Embryology: Respiratory System Flashcards
During which week of deveopment doe s the endoderm of the foregut evaginate ventrally to form the respiratory diverticulum?
At which level of the pharyngeal pouch does this occur?
4th week
4th pharyngeal pouch
What is the name change for hte respiratory diverticulum as it elongates?
After it bifurcates?
trachael bud
after bifurcation is the primary bronchi
The formation of the tracheoesophageal septum separates which two strucutures?
Does this occur before or after bifurcation of the primary brochi (lung buds)?
Where can a remnant of the connected respiratory system and digestive system be seen in adults?
esophagus and laryngotracheal tube
after bifurcation
glottis
The larynx forms from which pharyngeal arches?
The epiglottis is formed from what precursor strucutre? derived from which pharyngeal arches?
the larynx forms from the 4th and 6th pharyngeal arches
the epiglottis forms from the hypopharyngeal eminence, which forms from mesenchymal proliferation associated with 3rd and 4th pharyngeal arches
What is the mesenchyme proliferation forms the arytenoid cartilages? What is the function of these structures?
arytenoid swellings
the arytenoid cartilages reshaped the opening betweent eh esophagus adn the trachea to form the glottis
The tongue arizes from which pharyngeal arches?
1, 2, and 3
What imporant step happens to laryngeal epithelium during the 10th week of development?
What is the condition called when this step does not occur?
early proliferation of epithelial lining fill the larynd, occluding the laryngeal (glottal) orfice.
During 10th week of development, the epithelium recedes, forming the recesses adn mucus membranes used for vocalization
total or partial laryngeal atresia occurs if the epithelium does not fully recede and blocks the orfice or results in abnormal tissue covering the vocal folds
What is the name of the mesenchye derived strucutre that is situated between the heart and the yolk sac?
What is this structure the predecessor for?
How does it shape change throughotu development?
thickened mass = transverse septum = diaphragm & part of liver
the transverse septum elongates, pulling the phrenic nerve with it, making its way to the foregut
What is the imapct of the straightening out of the embryo on the shape of the transverse septum?
What cavities does this structure separate?
the transverse septum takes an oblique path, caudal, rather than completely ventral/dorsal
ventral surface at T7; dorsal surface at T12
partially divides abdominal and thoracic cavities
Even after the formation of the transverse septum, there is still continuation betweent the body cavities. Why is this and what are the names of these connective conduits?
the foregut is suspended byt he dorsal mesentary, and the transverse plate extends only to the foregut, leaving open space on either side of the foregut
These conduits are called pericardioperitoneal canals
What structure, once formed, creates a separated peritineal cavity and a pleuralpericardial cavity?
pleuroperitoneal folds extend to dorsal body wall adn fuse with dorsal surface fo transverse septum, separatign the caudal and cranial body cavities
What is the name of the strucutre that parallels the pleuroperitoneal fole/membrane, but separates the thoracic cavity instead? What neurovasculature does it carry with it?
What landmark is this fold on the cranial side of?
How does the shape of these canvities change as the embryo grow?
Pleuropericaridal membrane, carries with it the phrenic nerve and the common cardinal veins,
growing cranial to the respiratory direticulum
the pleuropericardial folds meet at the midline, forming distinct pleurla cavity and pericaridal cavity, and eventually forming the fibrous pericardium
As the lungs get bigger, the pleural cavity expands ventrally around the pericaridal cavity, taking some of its space
What strucutre trigers growth and division of the respiratory tree?
What happens if this induction does not take places?
messenger components from splanchnic mesoderm from the pleura
failure of broncial induction leads to pulmonary agenesis
What is the difference in shape as the right and left bronchial buds form?
the right is larger and more vertical
generally get 3 secondary bronchi on the right and 2 on the left
typically 10 tertiary bronchi on the right and 9 on the left
What arre ectopic lung lobes and what are they caused by?
they are accessory lobes that generally arise from extra respiratory diverticula
abnormal patterns lung lobs or abnormal bronchiopulmonary segmentation are caused by defects int eh branching/growth pattern of the bronchiole tree
both are rare
What are the 4 phases of lung development?
- pseudoglandulat (6-16 W)
- lined by columnar epithelium (non-respiratory)
- highly vascular but “isolated” from epithelial
- more glandular than respiratory
- terminal bronchiole most distal
- Canalicular Period (16-26 W)
- Respiratory bronchioles & alveolar ducts form
- columnar epithelium transists to ciliated cuboidal
- capillaries start to abut hte resp. epithelium
- Respiration is possible at the end of this level
- Terminal Saccular Period (26 W- Birth)
- simple squamous epithelium
- terminal sacs becoem alveolar sacs
- Type I pneumocytes & Type II (surfactant)
- alveoli form
- true blood/gas barrier is present
- Alveolar Period (birth- 8 years)
- Alveoli go from 150 million at birth to 300 million
- alveoli become septate
How do newborn lungs look different from adult lungs on an x-ray?
newborn lungs look denser
Growth of what structure is responsible for increased lung volume when comparing newborns to adults?
increase in lung volume is driven by increase in respiratory bronchioles, not an increas in alveoli
septa that form between the alveoli leads to increased gas exchange
The 4th pharyngeal arch carries what nerve?
The 6th pharyngeal arch carries what nerve?
These are both branches of which cranial nerve?
This explains the weird innervation pattern of what structure?
4th: superior laryngeal
6th: recurrent laryngeal
both branches of the vagus (CNX)
explains weird innervation of the larynx, b/c it is formed from 2 arches, it gets 2 sets of innervation
The central tendon of the diaphragm is formed from what precursor structure?
the crura is fromed from what precursor structure?
Central tendon: transverse septurm
Crura: dorsal mesentery
the segmented numbering portions of the lung represent invidual what?
What implications does this have for surgery?
each branch bronchiole tree supports a distinct portion of alveoli
there are no shared alveoli
individual bronchiole segment
you can go in an take out a single lobe w/o impairing function of the rest of the lung
On what surface of the lung do the visceral pleura and parietal pleura meet? Inferiorly they form what structure?
the meet on the medial surface of the lung aroudn the root
fused inferiorly, they form the pulmonary ligament
What condition is caused by sharply defined and typically fluid filled sac in the lung? What is it usually the result of? Where is it most commonly found?
Congenital Bronchogenic Cyst
Result from abnormal branching of the bronchial tree
found along mediastinum, but can be intralobular
What can happen if the pleuroperitoneal membranes are reduced or do nto form at all?
Congenital Diaphragmatic Hernia
results in continuity between peritoneal and throacic cavities, so the abdominal visera enters the thoracic cavity and results in pulmonary hypoplasia (v. serious, generally cannot support life)
What the most common presentation of a Tracheoesophageal Fistula?
What symptoms would lead you to consider this diagnosis?
bombines a fistula witha blind-endign terminaltion of the esophagus (esophagel atresia)
inability to swallow/regurgitation, abdominal distention due to gas, and food/fluids in the lungs
What is the name of the syndrom when the type II pneumocytes dont function adequately, so the surfactant production is not sufficient?
What is the result?
Respiratory Distress Syndrome
Reduction in tension, so alveolar ducts collapse down on themselves, tissue necrosis, build-up of eosinophilic membrane
most common cause of death in premature infants
What is pulmonary hypoplasia?
abnormally small lungs, usually cannot support life
can be diagnosed in utero by direct imaging or abnormal throax dimensions
can have primary of secondary causes; secondary cause diaphragmatic hernia and oligohydramnios
common cause neonatal death
