Respiratory System - Upper Respiratory Tract

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Respiratory system overview (stage 13)

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. In the head/neck region, the pharynx forms a major arched cavity within the phrayngeal arches.

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.

Note that some components of the upper respiratory tract development are covered in Smell Development and Head Development.

Respiratory Links: respiratory | Science Lecture | Lecture Movie | Med Lecture | Stage 13 | Stage 22 | upper respiratory tract | diaphragm | Histology | Postnatal | respiratory abnormalities | Respiratory Quiz | Respiratory terms | Category:Respiratory
Historic Embryology - Respiratory 
1902 The Nasal Cavities and Olfactory Structures | 1906 Lung | 1912 Upper Respiratory Tract | 1912 Respiratory | 1913 Prenatal and Neonatal Lung | 1914 Phrenic Nerve | 1918 Respiratory images | 1921 Respiratory | 1922 Chick Pulmonary Vessels | 1934 Right Fetal Lung | 1936 Early Human Lung | 1937 Terminal Air Passages | 1938 Human Histology
Respiratory epithelium cell development.[1]

Some Recent Findings

Human embryo (stage 22) nasal epithelium development.
  • Mechanisms of larynx and vocal fold development and pathogenesis[2] "The larynx and vocal folds sit at the crossroad between digestive and respiratory tracts and fulfill multiple functions related to breathing, protection and phonation. They develop at the head and trunk interface through a sequence of morphogenetic events that require precise temporo-spatial coordination. We are beginning to understand some of the molecular and cellular mechanisms that underlie critical processes such as specification of the laryngeal field, epithelial lamina formation and recanalization as well as the development and differentiation of mesenchymal cell populations. Nevertheless, many gaps remain in our knowledge, the filling of which is essential for understanding congenital laryngeal disorders and the evaluation and treatment approaches in human patients. This review highlights recent advances in our understanding of the laryngeal embryogenesis. Proposed genes and signaling pathways that are critical for the laryngeal development have a potential to be harnessed in the field of regenerative medicine."
  • Notch3-Jagged signaling controls the pool of undifferentiated airway progenitors[3] "Basal cells are multipotent airway progenitors that generate distinct epithelial cell phenotypes crucial for homeostasis and repair of the conducting airways. Little is known about how these progenitor cells expand and transition to differentiation to form the pseudostratified airway epithelium in the developing and adult lung. Here, we show by genetic and pharmacological approaches that endogenous activation of Notch3 signaling selectively controls the pool of undifferentiated progenitors of upper airways available for differentiation. This mechanism depends on the availability of Jag1 and Jag2, and is key to generating a population of parabasal cells that later activates Notch1 and Notch2 for secretory-multiciliated cell fate selection." Notch
  • Establishment of smooth muscle and cartilage juxtaposition in the developing mouse upper airways[4] "In the trachea and bronchi of the mouse, airway smooth muscle (SM) and cartilage are localized to complementary domains surrounding the airway epithelium. Proper juxtaposition of these tissues ensures a balance of elasticity and rigidity that is critical for effective air passage. It is unknown how this tissue complementation is established during development. Here we dissect the developmental relationship between these tissues by genetically disrupting SM formation (through Srf inactivation) or cartilage formation (through Sox9 inactivation) and assessing the impact on the remaining lineage. We found that, in the trachea and main bronchi, loss of SM or cartilage resulted in an increase in cell number of the remaining lineage, namely the cartilage or SM, respectively. However, only in the main bronchi, but not in the trachea, did the loss of SM or cartilage lead to a circumferential expansion of the remaining cartilage or SM domain, respectively. In addition to SM defects, cartilage-deficient tracheas displayed epithelial phenotypes, including decreased basal cell number, precocious club cell differentiation, and increased secretoglobin expression. These findings together delineate the mechanisms through which a cell-autonomous disruption of one structural tissue can have widespread consequences on upper airway function."
More recent papers  
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  • 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

Nasal Olfactory and Respiratory Epithelium

Olfactory epithelium

Respiratory histology 13.jpg Respiratory histology 14.jpg
Olfactory Epithelium (overview) Olfactory Epithelium (detail)
  • Olfactory cells
  • Sustentacular cells - located mainly in the superficial cell layer of the epithelium (difficult to distinguish from olfactory cells).
  • Basal cells - identified by their location in the epithelium.


  • Cilia are not visible
  • goblet cells are absent from the olfactory epithelium.

Lamina Propria

  • olfactory axon bundles (lightly stained, rounded areas) connected to olfactory cells.
  • Bowman's glands - (small mucous glands, olfactory glands) function to moisturise the epithelium.
Nasal Olfactory Histology: overview image | detail image | Smell Development | Histology | Histology Stains

Respiratory Epithelium

Respiratory histology 11.jpg Respiratory histology 12.jpg
Respiratory Epithelium (overview) Respiratory Epithelium (detail)

  • goblet cells
  • ciliated cells
  • basal cells

Lamina propria

  • connective tissue
  • cavernous sinusoids - large spaces (empty or filled with red blood cells)
  • glandular tissue - mucous glands (green) and muco-serous glands (brownish-green)


  • Lamellae and osteocytes in lacunae.
  • Haversian systems are rare or absent.
Nasal Respiratory Histology: overview image | detail image | Histology | Histology Stains
Respiratory Histology: Bronchiole | Alveolar Duct | Alveoli | EM Alveoli septum | Alveoli Elastin | Trachea 1 | Trachea 2 | labeled lung | unlabeled lung | Respiratory Bronchiole | Lung Reticular Fibres | Nasal Inferior Concha | Nasal Respiratory Epithelium | Olfactory Region overview | Olfactory Region Epithelium | Histology Stains

Paranasal Sinuses

frontal sinus

Paranasal sinuses are thought to develop as "pneumatisation" of bone and out-pocketing of the respiratory nasal epithelium. There are 4 paired sinuses, named by their anatomical location, and lined with respiratory epithelium. The sinuses begins to form at 10 weeks (GA) by primary pneumatisation, later in fetal development secondary pneumatisation occurs enlarging the existing spaces. These sinuses continue to enlarge postnatally.

Note that during development, these are amniotic fluid fluid-filled spaces, therefore pneumatisation (USA, pneumatization) is a misnomer as only postnatally fluid loss forms the air-filled (pneumatic) spaces.

A study of fetal cleft lip and palate[5] showed that sphenoid sinus was still present with variability in morphology compared to normal fetus perhaps due to altered shape and size of the adjacent hypertrophic cartilaginous structures.

Computed tomography measurements from a study of 120 adult (age 18-65 years) maxillary and frontal sinuses.[6]

  • mean maxillary sinus volume 15.7±5.3 cm3
  • larger in males than in females.
  • no correlation between the volume of maxillary sinuses with either age or side.
  • mean bone thickness at the canine fossa was 1.1±0.4 mm.

Frontal Sinus

Ethmoid Sinus

A 1997 article[7] based upon study of coronal sections of the heads of 23 human fetuses from 18-mm CR length to 282-mm CR length. The study suggests that the ethmoid sinus forms by: "constriction of the nasal cavity by a pair of turbinal cushions, and evagination from the nasal cavity by proliferation and subsequent disintegration of the nasal epithelium".

Sphenoid Sinus

Sphenoid Sinus

Data quoted in a 1996 article[8] on the sphenoid sinus.

  • 4 month - sphenoid sinuses can be identified.
  • at birth - sinus remains small and is little more than an evagination of the sphenoethmoid recess.
  • year 3 - invasion of the sphenoid bone is more rapid
  • year 7 - sinus has extended posteriorly to the level of the sella turcica.
  • year 12 - sphenoid pneumatization reaches its final form and a size equivalent to the adult
  • adult - further enlargement into the basisphenoid may occur.

Maxillary Sinus

Developmentally, the maxillary sinus originates in the middle meatus and extends into the ethmoid cartilage.

The data below is from a recent microscopical study of 100 human fetuses from the 9th to the 37th week (GA).[9]

  • week 10 - maxillary sinus begins development.
  • week 37 - the anterior-posterior diameter has a mean of 4.36 mm; ossification of the medial wall was absent, and the floor was located below the attachment of the inferior turbinate. Septa and recesses were temporarily observed.
  • maxillary sinus osmium (opening) was located at the anterior third of the ethmoid infundibulum
    • final dimensions were 1.96 mm in length and 0.44 mm in width.
  • mean length between the ostium to the lamina papyracea and nasolacrimal duct was 1 mm.


The larynx and vocal folds lie at the gastrointestinal tract and respiratory tract separation. Adult functions of this region are associated with breathing, protection and speech. Developmentally, this region goes through the early recanalization process. See the recent review.[2]

This is a historical pictorial description of larynx embryonic development.[10]

The following gallery shows the development of the human larynx from the embryonic to fetal period.[11]


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.

Stage13-GIT-icon.jpg Early embryo (stage 13)

3 dimensional reconstruction based upon a serial reconstruction from individual Carnegie stage 13 embryo slice images.

Stage22-GIT-icon.jpg 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: Movies


  1. <pubmed>26119728</pubmed>| Cell Rep.
  2. 2.0 2.1 Lungova V & Thibeault SL. (2020). Mechanisms of larynx and vocal fold development and pathogenesis. Cell. Mol. Life Sci. , , . PMID: 32253462 DOI.
  3. Mori M, Mahoney JE, Stupnikov MR, Paez-Cortez JR, Szymaniak AD, Varelas X, Herrick DB, Schwob J, Zhang H & Cardoso WV. (2015). Notch3-Jagged signaling controls the pool of undifferentiated airway progenitors. Development , 142, 258-67. PMID: 25564622 DOI.
  4. Hines EA, Jones MK, Verheyden JM, Harvey JF & Sun X. (2013). Establishment of smooth muscle and cartilage juxtaposition in the developing mouse upper airways. Proc. Natl. Acad. Sci. U.S.A. , 110, 19444-9. PMID: 24218621 DOI.
  5. Smith TD, Siegel MI, Mooney MP, Burrows AM & Todhunter JS. (1997). Formation and enlargement of the paranasal sinuses in normal and cleft lip and palate human fetuses. Cleft Palate Craniofac. J. , 34, 483-9. PMID: 9431465 <0483:FAEOTP>2.3.CO;2 DOI.
  6. Sahlstrand-Johnson P, Jannert M, Strömbeck A & Abul-Kasim K. (2011). Computed tomography measurements of different dimensions of maxillary and frontal sinuses. BMC Med Imaging , 11, 8. PMID: 21466703 DOI.
  7. Monteiro VJ & Dias MP. (1997). Morphogenic mechanisms in the development of ethmoidal sinuses. Anat. Rec. , 249, 96-102. PMID: 9294654
  8. Antoniades K, Vahtsevanos K, Psimopoulou M & Karakasis D. (1996). Agenesis of sphenoid sinus. Case report. ORL J. Otorhinolaryngol. Relat. Spec. , 58, 347-9. PMID: 8958546 DOI.
  9. Nuñez-Castruita A, López-Serna N & Guzmán-López S. (2012). Prenatal development of the maxillary sinus: a perspective for paranasal sinus surgery. Otolaryngol Head Neck Surg , 146, 997-1003. PMID: 22267494 DOI.
  10. Frazer JE. Development of the larynx. (1910) J Anat. 44: 156-191. PMID 17232839
  11. Template:Ref-GrosserLewisMcmurrich1912


Mirilas P. (2011). Lateral congenital anomalies of the pharyngeal apparatus: part III. cadaveric representation of the course of second and third cleft and pouch fistulas. Am Surg , 77, 1257-63. PMID: 21944636

Daniel SJ. (2006). The upper airway: congenital malformations. Paediatr Respir Rev , 7 Suppl 1, S260-3. PMID: 16798587 DOI.

Pohunek P. (2004). Development, structure and function of the upper airways. Paediatr Respir Rev , 5, 2-8. PMID: 15222948 DOI.


Teul I, Slawinski G, Lewandowski J, Dzieciolowska-Baran E, Gawlikowska-Sroka A & Czerwinski F. (2010). Nasal septum morphology in human fetuses in computed tomography images. Eur. J. Med. Res. , 15 Suppl 2, 202-5. PMID: 21147652

Martinez-Ten P, Adiego B, Perez-Pedregosa J, Illescas T, Wong AE & Sepulveda W. (2010). First-trimester assessment of the nasal bones using the retronasal triangle view: a 3-dimensional sonographic study. J Ultrasound Med , 29, 1555-61. PMID: 20966466

Asaumi R, Sato I, Miwa Y, Imura K, Sunohara M, Kawai T & Yosue T. (2010). Understanding the formation of maxillary sinus in Japanese human foetuses using cone beam CT. Surg Radiol Anat , 32, 745-51. PMID: 20490493 DOI.

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Search Pubmed: Upper Respiratory Tract Development | Upper Respiratory Tract Embryology


  • nasal concha - (turbinate) Within the nasal cavity the narrow, long and curled bone shelf increasing the nasal surface area and partially separating into smaller cavities. (concha = resemble a shell)

Additional Images

Adult upper respiratory tract conducting system

  • part of foregut development
  • anatomically the nose, nasal cavity and the pharynx
  • the pharynx forms a major arched cavity within the pharyngeal arches

Larynx Image Links: All cartilages of the larynx | Epiglottis cartilage | Thyroid cartilage | Cricoid cartilage | Arytenoid cartilage | Larynx ligaments anterior | Larynx ligaments posterior | Larynx sagittal section | Larynx and upper trachea | Larynx entrance | Larynx interior | Larynx muscular attachments | Larynx muscles 1 | Larynx muscles 2 | Larynx muscles 3 | Cartilage Development | Respiratory System Development

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Cite this page: Hill, M.A. (2024, June 16) Embryology Respiratory System - Upper Respiratory Tract. Retrieved from

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