Pediatric and Neonatal Respiratory Care Embryologic Development
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Transcript 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
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
7-16 week gestation
development of
conducting airways
7th week - epiglottis
formation starts
7th week - choana
disintegrates and
palates development
begins
Pseudoglandular Period (cont.)
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
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)
4th week - heart
begins to beat
Heart begins to twist
and fold
Eventually will form
four chambers
Development of Cardiovascular System
(continued)
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)
Bends in middle - S
shape
Rapid growth
Development of
chambers
Blood flow begins one way flow
Development of Cardiovascular System
(continued)
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
Flow chart of the most
oxygenated fetal blood
Bypasses liver ductus venosus
Bypasses lungs foramen ovale
Fetal Circulation (continued)
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
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