Download Embryology of the Lungs

Embryology of the Lungs
By: Alessandro Cau, Howell Liu,
Gregory Jen
Overview of Presentation
1. Gastrulation and the Early Embryo
2. The Development of the Lungs
3. The Development of the Pulmonary Vasculature
4. The Embryonic Origins of the Diaphragm
5. Formation of the Chest Wall
Case Study: Brandon
• Weighed just 4 lbs 9oz
• Frothy, white bubbles in the
mouth.
• Coughing or choking when
feeding
• Vomits frequently
• Very round, full abdomen
• History of hydramnios
Image from https://thriving.childrenshospital.org/one-patients-story-our-babys-esophagealatresia-and-tracheoesophageal-fistula/
Gastrulation: Development of the Three
Primary Germ Layers
• Epiblast is lined by
ectoderm
• Cells along primitive
streak ingress to form
endoderm, then
mesoderm
• This results in a
trilaminar structure
System Differentiation Begins:
Formation of Notochord and Somites
There are 5 phases of lung development.
1. Embryonic phase (3 weeks-7 weeks)
2. Pseudoglandular phase (5 weeks-18 weeks)
3. Canalicular phase (16 weeks-26 weeks)
4. Saccular phase (24 weeks until 36 weeks)
5. Alveolar phase (36 weeks until 8 years after birth)
Image from http://embryology4genius.weebly.com/maturation-of-the-lungs.html
Body wall lateral folding
encloses foregut endoderm to
form the intra-embryonic coelom
(Weeks 3 to 4)
Image from https://www.pinterest.com/pin/282319470368880617/
Appearance of the sulcus
laryngotrachealis and lung
buds mark the beginning of
the embryonic phase.
(Weeks 3 to 7)
Image from https://pedclerk.bsd.uchicago.edu/page/tracheoesophageal-fistula
Differentiation of the
lung buds form the
bronchi and pulmonary
lobes during the
embryonic phase.
(Weeks 3 to 7)
Image from http://slideplayer.com/slide/5258408/
As the lung buds differentiate,
they punch into the intraembryonic coelom.
(Weeks 4 to 8)
Image from http://discovery.lifemapsc.com/library/review-of-medical-embryology
Appearance of cartilage,
smooth muscle and tall
ciliated columnar cells are
hallmarks of the
pseudoglandular phase.
(Weeks 5 to18)
Image from http://slideplayer.com/slide/5258408/
Progression into the
canalicular phase is
indicated by the
formation of canaliculi.
(Weeks 16 to 26)
Image from http://slideplayer.com/slide/5258408/
Growth of the bronchial
tree and the appearance
of sacculi, precursors to
alveoli, define the saccular
phase.
(Weeks 24 to 36)
Image from http://slideplayer.com/slide/5258408/
Alveolarization and the
formation of secondary
septa mark the alveolar
phase and continues after
birth.
(Week 36 to 8 years)
Image from http://slideplayer.com/slide/5258408/
Image from http://embryology4genius.weebly.com/maturation-of-the-lungs.html
Case Study: Brandon
• Weighed just 4 lbs 9oz
• Frothy, white bubbles in the
mouth.
• Coughing or choking when
feeding
• Vomits frequently
• Very round, full abdomen
• History of hydramnios
Image from https://thriving.childrenshospital.org/one-patients-story-our-babys-esophagealatresia-and-tracheoesophageal-fistula/
Improper separation of the trachea and
esophagus leads to tracheo-oesophageal
fistula (TOF).
Image from http://flylib.com/books/en/3.98.1.127/1/
Image from https://tefnormalanatomy.wordpress.com/
Pulmonary vasculature develops
concurrently with the lungs.
• The pulmonary
arteries and veins
develop separately
from the capillaries
• The capillaries
form from the
splanchnopleuric
mesoderm
The diaphragm is formed from four
different structures.
1. Septum Transversum
2. Paraxial Mesoderm
3. Esophageal Mesenchyme
4. Pleuroperitoneal Membrane
Embryology
Image from https://embryology.med.unsw.edu.au/
embryology/index.php/File:Diaphragm_components.jpg
Different structures of the chest wall have
different embryonic origins.
Vertebrae:
• Paraxial mesoderm forms somites
• Forms sclerotome  migrate and
divide to wrap around the notochord
Image from http://www.innerbody.com/anatomy/
skeletal/cervical-vertebrae-lateral
Muscle:
• Sclerotome leaves cells known as
dermamyotomes  dorsal and
intercostal muscles
Image from
http://www.eastwestmassageboston.com/interco
stal-ribcage-muscle-tension.html
The ribs and sternum ossify between 5-6
weeks of age.
Ribs
• Condensations of mesenchyme
near vertebrae extend and lay
down cartilage
• Bone forms through
endochondral ossification
Sternum
• Longitudinal mesenchymal
condensation lay down cartilage,
and endochondral ossification
occurs
Image from http://diseasespictures.com/sternum-pain/
Summary
• The development of the lungs consists of the embryonic,
pseudoglandular, canalicular, saccular and alveolar phases.
• Each stage is characterized by a few key events.
ie. the embryonic stage is defined by the formation of the lung buds.
• The pulmonary vasculature develops concurrently with the
lungs, but the critical stages are the embryonic and
pseudoglandular phases.
• The diaphragm forms from four different embryonic structures.
References
• Ryan, S. (2008). Embryology and Anatomy of the Neonatal Chest (pp.
1–10). http://doi.org/10.1007/978-3-540-33749-2_1.
• Warburton et al. (201). Lung Organogenesis. Curr Top Dev Biol 90: 73158. DOI: 10.1016/S0070-2153(10)90003-3.