Formation Of The Respiratory System (EMB)

Question 1

What pharyngeal arch is the respiratory system primarily derived?

Answer 1

6th arch

Question 2

What embryonic layer is the respiratory system primarily derived from?

Answer 2

Endoderm

Question 3

What structure gives rise to the larynx and trachea?

Answer 3

The laryngotracheal diverticulum

The inferior portion gives rise to the lung bud

Question 4

When does the tracheoesophageal septum finish growing?

Answer 4

Week 5

Question 5

From where does the larynx form?

Answer 5

The foregut endoderm and the 6th pharyngeal arch

Question 6

When begins forming from the 6th pharyngeal arch?

Answer 6

Arytenoid swellings

Question 7

What are Arytenoid swellings derived from and what do they eventually give rise to?

Answer 7

Neural crest cells (mesenchyme) covered with endoderm

Give rise to laryngeal cartilages

Question 8

What is the significance of the hypobrancial/hypopharyngeal eminence?

Answer 8

It comes from the 3rd and 4th pharyngeal arches above the glottis and gives rise to the epiglottis

Question 9

Why does recanalization need to occur?

Answer 9

Endoderm from the 6th pharyngeal arch proliferates so much that it fills the glottal space

Question 10

What is recanalization/how does it occur?

Answer 10

It is the apoptosis of the endoderm in the glottal space during the 10th week, and allows the vocal and vestibular folds to develop

Question 11

What is laryngeal atresia and when does it develop?

Answer 11

It develops during the 10th week and it is an obstruction of the upper fetal airway due to failure of of recanalization

Infants present with asphyxia at the time of birth (no breathing) and requires an emergency tracheotomy

Question 12

What are laryngeal webs?

Answer 12

Another form of failure of recanalization but is incomplete atresia

There is still tissue between the vocal cords which blocks the glottis and can lead to respiratory distress and stridor

Question 13

What is laryngomalacia?

Answer 13

The collapse of the supraglottic structures (i.e. epiglottis, arytenoid cartilage, vestibular folds) during inspiration

Unknown mechanism

Question 14

What portion of the trachea are from endoderm?

Answer 14

The epithelium, glands, and pulmonary epithelium

Question 15

What portion of the trachea is from splanchnic mesoderm?

Answer 15

The cartilage, connective tissue, and smooth muscle

Question 16

What is a tracheoesophageal fistula?

Answer 16

It is an abnormal passage between the trachea and esophagus, and is almost always associated with esophageal atresia (blind end esophagus)

Due to failure of tracheoesophageal fold formation in week 5

Question 17

How do you diagnosis a TE fistula?

Answer 17

With an NG tube, and seeing that it coils after about 12 cm

Question 18

What are the different types of TE fistulas?

Answer 18

In 84% of cases, the esophagus has contents spill into the trachea

H-type happens in about 4% of the population and has a connection between the trachea and the esophagus (considered to be much harder to diagnose, but a much higher prevalence of respiratory infections)

Question 19

When does the lung bud form?

Answer 19

Week 4

Question 20

When do the primary bronchial buds form?

Answer 20

Week 5

Question 21

When do the secondary and tertiary bronchial buds form?

Answer 21

Week 6 and 7, respectively

Question 22

What do the secondary bronchial buds correspond to in lung anatomy?

Answer 22

They correspond to the lobes (2 on the left and 2 on the right)

Question 23

What do the tertiary bronchial buds correspond to in regard to lung anatomy?

Answer 23

They correspond to the lung segments (10 on the right, 9 on the left)

Question 24

By what week do we have our terminal bronchioles? What does this indicate?

Answer 24

10 weeks

Indicates that this is when our conduction system is complete

Question 25

What stage in lung development occurs between 15-17 weeks and what occurs during this stage?

Answer 25

Pseudoglandular: when terminal bronchioles are formed, connective tissue NO ALVEOLI If born: can’t survive

Question 26

What stage is between weeks 16-25 and what occurs during it?

Answer 26

Canalicular: vascularization, respiratory bronchioles (with primordial alveolar ducts) and terminal sacs (primitive alveoli) If born: 50/50 survival, but the later the better

Question 27

What demographics tend to do better with premature birth?

Answer 27

African Americans and females

Question 28

What aspect of the lungs develops first?

Answer 28

Superior aspect

Question 29

During what time period does the Terminal Sac stage happen in development? What occurs during this stage?

Answer 29

24 weeks - birth There’s gas exchange and Type I and II pneumocytes are developed (and surfactant produced), lymphatic capillaries are formed If born: will survive

Question 30

During what time period in development does the alveolar stage occur? What happens during this stage?

Answer 30

32 weeks - 8 years Develop the alveolocapillary membrane (both endoderm and mesoderm), more primitive alveoli along with mature alveoli 95% of mature alveoli form postnatally, up to 3 years If born: will survive

Question 31

What are fetal breathing movements (FBMs)?

Answer 31

The fetus forcefully breathes in amniotic fluid in utero in order to facilitate proper lung development

Question 32

What factors are important for proper lung development?

Answer 32

Adequate thoracic space, sufficient amniotic fluid volume, and FBMs Note: oligohydramnios (too little amniotic fluid) retards lung development

Question 33

How is amniotic fluid cleared from the lungs during birth?

Answer 33

Natural: when going through the vaginal canal, the pressure on the thorax pushes out the fluid C-section: the fluid drains into the pulmonary capillaries, arteries, veins, and lymphatics, and is processed that way

Question 34

What is Hyaline Membrane Disease/Respiratory Distress Syndrome?

Answer 34

Pt presents with tachypnea, nasal flaring, suprasternal/intercostal/subcostal retractions, grunting, cyanosis, ground glass appearance on CXR Due to a lack of surfactant which isn’t being produced by the type 2 pneumocytes (which could be due to the fact they haven’t differentiated yet)

Question 35

What is a congenital diaphragmatic hernia?

Answer 35

Pt presents with respiratory distress, cyanosis, lung hypoplasia (due to insufficient thoracic space), barrel chest, no breath sounds, scaphoid shaped abd, and displaced heart sounds Occurs when intestines migrate into the thorax due to failure of the septum transversum to fold and fuse with the peritoneal folds during week 6 (Also called Foramen of Bochdalek)

Question 36

How do congenital lung cysts present?

Answer 36

Cysts are filled with fluid or air and have a honeycomb appearance on X-ray