Respiratory Embryology Flashcards

1
Q

Starts as a median outgrowth

A

laryngotracheal groove,
Found in the floor of the caudal end of
the foregut/primordial pharynx

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2
Q

Primordium of tracheobronchial

tree

A

develops caudal to 4th

pharyngeal pouches

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3
Q

Endoderm of laryngotracheal

groove

A

pulmonary epithelium
& glands of larynx, trachea, &
bronchi

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4
Q

Splanchnic mesoderm

from lateral plate

A

CT,
cartilage, & smooth muscle in
these structures – surrounds
the foregut

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5
Q

Laryngotracheal groove

will evaginate to form

A

laryngotracheal

diverticulum (lung bud)

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6
Q

Diverticulum elongates &

A

invested w/ splanchnic

mesenchyme

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7
Q

Distal end enlarges to form a

globular

A

respiratory bud,

origin of respiratory tree

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8
Q

Tracheoesophageal folds

develop

A

fuse to form the
tracheoesophageal septum
(end 5th week)

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9
Q

Divides the cranial portion of the foregut:

A

• Ventral part = laryngotracheal tube (primordium of
larynx, trachea, bronchi, lungs)
• Dorsal part = primordium of oropharynx, esophagus

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10
Q

Epithelial lining of larynx

A
= endoderm of
laryngotracheal tube (cranial end)
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11
Q

Cartilages of larynx=

A

mesenchyme of 4th &

6th pairs of PAs (NCC derived)

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12
Q

Mesenchyme produces paired

arytenoid swellings

A

• Convert primordial glottis into

a T -shaped laryngeal inlet

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13
Q

Laryngeal epithelium proliferates

& occludes

A

laryngeal lumen

• Recanalization occurs by 10th
week

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14
Q

Laryngeal ventricles form during recanalization →

A

bounded by folds of mucous membrane to form vocal

folds (cords) & vestibular folds

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15
Q

Epiglottis develops from

A

hypopharyngeal eminence
• Produced from
mesenchyme of the 3-4th
PAs

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16
Q

Laryngeal muscles develop from

A

myoblasts of 4th & 6th PAs

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17
Q

Larynx is in a high position in

A

the neck of the neonate

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18
Q

Epiglottis in contact w/ soft palate →

A

separate respiratory & digestive tracts

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19
Q

Laryngeal descent occurs over

A

the first 2 years

20
Q

Laryngeal atresia

A

Rare birth defect, resulting from failure of
recanalization of the larynx

Obstruction of the upper fetal airway, or
congenital high airway obstruction syndrome
(CHAOS syndrome)
• Airways become dilated, lungs are enlarged &
filled with fluid
• Diaphragm flattened or inverted, & there is
fetal ascites and/or hydrops
• Treatment is by endoscopic dilation of the
laryngeal web.

21
Q

Laryngotracheal

diverticulum →

A
trachea & primary
bronchial buds (2)
22
Q

Endoderm →

A

differentiates
into the tracheal epithelium
& glands, & pulmonary
epithelium

23
Q

Splanchnic mesenchyme

A

tracheal cartilages, CT, &

muscle

24
Q

Tracheoesophageal

fistula:

A

an abnormal
connection between
trachea & esophagus

Most common
congenital anomaly of
the lower respiratory
tract

85% of cases associated with
esophageal atresia, blind
esophagus

Failure of foregut endoderm to proliferate rapidly
enough in relation to the rest of the embryo

25
Q

Tracheoesophageal fistula symptoms

A

Cannot swallow, frequently drool saliva, immediate regurgitation when fed
• Gastric & intestinal contents may also reflux through the fistula into the trachea and lungs
• Polyhydramnios: excess amniotic fluid
• Cannot enter the stomach/intestines for absorption
• Not transferred for disposal via the placenta

26
Q

Distal end of laryngotracheal diverticulum enlarges to form

A

the respiratory bud (4th week)

27
Q

Bud grows ventrocaudally & bifurcates, forming

A

primary bronchial buds

28
Q

Buds grow laterally into

A

pericardioperitoneal canals

29
Q

Primary bronchial buds
branch (begins 5th wk) to
form

A

secondary bronchial
buds → tertiary bronchial
buds

30
Q

Branching pattern of the
lung endoderm is regulated
by

A

splanchnic mesenchyme

31
Q

Bronchopulmonary segments (7th week) =

A

segmental bronchi + mesenchyme

32
Q

path of development

A

Main bronchi → secondary bronchi → lobar → segmental → intrasegmental branches

33
Q

As lungs develop, they acquire a

layer of

A

visceral pleura (splanchnic
portion of lateral plate
mesenchyme)

34
Q

• Lungs & pleural cavities grow

caudally into the

A

mesenchyme of
the body wall
• Will lie close to the heart

35
Q

Thoracic body wall becomes lined

by a layer of

A

parietal
pleura (somatic portion of lateral
plate mesoderm)

36
Q

• Pseudoglandular (5-17wks) lung maturation

A
• Looks like exocrine glands
• All major elements of the lung
have formed, except those
involved with gas exchange
• Fetus cannot survive
37
Q

Canalicular (16-25wks) lung maturation

A
• Overlaps pseudoglandular
• Vascularization
• Respiratory bronchioles
• Primordial alveolar & sacs
present (primitive alveoli)
• +/- surviva
38
Q

Terminal sac (24wks-birth) lung maturation

A
• Numerous alveoli form
• Thin epithelium w/increased
vascularization
• Type I pneumocytes
• Type II pneumocytes
(surfactant)
• Lymphatic capillaries
• Gas exchange can occur
• Survivable
39
Q

• Alveolar (32wks - 8yrs) lung maturation

A
  • Alveolocapillary membrane
  • Primitive alveoli
  • Form more primitive alveoli
  • Mature alveoli
40
Q

As the bronchi develop, splanchnic

mesoderm is critical:

A
esoderm is critical:
1. Cartilaginous plates (bronchial)
2. Bronchial smooth muscle &
connective tissue
3. Pulmonary connective tissue &
capillaries are also derived from
this tissue
41
Q

Fetal Breathing Movements (FBMs)

A

• Essential for normal lung development
• Intermittent pattern that conditions respiratory
muscles
• Used during fetal monitoring & as a predictor of
fetal outcome in preterm delivery
• Forceful enough to cause aspiration of amniotic fluid
• Helps to stimulate lung development
• At birth, aeration of the lungs requires rapid
replacement of intra-alveolar fluid with air

42
Q

FBMs Cleared via:

A
  1. Released from mouth/nose by pressure on the
    fetal thorax during vaginal delivery
  2. Pulmonary capillaries, arteries, & veins
  3. Lymphatics
43
Q

Pulmonary agenesis

A
• Complete absence of a lung
or a lobe & accompanying
bronchi
• Respiratory bud fails to split
into R/L bronchial buds
• Unilateral agenesis
44
Q

Oligohydramnios

A
• Insufficient amniotic fluid production
(<500mL)
• Severe &amp; chronic oligohydramnios
retards lung development
• Pulmonary hypoplasia → restriction
of fetal thorax (from uterine pressure)
• 14:10,000 births
• Decreased hydraulic pressure on the
lungs
• Affects stretch receptors &amp; lung growth
• Risks increases significantly with
oligohydramnios <26wks
45
Q

Respiratory Distress Syndrome

A

• Rapid, labored breathing develops shortly after birth
• Affects approximately 2% of neonates; accounts for 50-70% deaths in
premature infants
• Surfactant deficiency is a major cause of RDS:
• Lungs are underinflated
• Alveoli contain a fluid that resembles a glassy membrane (hyaline membrane
disease)
• Irreversible changes in the type II alveolar cells, making them incapable of
producing surfactant
• Signs and symptoms
• Tachypnea, nasal flaring
• Suprasternal, intercostal, or subcostal retractions
• Grunting & cyanosis

46
Q

Congenital Lung Cysts

A
• Filled with fluid or air
• Thought to be formed by the
dilation of terminal bronchi
• Disturbance in bronchial
development during late
fetal life
• May exhibit wheezing,
cyanosis, difficulty breathing