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Flashcards in Peds: Embryology Deck (37):

During week ___ the foregut endoderm evaginates ventrally to form the Respiratory Diverticulum, which occurs at the level of the ____ pharyngeal pouch. It is connected to the pharyngeal cavity by the ____

laryngotracheal orifice


The respiratory diverticulum elongates and its distal end expands (forming the ____). This will bifurcate to form the ____. As it expands, its connection to the foregut is altered by paired lateral indentations, the ____ which grow toward the, midline and fuse (forming the ____).

1. Lung Bud or tracheal bud
2. Primary Bronchi
3. Tracheoesophageal Folds
4. Tracheoesophageal Septum


The tracheoesophageal septum separates the ____. It is incomplete so there remains a cranial portal (the ____) which links the tracheal lumen with the pharyngeal lumen.

Ventral trachea from the more dorsal esophagus.
2. Laryngotracheal groove


What is the early development of the lower respiratory tract driven by?

Sox2 (dorsal-ventral)
Nkx2.1 (ventral-dorsal)


Barx1 gene drives what?

Formation of tracheoesophageal folds/septum, and thus the separation of the trachea and esophagus


What is the most common form of tracheoesophageal fistula?

Superior esophageal atresia and a link between the trachea and esophagus near the midpoint of the two


The laryngeal cartilages and muscles develop from the mesoderm of the _____ pharyngeal arches

4th and 6th


The hypopharyngeal eminence forms from the ____ pharyngeal arches. The caudal portion develops into the ___. A separate mesenchymal condensation forms the ____, which forms the ___ and reshapes the ___ into the ___

1. 3rd and 4th
2. Epiglottis
3. Arytenoid swelling
4. Arytenoid cartilages
5. Laryngotracheal groove
6. Glottis


The 4th and 6th pharyngeal arches are innervated by the ___

Vagus n.


Development of the larynx typically spans from week ____ to ___



The laryngeal epithelium is derived from the ____. During weeks 8-9, the proliferating epithelium occludes the ___. Typically during week 10 the epithelium regresses leaving an opening superiorly and the ventricles and folds of the larynx laterally



Failure of ____ results in laryngeal atresia. A baby born with this will be unable to breathe or cry and this requires immediate tracheostomy

the epithelium to clear the glottal opening


Partial laryngeal atresia (laryngeal web) will typically present as ____

Disphonic with a range of airway obstruction


The intraembryonic (coelomic) cavity forms as a split between ___

Splanchnic and somatic lateral plate mesoderm


The transverse septum is innervated by the ___ and forms during weeks ___

Phrenic n.


The transverse septum only extends to the ___ surface of the foregut. The foregut is suspended by the dorsal mesentery. After the transverse septum partitions the ventral portion of the coelomic cavity, the dorsal portion remains continuous on either side of the foregut. This paired dorsal connection is the ____

Pleuroperitoneal canals


The pleuroperitoneal folds form on the ____ margin of the pleuroperitoneal canals and grow toward the ____ free edge of the transverse septum. The folds expand into the pleuroperitoneal membranes which fuse with the transverse septum during week ___. This fusion partitions the pleuroperitoneal canals



Central tendon on the diaphragm = ___ + ____

Transverse septum + pleuroperitoneal membranes


Crura of the diaphragm = ___

Dorsal mesentery of the esophagus


Peripheral mesentery = ___

Peripheral muscles of the transverse septum and pleuroperitoneal membranes


Failure of ____ results in congenital diaphragmatic hernia. This is more common on the left and can result in pulmonary hypoplasia (due to the peritoneal viscera expanding and blocking the development of the lung)

One of the pleuroperitoneal membranes to form and/or fuse with the transverse septum


Pleuroperitoneal membranes develop parallel but superior to the pleuropericardial folds (membranes). As the folds extend from the body wall they carry with them the ____ and ____. The pleuropericardial membranes meet in the midline, separating the ____ from the ____

1. Phrenic n. and Common Cardinal v.
2. Dorsal pleural cavity from the ventral pericardial cavity


The ___ forms the fibrous pericardium, and the phrenic n. remain coursing along the surface.

Pleuropericardial membrane


The right common cardinal v. forms the ___ and the left forms the ___

Proximal end of SVC
Part of coronary sinus and oblique v. of left atrium


What are some of the messenger compounds released but the mesoderm lining the medial side of the pleuroperitoneal canal/pleural cavity?
What do they do?

(FGF-10, Wnt7b, bmp4, Shh)
Induce expansion and division within the bronchial tree


The lining of the pleural cavity that covers the expanding bronchial tree is the ____

Splanchnic pleura


By week __ the expanded lung bud has bifurcated to form the bronchial buds (primary bronchi). The right is larger in diameter and more vertical than the left. By week ___ the primary bronchi divide to form the secondary bronchi (3 on the right, 2 on the left). By week ___ the tertiary (segmental) bronchi will form (10 right, 9 left)



____ form due to abnormal bronchial tree branching. They are most common on the mediastinal surface. Initially they are fluid filled, but may become air filled over time. Typically leads to lobular pulmonary hypoplasia.

Congenital bronchogenic cysts


What are the stages of lung maturation and what weeks do they occur in?

1. Pseudoglandular phase (W 6-16)
2. Canalicular phase (W 16-26)
3. Terminal sac phase (W 26-birth)
4. Alveolar period (W 32-8yrs)


The increase in size between a newborn and adult lung is due to ___

Formation of more respiratory bronchioles NOT alveoli.


What happens during the pseudoglandular phase of lung development?

-lung resembles exocrine gland
-endodermal tubules terminate in terminal bronchioles, lined w/simple columnar epithelium
-no direct interaction between capillaries and terminal bronchioles
-no respiration occurs in this phase


What happens during the canalicular phase of lung development?

-terminal bronchioles give rise to respiratory bronchioles which give rise to alveolar ducts
-simple columnar epithelium transitions to simple cuboidal
-increase in capillary density within mesoderm and capillary beds abut the alveolar ducts
-limited respiration is possible toward the end of this phase


What happens during the terminal sac phase of lung development?

-Terminal sacs expand off of alveolar ducts
-simple cuboidal epithelium transitions to simple squamous (when epithelium transitions the terminal sacs are called alveolar sacs)
-Type I and II pneumocytes differentiate
-capillary beds proliferate and form close contact wit Type I pneumocytes


Type I vs Type II pneumocytes

I: forms blood-air barrier
II: not as flat, produce surfactant


What happens during the alveolar period of lung development?

-secondary septa partition the alveolar sacs into alveoli
-# of alveoli increase from 30 mil to 300 mil during this phase


What causes respiratory distress syndrome?

Failure of type II pneumocytes to produce enough surfactant


1. How does RDS appear radiographically?
2. Histologically?

1. Thorax will look Bell-shaped
Marked reticulogranularity within the lungs
2. Acinar atelectasis
dilation of terminal bronchioles
deposition of an eosinophilic membrane (hence the previous name Hyaline Membrane Disease)