41. Fetal and Neonatal Physiology Flashcards by Deleted Deleted

Gestational age

Day 1 is last day of normal menstrual period

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Fertilization age (aka embryonic age or fetal age)

Day 1 is fertilization

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How do you calculate gestational age using fertilization age?

Gestational age = fertilization age + 2 weeks

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Prenatal hematopoeisis takes place primarily in the _____ from fetal months 1-3

Yolk sac

[considered primitive erythropoiesis]

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Prenatal hematopoeisis takes place primarily in the _____ from fetal months 3-7

Liver

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Prenatal hematopoeisis takes place primarily in the _____ from fetal months 7-birth

Bone marrow

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After ____ weeks gestation, hematopoietic progenitors are no longer detected in the yolk sac

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The _____ serves as the primary source of red cells from the 9th to the 24th week of gestation

Liver

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Liver is primary site of _____ transcription throughout fetal life

The _______ production of this factor increases throughout fetal life

EPO; kidney

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________ becomes the major site of hematopoiesis after the 24th week of gestation and remains so throughout the remainder of fetal life

Bone marrow

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Major hemoglobin of fetal life

HbF (alpha2gamma2)

[contrast with adult HbA (alpha2beta2)]

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Normal adult levels of ____ are achieved by ~12 weeks of life (full term)

HbA2

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Hyperbilirubinemia during first 2 weeks of life (full term) = ______ jaundice

Physiological

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The mean hemoglobin level in cord blood at term is 16.8 g/dL, with 95% of the values falling between 13.7 and 20.1 g/dL

What accounts for this variation?

This variation reflects perinatal events, particularly asphyxia and also the amount of blood transferred from the placenta to the infant after delivery

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What iatrogenic cause appears to heighten the occurrence of anemia at 2 months and to impair cardiopulmonary adaptation

Early cord clamping

[delay of cord clamping may increase the blood volume and red cell mass of the infant by as much as 55%, resulting in fewer transfusions and fewer days requiring oxygen and ventilation in preterm infants]

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The serum ____ level in cord blood of the normal infant is elevated compared to normal levels

Iron

[the mean serum ferritin levels in iron-sufficient infants are high at birth, 160 mcg/L, rise further during the first month, and then fall toa mean of 30 mcg/L by 1 year of age]

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Describe the amount of iron in the marrow at birth and how this changes up to 6 months of age

The amount of iron in marrow at birth is small but increases in both term and premature infants during the first weeks after birth

Marrow iron begins to decrease after 2 months and is gone by 4-6 months in term infants and earlier in premature infants

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Iron is preferentially allocated to ________ if the availability of iron is limited

Erythropoisis

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When does nephrogenesis occur and when is it completed

Begins at 8 wks getation and completed ~36 weeks

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When does fetal urine production begin?

Begins as early as 10 weeks through 20 weeks gestation

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________ accounts for 70-80% of amniotic fluid

Fetal urine

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During what trimester of pregnancy does renal function mature rapidly? When does functional development complete?

3rd trimester — resulting in body fluid balance, acid-base balance, and electrolyte balance

Functional development completes closer to 1 month of age

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Describe the fetal liver handling of bilirubin, plasma proteins and coagulation factors, and gluconeogenesis

Poor conjugation of bilirubin

Deficiency in forming plasma proteins and coagulation factors

Deficient gluconeogenesis (blood glucose levels the 1st day could be as low as 30-40 mg/dL of plasma)

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Since the fetal liver has lacking gluconeogenesis ability, what does the infant use for metabolism?

Stored fats and proteins until mother’s milk can be provided

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Since the neonate is in a stage of rapid ossification of its bones at birth, a ready supply of _____ throughout infancy is necessary Normally the adequate amount can be supplied by the usual diet of ________

Calcium Milk

Absorption of calcium by the GI tract is poor in the absence of ______ _____ can develop in infants who have this deficiency

Vitamin D Rickets

The fetus has distinct goals in terms of Ca, Phosphorus, and bone homeostasis regulation. What are they

Fetus must actively pump calcium, phosphorus, and magnesium from maternal circulation against concentration gradients, maintain serum mineral concentrations at higher levels than in maternal circulation, rapidly mineralize the skeleton during the final quarter of gestation, and achieve overall positive mineral balance

The infant’s _____ has stored enough iron to keep forming blood for ____ months after birth — provided that the mother has provided adequate iron in her diet during pregnancy

Liver; 6

Describe iron content of breast milk vs. infant formula

Iron content is low, but bioavailability is high Studies show that infants exclusively breastfed for first 6 months of life have normal iron status at 6 months, provided mother has adequate iron status Iron content of infant formula is high because bioavailability is lower than breastmilk

If the mother has iron insufficiency in her diet, _______ is likely to occur in infant after 3 months of life

Severe anemia

What vitamin, necessary for appropriate formation of intercellular substances, especially the bone matrix and fibers of CT, is not stored in significant quantities in fetal tissues but can be provided by breastmilk?

Vitamin C

T/F: the neonate does not form antibodies of its own to a significant extend, requiring dependence on mother

True

By the end of ____ month, there is a decrease in the baby’s gamma globulins (contain the antibodies)

1st

The baby’s own immune system begins to form Abs and gamma globulin concentration returns to normal by the age of _____

12-20 mos

Antibodies inherited from the mother protect the infant for about ____ months against most major diseases. However, inherited antibodies against ________ are normally insufficient to protect the neonate - so they require immunization against this illness within the ~1st month of life

6 Whooping cough

T/F: other than whooping cough, immunization against most other diseases is usually not necessary before 6 months of age

True

Since most maternal-fetal iron transfer occurs in the 3rd trimester, low birth weight pre-term infants are at higher risk of what condition?

Iron-deficient anemia

Respiratory consequences of preterm birth

Respiration is usually underdeveloped; respiratory distress syndrome is common cause of death

GI consequences of premature birth

Poor ingestion and absorption of food

Complications of premature birth include mmaturity of liver, kidneys, blood forming mechanism of the bone marrow, as well as depressed formation of _____ by the lymphoid system They also struggle with instability of different homeostatic control systems.

Gamma globulin

Why is the neonate particularly susceptible to stress?

Underdeveloped HPA axis lacks synaptic maturity in the hypothalamus and related brain centers Neonatal glucocorticoid response (cortisol level) is blunted because GC’s are toxic to developing nervous system

Neonatal glucocorticoid response (cortisol level) is blunted because GC’s are toxic to developing nervous system Buffering to this response is maintained by what?

A consistent caregiver relationship with an adult (e.g., the mother)

Consequences of “toxic stress” experienced by the neonate in critical period of development

Increased risk of psychological disorders, physiological dysregulation, and chronic pain in adulthood

The fetal lungs develop slowly and there is no true respiration during fetal life. However, some respiratory movements will occur over the last ___-____ months of gestation What is the purpose of inhibited respirations?

3-4 Inhibited respiratory development prevents lungs from filling with fluid and debris

Small amounts of fluid are secreted into the lungs by the _____ ____ up until birth

Alveolar epithelium

What occurs in weeks 4-5 of respiratory development?

Week 4: respiratory diverticulum forms Week 4-5: respiratory diverticulum branches into left and right bronchial buds; stem of diverticulum will differentiate into trachea and larynx

What happens in weeks 5-7 of respiratory development

Branching yields secondary bronchial buds, which represent future lung lobes Closer to week 7, branching yields tertiary bronchial buds, which represent future bronchopulmonary segmens

When in respiratory development do terminal bronchioles form? Is the next step after this?

Week 16 Week 16-36 respiratory bronchioles form, surrounding mesenchyme becomes highly vascular; first terminal sacs (primitive alveoli) form

From week 36 to birth, ________ ____ begin to differentiate into mature alveoli. Alveoli continue to form through the ___ year

Terminal sacs; 8th

Function of surfactant

Decreases surface tension

Surfactant is secreted by what cell type

Type II alveolar epithelial cells

When does surfactant production begin

Synthesis begins in last trimester

T/F: once alveoli open, it is harder to close them when exhaling without surfactant

True

Breathing initiates within seconds of birth. What are the stimuli for this?

Asphyxiation during birth Sudden drop in temperature/cooling of skin

What might cause delayed breathing upon birth?

Use of general anesthesia during delivery Prolonged labor Head trauma

Describe the alveoli at birth

Alveoli are collapsed, amniotic fluid fills them

More than _____ mm Hg negative inspiratory pressure is needed to overcome surface tension and open alveoli at birth The 1st inspiration — infant capable of ______ mm Hg The 1st inspiratory movements — brings in nearly ____ mL air

25 -60 40

Deflation of lungs after birth requires strong _____ pressure to overcome viscous resistance of fluid in bronchioles

Positive

How long after birth does breathing normalize? What is the respiratory rate at that point?

~40 mins Settles into 40 breaths per minute with a tidal volume of 6-10 mL/kg

Causes of hypoxia during delivery

Compression of umbilical cord Premature separation of placenta Excessive uterine contractions Excessive anesthesia of the mother (depressed maternal breathing)

T/F: Neonates have a lower tolerance for hypoxia than adults

False: they have higher tolerance Adults tolerate for 4 mins while neonates tolerate for 8-10 mins

Failure to secrete adequate amounts of surfactant resulting in collapsed alveoli and development of pulmonary edema

Respiratory distress syndrome

RDS is common in premature infants and infants born to mothers with _____

Diabetes

Common sign of RDS

Pulmonary edema

The heart begins to beat during the ____ week after fertilization with an intial HR of ___ bpm This increases steadily to _____ bpm pre-birth

4th 65

The fetal heart does not pump much blood through the lungs or liver, but does through the ________

Placenta

Four unique shunts for fetal blood flow

1. Placenta 2. Ductus venosus 3. Foramen ovale 4. Ductus arteriosus

Massive blood flow to the placenta shunts blood away from what body region?

Lower trunk

Describe umbilical arteries

Branch repeatedly Return deoxygenated blood Dense capillary network at terminal villi “Legs” connect to inferior vena cava

Describe umbilical vein

Returns oxygenated blood to fetus from placenta PO2 = 30-35 mm Hg

Blood from the umbilical vein enters the ___ ____

Ductus venosus

The ductus venosus serves as the ____ bypass, since this organ is largely non-functional Thus the ductus venosus is a direct route from umbilical vein to _____

Liver IVC

Hole in septum dividing the atria, posterior aspect of right atrium

Foramen ovale

The foramen ovale is a ___ to ___ shunt

Right to left

The foramen ovale bypasses what heart region

Right ventricle

The foramen ovale allows blood at PO2 ~27 mm Hg (high) to pass right through to the _________ to supply the carotid arteries and brain

Left ventricle

T/F: of the blood entering the right atrium, almost all is shunted through the foramen ovale

False - about 27% is shunted through foramen ovale, the remainder enters the right ventricle

T/F: blood from the superior vena cava is not shunted through the foramen ovale

True

Is PO2 greater in left ventricle or right ventricle in fetus?

Greater in left ventricle. Blood from right ventricle enters the trunk of pulmonary artery

What serves as shunt from pulmonary artery to aorta?

Ductus arteriosus

The ductus arteriosus is a ____ to ____ shunt

Right to left

The ductus arteriosus is associated with a substantial amount of smooth muscle that is being dilated by _______

Prostaglandins (PGE2)

Blood flow changes upon birth include ______ pulmonary vascular resistance and ______ systemic vascular resistance

Decreased; increased

Describe reasoning for decreased pulmonary vascular resistance at birth

Lung expansion Vasodilation due to aeration of lungs eliminating hypoxia (local prostaglandins) Reduced pulmonary arterial pressure, right ventricular pressure, and right atrial pressure

Describe reasoning for increased systemic vascular resistance

Loss of blood flow from placenta doubles systemic vascular resistance Increases aortic pressure, left ventricular pressure, and left atrial pressure

What causes closure of foramen ovale

Reversal of pressure gradient across atria which pushes foramen ovale’s “valve” shut This is due to increased venous return to left atrium and elevated left atrial pressure, as well as reduced right atrial pressure Eventually the flap seals

What causes closure of ductus arteriosus?

Aortic pressure rises above pulmonary artery pressure — blood flows the wrong way Now well-oxygenated aortic blood flows through the ductus arteriosus; high PO2 —> vasoconstriction within a few hours, which when coupled with falling prostaglandin levels leads to sufficient constriction within 1-8 days, and full anatomical occlusion in 1-4 months

Closure of what 2 shunts establishes separate right and left circulatory systems?

Foramen ovale | Ductus arteriosus

What causes patent foramen ovale

Increased right atrial pressure can push flap open Sustained pulmonary HTN or transient increases with BM, coughing, or sneezing [occurs in 20% of individuals by 2 years of age]

Describe patent ductus arteriosus

Heart problem that occurs soon after birth Can be heard as heart murmur with stethoscope Oxygenated blood mixes with deoxygenated blood in pulmonary artery — puts strain on heart and increases pulmonary blood pressure

Immediately after birth, most portal blood flows through the __________ Describe closure of this structure

Ductus venosus [within 1-3 hours, the muscle wall of ductus venosus contracts and closes; portal venous pressure rises, forcing venous blood through liver sinuses]

Neonatal HR

100-150 bpm (higher in premature neonate)

Neonatal BP

During 1st day after birth: 70/50 After few months increases to 90/60 Adult pressure is attained during adolescence 115/70

Neonatal respiratory rate

~40 breaths/min

Neonatal metabolism

2x adult

Neonatal kidneys

Immature — functional development is not complete until end of 1st month of life High fluid turnover rate (rate of fluid intake and fluid excretion relative to weight is 7x greater than in adult) Rapid acid formation — can only concentrate urine to only 1.5x osmolality of plasma (adult can concentrate urine to 3-4x plasma osmolality); problems with acidosis and dehydration

Erythropoiesis pathway

Multipotent hematopoietic stem cell Common myeloid progenitor Proerythroblast Basophilic erythroblast Polychromatic erythroblast Orthochromatic erythroblast Polychromatic erythrocyte Erythrocyte (RBC)