Embryology of Respiratory System

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Questions and Answers

Which structure connects the greater and lesser sacs?

Greater omentum

Epiploic foramen (correct)

Hindgut

Lesser omentum

How many layers of visceral peritoneum does the greater omentum have?

Five

Three

Four (correct)

Two

Which nerve supplies the foregut?

Vagus nerve

Greater splanchnic nerve (correct)

Intercostal nerve

Phrenic nerve

Which of the following organs does not develop from the foregut?

Small intestine Signup and view all the answers

In which week of development does the stomach begin to form?

4th week Signup and view all the answers

Pain in which region is associated with the foregut?

Epigastric region Signup and view all the answers

What is the stage of lung development where the respiratory bronchioles and primitive alveoli develop?

Canalicular Signup and view all the answers

Which embryonic layer gives rise to the glands of the respiratory tract?

Endoderm Signup and view all the answers

What is the function of the saccular stage of lung development?

Production of surfactant Signup and view all the answers

What is the stage of lung development where the trachea and primary bronchial buds form?

Embryonic Signup and view all the answers

Which structure is formed from the somatopleuric layer of the mesoderm?

Parietal pleura Signup and view all the answers

What is the final stage of lung development where the number of alveoli and capillaries increases?

Alveolar Signup and view all the answers

What is the origin of the bronchial tree during embryonic development?

Foregut of the embryonic gut tube Signup and view all the answers

Which structure is not formed during the embryonic stage of lung development?

Alveoli Signup and view all the answers

During which weeks of conception does the embryonic gut tube form?

4–7 weeks Signup and view all the answers

What are the three sections of the embryonic gut tube?

Foregut, Midgut, Hindgut Signup and view all the answers

What is the result of the tracheoesophageal grooves failing to fully close in the midline?

Tracheoesophageal fistula (TEF) Signup and view all the answers

What happens to the lung bud as it grows out and down?

It includes both endoderm and surrounding splanchnopleuric mesoderm Signup and view all the answers

What is the result of the trachea bifurcating into the right and left bronchial buds?

Formation of the primary bronchial buds Signup and view all the answers

What is the characteristic of the pseudoglandular stage of respiratory system development?

Development of the conducting portion of the airways Signup and view all the answers

What is bronchopulmonary sequestration?

Abnormally formed non-functioning accessory lung tissue Signup and view all the answers

What is the consequence of tracheal atresia?

Lethal Signup and view all the answers

What type of innervation is present in the anal canal above the pectinate line?

Parasympathetic innervation Signup and view all the answers

What is the blood supply to the anal canal below the pectinate line?

Pudendal artery Signup and view all the answers

What is the result of a failure in septation of the cloaca during development?

All of the above Signup and view all the answers

What is the genetic mutation associated with Hirschsprung disease?

Mutation in the RET gene Signup and view all the answers

What sensations can be detected in the anal canal above the pectinate line?

Stretch only Signup and view all the answers

What is the term for the abnormal connections between the anus and bladder?

Fistulae Signup and view all the answers

What occurs during the development of the stomach due to the posterior wall growing more quickly than the anterior wall?

It develops a C shape Signup and view all the answers

What is the result of the smaller rotation of the stomach around the anteroposterior axis?

The cardiac portion of the stomach moves down and to the left Signup and view all the answers

What is the fate of the caudal part of the foregut in the development of the duodenum?

It gives rise to the above the ampulla of Vater Signup and view all the answers

What is the clinical relevance of failure of the lumen to fully recanalize during duodenal development?

Duodenal stenosis or atresia Signup and view all the answers

What forms from the caudal side of the hepatic diverticulum?

The gallbladder Signup and view all the answers

What is the result of the connection between the caudal bud and the gallbladder?

The formation of the cystic duct Signup and view all the answers

What is the source of blood supply to the part of the duodenum derived from the cranial part of the midgut?

Superior mesenteric artery Signup and view all the answers

What occurs to the duodenal lumen during the 5th week of development?

It becomes completely obstructed Signup and view all the answers

Study Notes

Embryology of the Respiratory System

The respiratory system consists of the upper respiratory tract (nose, nasal cavity, paranasal sinuses, laryngo-pharynx, and larynx) and the lower respiratory tract (trachea, bronchi, and lungs)
Lung development consists of 5 stages: embryonic, pseudoglandular, canalicular, saccular, and alveolar

Embryonic Stage

Development of the bronchial tree begins in the embryonic stage, with budding of the embryonic gut tube to form the larynx, trachea, and lungs by the end of the stage
The embryonic layers and their associated bronchial tree structures are:
- Endoderm: respiratory epithelium, glands of the respiratory tract
- Mesoderm (splanchnopleuric layer): visceral pleura, connective tissue, bronchial musculature, cartilage
- Mesoderm (somatopleuric layer): parietal pleura
The bronchial tree develops off of the foregut of the embryonic gut tube, which forms from the laterally folded endoderm layer and is surrounded by mesoderm
The lung bud buds off of the ventral side of the foregut around week 4 and grows out ventrally and down caudally, including both endoderm and surrounding splanchnopleuric mesoderm
The tracheoesophageal groove appears as lateral indentations between the new lung bud and the foregut, which move in medially, "pinching off" the lung bud and forming the tracheoesophageal septum
Defects at this stage can cause tracheoesophageal fistula (TEF), esophageal atresia, tracheal atresia, or bronchopulmonary sequestration

Pseudoglandular Stage

Weeks 8-16: the conducting portion of the airways continues to develop, forming bronchioles from the tertiary bronchi
At this point, the mesoderm that will develop into alveoli has not completed development, so there are no formed alveoli

Foregut Development

The foregut is supplied by the coeliac trunk and the greater splanchnic nerve (T5-9 nerve roots)
Pain in these organs will localize to the epigastric region (T5-9 dermatomes)
Organs that develop from the foregut are:
- Oesophagus
- Stomach
- Pancreas
- Liver
- Gallbladder
- Portion of the duodenum that is proximal to the entrance of the bile duct

Development of the Stomach

Development begins around the 4th week
Fusiform dilation of the foregut: site of primordial stomach
The lengthening oesophagus places the stomach below the diaphragm
Posterior wall grows more quickly than anterior wall → develops a C shape
- Posterior wall → greater curvature
- Anterior wall → lesser curvature
90-degree rotation clockwise around longitudinal axis:
- Greater curvature (dorsal): rotates anteriorly and to the left
- Lesser curvature (ventral): rotates posteriorly and to the right

Development of the Duodenum

Development begins in the 4th week
Above the ampulla of Vater: derived from caudal part of the foregut → supplied by the celiac artery
Below the ampulla of Vater: derived from cranial part of the midgut → supplied by SMA
Elongates and forms C-shaped loop
Joins together with the developing pancreas attached to the posterior body wall

Duodenal Obliteration and Recanalization

Week 5: rapid cell proliferation in its walls leads to complete obstruction of the duodenal lumen
By the end of week 8: vacuoles form within the duodenum, grow and merge → lumen recanalization
Clinical relevance: failure of the lumen to fully recanalize results in duodenal stenosis or duodenal atresia

Liver and Biliary Ducts

Development begins in the 3rd-4th week
Appears from the caudal portion of the foregut as the hepatic diverticulum, which goes on to form the liver (endoderm differentiates into hepatocytes), intrahepatic ducts, and extrahepatic portions of the hepatic ducts
A smaller bud grows off the caudal side of the hepatic diverticulum: forms the gallbladder and connection between the caudal bud and the gallbladder → cystic duct

Hindgut Abnormalities

If there are issues in septation of the cloaca or rupture of the membrane, this can cause abnormalities in the adult anatomy
Imperforate Anus – the cloacal membrane does not rupture and so persists, meaning there is no outlet from the gastrointestinal tract and therefore no anus
Fistulae – if there are holes in the septum, there can be abnormal connections between the anus and the bladder as they are not properly separated in development
Anorectal Agenesis – a severe defect where there is no development of the anus or rectum rather than simply no outlet

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Description

This quiz covers the development of the upper and lower respiratory tracts, including the formation of the trachea, bronchi, and lungs. It also explores the 5 stages of lung development, from embryonic to canalicular.