that information please send as fast as u can
Sai
me too if possible?
Ramsin
of course
mukhtaar
I want too
Nazirullah
now you want to look the format of question or because i need to explain on you?
Juma

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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