Download Pediatric and Neonatal Respiratory Care Embryologic Development

Pediatric and Neonatal
Respiratory Care
Embryologic Development
Mary P. Martinasek, BS, RRT
Overview
Introduction
 Development of the Pulmonary System
 Development of the Cardiovascular System
 Fetal Circulation
 Development of Other Intrauterine
Structures

Introduction
 General
Fetal Development
Ovum
 Embryo
 Fetus
 Cellular Development

Germ Layers of the Embryo
Endoderm
 Respiratory Tract
 Mesoderm
 Ectoderm

General Development
Endoderm
Mesoderm
Ectoderm
Respiratory
Tract
Dermis and
Muscles
Epidermis, Hair,
and Nails
Digestive Tract,
Bladder and
Thyroid
Liver and
Pancreas
Bone,
connective and
lymph tissue
Reproductive &
Cardiovascular
System
Lens of Eye and
Skin Glands
Central and
Peripheral
Nervous System
Development of the
Pulmonary System
Embryonic
Period
Pseudoglandular Period
Canalicular Period
Saccular and Alveolar Period
Embryonic Period
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From Conception to 46 weeks gestation
Development of
proximal airways
0-24 days one central
tube
24 days - primitive
lung bud appears
Embryonic Period (continued)




26-28 days form right
and left lung buds
Primitive airways
progress in dividing
Lobar bronchi - day 31
diaphragm starts and
is completely
developed by 8th
week
Pseudoglandular Period

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7-16 week gestation
development of
conducting airways
7th week - epiglottis
formation starts
7th week - choana
disintegrates and
palates development
begins
Pseudoglandular Period (cont.)


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8th week - vocal cord
development begins
Lung resembles gland
Dichotomy results
11th week - cartilage
in airways appears
12th week - major
lobes identifiable
Pseudoglandular Period (cont.)



13th week - goblet
cells form
13th-24th week
bronchial glands
develop
10 week - ciliated cells
start to appear
Canalicular Period
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17-24 weeks gestation
Development of
acinus
Tremendous amount
of vasularization
Outpouchings appear
on wall of bronchioles
Canalicular Period (continued)


Two types of cells
start to differentiate
Capillaries present but
too far away from
alveolar cavity
Saccular (Alveolar) Period



24th week - birth
Development of gas
exchange units
25th-26th week
alveolar-capillary
membrane able to
sustain extrauterine
life
Saccular Period (continued)



28-29th week
terminal sacs line with
mature Type II cells surfactant appears
34-36th week
mature alveolar
structure evident
approximately 55
million alveoli (10 m2)
Surfactant

Composition
 Phospholipids and Protein
Phosphoatidylcholine (Lecithin) – Major
surfactant appears at 18 weeks and peaks at 38
weeks
Sphingomyelin – Surfactant found in the
amniotic fluid (decreases after 30 weeks)

Production
 Secreted by Type II Alveolar Cells
Fetal Lung Fluid

Composition
 Different than amniotic fluid
 Decreased levels of bicarbonate and
protein
 Increased levels of Sodium and Chloride
Fetal Lung Fluid cont.

Function: Maintain patency
Term = 20-30 ml/kg in lungs
Production decreases days prior to clinical
detection of labor
Hazards of Retention
TTN – Transient tachypnea of the newborn
 May present as RDS
 Grunting, flaring and retracting (GFR)

Determination of Lung Maturity
Shake (Foam) Test
 LS ratio (Lecithin to sphingomyelin ratio)
 Lungs mature when 2:1 (35 weeks)
 PG detection (Phosphatidylglycerol)
 Lipid
 Absent until about 35 weeks gestation

Lung Maturity Cont.
FLM or FP Assay – Fluorescence
Polarization
 Surfactant to Albumin
 Quick and Reliable
 Lung Profile
 L:S and PG detection

Conditions that Delays
Surfactant Production
 Acidemia
 Mechanical
Ventilation
 Hypercapnia
 Shock
 Maternal
 Overinflation
Diabetes
(A,B,C)
 Underinflation
 Smaller of Twins
 Pulmonary Edema
 Hypoxia
Conditions that Accelerate
Surfactant Production
Maternal diabetes
(D, F, and R)
 Maternal heroin
addiction
 Premature rupture of
membranes
 Maternal
hypertension

Maternal infection
 Placental
insufficiency
 Betamethasone or
thyroid hormone
 Abruptio placentae

Development of the
Cardiovascular System
Development of Cardiovascular System


3rd week - two tubes
surrounded by
myocardial tissue
Tubes fuse form single
chamber
Development of Cardiovascular System
(continued)
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4th week - heart
begins to beat
Heart begins to twist
and fold
Eventually will form
four chambers
Development of Cardiovascular System
(continued)

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Sinus venosus - horns
at bottom of
embryonic heart - will
become vena cava’s
and portion of right
atrium
Truncus arteriosus will form pulmonary
artery and aorta
Development of Cardiovascular System
(continued)
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Bends in middle - S
shape
Rapid growth
Development of
chambers
Blood flow begins one way flow
Development of Cardiovascular System
(continued)
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5th week - heart takes
on shape of adult heart
Developing veins and
arteries couple the
heart to circulatory
system
Separate blood paths
created
Development of Cardiovascular System
(continued)


Four chambers formed
with openings between
the atria and the
ventricles
Truncus arteriosus
allows blood to exit
right ventricle
Fetal Circulation

Pressure in the fetal vasculature
 Systemic – Low resistance
 Placental – Low resistance
 Pulmonary – High resistance
Characteristics of Fetal
Circulation

Normal shunts in the fetus
 Foramen ovale – bypasses lung
 Ductus arteriosus – bypasses lung
 Ductus venosus – bypasses liver
Fetal Circulation
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Flow chart of the most
oxygenated fetal blood
Bypasses liver ductus venosus
Bypasses lungs foramen ovale
Fetal Circulation (continued)
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Flowchart of
least oxygenated
fetal blood
Small amount
feed lungs (high
resistance)
Most bypasses
lungs - ductus
arteriosus
Development of Intrauterine
Structures
Placenta
 Umbilical cord
 Amnion
 Amniotic fluid

Placental Development
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Placenta organ of
respiration for fetus
Umbilical arteries carry
unoxygenated blood from
fetus
Intervillous space acts as
alveolar-capillary
membrane
Umbilical vein carries
oxygenated blood to fetus
Umbilical Cord
Life line
 Wharton’s Jelly
 2 arteries and 1 vein

Amnion
Sac surrounding fetus containing amniotic
fluid
 Possible rupture can occur in utero

Amniotic Fluid
1 liter at term
 Constantly recirculated and replenished
through lung fluid and urination
 Amount of fluid depends on recirculation

Function of Amniotic Fluid
Thermoregulation
 Facilitation of movement

Amniotic Fluid Abnormalities

Polyhydramnios – large amount of amniotic
fluid ( greater than 200cc’s)
 Causes:
 CNS malformation
 Orogastric malformation
• Esophageal atresia
• Pyloric stenosis
Abnormalities Cont.

Causes of polyhydramnios cont.
 Down’s syndrome, CHD, IDM, and
prematurity
Amniotic Fluid Abnormalities
Cont.

Oligohydramnios – decreased amount of
amniotic fluid
 Usually defect in urinary system
 Renal agenesis (Potter’s syndrome)
 Urethral stenosis
 Risk of asphyxia due to cord compression
 Possible skeletal deformities