Cardiopulmonary Embryology and Fetal Development Flashcards
what are the timelines of trimesters and pulmonary development
1st: 0-12
2nd: 13-27
3rd: 28-40
Embryonic: 3-6
Pseudoglandular: 7-16
Canalicular: 17-27
Saccular: 28-35
Alveolar: 36-2yrs
germ layers and structures formed
Endoderm - pulmonary, GI systems
Mesoderm - CT, bone, mm, some organs (CV system), pleura, pericardium, ovaries, GU tract
Ectoderm - CNS, PNS, glands, nerves, skin, hair
what week and stage does immature surfactant appear? from what type of alveolar cells?
when does mature surfactant appear?
Immature: Week 24, Type II cells
Mature: week 35
7 factors that affect fetal lung growth
- amniotic fluid and changes
- fetal lung fluid
- fetal breathing
- altered metabolism
- chest wall compression
- genetics
- maternal behaviours
amounts of amniotic fluid at various points
3 wks - first drop
8 wks - 7mL
16 wks - 200mL
25 wks - 400mL
Term - average 1L
functions of amniotic fluid
- protection
- thermoregulation
- movement/muscular-skeletal development
- lung development/stretch
causes of oligohydramnios
- birth defects/congenital abnormalities
- uretoplacental insufficiency (resulting in poor perfusion to fetal kidney)
- leaky amniotic fluid d/t PROM/P-PROM
- dehydration
- post-dates baby
- twin-twin transfusion
- NSAIDS/ACE inhibitors
effects of oligohyramnios
- low AF leads to less fetal lung fluid production resulting in less lung stretch leading to pulmonary hypoplasia
- less buffering against mechanical restrictions on the chest wall which can lead to fetal adhesion of body parts or uterine wall/umbilical cord compression
- miscarriage/premature labour
causes of polyhydramnios
- inability to swallow AF d/t CNS (micro/anecephaly, myotonic dystrophies) or orogastric issues (TEF, pyloric stenosis, Down’s syndrome)
- fetal anemia
- gestational diabetes or IDDM
- infection
- twin-twin transfusion
- multiple gestation
effects of polyhydramnios (if severe)
- maternal dyspnea/swelling of extremities; severe bleeding after delivery
- easy labour/prematurity
- fetal malposition
- PROM
- placental abruption
- umbilical cord prolapse
fetal lung fluid properties and composition
- helps develop develop size and shape of lungs (FRC, airway patency, air spaces)
- 250-300mLs/day starting week 6
- high NaCl, some components of surfactant; lower pH, HCO3 and K+ proteins than amniotic fluid
causes of altered metabolic rate (pre + postnatal)
prenatal: hypoxia, starvation/malnutirion, connective tissue issue
post natal: BPD (o2 toxicity)
Causes of chest wall compression on fetal lung
- physical obstruction (fibroid)
- diaphragmatic hernia
- chest wall abnormalities (pectus excavatum)
- hydrops fetalis (hydrothorax, edema, ascites)
Septum Primum
- septum primum: first thin wall (day 28) divides common atrial chamber
- foramen primum becomes foramen secundum
- septum secundum: second thicker parallel wall grows off septum primum (day 33); has hole called foramen vale
- septum primum is one way flap allowing maternal o2 to bypass the fetal lungs
ASD vs VSD cause
ASD: failure of fossa ovals fusion after birth, or atrial separation abnormalities
VSD: membrane fails to rm completing separation of ventricles
how do the aorta and PA form? when?
twisting of trunks arterioles creates septum which eventually forms aorta and pulmonary arteries
