Transcript PHYSIOLOGY OF THE NEWBORN

PHYSIOLOGY OF
THE NEWBORN
Belen Amparo E. Velasco, M.D.
The fetus has a recognizable human form
by the 12th week of development.
The vital organs are not sufficiently
developed to sustain life outside the uterus until
the seventh month. While in the womb, the
fetus is especially susceptible to the effects of
drugs, alcohol, and X rays.
"Human Fetus."Microsoft® Encarta® Encyclopedia 2001. © 1993-2000 Microsoft
Corporation. All rights reserved.
CIRCULATORY SYSTEM
FETAL CIRCULATION
Presence of 3 shunts:
Patent foramen ovale
Patent ductus arteriosus
Patent ductus venosus
CIRCULATORY SYSTEM
FETAL CIRCULATION
OXYGENATED BLOOD FROM MATERNAL BLOOD:
PLACENTA (Clearing house)

Umbilical vein  Ductus venosus  liver 
hepatic veins  Inferior vena cava

Superior vena cava  Right auricle  foramen ovale
 left auricle  left ventricle
 ascending aorta

CIRCULATORY SYSTEM
FETAL CIRCULATION
UNOXYGENATED BLOOD:
 Right ventricle  pulmonary artery  lungs

ductus arteriosus  descending aorta
CIRCULATORY SYSTEM
CHANGES AT BIRTH  ADULT TYPE OF
CIRCULATION
Cessation of placental circulation
Physiologic closure of foramen ovale ( L atrial
pressure)
Functional closure of patent ductus arteriosus (O2
content)
RESPIRATORY SYSTEM
FETAL LUNGS
Filled with respiratory (filtrate of plasma) fluid
Metabolic functions;
Production of surfactant
Occasional gasps
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
RESPIRATORY SYSTEM
NEWBORN LUNGS
Establishment of FRC to permit gas exchange even
during expiration
Alveolar structure
Periodic breathing with apneic pauses in premies
GASTROINTESTINAL SYSTEM
FETAL GI SYSTEM
Swallowing as early as the 12th week of gestation
Absence of excretion via the GIT unless with sphincter
relaxation during hypoxic event.
Accumulation of epithelial debris and conjugated
bilirubin in small intestine
GASTROINTESTINAL SYSTEM
NEWBORN GI SYSTEM
Passage of meconium (mixture of epithelial debris &
mucopolysaccharide with conjugated sbilirubin) within the
1st 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
RENAL SYSTEM
FETAL RENAL SYSTEM
Production of urine as early as 4th month
Renal function (GFR, tubular mass and RPF) not reach
adult levels till 2nd year of life
Glomerular filtration begins at about 9 weeks
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 and
pyruvic acid.
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
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
CENTRAL NERVOUS SYSTEM
NEONATAL BRAIN
Soft spots on a baby’s
head, called fontanels, are
areas that have not yet
hardened to bone.
The skull is subjected to
great pressure as it passes
through the birth canal. Were
it inflexible, the tight squeeze
might injure the brain.
Growth is complete by
one year of age, and lines
called sutures are visible
where the plates fuse.
CENTRAL NERVOUS SYSTEM
SPECIFIC REACTIONS:
Moro reflex
Grasp reaction
Tonic and righting reflex
Rooting, sucking, tongue retrusion and
swallowing reflexes
CENTRAL NERVOUS SYSTEM
RESPONSE
stereotyped
TO
STIMULI:
Simple
and
SENSES:
Regards moving objects & changing light
intensity
Hears loud sound
ENDOCRINE SYSTEM
FETAL ENDOCRINE SYSTEM
The pituitary adrenal axis and thyroid gland
function separately from that of the mother to ensure
adequate growth of infant.
Peculiarities in the fetus:
Maternal estrogenic effects
urinary 17-ketosteroids
PITUITARY GLAND
ENDOCRINE SYSTEM
NEONATAL ENDOCRINE SYSTEM
MATERNAL ESTROGENIC EFFECTS
Hypertrophied mammary glands
Witch milk
Mucoid to bloody vaginal discharge
ENDOCRINE SYSTEM
NEONATAL ENDOCRINE SYSTEM
NEONATAL OUTCOME IN MATERNAL DIABETES
Immaturity of lungs – Hyaline membrane disease
Hypoglycemia
Hypocalcemia
Anomalies: Ventricular septal hypertrophy
Microcolon
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 hemoglobin is as high as 20g/dl
Blood formation as early as 3rd wk after conception:
Mesodermal tissue in the 1st month
Liver in the 2nd month
Medullary spaces from the 6th month onward
HEMATOLOGIC SYSTEM
NEOWBORN HEMATOPOIETIC SYSTEM
At birth, still with high hgb. Starts to drop on the 3rd day
of life until a minimum of 10-12g/dl on the 2nd-3rd month of
life – PHYSIOLOGIC ANEMIA - a result of the following:
 in bone marrow activity
 in 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
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
IMMUNOLOGIC SYSTEM
NEWBORN IMMUNE SYSTEM
Considered completely developed immunological system
but with inadequate antigenic stimulus
IMMUNOLOGIC SYSTEM
NEWBORN IMMUNE SYSTEM
Antibodies (maternal in origin) present – 7s or IgG
antibodies
Tetanus antitoxin
Diphtheria antitoxin
Smallpox agglutinins
Antistreptolysin
Toxoplasma antibodies
Salmonella H antibodies
Rh blocking antibodies
IMMUNOLOGIC SYSTEM
NEWBORN IMMUNE SYSTEM
Antibodies absent – 19s gammaglobulins
Streptococcus agglutinins
H. influenza antibodies
Blood 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
T lymphocytes are specialized white blood cells
that identify and destroy invading organisms such as
bacteria and viruses. Some T lymphocytes directly
destroy invading organisms, whereas other T
lymphocytes regulate the immune system by
directing immune responses.
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 activity
E. Depressed bone marrow activity due to
hyperoxia
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 right
auricle
E. Oxygenated blood from placenta supplies upper
half of body
Physiologic weight loss due to:
A. Polyuria
B. Diuresis
C. Adequate caloric intake
D. Retention of meconium
E. Transient metabolic acidosis