UNSW Embryology
Respiratory Development
© Dr Mark Hill (2008)
Introduction
The respiratory system does not carry out its physiological function (of gas exchange) until after birth. The respiratory tract, diaphragm and lungs do form early in embryonic development.
Lung buds (stage 13)
Lungs (stage 22) |
Fetal lung histology (Image: Lutz Slomianka, UWA Blue Histology) |
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In
the head/neck region, the pharynx forms a major
arched cavity within the phrayngeal arches. The
lungs go through 4 distinct phases of development
and late in foetal development respiratory motions
and amniotic fliud are thought to have a role in
lung maturation.
Development of this system is not completed until the last weeks of Fetal development, just before birth. Therefore premature
babies have difficulties associated with insufficient surfactant (end month 6 alveolar cells type 2 appear and begin to secrete surfactant).
Page Links: Introduction | Reading | Computer
Activities | ObjectivesLearning
activities | Development Overview | Stage 13 Overview
| Glossary | Respiratory Terms | References
Some Recent Findings
Shu W, Lu MM, Zhang Y, Tucker PW, Zhou D, Morrisey EE.
Foxp2 and Foxp1 cooperatively regulate lung and esophagus development. Development. 2007 May;134(10):1991-2000.
(More? Respiratory Molecular Development)
Cardoso WV, Lu J.
Regulation of early lung morphogenesis: questions, facts and controversies. Development. 2006 May;133(9):1611-24.
"During early respiratory system development, the foregut endoderm gives rise to the tracheal and lung cell progenitors.
....Here, we review early stages in lung development and highlight questions and controversies regarding their molecular regulation."
Harris KS, Zhang Z, McManus MT, Harfe BD, Sun X.
Dicer function is essential for lung epithelium morphogenesis.
Proc Natl Acad Sci U S A. 2006 Feb 14;103(7):2208-13.
"DICER is a key enzyme that processes microRNA and small interfering RNA precursors into their short mature forms, enabling them to regulate gene expression.
Only a single Dicer gene exists in the mouse genome, and it is broadly expressed in developing tissues.
Dicer-null mutants die before gastrulation.......leading us to propose that Dicer plays a specific role in regulating lung epithelial morphogenesis independent of its requirement in cell survival."
Reading
- Human Embryology (2nd ed.) Larson
Ch6: p127-149
- The Developing Human: Clinically Oriented
Embryology (6th ed.) Moore and Persaud Ch11:
p226-233
- Before we Are Born (5th ed.) Moore and
Persaud Ch12; p241-254
- Essentials of Human Embryology Larson Ch6
p81-96
- Human Embryology Fitzgerald and Fitzgerald
Ch18 p113-118
- Additional References- Selected,
Lung
Development, Respiratory
Development
- Search PubMed-
Medline
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 |
Objectives
- Describe the development of the respiratory
system from the endodermal and mesodermal
components.
- Describe the main steps in the development
of the lungs.
- Describe the development of the diaphragm
and thoracic cavities.
- List the respiratory changes before and
after birth.
- Describe the developmental aberrations
responsible for the following malformations:
tracheo - oesophageal fistula (T.O.F);
oesphageal atresia; diaphragmatic hernia; lobar
emphysema.
Learning activities
- Summarise the changes in the respiratory
system and the C.V.S. at birth.??
- To discuss the main features of
physiological maturation of the lung and the
importance of this to fetal and newborn
viability.
- Examine the serial sections of human and pig
with reference to the respiratory system.
- Discuss the selected malformations; tracheo
- oesophageal fistula (T.O.F.) diaphragmatic
hernia and lobar emphysema giving special
reference to the developmental aberrations
causing the malformations to the
individuals
Stage 13/14 Cross Sections
Note: Click on the small cross-section extract to view entire section.
Developmental Overview
Week 4 - laryngotracheal groove forms on floor foregut.
Week 5 - left and right lung buds push into the pericardioperitoneal canals (primordia of pleural cavity)
Week 6 - descent of heart and lungs into thorax. Pleuroperitoneal foramen closes.
Week 7 - enlargement of liver stops descent of heart and lungs.
Month 3-6 - lungs appear glandular, end month 6 alveolar cells type 2 appear and begin to secrete surfactant.
Month 7 - respiratory bronchioles proliferate and end in alveolar ducts and sacs.
Lung Development 4 histological periods
- 5-17 week pseudoglandular
- 16-25 week canalicular
- 24-40 week terminal sac
- late fetal-8years alveolar
Diaphragm 5 elements contribute to the diaphragm (More? Respiratory - Diaphragm | Musculoskeletal System - Muscle)
- septum transversum- central tendon
- 3rd to 5th somite- musculature of
diaphragm
- ventral pleural sac- connective tissue
- mesentry of oesophagus- connective tissue
around oesophasus and IVC
- pleuroperitoneal membranes- connective
tissue around central tendon
Blood Supply
- pulmonary system not "functional" until after birth
- 6th aortic arch arteries generate pulmonary arteries
- veins drain into pulmonary vein then left atrium
- branches from dorsal aorta generate bronchial arteries
References
Reviews
Cardoso WV, Lu J.
Regulation of early lung morphogenesis: questions, facts and controversies. Development. 2006 May;133(9):1611-24.
Warburton D, Bellusci S, De Langhe S, Del Moral PM, Fleury V, Mailleux A, Tefft D, Unbekandt M, Wang K, Shi W.
[See Related Articles]
Molecular mechanisms of early lung specification and branching morphogenesis.
Pediatr Res. 2005 May;57(5 Pt 2):26R-37R.
Kumar VH, Lakshminrusimha S, Abiad MT, Chess PR, Ryan RM.
[See Related Articles]
Growth factors in lung development.
Adv Clin Chem. 2005;40:261-316. Review.
Groenman F, Unger S, Post M.
[See Related Articles]
The molecular basis for abnormal human lung development.
Biol Neonate. 2005;87(3):164-77. Epub 2004 Dec 9. Review.
Chinoy MR.
[See Related Articles]
Lung growth and development.
Front Biosci. 2003 Jan 1;8:d392-415. Review.
[No authors listed]
[See Related Articles]
Surfactant replacement therapy for respiratory distress syndrome. American Academy of Pediatrics. Committee on Fetus and Newborn.
Pediatrics. 1999 Mar;103(3):684-5.
O'Rahilly R, Tucker JA.
[See Related Articles]
The early development of the larynx in staged human embryos. I. Embryos of the first five weeks (to stage 15). Ann Otol Rhinol Laryngol. 1973 Sep-Oct;82:1-27.
Selected Lists of References from PubMed March 1999 search results are available for Department of Anatomy computers without internet access. Computers with internet access can
search from either Selected Research Articles and Reviews | Respiratory/development/review/5year limit" | "Lung development/review/5year limit"
Search PubMed Now: term= lung+development |
diaphragm+development |
pulmonary+development (Requires internet connection)
Glossary of Terms
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Respiratory Terms
- atresia obstruction.
- eppiglottis develops from
hypobrachial eminence.
- fistula abnormal comunication.
- hypopharyngeal eminence fusion of
3rd pharyngeal arches, precursor of root of
tongue.
- laryngotracheal groove forms on
anterior (ventral) wall of pharynx, gives rise
to larynx, trachea, respiratory tree.
- larynx lining from endoderm,
cartilage from pharyngeal arch 4 and 6.
- lung buds primordia of lungs.
- parietal pleura outer lining of
pleural cavity derived from epithelia of
pericardioperitoneal canals from intraembryonic
coelom.
- pleural cavity walls derived from
pericardioperitoneal canals -> intraembryonic
coelom ->coelomic spaces -> lateral
mesoderm -> mesoderm.
- pleuropericardial fold restricts the
communication between pleural cavity and
pericardiac cavity, contains cardinal vein and
phrenic nerve.
- pleuroperitoneal membrane forms
inferiorly at transverse septum to separate
peritoneum from pleural cavity.
- septum transversum mesoderm
separating thoracic cavity and yolk sac, forms
central tendon of diaphragm (and some of
liver?).
- stenosis narrowing
- surfactant a detergent secreted by
Type 2 alveolar cells between alveolar
epithelium. Functions to lower surface tension,
allowing lungs to remain inflated.
- visceral pleura inner lining of
pleural cavity derived from contact epithelia
with lung bud of pericardioperitoneal canals
from intraembryonic coelom.
UNSW Embryology ISBN: 978 0 7334 2609 4
UNSW CRICOS Provider Code No. 00098G
Comments
The respiratory system is an very interesting developing system at many different levels.
Firstly, in not carrying out its physiological function (gas exchange) prenatally. The lungs also continue to
grow for about 8+ years postnatally.
Secondly, while the respiratory tract and aveolar epithelium are endoderm in origin (with mesoderm contributing surrounding tissue) many other tissues/systems are involved
in respiratory function: musculoskeletal (ribs and diaphragm) cardiovascular (pulmonary circulation). The musculoskeletal
begins functioning prenatally, the cardiovasular pulomonary circulation is activated and altered postnatally.
Thirdly, lung development goes through 4 stages, the final stage (type 2 surfactant secretion) only occurs in the final weeks of development.
This means that premature infants have respiratory difficulties due to the still immature respiratory system. More recently, this has
been treated in these infants with humidicribs and various surfactant therapies.
Please email Dr Mark Hill if you wish to make a comment about this current project.
