HSF 2 - Embryology: Respiratory System Development

Question 1

what is the early phase of lung development?

Answer 1

positioning of the lung primordium and primary lung bud formation

Question 2

what is the late phase of lung development?

Answer 2

mechanism of bronchial branching and cytodifferentiation

Question 3

how is the location of the lungs determined in the early phase?

Answer 3

TBX4 from the T-box transcription factor gene family; linked to increase in RA produced by adjacent mesoderm and expressed in endoderm surrounding the foregut; induces the formation, growth and continued differentiation

Question 4

when does the respiratory system begin to develop? into what?

Answer 4

week 4, formation of laryngeotracheal diverticulum

Question 5

what does the original opening of the respiratory system become? what about the surrounding mesenchyme?

Answer 5

laryngeal orifice; supporting cartilages

Question 6

what separates the trachea from the esophagus?

Answer 6

dorsally by the tracheoesophageal septum

Question 7

what is a tracheoesophageal fistula?

Answer 7

most common malformation in infants, abnormal communication between the trachea and esophagus which is caused by improper formation of tracheoesophageal septum; about 90% come with an esophageal atresia

Question 8

what can misexpression of TBX4 cause?

Answer 8

ectopic endodermal budding and tracheoesophageal fistual

Question 9

how can an esophageal atresia be diagnosed and treated?

Answer 9

suspected in an infant with excessive drooling that is accompanied by choking, coughing, and sneezing; when fed these infants swallow normally but cough and struggle as the fluid returns through the nose and mouth; can become cyanotic and may stop breathing as the overflow of fluid from the blind puch is aspirated the trachea and lungs; can be fixed surgically

Question 10

what are the laryngotracheoesophageal clefts?

Answer 10

1: supraglottic interarytenoid cleft
2: partial cricoid cleft
3: total cricoid cleft
4: laryngoesophageal cleft
air can leak out of the trachea reducing air to the lungs and increasing air in the thoracic cavity

Question 11

what is tracheal stenosis?

Answer 11

narrowing of the trachea

Question 12

what happens at week 5 of development?

Answer 12

buds divide into 2 bronchial buds that will become the primary bronchi

Question 13

what happens to the splanchnic mesoderm of the respiratory system?

Answer 13

differentiates into the smooth muscle, nerves, and blood vessels of the lungs

Question 14

how is the pattern of branching of the lung endothelium regulated?

Answer 14

by the surrounding mesenchyme

Question 15

as you move further into the system, what happens to resistance?

Answer 15

goes up

Question 16

airway segment length is ….. than its diameter

Answer 16

never more than 3x larger

Question 17

what are the different stages in lung development?

Answer 17

embryonic (4-7)
psuedoglandular (8-16)
canalicular (17-26)
terminal sac (26-birth)
postnatal (alveolar development)

Question 18

what happens during embryonic stage of development of the lungs?

Answer 18

initial formation of respiratory diverticulum up to formation of all major bronchopulmonary segments, lungs grow into pleural cavities, differentiation of pleura

Question 19

what happens during psuedoglandular stage of development of the lungs?

Answer 19

major formation and growth of duct systems within bronchopulmonary segments, no respiratory components, no gas exchange, histological structure resembles a gland, induction of vasculogenesis of pulmonary veins is thought to be mediated by vascular endothelial growth factor (VEGF), which is expressed in the epithelium of terminal buds in the human fetal lung during the late parts of this stage

Question 20

what happens during canalicular stage of development of the lungs?

Answer 20

formation of respiratory bronchioles and terminal sacs (primitive alveoli), vascularization increases, capillaries found in walls

Question 21

what happens during terminal sac stage of development of the lungs?

Answer 21

alveoli develop from the respiratory bronchioles, epithelium lining alveoli differentiates into 2 cell types

Question 22

what happens during postnatal stage of development of the lungs?

Answer 22

up to 90% of alveoli can be formed, primary mechanism is septation of pre-existing alveoli

Question 23

how do ectopic lung lobes form?

Answer 23

from additional respiratory buds of the foregut or from misexpression of TBX4 or FGF10

Question 24

what is atelectasis?

Answer 24

incomplete expansion or collapse of parts of or a whole lung

Question 25

what is in the alveolar ducts of infants with IRDS?

Answer 25

covered with fibrin-rich hyaline membranes (damaged cells from collapsed alveoli); cellular debris, proteinaceous edema fluid and some RBCs accumulate

Question 26

what is congenital neonatal emphysema?

Answer 26

no destruction of the alveolar walls; over-distention with air of one or more lobes of the lung caused by collapsed bronchi, bronchial cartilage does not develop

Question 27

what is pulmonary hypoplasia?

Answer 27

poorly developed bronchial tree and can be partial or total; bilateral renal agenesis, insufficient amniotic fluid (oligohydraminos) and increased pressure on fetal thorax - hard to inflate the lungs and limb defects

Question 28

what is potter syndrome?

Answer 28

pulmonary hypoplasia with renal agenesis; for normal development the amniotic fluid must be brought into the lung by fetal breathing movements, leading to distention of the developing

Question 29

polyhydraminos

Answer 29

high volume of amniotic fluid, associated with CNS anomalies and esophageal atresia (including TEF)

Question 30

what forms the diaphragm?

Answer 30

septum transversum forms central tendon; crura develop from mesenchyme around the foregut (dorsal mesentery); peripheral portions from somatic body wall mesoderm

Question 31

what does the pleuroperitoneal membrane form?

Answer 31

separates the pleural and peritoneal cavities

Question 32

what does the pleuropericardial membrane form?

Answer 32

separates the pleural and pericardial cavities

Question 33

where does the phrenic nerve run during development?

Answer 33

within the pleuropericardial membranes

Question 34

what are congenital diaphragmatic hernias?

Answer 34

herniation of abdominal contents into pleural cavity that is caused by failure of pleuroperitoneal membranes to fuse with other components; most common on left posterolateral side; presents with unusually flat abdomen, breathlessness and cyanosis

Question 35

when does the diaphragm become innervated?

Answer 35

week 4; by the phrenic nerve (C3-5)

Question 36

what happens to the diaphragm at week 8?

Answer 36

descent of it to L1

Question 37

the intraembryonic coelom is a _________ _______. what happens to it during development?

Answer 37

continuous space; divides into thoracic cavity and abdominopelvic cavity, then further divides thoracic into 1 pericardial cavity and 2 pleural cavities

Question 38

what is oligohydramnios?

Answer 38

low volume of amniotic fluid that is associated with renal agenesis and obstructive uropathy. complications include pulmonary hypoplasia and limb defects

Question 39

what are congenital bronchial cysts?

Answer 39

airways are baggy and enlarged with collections of mucus in pockets thus increasing incidence of infections; has bronchiectasis (abnormal destruction and dilation of the large airways); cysts can be air or fluid and solitary or multiple, present in honeycomb appearance on radiograph