Embryo respiratory system Flashcards by Tyler Davis

What is the septum transversum?

Part of mesoderm above buccopharyngeal membrane that develops into mesenchymal cell mass below the heart, forming the majority of the diaphragm and contributing to mesenchyme of liver, etc.

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2 general EARLY steps of lung development

Position lung primordium

2. Primary lung bud formation

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General LATE step of lung development

Bronchial branching and cellular differentiation

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Txn factor that determines location of initial lung development

Linked to increase of what molecule produced by mesoderm

TBX4

Retinoic acid

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When does lung development begin?

From what structure do the lungs/trachea form from?

Week 4

Off of the foregut - to become the esophagus

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Very first step in tracheal development

What does the original opening become?

Bulging of laryngeotracheal (respiratory) diverticulum from the endoderm (foregut/esophagus)

The laryngeal orifice

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What forms just below the laryngeal orifice (split off of the trachea from the esophagus)?

Tracheoesophageal septum

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What tissue layer is directly covering the esophagus and start of the trachea?

What is covering that?

Endoderm

Splanchnic mesoderm

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SO, the opening of the trachea and start of it is called what again?

Laryngeotracheal diverticulum

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Most common malformation during lung/esophageal development

What is it?

Tracheoesophageal fistula

Improper formation of TE septum leads to an esophagus dead end, and the esophagus continuing down from off the trachea

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What’s the name of an esophagus dead?

What’s the name of the esophagus that branches down from off the trachea (comes w/ a dead end higher up)?

Root cause?

Esophageal atresia

TE fistula

Malformation of TE septum

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The esophageal atresia (dead end) fills with air and causes what?

An anterior displacement of the trachea

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How is esophageal atresia diagnosed/presented?

Infant w/ excessive salivation, frequently w/ choking, coughing, sneezing

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How is swallowing vs. movement of food to stomach affected in these cases?

Swallowing = normal

Immediate coughing as fluid returns up through nose and mouth (goes into trachea, causing the cough)

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W/ esophageal atresia and TE fistula, how might the skin of the infant present?

Why?

Cyanotic (blue)

Overflow of fluid into trachea and lungs prevents breathing

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How to surgically fix TE fistula?

Cut distal esophagus from trachea, fix the hole, then suture the esophagus to the proximal (upper) atresia portion to make a normal esophagus

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What is a laryngeal cleft?

Due to what?

Common when?

Space between esophageal opening and tracheal opening, causing food to pass into airways

Difficulty w/ cartilage separating trachea from esophagus

Associated w/ TE fistula, etc.

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Other tracheal structural abnormality associated w/ TE fistula, etc.?

What is it?

Treatments?

Tracheal stenosis

Abnormal narrowing

Balloon dilation and tracheal stents

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When do the primary bronchi begin to form?

Start as what?

Week 5

Bronchial buds

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How is bronchial branching developed?

Sequential budding of primary, secondary, tertiary bronchii, bronchioles, etc.

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Name of lining around lungs themselves

Comes from what layer?

Name of lining around pulmonary cavities

Comes from what layer?

Visceral pleura - splachnic mesoderm

Parietal pleura - somatic mesoderm

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When do the tertiary bronchial buds form?

Week 6

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The splanchnic mesoderm differentiates into the ___, ___, and ___ of the lungs

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Smooth muscle

Nerves

Blood vessels

The ___ regulates the pattern of branching of lung endoderm (inner lining)

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Surrounding mesenchyme

Bronchioles and alveoli are designed to maximize ___ while minimizing ___

Surface area for gas exchange Resistance to air flow

According to what equation, increased alveolar surface area (more branches) should ___ resistance due to decreased diameter SO, an airway segment is never more than ___ its diameter

R = L/r4 Increase 3x

5 main stages of lung development (w/ time periods) At what stage is a fetus technically viable for birth?

``` Embryonic - weeks 4-7 Glandular - weeks 8-16 Canalicular - weeks 17-26 Terminal sac - weeks 26-birth Postnatal (alveolar) ``` Canalicular

What happens in the embryonic stage of lung development? Weeks?

Form diverticulum --> form major bronchopulmonary segments Lungs grow into pleural cavities 4-7

What happens in the glandular stage of lung development? Weeks?

Duct systems w/in BP segments form 8-16

Induction of vasculogenesis of pulmonary veins is mediated by what txn factor? Expressed where? When?

VEGF Epithelium of terminal buds of fetal lung Late glandular stage

What happens in the canalicular stage of lung development? Weeks?

Respiratory bronchioles, terminal sacs form Increased vascularization, capillaries in walls 17-26

2 main cell types in alveoli differentiate from what common cell type?

Epithelial lining of alveoli

Two cell types w/in alveoli (w/ functions)

Type 1 pneumocyte - blood-air barrier Type 2 pneumocyte - secrete surfactant to reduce surface tension and expand alveoli w/ the liquid

Which surfactant type forms first? Which types come later?

Surfactant C A and B

Why is lung surfactant so important in development?

Allows easy expansion of alveoli while reducing surface tension

What % of alveoli form before birth? Mechanism of alveolar growth/division?

10% Septation of pre-existing alveoli

Which alveolar cell type develops first? During what stage? When does the other cell type form?

Type 2 Glandular Canalicular

What is a supernumary bronchus? Main type? Symptoms?

Abnormal division, leading to extra primary/secondary bronchioles Main = bronchus to right upper lobe is directly from trachea, NOT from right primary bronchus NONE (usually)

An additional respiratory bud from the foregut can cause the formation of what irregularity? Generally via misexpression of what txn factor?

Ectopic lung lobe FGF10

What is infant respiratory distress syndrome (IRDS)? Can cause what?

Labored breathing due to lack of surfactant Atelectasis - incomplete expansion or collapse of parts or whole lung

If an alveolus collapses, what happens around it? Why is this bad?

Other alveolus gets bigger Bigger radius = worse surface area for gas exchange

If alveoli are collapsed, what else would be seen?

Dilated bronchioles

W/in collapsed alveolar spaces, what accumulates?

Debris, edema, RBCs

What would you see in alveolar ducts near a collapsed alveolus?

Fibrin-rich hyaline membrane from damaged alveolar cells

Hyaline membrane disease X-ray appearance?

Alveoli filled w/ debris "Ground glass" appearance in chest x-ray

Congenital neonatal emphysema Developmental cause?

Collapsed bronchi cause over-distention of one or more lobes w/ air caught inside Bronchial cartilage doesn't develop

Congenital bronchial cysts Increased incidence of what? Radiograph appearance?

Destruction and dilation of large airways, filled w/ mucous pockets Infection Honeycomb appearance

Pulmonary agenesis Developmental cause?

Complete lack of lung Bronchial bud doesn't develop

Pulmonary hypoplasia Cause? Secondary result? External structural result?

Poorly developed bronchial tree due to insufficient amniotic fluid (oligohydramnios) Renal agenesis, causing lack of fluid to help develop renal system Limb defects b/c not enough room in amniotic sac to move limbs around

Potter syndrome

Pulmonary hypoplasia and kidney failure due to lack of amniotic fluid

Polyhydramnios Cause?

High volume of amniotic fluid Infant can't swallow fluid

The intraembryonic coelom (initial body cavity) is first partitioned into the thoracic and abdominal portions via what?

Formation of the septum transversum and pleuroperitoneal membranes, forming the diaphragm

The thoracic cavity is further divided into pericardial and pleural cavities via what? What nerves run through this structure?

Pleuropericardial membranes Phrenic and vagus

When does the diaphragm become innervated by the phrenic nerve? When does it move down to L1?

Week 4 Week 8

Congenital diaphragmatic hernia Caused by what? Most commonly where?

Hole in diaphragm, causing leaking of abdominal viscera into the thoracic cavity Failure of pleuroperitoneal membranes to fuse Left posterolateral side

Clinical signs of a congenital diaphragmatic hernia

Unusually flat abdomen, breathlessness and cyanosis (compressed lungs)

Common surgical tx for diaphragmatic hernia

Tie of trachea so fluid builds up in lungs and causes herniated organs to be pushed out Then untie trachea, let baby breathe, and cut umbilical cord

Embryo respiratory system Flashcards

(57 cards)