Respiratory System - Carnegie Stage 22

From Embryology


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Respiratory System

Based upon a serial reconstruction from individual embryo slice images (27 mm Human embryo, Carnegie Stage 22 approximate day 56).

Note the relative size and position of individual structures and organs at this early stage of development. The respiratory system is endodermal in origin, initially "budding off" the foregut during week 3. This bud forms the respiratory diverticulum, at the level of the glottis between the adult oesophagus and trachea. It continues to bud in week 4, forming a pair of lung buds.

 ‎‎GIT Stage 22
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Links: MP4 version | Quicktime version | Carnegie stage 22 | Gastrointestinal Tract 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
Virtual Slides
Stage 22 - Larynx and Medulla

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Stage 22 | Embryo Slides
Stage 22 - Neck

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 ‎‎Mobile | Desktop | Original

Stage 22 | Embryo Slides
Stage 22 - Atria and Lungs

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Stage 22 | Embryo Slides
Stage 22 Histology Links: Both lungs overview | Lung and pleural cavity | Right and Left Main Bronchi | Lung Bronchi
Stage 22 (serial labeled images)
Section Name Description
Stage 22 image 054.jpg A5L Bridge of nose.

R and L olfactory bulbs from forebrain.

Stage 22 image 055.jpg A6L Nose. Nasal septum. Nasal capsule.

Olfactory epithelium lining roof of nasal cavity.

Orbital part of the developing sphenoid bone (intramembranous ossification).

Stage 22 image 056.jpg A7L Conchae. Nasal capsule and septum.
Stage 22 image 057.jpg B1L Conchae. Optic nerve.
Stage 22 image 058.jpg B2L Description
Stage 22 image 059.jpg B3L Perpendicular plate of ethmoid cartilage. Adenohypophysis. Neurohypophysis. Ant. and post. walls of hypopophysial fossa. Lesser wings of sphenoid cartilage. Internal carotid arteries.
Stage 22 image 060.jpg B4L Dorsum of tongue. Oropharynx communicating with naso-pharynx (cf. B3L - palatal processes not fused).
Stage 22 image 061.jpg B5L Tongue with palatal processes at either side. Transverse (intrinsic) muscle of tongue.

Pharyngotympanic tubes.

Stage 22 image 062.jpg B6L Tongue with transverse muscle, genioglossus muscle (medial) and hyoglossus muscle (lateral).

Palatal processes.

Meckel's cartilage. Note teeth enamel organs (dark masses at sides of tongue attachment).

Stage 22 image 063.jpg B7L Transverse caudal pharynx. epiglottis. Hyoid musculature. Pharyngeal constrictor muscle. Submandibular gland.
Stage 22 image 064.jpg C1L Pharynx. Pharyngeal constrictor muscle. laryngeal caecum (ventral). Arytenoid swellings in contact.

Thyroid cartilage laminae (anterolateral), with superior horns (posterolateral). Hyoid cartilage. Internal jugular veins.

"Muz's cheshire cat"

Stage 22 image 065.jpg C2L Pharynx. Thyroid cartilage. Smaller laryngeal caecum (cf.C1). Carotid neurovascular bundle.
Stage 22 image 066.jpg C3L Pharynx with its inferior constrictor muscle. Glottis region.
Stage 22 image 067.jpg C4L Oesophagus with muscle layer and trachea with thyroid gland laterally.

Common carotid arteries. Vagus nerve. Internal jugular veins.

(Section damaged)

Stage 22 image 068.jpg C5L Oesophagus, smaller than in C4. Trachea.

Thyroid gland (isthmus). Clavicle. Small dark masses near posterolateral borders of thyroid gland are the parathyroid glands from the caudal part of 3rd pharyngeal pouch.

Stage 22 image 069.jpg C6L Trachea.

Clavicles. Dark connecting stalk between parathyroid gland and thymus (rostral end of 3rd pharyngeal pouch).

Common carotid artery.

Stage 22 image 070.jpg C7L Trachea.

Oesphagus. Apex of R lung in pleural cavity

Sternum. Thymus gland. L brachiocephalic vein. Brachiocephalic trunk.

Stage 22 image 071.jpg D1L Lungs. Visceral and parietal pleurae. Pleural cavities.

Sternum. Thymus.

Other contents of superior mediastinum.

Stage 22 image 072.jpg D2L Lungs.
Stage 22 image 073.jpg D3L Tracheal bifurcation.
Stage 22 image 074.jpg D4L Right primary bronchus (torn) and right superior lobe bronchus.

Left primary bronchus.

Left and right pulmonary arteries.

Ribs joining to sternum.

Stage 22 image 075.jpg D5L R, L primary bronchi. R anterior and posterior segmental bronchi coming off R superior lobe bronchus. L, R pulmonary arteries. Hilar attachments of lungs to mediastinal tissues - note extent of R, L pleural cavities.
Stage 22 image 076.jpg D6L R, L primary bronchi (note left still has not branched). R pulmonary artery.
Stage 22 image 077.jpg D7L R, L primary bronchi: note distinct horizontal course of L, vertical course of R, L pulmonary veins (L empty). R pulmonary artery.
Stage 22 image 078.jpg E1L Pulmonary veins. Azygos, hemiazygos veins. Ribs. Intercostal muscles.
Stage 22 image 079.jpg E2L Pulmonary veins. Azygos, hemiazygos veins. Ribs. Intercostal muscles.
Stage 22 image 080.jpg E3L R dome of diaphragm. R long middle and inferior lobes. L long superior and inferior lobes. Xiphoid process.


Stage 22 image 081.jpg E4L Diaphragm (note costal attachment). R lung inferior lobe.

Inferior vena cava, dorsal to diaphragm.

Stage 22 image 082.jpg E5L Inferior lobes of lungs.

Diaphragm with sternal attachments.

Inferior vena cava, now ventral to diaphragm (vena caval foramen).


Stage 22 image 083.jpg E6L Liver. Thoracic aorta. Large adrenal glands.
Stage 22 image 084.jpg E7L Lumbar diaphragm. Thoracic aorta. Note ribs 11 and 12 on L and three layers of abdominal muscles extending ventrally.
Stage 22 image 085.jpg F1L Lumbar diaphragm. Thoracic aorta.
Stage 22 image 086.jpg F2L Attachment of lumbar diaphragm near L 1 on R with psoas muscle dorsal to it. Note abdominal aorta giving rise to superior mesenteric artery.

All Sections

Stage 22L serial labeled images
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Cite this page: Hill, M.A. (2024, June 15) Embryology Respiratory System - Carnegie Stage 22. Retrieved from

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G