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PHYSIOLOGY OFTHE NEWBORN

Belen Amparo E. Velasco M.D.

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The fetushas a recognizable human formby the 2th weekof development.

The vital organs are not sufficiently

developed to sustain life outside the uterus untilthe seventh month. While in the womb, thefetus is especially susceptible to the effects ofdrugs, alcohol, and X rays.

"Human Fetus."Microsoft Encarta Encyclopedia 2001. 1993-2000 MicrosoftCorporation. All rights reserved.

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CIRCULATORY SYSTEM

FETAL CIRCULATION

Presence of 3 shunts:

Patent foramen ovale

Patent ductus arteriosus

Patent ductus venosus

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CIRCULATORY SYSTEMFETAL CIRCULATION

OXYGENATED BLOOD FROM MATERNAL BLOOD:

PL CENT (Clearing house)Umbilical vein Ductus venosus liver

hepatic veins Inferior vena cavaSuperior vena cava Right auricle foramen ovale

left auricle left ventricle

ascending aorta

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CIRCULATORY SYSTEM

FETAL CIRCULATION

UNOXYGENATED BLOOD:

Right ventricle pulmonary artery lungsductus arteriosus descending aorta

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CIRCULATORY SYSTEM

CHANGES AT BIRTH ADULT TYPEOF

CIRCULATION

Cessation of placental circulation

Physiologic closure of foramen ovale ( L atrialpressure)

Functional closure of patent ductus arteriosus (O2content)

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RESPIRATORY SYSTEM

FETAL LUNGS

Filled with respiratory (filtrate of plasma) fluid

Metabolic functions;

Production of surfactant

Occasional gasps

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RESPIRATORY SYSTEM

NEWBORN LUNGS

Possess all equipment necessary for respiration incl.

chemoreceptors and baroreceptors

High negative intrathoracic pressure (10-70cms H2O)

Clearance of respiratory fluid with replacement by air

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RESPIRATORY SYSTEM

NEWBORN LUNGS

Establishment of FRC to permit gas exchange even

during expiration

Alveolar structure

Periodic breathing with apneic pauses in premies

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GASTROINTESTINAL SYSTEM

FETAL GI SYSTEM

Swallowing as early as the 12thweek of gestation

Absence of excretion via the GIT unless with sphincter

relaxation during hypoxic event.

Accumulation of epithelial debris and conjugatedbilirubin in small intestine

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GASTROINTESTINAL SYSTEM

NEWBORN GI SYSTEM

Passage of meconium (mixture of epithelial debris &

mucopolysaccharide with conjugated sbilirubin) within the1st 24 hours transitional stools (greenish soft stools) in

the next 4 days milk stools (normal pasty consistency

and yellow color)

Adequate levels of pancreatic enzymes except for

amylase and lipase

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RENAL SYSTEM

FETAL RENAL SYSTEM

Production of urine as early as 4thmonth

Renal function (GFR, tubular mass and RPF) not reach

adult levels till 2ndyear of life

Glomerular filtration begins at about 9 weeks

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RENAL SYSTEM

NEONATAL RENAL SYSTEM

Passage of dilute urine due to inability to concentrate

urine adequately

Transient metabolic acidosis due to inadequate removal

of acid ions, limited formation of NH3 for acid removal with

minimum loss of base and overproduction of lactic andpyruvic acid.

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RENAL SYSTEM

NEONATAL RENAL SYSTEM

6-10% physiologic weight loss(loss of body water)due to:Diuresis

Expulsion of meconium

Withholding of water and calories

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CENTRAL NERVOUS SYSTEM

FETAL CNS

Rapid growth of fetal brain during last half of

fetal life with peak near time of birth

Posture of late fetal flexion attitude

Generalized symmetric muscular activity

Simple & stereotyped response to various

environmental and internal stimuli

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CENTRAL NERVOUS SYSTEM

NEONATAL BRAIN

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Soft spots on a babys

head, called fontanels, areareas that have not yethardened to bone.

The skull is subjected togreat pressure as it passesthrough the birth canal. Wereit inflexible, the tight squeezemight injure the brain.

Growth is complete by

one year of age, and linescalled sutures are visiblewhere the plates fuse.

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SPECIFIC REACTIONS:

Moro reflex

Grasp reactionTonic and righting reflex

Rooting, sucking, tongue retrusion and

swallowing reflexes

CENTRAL NERVOUS SYSTEM

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RESPONSE TO STIMULI: Simple and

stereotyped

SENSES:

Regards moving objects & changing light

intensity

Hears loud sound

CENTRAL NERVOUS SYSTEM

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ENDOCRINE SYSTEM

FETAL ENDOCRINE SYSTEM

The pituitary adrenal axis and thyroid gland

function separately from that of the mother to ensureadequate growth of infant.

Peculiarities in the fetus:

Maternal estrogenic effectsurinary 17-ketosteroids

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PITUITARY GLAND

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ENDOCRINE SYSTEM

NEONATAL ENDOCRINE SYSTEM

MATERNAL ESTROGENIC EFFECTS

Hypertrophied mammary glands

Witch milk

Mucoid to bloody vaginal discharge

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ENDOCRINE SYSTEM

NEONATAL ENDOCRINE SYSTEM

NEONATAL OUTCOME IN MATERNAL DIABETES

Immaturity of lungsHyaline membrane disease

Hypoglycemia

Hypocalcemia

Anomalies: Ventricular septal hypertrophy

Microcolon

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HEMATOLOGIC SYSTEM

FETAL HEMATOPOIETIC SYSTEM

Erythropoietin: hormone produced in the glomerular

tuft responsible for the production of RBC

Due to relative hypoxia of the fetus stimulating the bone

marrow, the fetal hemoglobinis as high as 20g/dl

Blood formation as early as 3rdwk after conception:Mesodermal tissue in the 1stmonth

Liver in the 2ndmonth

Medullary spaces from the 6thmonth onward

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HEMATOLOGIC SYSTEM

NEOWBORN HEMATOPOIETIC SYSTEM

At birth, still with high hgb. Starts to drop on the 3rdday

of life until a minimum of 10-12g/dl on the 2nd-3rdmonth of

life

PHYSIOLOGIC ANEM IA- a result of the following:in bone marrow activityin rate of hemolysis

hemodilution due to rapid expansion of blood volume

Normal blood volume ranging from 80-90ml/kg

WBC ranging from 10,000-30,000/mm3 with PMN

predominance

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IMMUNOLOGIC SYSTEM

FETAL IMMUNE SYSTEM

Liver serves as the repository for lymphoid precursor

cells during early intrauterine life.

T cell functions begin as early as 7 weeks

Circulating B cells are seen as early as 13 weeks. IgM

antibodies are first to develop

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IMMUNOLOGIC SYSTEM

NEWBORN IMMUNE SYSTEM

Considered completely developed immunological system

but with inadequate antigenic stimulus

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IMMUNOLOGIC SYSTEM

NEWBORN IMMUNE SYSTEM

Antibodies (maternal in origin) present7s or IgG

antibodiesTetanus antitoxin

Diphtheria antitoxin

Smallpox agglutinins

Antistreptolysin

Toxoplasma antibodies

Salmonella H antibodies

Rh blocking antibodies

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IMMUNOLOGIC SYSTEM

NEWBORN IMMUNE SYSTEM

Antibodies absent19s gammaglobulins

Streptococcus agglutinins

H. influenza antibodiesBlood group isoagglutinins

Shigella antibodies

Poliomyelitis antibodies

Salmonella O antibodies

E. coli H and O antibodies

Less capacity to produce antibodies and lower ameboid

and phagocytic activities of neonatal leukocytes

susceptibility to infection esp of the preterm

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T lymphocytesare specialized white blood cellsthat identify and destroy invading organisms such asbacteria and viruses. Some T lymphocytes directlydestroy invading organisms, whereas other Tlymphocytes regulate the immune system bydirecting immune responses.

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Antibodies absent in the newborna.m EXCEPT:

A. Streptococcus agglutinins

B. H. influenza antibodies

C. Poliomyelitis antibodies

D. E. coli H and O antibodies

E. Tetanus antitoxin

Physiologic anemia:

A. Increased RBC turnover due to hemolysis

B. Decreased RBC turnover due to hyperoxia

C. Decreased blood volume expansion

D. Increased erythropoietic activityE. Depressed bone marrow activity due to

hyperoxia

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True of fetal circulation, EXCEPT:

A. Ductus arteriosus shunts blood from pulmonary

artery to aorta

B. Foramen ovale shunts blood from right to left

auricle

C. Ductus arteriosus shunts blood from right to left

side of heart

D. Foramen ovale shunts blood from left to rightauricle

E. Oxygenated blood from placenta supplies upper

half of body

Physiologic weight loss due to:

A. PolyuriaB. Diuresis

C. Adequate caloric intake

D. Retention of meconium

E. Transient metabolic acidosis

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