Embryology Flashcards
Parts of the upper respiratory tract
Nasal cavity
Pharynx
Larynx
Parts of the lower respiratory tract
Trachea
Bronchi
Lungs (bronchioles to alveoli)
Which portions of the lower respiratory tract can actually take part in gas exchange
Respiratory bronchioles
Alveolar duct
Alveolus
Gas exchange (oxygen and CO2) are exchanged between blood and air in the…
alveoli
In order for gas exchange to occur, the alveoli must be….
really thin
Lipid layer that lines the lumens of alveoli; keeps surface tension low to they don’t collapse (atelectasis)
surfactant
Collapse of alveoli; can be caused by loss/absence of surfactant; causes respiratory distress
atelectasis
From which germ layer does the respiratory system arise from (ecto-, endo- or meso-)
Endoderm
The lower respiratory tract arises from what part of the early GI tract?
anterior diverticulum (specifically, pharynx/upper esophagus)
At what week does the lower respiratory tract arise from the anterior diverticulum?
Week 4
The lower respiratory tract develops in what direction (caudal vs. cranial)?
Cranial to caudal (alveoli are last to form)
How many “generations” of branching of the airway are there?
23
Which structures of the respiratory system are the last to form?
Alveoli
There is respiratory function in utero because the fetus makes respiratory movements (True or False)
False; fetus does “breathe” amniotic fluid, but the movement is necessary for normal lung development (but no gas exchange occurs)
Gas exchange for the fetus occurs in the…
placenta
vascular structure formed by the embryo; where gas exchange occurs for the fetus; no mixing of fetal and maternal blood occurs
Placenta
The placenta allows for gas exchange via the mixing of fetal and maternal blood supplies (True or False)
False
What properties of the alveoli help promote gas exchange
Thin walls
Surfactant
How many weeks constitutes a full-term fetus?
38 weeks
What week do primitive, thick-walled alveoli begin to develop?
Week 22
What week does surfactant begin to be produced?
Week 24
Premature infants with underdeveloped lungs can be given artificial surfactant to aid in respiratory function (True or False)
True
What defines a “premature” baby?
at least 3 weeks before due date
congenital anomaly; arises early (4-7 weeks); an abnormal opening of the esophagus into the trachea; can present with polyhydramnios (excessive amniotic fluid), choking, coughing, cyanosis and vomiting
Tracheoesophageal fistula
Most common form of tracheoesophageal fistulas
Type C (proximal esophagus terminates, and distal is connected with trachea)
Possible symptoms of tracheoesophageal fistulas (in utero and after birth)
in utero: polyhydramnios (excess amniotic fluid)
after birth: choking, coughing, cyanosis and vomiting
congenital anomaly; hole in posterolateral diaphragm, usually on left; abdominal organs can herniate into thorax, especially the small intestine; can crowd the lungs and heart, resulting in malformed lungs (hypoplasia) and pulmonary hypertension
Congenital Diaphragmatic Hernia (CDH)
Potential complications with congential diaphragmatic hernia
Pulmonary hypoplasia
Pulmonary hypertension
Life threatening breathing difficulties
Fetal cardiopulmonary physiology
Relative hypoxic environment (compared to mom)
Fetal shunts
Fetal lungs produce fluid
Erythropoiesis shifts from liver to bone marrow
Steps for fetal cardiopulmonary transition prior to the onset of labor
Lung maturity (surfactant)
Absorb lung fluid
Inc. blood oxygen content
Loss of placental circulation
Fetal shunts
Ductus venosus (bypass liver) Ductus arteriosus (bypass lungs) Foramen ovale (RA to LA)
Pulmonary circulation oxygen saturation in fetuses
~55%
When does cortisol peak during gestation
30-36 weeks
What does the cortisol peak do during gestation?
Influences angiogenesis and matures parenchyma; enhances clearance of lung fluid and production of surfactant
Secretion of fetal lung fluid begins at what week of gestation?
~6th week
How does the fetal lung secret fluid?
Produced by active secretion of chloride, creating an osmotic gradient
Why does preterm labor and c-section delivery result in fluid retention in lungs?
Fetal lung clearance begins several days before labor. Failure of normal absorption results in respiratory distress
Fetal lung fluid is cleared and drained via ___________ circulation
pulmonary
Ion transporter involved in fetal lung fluid reabsorption shortly before labor
ENaC (moves Na in, which also draws Cl and water in as well)
How might the presence of fetal lung fluid help the first breath?
By establishing a lower opening pressure
When does the ductus venosus close?
1 week after birth
When does the ductus arteriosus close?
4-8 weeks after birth
When does the foramen ovale close?
months to years after birth
How long does it take for an average baby to reach 90% oxygen saturation after birth (in minutes)
~5-6 minutes
Why might it be detrimental to clamp the umbilical cord before the baby has the chance to establish ventilation?
Causes dec. venous return
Cardiac output dec.
Systemic BP increases to compensate
Low pulmonary blood flow
congenital anomaly; most common developmental lesion of the respiratory tract; previously known as congenital cystic adenomatoid malformation
Congenital Pulmonary Airway Malformation (CPAM)
- previously known as CCAM
When does CPAM often diagnosed in the US?
weeks 18-22 gestation
Blind pouch/tube
diverticulum
