Respiratory System Development
- 1 Introduction
- 2 Some Recent Findings
- 3 Textbooks
- 4 Objectives
- 5 Embryonic Respiratory Development
- 6 Development Overview
- 7 Lung Histology
- 8 Movies
- 9 Molecular
- 10 References
- 11 Additional Images
- 12 Terms
- 13 Glossary Links
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. The respiratory tract is divided anatomically into 2 main parts: 1. upper respiratory tract, consisting of the nose, nasal cavity and the pharynx; 2. lower respiratory tract consisting of the larynx, trachea, bronchi and the lungs.
In the head/neck region, the pharynx forms a major arched cavity within the phrayngeal arches. The lungs go through 4 distinct histological phases of development and in late fetal 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).
|System Links: Introduction | Cardiovascular | Coelomic Cavity | Endocrine | Gastrointestinal Tract | Genital | Head | Immune | Integumentary | Musculoskeletal | Neural | Neural Crest | Placenta | Renal | Respiratory | Sensory | Birth|
Some Recent Findings
- Human Embryology Larson Chapter 9 p229-260
- The Developing Human: Clinically Oriented Embryology (6th ed.) Moore and Persaud Chapter 12 p271-302
- Before We Are Born (5th ed.) Moore and Persaud Chapter 13 p255-287
- Essentials of Human Embryology Larson Chapter 9 p123-146
- Human Embryology Fitzgerald and Fitzgerald Chapter 19,20 p119-123
- Anatomy of the Human Body 1918 Henry Gray 1. The Respiratory Apparatus
- 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.
Embryonic Respiratory Development
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 Stages
- week 4 - 5 embryonic
- week 5 - 17 pseudoglandular
- week 16 - 25 canalicular
- week 24 - 40 terminal sac
- late fetal - 8 years alveolar
|Fetal lung histology|
The animations below allow a comparison of early and late embryonic lung development. Compare the size and relative position of the respiratory structures and their anatomical relationship to the developing gastrointestinal tract.
|Early embryo (stage 13)
3 dimensional reconstruction based upon a serial reconstruction from individual Carnegie stage 13 embryo slice images.
|Late embryo (stage 22)
3 dimensional reconstruction based upon a serial reconstruction from individual embryo slice images Carnegie stage 22, 27 mm Human embryo, approximate day 56.
- Links: Flash Movies
- Opposing Fgf and Bmp activities regulate the specification of olfactory sensory and respiratory epithelial cell fates " In this study, we provide evidence that in both chick and mouse, Bmp signals promote respiratory epithelial character, whereas Fgf signals are required for the generation of sensory epithelial cells. Moreover, olfactory placodal cells can switch between sensory and respiratory epithelial cell fates in response to Fgf and Bmp activity, respectively. Our results provide evidence that Fgf activity suppresses and restricts the ability of Bmp signals to induce respiratory cell fate in the nasal epithelium."
- Heparan sulfate in lung morphogenesis "Heparan sulfate (HS) is a structurally complex polysaccharide located on the cell surface and in the extracellular matrix, where it participates in numerous biological processes through interactions with a vast number of regulatory proteins such as growth factors and morphogens. ...he potential contribution of HS to abnormalities of lung development has yet to be explored to any significant extent, which is somewhat surprising given the abnormal lung phenotype exhibited by mutant mice synthesizing abnormal HS."
- Signaling via Alk5 controls the ontogeny of lung Clara cells "Clara cells, together with ciliated and pulmonary neuroendocrine cells, make up the epithelium of the bronchioles along the conducting airways. Clara cells are also known as progenitor or stem cells during lung regeneration after injury. ...Using lung epithelial cells, we show that Alk5-regulated Hes1 expression is stimulated through Pten and the MEK/ERK and PI3K/AKT pathways. Thus, the signaling pathway by which TGFbeta/ALK5 regulates Clara cell differentiation may entail inhibition of Pten expression, which in turn activates ERK and AKT phosphorylation."
- Wt1 and retinoic acid signaling in the subcoelomic mesenchyme control the development of the pleuropericardial membranes and the sinus horns "Pericardium and sinus horn formation are coupled and depend on the expansion and correct temporal release of pleuropericardial membranes from the underlying subcoelomic mesenchyme. Wt1 and downstream Raldh2/retinoic acid signaling are crucial regulators of this process."
- <pubmed> 20301217</pubmed>
- <pubmed> 20147383</pubmed>
- <pubmed> 20185795</pubmed>
<pubmed>20691848</pubmed> <pubmed>20152174</pubmed> <pubmed>16770071</pubmed> <pubmed>12456356</pubmed> <pubmed>6370120</pubmed>
Search April 2010
- Respiratory System Development - All (30795) Review (3706) Free Full Text (7943)
- Respiratory Development - All (28939) Review (5876) Free Full Text (7203)
Upper respiratory tract
Lower respiratory tract
- Adult diaphragm.jpg
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Cite this page: Hill, M.A. (2020, May 26) Embryology Respiratory System Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Respiratory_System_Development
- © Dr Mark Hill 2020, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G