Embryology Flashcards
Define Fetus
unborn offspring that develops from an embryo
Define neonate
A baby that is less than 4 weeks old
Define infant
Infancy is the period from birth until 2 years of age
Define zygote
fusion of egg and sperm
What does the zygote become once there are more than 16 cells?
Morula
When does the yolk sac develop?
approximately 3 weeks after implantation
What are the 3 layers of the blastocyst?
- Ectoderm
- Endoderm
- Mesoderm
What is gastrulation?
An early developmental process in which an embryo transforms from a one dimensional layer of epithelial cells and reorganizes into a multilayered and multidimensional structure
What group of cells do the lungs originate from?
the endoderm
Which portion of the gut tube do the lungs come from?
The lungs, esophagus, trachea and respiratory tract derive from the midgut
What are the 5 stages of fetal lung development?
- Embryonic
- Pseudoglandular
- Canalicular
- Saccular
- Alveolar
What is the time frame for embryonic lung development?
0-8 weeks
What is the time frame for pseudoglandular lung development?
8-16 weeks
What is the time frame for canalicular lung development?
16-26 weeks
What is the time frame for saccular lung development?
26-36 weeks
What is the time from for alveolar lung development?
36+
When are fetal breathing movements detected?
Can be detected as early as 10 weeks
When are fetal breathing movements strong, organized and consistent?
30-40 weeks
T/F: Fetal lungs are collapsed
False, fetal lungs are fluid filled
How much fluid is produced by fetal lungs per day?
250-300 ml
What occurs in the embryonic stage of lung development?
Lung buds, trachea, bronchi and central bronchial arteries are formed
What occurs in the pseudoglandular stage of lung development?
- Formation of terminal bronchioles
- branching of bronchopulmonary trees as far as terminal bronchioles
- Formation of Cilia
- Mucus production
- Vascular branching of arteries and veins alongside airways
When do the Cilia form?
in the pseudoglandular stage of lung development
When are the terminal bronchioles formed?
In the pseudoglandular stage of lung development
What occurs in the Canalicular stage of lung development?
- Development of primitive acini
- Appearance of Type 1 and 2 pneumocytes with lamellar bodies
- Surfactant production
- Formation of air blood barrier
T/F: Respiration is possible in the pseudoglandular stage?
False
T/F: Respiration is possible in the canalicular phase
True
What occurs in the saccular stage?
- Formation, growth and branching of terminal saccules
- Growth in number of lamellar bodies
- Increase in Surfactant production
- Growth of capillary networks around saccules
- Formation of conducting and respiratory bronchioles completed
In what stage do the capillary networks begin to form around saccules?
Saccular stage
What occurs in the alveolar stage?
- Formation and maturation of alveoli
- Increased growth in diameter and number of alveoli
At what stage is extrauterine viability possible and why cant it occur sooner?
- Canalicular
- The fetus is not viable because surfactant production has not begun, the fetus is incapable of respiration, and the airways are not developed enough yet
Describe type 1 pneumocytes
- Squamous cells
- thin for gas exchange/diffusion
- 97% of alveolar surface area
Describe type 2 pneumocytes
- Cuboidal cells
- Production, storage, secretion and reuse of surfactant
- Houses lamellar bodies which store surfactant
How can we assess fetal lung development?
- L/S ratio
- Lamellar body Count
- PG?
- PC/DPPC
What aspects can stimulate surfactant secretion?
Andosine
Mechanical stretch
Hormones
What are the proteins that make up surfactant?
- DPPC
- Protein A (SP-A)
- Protein D (SP-D)
- Protein B SP-B)
- Protein C (SP-C)
What is the most abundant phospholipid in surfactant?
DPPC aka Lecithin
What is the function of protein A?
- Regulates synthesis and secretion of phospholipids
- Promotes bacterial and viral clearance
What is the function of protein D
Promotes bacterial and viral clearance
