respiratory embryo. - Cole

Question 1

respiratory diverticulum (lung bud) appears as an outgrowth from the ventral wall of the foregut in week..

Answer 1

4

Question 2

appearance, locaiton of lung dependent upon

Answer 2

increase in retinoid acid (RA) produced by adjacent mesoderm

• which upregulates TBX4 expressed in endoderm of gu tube at site of resp. diverticulum.
• TBX4 induces formation of th e ‘bud’ and continued growth and differentiation of the lungs

Question 3

endoderm gives rise to

Answer 3

• epithlium of internal lining of the larynx
• trachea
• bronchia

Question 4

splanchnic mesoderm gives rise to

Answer 4

-cartilaginous, muscular, CT components of trachea and lungs

Question 5

describe differentiaiton of lung buds from foregut

Answer 5

• initially open communication
• diverticulum expands caudally, 2 longidutinal ridges the ‘tracheoesophageal ridges’ separate from the foregut
• then fuse to form ‘tracheoesophageal septum’ which divides dorsal portion into esophagus and ventral portion, the trache and lung buds

Question 6

resp. primordium maintains its communicaiton with the pharynx through the

Answer 6

laryngeal orifice

Question 7

improper separation of esophagus and trachea by the tracheoesophageal septum can result in

Answer 7

• esophageal atresia with or w/o tracheoesophageal fistulas (TEFs)
• 90% result in upper portion of esophagus ending in a blind pouch and lower segment forming fistula
  4% are isolated esophageal atresia nad H-type TEFs

Question 8

TEFs are a component of…, a collection of defects of unknown causation, occuring more frequently than predicted by chance alone

Answer 8

VACTERL association

• Vertebral anomalies
• Anal atresia
• Cardiac defects
• TEF
• Esophageal atresia
• Renal anomalies
• limb defects

Question 9

indicative of TEF, can be picked up on ultrasound

Answer 9

• polyhydramnios
• amnioitic fluid doesn’t pass ot stomach and instestine
• gastric contents/ amnoitic fluid at birth may enter trachea through a fistula, causing pneumonitis and pneumonia

Question 10

during its separation from the foregut, the lung bud forms the…

Answer 10

trachea
- two lateral outpocketings, the bronchial buds (week 5)
week 6: primary bronchi
week 8: secondary bronchi

Question 11

the narrow spaces for the lungs lying on each side of the foregut

Answer 11

pericardioperitoneal canals

Question 12

mesoderm, covering the outside of the lung, forms the

Answer 12

visceral pleura

Question 13

somatic mesoderm, covering the body wall from the inside becomes the

Answer 13

parietal pleura

Question 14

space b/w the parietal and visceral pleura is the

Answer 14

pleural cavity

Question 15

secondary bronchi to tertiary

Answer 15

2ndary divide repeatedly in a dichotomous fashion, forming 10 tertiary (segmental) bronchi in right lung, and 8 in left, creating the ‘bronchopulmonary segments’ of adult lung

Question 16

before the bronchial tree reaches its final shape..

Answer 16

an additional six divisions form during postnatal life

Question 17

signals for branching emit form the mesoderm and involve

Answer 17

FGFs

Question 18

sufficient no. of mature alveolar sacs and capillaries are present to guarantee adequate gas exchange and ensure premees survivability by the end of the

Answer 18

seventh month

Question 19

terminal bronchioles divide to form.. which divide..

Answer 19

form resp. bronchioles which further divide into 3-6 alveolar ducts
- ducts end in ‘terminal sacs’ (primitive alveoli) surrounded by flat alveolar cells in close contact w/ neighboring capillaries

Question 20

importance for fetal breathing movements?

Answer 20

• begin before birth, cause aspiration of aminiotic fluid

- important for stimulating lung development and conditioning resp. muscles

Question 21

without surfactant…

Answer 21

alveoli would collapse during expiration (atelectasis)

surfactant offsets this surface tension

Question 22

explain role of surfactant and macrophages in delivery

Answer 22

• during 34th week, some of the surfactant enters amniotic fluid and acts on macrophages in the amniotic cavity
• macrophages get activates, migrate across chorion into uterus and begin producing Interleukin-1 beta
• upregulation of these upregulates prostaglandins which cause uterine contractions

Question 23

absent or insufficient surfactant in premature baby causes

Answer 23

respiratory distress syndrome (RDS)

- because of collapse of the primitive alveoli (hyaline membrane disease)

Question 24

growth of the lungs after birth is primarily due to

Answer 24

an increase in the no. of resp. bronchioles and alveoli

• and NOT due to an increase in alveolar size.
• new alveoli formed during first 10 years of postnatal life

Question 25

how do ectopic lung lobes come about?

Answer 25

• formed from additional resp. buds of the foregut that develop indpendent of the main resp. system

Question 26

RDS treatment

Answer 26

• babies w/ artificial surfactant

- mothers w/ premature labor with glucocorticoids to stimulate surfactant production

Question 27

congenital lung cysts description, etiology, radiograph, result in

Answer 27

• formed by dilation of terminal or larger bronchi
• could be small, multiple giving a honeycomb experience in radiograph
• or restricted to one or more larger ones
• usually drain poorly, frequently cause chronic infections

Question 28

lung maturation: pseudoglandular period

Answer 28

5-16 week
branching continued to form terminal bronchioles
- no. resp bronchioles/ alveoli present

Question 29

canalicular period

Answer 29

16-26 week

- each terminal bronchiole divides into 2 or more resp. bronchioles, which in turn divide into 3 to 6 alveolar ducts

Question 30

terminal sac period

Answer 30

26 week to birth

• terminal sacs [primitive alveoli] form
• capillaries establish close contact

Question 31

alveolar period

Answer 31

8 mo to childhood

- mature alveoli have well-developed epithelial endothelial [capillary] contacts