Fetal or Neonatal Physiology, today we will discuss chapter 84 of Gaitan and this is going to be the last chapter of Endocrine and Reproductive Physiology. So, unit number 14 will be over today. My name is Asif Qureshi, you are watching Dr. Asif Lectures. A complete discussion of fetal development, physiology of child immediately after birth and growth and development through the early years of life lies within the province of formal course in obstetrics and pediatrics so basically here he is telling that actual the whole baby formation after delivery the development which is to be done the growth and development phases are actually you will study in obs and gyne and gyne will be less in obs and will study more in peds but some basic physiological principles which you will learn in this video they will help you understand pediatrics and also one thing which they have not mentioned is embryology which is very much interlinked with the early developmental things. But in today's video we are going to talk about some very basic physiological principles which will help you understand the neonatal and fetal physiology.
You will note in this chapter that almost all of this chapter is in the blue box. The reason for this is that this is all clinically associated information. It is linked to the ovs, peds and embryology. It is in the book of physiology.
I think it is very relevant to go through this blue box so that you can understand the basic principles of fetal and neonatal physiology. So heading wise we will do one by one. The first thing is growth and development of the fetus.
This is the topic of pure embryology. The placenta and fetal membranes initially develop far more rapidly than the fetus. So initially you know that in the days of embryogenesis, placental system, membrane system, the embryo develops very fast and rapidly. growth in fact during the first two to three weeks after implantation of the blastocyst the fetus remain almost microscopic there is a reason for the growth of the fetus first it is made sure that placental and membranous structures are developed properly reason being because here nutrition is to be done so first the nutrition is arranged then the growth will be done and therefore initially the embryo itself remains miniature ok actually at 12 weeks the length is about 10 centimeters 20 weeks only 25 centimeter and at the term it is which is at 40 weeks around 53 centimeters which is equivalent to 21 inches because the weight of the fetus is approximately proportional to the cube of length the weight increases almost in proportion to the cube of the age of the fetus so that's how it is a two is its cube for a toaster cubes barrel these are important numbers for you to remember I get asked a lot about PEDS in gynecology and embryos it's an important thing note that in figure 84.1 that the weight remains miniscule during the first 12 weeks it remains very very small and reaches about 1 pound only at the age of 23 weeks thus during the last trimester of pregnancy actually this is the time last trimester of pregnancy where fetus rapidly gain weight and so the two months before birth the weight averages about three pounds one month before birth it averages about 4.5 pounds so these numbers are important for you to remember I think they are given somewhere in a diagram or so this is where it is you see up till this point it is such a little weight you see very very little weight and length but as compared to the I mean when it goes towards the later half of the pregnancy then you see increase in weight so there you are seeing weight on the right side of the y-axis okay so weight catches up later on okay so that's an important general concept where you have to understand that weight gain will be major during the last which is what we call the third trimester of pregnancy development of the organ system within one month after fertilization of the ovum the gross characteristics for all different organs of the fetus have already begin to develop and during the next two months, most of the details of the different organs are already established.
Beyond four months, the organ of the fetus are grossly the same as that of the neonate. So, after four months, the organ system in which the baby is born is almost already developed. However, cellular development in each organ is usually far from complete and requires the remaining five months.
The basic skeleton of the organs is generated and forms the shape of the main organs. But obviously, different cells have to divide and mature in them. Even at birth, certain structures lack full development. Particularly the nervous system, myelination issues take time to complete. Kidneys, liver, circulatory system, the human heart begins beating.
as early as the fourth week after fertilization so it not early human heart key first beach is started at here and initial the rate your hair that is 65 minute beats per minute this rate increases steadily later on to 140 beats per minute just before births red blood cells nucleated red blood cells begin to be formed in the York sack initially and mesothelial cells of the placenta as early as third week of fetal development this is followed one week later by the formation of non-nucleated rbcs by fetal mesenchyme so red just heart coming up with a fourth week the beating started at six weeks the liver begins to form blood cells and in the third month the spleen and the lymphoid tissue of the body begin forming the blood cells as well finally from the third month on the bone marrow gradually becomes principal source so you see the shift of organs Starting from the yolk sac and then ultimately to the bone marrow. This is also important to remember. The respiratory system.
Respiration cannot occur during fetal life because there is no air. Your lungs should have air to inflate. Whereas in babies there is no air. There is only amniotic fluid. However, attempted respiratory movements do take place at the beginning of the first trimester.
Tactile stimuli and fetal asphyxia especially cause these attempted. So these are only attempted premature movements which are trying to inflate the lungs but it never happens because there is no air. During the last 3-4 months of pregnancy, the respiratory movements of the fetus are mainly inhibited for reasons unknown and the lungs remain almost completely deflated.
The inhibition of respiration during the later months of fetal life prevent filling of the lung with the fluid and debris. and meconium etc. because if it inflates at this stage, it will fill all the waste, liquid etc. will go, we don't want that to go. What happens to the nervous system? Most of the reflexes of the fetus that involve the spinal cord and even the brain stem are present by 3rd to 4th month.
You can see how much early stages of pregnancy have structures in their place. However, the nervous system function that involves the higher centers, like the cerebral cortex, that develops at a later stage. It is not early development.
Even it continues to about an year postnatally. The baby is born with full cerebral cortex, higher centers and myelin formation of the tracts. It does not born with them. It takes about a year. Gastrointestinal tract by mid pregnancy the fetus begins to ingest and absorb large quantities of food.
So basically it starts eating. So things are going in its body. By that time small quantities of meconium are continually formed in the GI tract and excreted to kind of feces.
So, swallowing and feces. Meconium is composed partly of the residue from the swallowed amniotic fluid and also contains mucus. So, basically, I explain to students that the eating system starts very soon. Kidneys begin to excrete urine in the second trimester. And fetal urine accounts for about 70-80% of the amniotic fluid that the baby is bathing in.
Abnormal kidney development or severe impairment of the kidney function will cause the formation of amniotic fluid, amniotic fluid, amniotic fluid, reduces the formation of amniotic fluid, oligohydramnios, it can even lead to fetal death. So, it is important to work on the kidneys. Although the fetal kidneys form urine, the renal control system for regulating fetal extracellular volume, electrolyte balances and the acid-base balances are non-existent. Until the late fetal life and do not reach full development until after a few months of birth So what is our story till now? We have taken the names of different organ systems We talked about weight increment then we talked about circulatory system, respiratory system nervous system even GI tract and we Have one single conclusion or one single conclusion is that many of the organ system developed very early in the lifetime of the developing embryo or third month to burn dry for week to burn rice very very early in the pregnancy as a me a mucha pita hona wala top cheese about the air is say may hamsha physiology make a tonk a general lessons in life see kagare is he a couple lesson or milta nine month pay delivery honey here making third month or coffee sorry cheezer to your hair so actually a push a life lesson given a chai a kibai there you know you're planning should be in such a way you should be prepared for your deadline now fetal metabolism fetus mainly uses glucose as a source of energy the fetus has a high capability of storing fat and protein with much if not most of the fat being synthesized from the glucose so glucose is the key molecule in addition to these generalities there are special problems of fetal metabolism related to calcium phosphate iron and some income discuss the theme and abolish them of calcium and phosphate okay if you look at the rate of calcium and phosphate accumulation in fetus it demonstrates that about twenty two point five grams of calcium and about roughly the half amount thirteen point five of phosphorus are accumulated in average fetus during gestation about one half of these accumulate during the last four weeks of gestation which is coincident with the period of rapid ossification now you have more calcium you have more phosphate and it is exactly happening at the time when bones need it they need it for ossification okay and this is exactly the time when there is rapid weight gain also happening now during the earlier part of the fetal life the bones are relatively unossified to the calcium and phosphate level high and they have mainly only cartilaginous matrix ossification does not occur until after four months of pregnancy so Basically, it's the second part of the pregnancy, you can say second trimester or third trimester.
These are the areas where ossification is happening basically. And this is the time period when calcium phosphate accumulates in the baby. Note especially that the total amount of calcium and phosphate needed by the fetus during gestation represent only about 2% of the quantities of these substances in the mother's bone. And thus the drain of these substances from the mother is minimal. A much greater drain occurs.
after birth during lactation. This is an important paragraph. It also has a concept. This is a developing baby. So, this is the developing baby, for example.
And that is the mother in which this is developing. Now, the bones that are to develop it will obviously require calcium and phosphorus. Where will this come from? It will come from the mother.
In the mother, these things will be demineralized. And from that, calcium and phosphorus will come out and come to the baby. And the process that will take place in the baby that is what we call the process of ossification.
So for baby to have ossification, mother has to have demineralization. But baby needs calcium phosphate only 2% of the mother's demineralization. So if mother has 100% of calcium, then only 2% of that will be used for baby.
And these 2 is enough for baby. So it is not giving much harm to the mommy. But when lactation happens, then in lactation, calcium and phosphate are demineralized.
And that causes bigger harm. So if you one more time read this statement again, see note especially that the total amounts of calcium and phosphate needed by the fetus during gestation represent only about 2% of the quantities of these substances in the mom. And therefore the drain of the substance in the mother is minimal.
A much greater drain is observed during lactation. Accumulation of iron. Iron accumulates in the fetus even more rapidly than does the calcium and phosphate.
Calcium and phosphate accumulate after the second trimester. Iron is rapidly accumulated from them. And the reason is that they start making RBCs very early and therefore iron is needed to make hemoglobin. So everything makes sense. A small amount of iron are concentrated in the mother's uterine progestational endometrium even before implantation of the ovum.
So the preparation is done early and the iron is stored early. Because tomorrow we have to make RBCs. in quantity same life principle work before deadline about 1 third of iron is fully developed in fully developed fetus is normally stored in the liver the iron can then be used by the neonate to form additional hemoglobin so basically iron has this purpose to make hemoglobin in the developing RBCs utilization and storage of vitamins fetus need vitamins equally as much as any adult would need it In general, the vitamin function the same in the fetus as they do in the adult. It's not like vitamin C is working in the fetus and working in the adult. The B vitamins, especially B12 and folic acid are required for red blood cell formation.
Vitamin C is appropriate formation of the intercellular substances such as bone matrix and connective tissue. Vitamin D is necessary for bone stuff. If mother has plenty vitamin D in her body fluids, larger quantities of vitamin will be sorted because it will move through diffusion. The mechanism and function of vitamin E are not very clear in the fetus but it is necessary for normal development.
If there is no vitamin E then normal development will be affected. Vitamin K is important for formation of important factors such as factor VII, prothrombin and other coagulation factors. Vitamin K is insufficient in the mother then there is a problem.
Factor VII, prothrombin become deficient in the fetus because most vitamin K is formed by the bacterial action in the mom, colon. The neurite has no adequate source of vitamin K for the first week or so of life after birth. That means the baby was getting all the vitamin K from his mom. Mom was giving him from every column. Baby's colon is naive.
When the baby is born, he does not have vitamin K for about a week. Therefore, prenatal storage in fetal liver for at least small amounts of vitamin K derived from mother is helpful in preventing fetal hemorrhage. And this is what we do actually.
So, it is stored in the liver. Adjustment of infant to extra uterine life. Now, that is something which I say is a super important concept. It seems like a small heading but think about it. It is a very important thing.
Keep in mind that you live in a certain area for a long time and that's your beautiful home in which you are living. There is a beautiful surrounding, you have friends, an environment in which you are used to. Now suddenly you have to move from here to another area. Job changes or whatever, you change the country, sometimes you change the city, sometimes within the city you change the locality.
But that change is not easy. You have to adapt to the new change. And the process of adaptation is sometimes not easy.
Now this is such a big adaptation. Subtitles by the Amara.org community Baby was all the time inside uterus Coverings me lip, Tahua bathroom environment. We come together even respiration me Can you lungs go inflate nigga relax, but I am protected my protect your why her cheese placenta similar Yeah, and now suddenly the baby is born once the baby is born.
It's now the extra you try in life I'm boss are a changes. I'm giving me life may for example onset of breeding The most obvious effect on birth is baby's placenta connection is over. Now the baby is not getting nutrition or oxygen from the mother.
Now the baby has to start breathing. So what happens after the birth of the baby? The baby starts breathing by itself. Actually after normal delivery from a mother whose system has not been depressed by any anesthetic.
Meaning it is a normal subsystem. The child ordinarily begins to breathe within seconds. And has a normal respiratory rhythm within less than one minute after birth.
and as soon as they are born, they start breathing normally. This promptness with which the fetus begins to breathe indicates that breathing is initiated by sudden exposure to the exterior world. That is, as soon as it enters the world, it starts breathing. Probably resulting from slightly asphyxiated state that is incident to the birth process and from sensory impulses that originate in the suddenly cooled skin.
So there are receptors that make the temperature change and environmental change sense. at the higher centers and the respiratory centers become active. In an infant who does not breathe immediately, the body becomes progressively more hypoxic because oxygen is not going in the body. And hypercapnic, carbon dioxide is not releasing, so that is coming out of the body cells and accumulating in the body which provide additional stimulus to the respiratory center.
So all these things, as soon as the baby is born, he starts crying, breathes. Delayed or abnormal breathing at birth, then there is danger of hypoxia. Obviously if the baby is not breathing well then there is hypoxic chances oxygen will not be used. If the mother system has been depressed by general other C-section or severe category of operations in which a lot of general anesthesia is used then in these cases baby does not breathe immediately because of the effect of the anesthesia.
As many infants who have had head trauma during delivery or who undergo prolonged delivery are slow to breathe as well. This can result from two possible factors in a few infants intracranial hemorrhage or brain contusions head trauma then probably much more important prolonged fetal hypoxia during delivery can cause serious depression of the rest anything which depresses the respiratory center in the baby will have delayed respiratory beginning in the baby after birth hypoxia may be during delivery because of compression of the umbilical cord premature separation of the placenta you Excessive contraction, all these things are reducing oxygen delivery to the baby even before birth. Degree of hypoxia that an infant can tolerate, means there is a limit, the baby is born, now he is not breathing immediately, level of oxygen is decreasing, how much it will decrease is very dangerous.
In adults, failure to breathe only for 4 minutes can cause death. 4 minutes is more, you just don't try to stop breathing, but 4 minutes is the maximum, in a few seconds your condition will get worse. But neonates may survive as long as 10 minutes without breathing. Permanent and serious brain disease, impairment often you know in shoes if breathing is delayed for more than 8 to 10 minutes so this is the time period critical expansion of lungs in birth at birth the wall of the alveoli are at first collapsed because lung pura deflated because of the surface tension of the viscous fluid that fills with them within them More than 25 millimeter of mercury of negative inspiratory pressure in the lungs is required So this is the pressure which will expand the lungs and now the alveoli will become open and once they are open further respiration can be affected by relatively weak respiratory movements and Fortunately the first inspiration of the normal neonate are extremely powerful. They are usually capable of creating You know 60 is the negative pressure so that the whole alveoli opens properly.
It pulls the alveoli. The child cries so loudly. Tremendous negative intrapleural pressure required to open the lung at the onset of the breathing is helped by actually crying mechanism.
So just remember this. These numbers are there. Minus 30, minus 40. Never asked in the exams. Not important for you to remember. If you want to impress somebody then that's fine.
Otherwise they are not important. Note that the second breathe is much easier. First breath is difficult.
After that it is easy. There are many things that are difficult at first and then become easy. I am not giving an example of all of them. I can't give.
Requiring far less negative and positive pressures. Breathing does not become completely normal until about 40 minutes. Obviously, he is just born.
He has started breathing for the first time. It will take half an hour to get into the setting. Respiratory distress syndrome occurs when surfactant secretion is deficient. That's a problem. In a small number of infants, what happens is especially premature infants, who are born before time, are not able to breathe.
infants born to mothers who have diabetes mellitus for example or respiratory distress or some other diseases only surfactant come and then the surface tension issues come into play the alveoli of these infants and death contain large quantities of proteinaceous fluid almost as if the pure plasma has leaked out from the alveoli and inside the alveoli from the capillaries the fluid also contain disquamated alveolar cells this condition is called highline membrane disease because now this happened that the alveoli had to be filled with air but all the protein is filled with liquid a characteristic finding in respiratory distress syndrome is failure of the respiratory epithelium to produce surfactant a substance which is normally secreted into the alveoli that decreases the surface tension it's very important that the alveoli remain open if this surfactant is not produced then they will collapse and that's a problem the surfactant secreting cells which are type 2 alveolar cells do not begin to secrete surfactant until one to three months of gestation or for any reason if surfactant is not produced that is the problem and death can happen circulatory readjustments this is a very important topic to consider embryology many alexa bharaya general anatomy malik sabaraya so there are a lot of adaptations till now we were talking about the respiratory adjustments that he has to breathe as soon as he is born now there are some major important circulatory adjustments after birth equally as essential as the onset of breathing which we talked about earlier also are important the circulatory adjustments that allow adequate blood flow through the lungs in addition circulatory adjustments during the first few hours of life cause more and more blood flow through the baby's liver which up to this point has little blood flow to describe these readjustment we first consider the anatomical structure to a couple of our a couple which anatomy what I think a fetal circulation key and then we will talk about what changes happen after the delivery now a specific anatomical structures of fetal circulation so whatever we now discuss is in the fetal circulation because the lungs are mainly non-functional not but Jimmy lungs for comkering a rotate So, when the lungs are not functioning, this statement should make sense. Because the lungs are mainly non-functional during fetal life, and because liver is only partially functional as well, it is not necessary for the fetal heart to pump blood through the entire lungs or the liver. Now, normally, in every heartbeat, where should I make it?
Give me a place for a diagram. Let me generate some space here. So, usually, when your heart pumps, then with each cycle, your blood obviously from the right side of your heart it goes to the lungs with each circulatory beat but in the child, the blood doesn't go to the lungs because the lungs are blocked, it doesn't go there however fetal heart must pump large quantities of blood through the placenta the work of the fetal heart is to communicate with the placenta therefore special and real arrangements causes fetal circulatory system to operate much differently than from the newborn baby first blood returning from the placenta through the umbilical vein passes through the ductus venosus mainly bypassing the liver so now this is important now you have to understand special fetal circulatory arrangements first the first name is ductus venosus so look at the diagram first of all locate where is placenta so this is placenta the blood coming from placenta that is in the umbilical vein here it is the opposite matter like pulmonary vein Like pulmonary vein which comes from the lungs, it has oxygenated blood which is represented by red. But the umbilical vein is coming with oxygen from the mother's body so it contains oxygenated blood therefore it is represented as red. So this umbilical vein is passing through ductus venosus and then getting into where?
Into the heart. So that is the first thing that you have to understand. umbilical vein is giving blood that is coming through the placenta passes through the ductus venosus bypassing the liver it is not distributing blood in the liver so this is not distributing any blood in the liver it is just taking it directly to the heart because liver doesn't need it so liver is no tension, blood is not going there first you have to remember the pipeline is ductus venosus then most of the blood entering the right atrium now blood is coming in the right atrium from the inferior vena cava is directed in a straight pathway across the posterior aspect of the right atrium through the foramen ovale directly into the left atrium. Now this is another interesting thing. This is the second bypass system.
Usually it happens, if I talk about adult heart, that the blood that comes on the right side from the inferior vena cava and from any other you know blood vessel, superior vena cava or whatever, the deoxygenated blood that comes on the right side first goes to the right atrium, then to the right ventricle, then to the pulmonary artery. The pulmonary artery goes to the right atrium. so that it gets oxygenated in the lungs but here it is not happening here what is happening is the blood coming in the right side of the heart it is going directly from the right atrium into the left atrium by the foramen ovale thus the well oxygenated blood from the placenta enters mainly the left side of the heart all this oxygenated blood comes directly in the right atrium and from right atrium it directly reaches into the left atrium and from left atrium it is ready to circulate in the whole body so it is not coming in the right side the bypassing system is going on in the right side infact the blood that comes in the right side is through a hole and the name of that hole is foramen ovel so that is shunt number 2 first shunt ductus venosus, second shunt foramen ovel now the blood has come in the left atrium the blood entering the right atrium from the posterior vena cava is directed downward through the trachea squid valve into the right ventricle the blood is mainly deoxygenated obviously it's coming in the right atrium from the head region of the fetus it is pumped by the right ventricle into the pulmonary artery now pulmonary artery will not go into the lungs because lungs are not working right so now this blood is also put into the aorta through ductus arteriosus this is the third blood vessel in the blood vessel and this is the third blood vessel in the blood vessel You have to remember that the oxygenated blood coming through the umbilical vein, it comes in the right side of the heart, that is number one, bypassing the liver. Then from the superior vena cava comes in here and from some other veins as well, the oxygenated blood coming into the right atrium, it goes straight to the left atrium. And then number three, the blood that came in the right atrium and then went to the right ventricle.
and then it goes to pulmonary artery, and it should have gone to lungs but lungs are not working so it goes to ductus arteriosus and direct descending aorta so blood is shifted to descending aorta which is still deoxygenated from the head region through the two umbilical and then what happens is that blood goes back to the placenta through descending aorta where it is oxygenated from deoxygenator so this whole system is I say that Khichdi system is not available in adults and newborn babies Because adult system is very simple I have told you many times that if this is your heart Right side and left side So all the deoxygenated blood will come in right atrium From there in right ventricle From here in lungs Lungs oxygenate and left atrium Left ventricle aorta This is our system But here circulation of lungs is not getting over Similarly, the GI tract that goes all the blood to the liver, that also does not happen in the baby. So in the baby, there is no blood going in the liver and there is no blood going in the lungs. And for this no blood going, a lot of arrangements have to be done and you should know those anatomical changes. Okay.
Now this figure is a very important figure shows relatively percentages of total blood pump by the heart that passes through the different vascular circuits of the fetus approximately 55% of all the blood goes through the placenta leaving only 45% to pass through all tissues of the baby. Furthermore during fetal life only 12% of the blood flows through the lungs. Because there is no blood supply in the lungs and there is no resistance in the lungs. Now what happens at birth? So I am telling you this paragraph again and again Stop the video, rewind the video and read it again and again Once the concept is clear, then come to this heading Basic changes in the fetal circulation after birth We have already discussed this separately, but we will do it here So that the concept is complete Decreased pulmonary and increased systemic vascular resistance and but so pulmonary resistance decrease with pulmonary circulation and blood lungs are directed the primary changes in the circulation at birth are first loss of the tremendous blood flow through the placenta that is you have cut the umbilical cord and blood flow of placenta is finished which approximately doubles the circulation within the fetus or vascular resistance increases this doubling of the systemic vascular resistance increasing increases the aortic pressure as well as the pressure in the left ventricle and the left atrium Second, the pulmonary vascular resistance greatly decreases Also in fetal life, the hypoxia of the lung causes considerable tonic vasoconstriction of the lung vessels But now because after birth, lungs are inflated, alveoli are oxygenated, so the blood vascular resistance decreases.
And all these changes together reduce the resistance to the blood flow through the lungs. Blood flow resistance decreases means that blood flow will go more towards the lungs. So as much as 5 fold reduction happens which reduces the pulmonary arterial pressure and right ventricular and atrial pressure as well.
Overall impact will be that now blood will go to the lungs. and the foramen ovale closes what was the foramen ovale? which was shifting blood from right side to left side now that is closed so now blood has to go from right side to right ventricle from atrium the low right atrial pressure and the high left atrial pressure actually causes closure of the foramen ovale and consequently the small valve that lie over the foramen ovale on the left side of the atrium also closes this opening in 2 third of the people the valve become adherent to the foramen ovale from few months to few years forming a permanent closure however sometimes there is a patent for a min ovale throughout the life and that is a disease condition okay closure of the ductus arteriosus it was also a shunt it was a shunt which was connecting the pulmonary artery listen to this sentence properly pulmonary artery with the aorta now this shunt closes now when this shunt closes pulmonary artery blood does not go to the aorta this is ductus this is closed blood will enter the lungs and not the aorta so ductus arteriosus will stop and the blood flow will be less in the lungs so there is no other way, if you close this pipe it will not enter the aorta it will enter the right and left pulmonary arteries simply go to the lungs, so that is what we call the closure of ductus arteriosus ductus arteriosus closes but for a different reason, first increase systemic reasons I'm not going to go into detail embryology when I'm a power what you would even have a Connie but Ali but there is a foreign molecule which you have to remember that is you know associated with the prostaglandin e2 remember this point okay in fetal life the partial pressure of oxygen of the ductus blood is only 15 to 20 millimeter but it increases to about 100 millimeter within a few hours after birth further more experiments have shown that degree of contraction of the smooth muscle in the ductus is highly related to this availability of oxygen and that is associated with prostaglandin E2 the cause of the ductus arteriosus closure relates to increased oxygenation of the blood flowing through the ductus as well as the loss of vascular relaxing factor PGE2 relaxes the ductus and when PGE2 is over the oxygen level increases after birth the blood passing through the ductus arteriosus prostaglandin E2 decreases and the patent ductus arteriosus now closes it is no more a patent channel it closes and once it closes blood goes not into the aorta but into the lungs okay right in one of the several thousand infects the ductus failed to close resulting in PDA patent ductus arteriosus the failure of closure has been postulated to result from excessive ductus dilation because the prostaglandin E2 is not reduced okay in fact administration of indomethacin which blocks synthesis of prostaglandin can help for the closure because it will inhibit prostaglandin and then closure can be facilitated closure of ductus venosus it was bypassing the liver In fetal life the portal blood from the fetus abdomen joins the blood from the umbilical vein and these together pass by way of ductus venosus bypassing the liver. Immediately after birth this also closes.
So, here also the closure will happen. So, all these bypass channels, foramen ovale was one bypass channel, ductus arteriosus was another bypass channel, ductus venosus was another bypass channel, all of them close after birth. so that the blood circulation becomes adult type after birth so these circulatory changes are very important so up till now we have talked about respiratory changes we have talked about circulatory changes now let's talk about the nutrition of neonate before birth the fetus drives almost all its energy from glucose obtained from the mother's blood whereas after birth obviously there is no connection with mommy's body placenta is gone what happens is that glucose is stored in the body of the mother infant in the form of liver and muscle glycogen is now helping the baby the liver of the neonate is still far from functionally irrigated birth your liver abhi bhi theek se kaam nahi kar raha which prevents significant new glucose nahi manega jo glucose store hua tha wohi use hoga therefore the infant's body glucose concentration frequently falls in the first few hours to days as low as 30 to 40 milligrams because jitna bhi glucose tha use ho raha hai aur new glucose ban nahi raha Fortunately, appropriate mechanisms are available that allow infant to use its stored fats and proteins as well.
And special problems are also frequently associated with getting an adequate fluid supply to the neonate because infant's rate of body fluid turnover averages 7 times that of an adult. And the mother's milk supply requires several days to develop. Usually, 1 to 7 days may not generate enough supply from the lactating breast. that can be enough for the baby so for first few days at least the baby is at its own the stored glycogen in the liver is being used so the body's requirements like fat, protein are being used ordinarily the infant's weight decreases 5-10% sometimes even more in the first 2-3 days of life and that is the reason that all the stores that were there in the body are being used new glucose is not being generated, milk is not ready to provide nutrition that sort of thing and that's very very normal and then once the milk supply is ample available then things become normal special functional problems in neonate and important characteristic of neonate is instability of the various hormonal and the neurological control mechanisms or what we have discussed about respiratory system for example the normal rate of respiration in neonate is about 40 breaths per minute and tidal air with each breath average is about 16 ml which results in total minute respiratory volume of 640 about twice as that in relation to the body weight of an adult the functional residual capacity of infant lung is only one half that of an adult in relation to the body weight so I would say not super important paragraph but anyways if you are fond of remembering the numbers then you should go ahead with this the difference causes excessive cyclical increase in decrease in the newborn's baby blood gas concentrations if the respiratory rate becomes slowed Okay, I mean nothing so important there circulation Yeah, well is which important about them the blood volume of a new lady immediately after birth is about 300 ml only But if the infant is left attached to the placenta for a few minutes after birth or if the umbilical cord is stripped to force Blood out of it vessels into the baby Additional 70 to 100 ml of blood can enter in the baby and then it will be 3 to 400 ml in total Then during the ensuing few hours fluid is lost into the unit tissue space from this blood and I mean whatever 300 ml is on average the blood in the newborn baby and if you talk about the cardiac output it's about 500 ml per minute that's the speed and the cardiac output. Articular pressure at birth is about 70 millimeters systolic and 50 so as opposed to 120 in adults it is 70-50 in the baby but in some months it becomes 90-60 and in the coming years it goes to 120-170 that comes at adolescence Blood characteristics The red blood cell count in the neonate is about 4 million per cubic millimeter it is blood if this blood is a stripped from the cord into the infants the red blood cell count obviously will go up additional 0.5 to 7.5 million but okay nothing too important there to remember neonatal joandera this is important bilirubin formed in the fetus can cross the placenta into the mother and may be executed through the liver of the mother immediately after birth what happens here the only means of you know getting rid of the neonate bilirubin is through the neonate's own liver which for the first few weeks is not working fantastically so basically what happens is that it is incapable of conjugating significant quantities of bilirubin because the appropriate liver functioning is not happening the result of this is that bilirubin concentration will rise in the plasma and this will lead to jointness and this is called physiological hyperbilirubinemia or physiological jointness of the baby However, by far the most important abnormal cause, this is absolutely normal, this is physiological, but abnormally there can be atheroblastosis fatalis, which is discussed elsewhere.
And its basic details are that there is blastosis of the red blood cell. There is Rh factor incompatibility between the fetus and the mother. So if there is a baby who is born to a mom who is for example Rh negative and was previously born with an Rh positive baby and the second baby will be affected. because of the antibodies to the RH so these sort of thing you know a disease called erythroblastosis fatalis that also because there is rupture of red blood cells so there is a lot of bilirubin in the system and liver is not capable of handling that bilirubin so the levels of bilirubin goes super high and that leads to joint disease as well okay and fluid balance acid-base balance and renal function obviously they are not very mature at the time of birth the rate of fluid intake and fluid excretion in the newborn is seven times as great in relation to the weight so not very important paragraph the rate of metabolism in the infant is higher it's twice as in relation to body mass in adults which means that twice as much acid is normally produced in the baby okay so there is an acid loading environment functional development of the kidney is not complete until the first month of completing for example the kidneys of the neonate can concentrate urine to only 1.5 times you the osmolarity of the plasma so it's not fully functional but with passage of time it gets all right liver function during the first few days of life up to now you have got the idea i am repeating this again and again that liver is not fully functional so there are problems with bilirubin handling the liver of the neonate conjugate bilirubin with glucuronic acid poorly because of the liver of the neonate is deficient in forming plasma proteins as well The plasma protein concentration falls initially in the first few days of life.
Gluconeogenesis is impaired in the early time period. The liver of the neonate usually also forms too little blood factor. So, these are all important features which you should know in reference to the liver function.
So, actually all organ systems in newborn babies are not at 100% functional capacity on day 1. Obviously, and it makes sense. Digestion, absorption and metabolism of energy. foods and nutrition. We have said this many times that in general the ability of the neonate to digest, absorb and metabolize food is not much different from that of the older child. But there are some exceptions which you have to remember from digestion, absorption, metabolism.
Number one, secretion of pancreatic amylase in the neonate is deficient. That is why their starch handling is not that efficient. Number two, absorption of fats from the GI tract is somewhat less as compared to the older child.
So there are some differences. Thank you. Consequently, milk with high fat content such as in the cow's milk is often inarrogately absorbed in babies.
And number three, because of the liver function imperfectly during at least the first week of life, glucose concentration in the blood is unstable and low. Because liver works to maintain the concentration of glucose in the blood, it doesn't work properly. Now the neonate is especially capable of synthesizing and storing protein. So this is something that the neonate can do. Indeed with an etiquette diet up to 90% of the ingested amino acid is used for the formation of proteins Which is actually a much higher percentage as we and as adults can do We can do more protein synthesis and store more protein Increased metabolic rate and poor body temperature regulation The normal metabolic rate of the neonate in relation to the body weight is about twice as that of the adult Which also accounts for the fact that cardiac output and the minute minute respiratory not the minute well by the way i just discovered minute minute spelling wise minute respiratory volume are twice as great in relation to the body weight in infant so basically heart rate is more than respiratory rate is different from adults so metabolic rate that's also different because the body surface area is large in relation to the body mass the heat is readily lost from the body so temperature regulation is not very good okay now nutritional needs during the early weeks of the life at birth and unit is usually in complete nutritional balance provided by the mother obviously by the placenta but i mean later on the baby has to feed on itself that he will up a nutritional status quo homeostatic rucksack a furthermore the function of the GI system is usually more than etiquette to digest and assimilate all the nutritional needs of the infant if appropriate nutrients are provided so GI tract is well formulated however three specific problems occur in the early nutrition of the infant number one need for calcium and vitamin D because the new age in is in the stage for rapid ossification bones massification or a already supply of calcium throughout the infancy is very much necessary this is ordinarily supplied adequately by the milk however absorption of calcium by the GI tract is poor in the absence of vitamin D therefore within only a few weeks severe rickets can actually develop in the infants those who do not have vitamin D so they need vitamin D as well as calcium because they have bones to ossify number two need for iron in the diet If the mother has had adequate amounts of iron in the diet, the infant's liver usually has stored enough iron for 4-6 months formation of red blood cell.
Why does the baby need iron? For the formation of red blood cell. Now, if the iron levels in the mother's body were correct, then they would have been transferred to the baby and the liver would have stored them, which are enough for 4-6 months. However, if the mother has had insufficient iron, then the baby may have anemia as soon as 3 months of life. Because now the iron stores are over.
or Naya Red Blood Cell Kaise Banega? Early feeding of infant with egg yolk which contains reasonably large amount of iron or the administration of iron in some other form is desirable if there is severe iron deficiency anemias. Third problem which is to be faced by the baby early on is vitamin C deficiency.
Ascorbic acid, vitamin C is not stored in secret because it's a water soluble vitamin. So it is not stored with great... quantities however adequate amounts of vitamin c are normally provided in mother's breast milk unless mother has severe vitamin c deficiency which is very rare cow's milk has only one-fourth as vitamin c as human milk in some cases orange juice or other sources of ascorbic acid are prescribed to the infant if vitamin c deficiency is suspected so earlier only three major problems first few weeks of life man number one is calcium and vitamin d status number two is iron in the diet number three is vitamin c deficiency okay immunity wise the neonate inherits a great degree of immunity from the mothers because the protein antibodies are transferred number one through the placenta also they are present in the milk in significant amount by the end of the first month the baby's gamma globulins which contain antibodies have decreased to less than half the original level and a corresponding decrease in immunity also happens.
Therefore, the baby's own immune system begins after a few months. In the initial few months, the antibodies transported through the placenta help. Despite the decrease in the gamma globulin soon after the birth, antibodies inherited from mother protect the infant for about 6 months because it is the lifespan of the antibodies.
That means the antibodies that have reached the baby are okay for about 6 months. Therefore, immunization against these diseases before six months is usually not required. Because in the initial six months, the antibodies that are transported from the mother are enough. However, the inherited antibodies against whooping cough are normally insufficient.
That is why immunization is taken into consideration, which shots to give early and which later. And it has a full schedule and in different countries, but most of them follow the WHO schedule. which is an extended program of immunization in developing countries they follow it and vaccinate the children Now allergy, newborn infants are seldom subject to allergies very rare allergies in newborns because they don't have fully formed immune system for allergy response you need a fully fledged immune system several months later however when infant's own antibodies first begin to form allergic states can develop because this is a newborn baby and it does not have any antibodies, how will the allergy respond?
but after a few months such as 5-6 months it starts making its own antibodies then the allergy can start Endocrine issues, ordinarily the endocrine system of the infant is highly developed at birth and infants seldom exhibit any immediate endocrine abnormalities, so this is one of the rare abnormalities reported however, unless there is a congenital malformation of one of the endocrine So if that is the issue then it is a different matter. Otherwise, like liver, liver is ill formed. It is not fully functional. Because it is not fully functional, it gets jointed in early times.
But the problem of endocrine is not reported as such. If a pregnant mother bearing a female child is treated with an androgenic hormone or if an androgenic tumor develops during the pregnancy, mother is talking about, the child will be born with a high degree of masculinization because of the androgens and that in that the female sexual organs may hyperploriphrate and they can masculinize leading to hermaphroditism means they will have the female gender but they will also develop genitals which are male looking and that is because of the masculinization of the genitals because of the androgens which are produced in high amount in the mommy now the sex hormones secreted by the placenta and by the mother's gland during pregnancy occasionally cause the neonates breast to form milk as well that sometimes happens that the baby is getting milk from the breast during the first days of the life sometimes the breast then become inflamed or infectious as well So that is again because there are sex hormones secreted by the placenta, by the mother's gland and they transport it to the baby and they cause the effect. So I am telling you the associated issues of endocrine.
An infant born to an untreated diabetic mother will have considerably hypertrophy and hyperfunction of the islets of the pancreas. As a consequence, the blood glucose of the infant may fall to a very low level. more islets will create more insulin and more insulin will create hypoglycemia that can happen fortunately in neonate unlike the adult insulin shock and coma from this low level of glucose rarely occur because children are already used to low glucose so low glucose is not a big problem in babies maternal type 2 diabetes is the most common cause of large babies humongous big babies born to diabetic mothers is a common phenomena Type 2 diabetes in mother is associated with resistance to metabolic effects of insulin and compensatory increase in the plasma insulin concentration. The high levels of insulin are believed to stimulate the fetal growth because that behave like growth hormone like factors.
However, most of the increased fetal weight is due to increased body fat. There is some more lipogenesis basically organomegaly. And among the fetuses who do come to term, there is a high mortality rate.
Two-thirds of the infant die. succumb to respiratory distress syndrome occasionally a child is born with hypo functional adrenal cortex resulting from agenesis and exhausting atrophy so if the cortex is not working then you know what are the hormones associated with cortex and they will not be functional if a pregnant woman has hyperthyroidism or is treated with excess thyroid hormone the infant is likely to be born with a temporarily hypo secreting thyroid because high levels of thyroid they will suppress the thyroid gland so the thyroid gland of the baby will not work in a fetus lacking thyroid hormone secretion the bones grow poorly and there is mental retardation called creatinidrophism so the point is that most of the endocrine issues they are there because there was something wrong in the mother as a result of which the baby is now suffering so that sort of thing special problems of prematurity all the problems in neonatal life just noted are severely exacerbated in prematurity Prematurity means if the baby is born before the term date So all these issues we have discussed that the liver is not working properly Imagine if the baby is not working properly on the 40 weeks of gestation then it will work a little less than 37 weeks Alveoli which are releasing surfactant if it is not fully mature then if the baby is born early then it will not be mature at all Nervous system is not fully developed, myelination is not done, 40 weeks is not done, so 37 weeks is less. So all the issues we have discussed are exacerbated. They are further augmented. They can be categorized under two headings.
Number one, immaturity of certain organ system. And number two, instability of different homeostatic controls. We will discuss that now.
Advances in medical care have greatly improved the outcomes of the preterm babies in recent years. There was a time, that if premature baby is born and earlier in some time this used to happen that delivery used to happen at home now also in some villages, in ghauts these kind of things happen but not in the you know big cities obviously there are hospitals now and the care is very very improved so preterm babies now get a good amount of care so the survival rate for extremely preterm which is less than 28 weeks that's extreme preterm as compared to 40 weeks of gestation in fact about 80-90% with modern medical care are actually alive So the baby born in such a short time also survives. However, with each week of shortened gestation, below 28 weeks the survival goes down. At 22 weeks or less, preterm babies rarely survive. So that's the, I mean, already 28 is too less of a time for the baby to have in the uterus.
So its survival is not that easy. If the baby is in good health care setup, then the 28 week baby might survive. Now I want to tell you about two types of problems. Immaturity of organ systems.
Almost all the organ systems of the body are immature. Immature. in the premature infant and require particular attention. So obviously, the systems are not properly made yet and there could be issues in the respiration. Respiratory distress syndrome can be very common in such babies.
Therefore, the babies have to be You know continuously monitored Surfectant secretion in the ovals can there just give it as a respiratory distress syndrome Oh God GI functions affected on this I read the babies are premature to the but though my You know 28 weeks up the arena that even two months early here But I'll get baby and the major problem of a premature in fact is ingesting and absorbing adequate food in infants Who are born two months premature the digestive in the absorptive systems are almost always inadequate Furthermore because the absorption of calcium is unusually difficult you premature infants so some bone chemistry or rickets get my common or in my Hannah further function of other organs immaturity of the liver is a problem immaturity of kidney blood forming mechanism so we have a globulin forming mechanisms all these functions will be so what you have to do is to monitor the baby with great care usually in a hospital setting a chap then there are some homeostatic control systems which are not working Immaturity of the different organ system in premature infant creates high degree of instability in the homeostatic systems For example acid-base balance are disturbed temperature regulations are disturbed You know edema can develop because liver proteins are not working, kidneys are not working Calcium regulation is affected hypocalcemic tetany also the blood glucose concentration can vary between low limits to a very high limit Depending upon how the baby is being fed Inestability of body temperature is another issue. One important problem of premature infant is the inability to maintain the normal body temperature. The premature infant's temperature tend to approach that of the surrounding.
So that kind of the, you know, other animals, humans tend to maintain their temperature, but these babies reach the surrounding temperature. At normal room temperature, the infant's temperature may stabilize at okay temperature. But if the temperature goes high or the temperature goes low, then there can be a problem. Baby is not able to maintain the body temperature.
Danger of blindness caused by excess of oxygen therapy. This is another very big problem. Because premature infants frequently experience respiratory problems, they are given oxygen, which is what we call the oxygen therapy. However, excess use of oxygen in treating premature infants, especially in early prematurity, can lead to blindness because too much oxygen stops the growth of the new blood vessels. and when this happens then retina is affected and the person goes blind this condition is known as retro lentil fibroplasia as cause permanent blindness so other retina may go issue permanent blindness that's the end of the story for vision for this reason it is particularly important to avoid treatment of premature infants with high concentration of respiratory oxygen obviously if hospital settings mother bacha head so it will be taken care of so that has to be you know considered as an important point The major physiological problems of a child beyond neonatal period are related to special metabolic needs of the body.
Now this is a topic of neonatal period until the age of 20 years for example. Note especially that these heights parallel each other. So not the topic to be discussed here at the moment because they have gone up to very very I would say elderly age, 20 years.
Behavioral growth. Behavioral growth is principally related to the maturity of the nervous system. It is difficult to dissociate maturity of the anatomical structure of the nervous system from the maturity caused by the training. Anatomical studies show that certain major tracts in the central nervous system are not completely myelinated until the end of the first year. For this reason, it is frequently stated that the nervous system is not fully functional at birth.
The brain cortex and its associated functions such as vision seem to require several months. This is very normal. You all have kids at home. You see the child at the start, he is looking at you but you are not seeing him clearly.
Because you know higher centers, the cortical higher centers, they develop in the first year of life. And then the myelination happens in the ascending descending major tracts during the first year. So after the birth of the child, the nervous system becomes stable for a year.
And in this year, his behavioral growth occurs, his personality starts to develop. At birth, the infant brain mass is only about 26% of the brain mass in adults and 55 year at one year But it reaches almost the adult portion by the end of the second year So second year per uska brain mass It adults as a ratio but I got this process also associated with closure of the fontanelles the sutures of the skull Which allows only 20% of additional growth by the end of the second year a comparison of this jar was not Going to do the comparison so that's basically it and we finished congratulations the reproductive physiology we are just done with so many chapters which were part of endocrine physiology or endocrine physiology last 4-5 chapters they belong to particularly reproductive physiology unit 14 we completed the guidance so that's bit success or if you If you are watching these lectures with me, then all the very best. Do let me know in the comments, which unit should I start next.
I am getting a lot of requests for neurophysiology. So, confirm which unit should I start next. I will see you in the next video.
Take care.