13. Respiratory System and Thoracic Cavities

Question 1

Laryngotracheal groove forms from the 6th arch, is the primitive pharynx, on the outside of the groove what is it called? (2 names )

Answer 1

Called the laryngotracheal diverticulum or lung bud (respiratory diverticulum) outside of embryo

Question 2

What is the orientation of the esophagus and the trachea at the beginning of formation?

Answer 2

the trachea is anterior to the esophagus

Question 3

How are the trachea and the esophagus separated?

Answer 3

tracheoesophagela folds

Question 4

There are indentation on either side of the tube, the folds will then fuse in the midline, it forms the?

Answer 4

tracheoesophageal septum, separating esophagus from the larynx

Question 5

When are the laryngotracheal diverticulum and the tracheoesophageal septum formed?

Answer 5

4th and 5th week

Question 6

What is important to notice of the tracheoesophageal ridge and why?

Answer 6

It is very long/longitudinal. Defects will be formed d/t it

Question 7

Where does the larynx come from?

Answer 7

the forgut endoderm, laryngotracheal groove (6th pharyngeal arch (4/6 are considered together, there is no 5th arch))

Question 8

What is the first thing seen in the formation of the larynx?

Answer 8

Bilateral arytenoid swellings, which are endoderm covered in mesenchyme (neural crest), which diverge into cartilage

Question 9

What do the arytenoid swellings do?

Answer 9

They grow towards tongue, converting groove to T shaped opening called the glottis (opening/space for air to get through to vocal cords)

Question 10

Hypobranchial/Hypopharyngeal eminence found in arches 3/4, looking at arch 4. What do you see forming in this area?

Answer 10

formation of the epiglottis

Question 11

While the arytenoid swellings are converging, the endoderm proliferates and fills up the glottis, then undergoes apoptosis and that is when you get_____?

Answer 11

recanalization, which is complete by week 10, afterwards there is a space/opening to get into lungs

Question 12

What else does recanalization form within the larynx?

Answer 12

Laryngeal ventricles (later)
Vocal and vestibular folds

Question 13

What congenital abnormality occurs when recanilization (apoptotic process) has failed during week 10. They present with asphyxia at the time of birth and have obstruction of the upper fetal airway?

Answer 13

Laryngeal Atresia

Question 14

What congenital abnormality occurs when there is incomplete atresia and tissue between vocal folds, which block the glottis. Present with respiratory distress, unusual cry and stridor (high pitched cry)? Caused by failure of recanalization in week 10

Answer 14

Laryngeal webs

Question 15

What congenital abnormality occurs when there is collapse of the supraglottic structures during inspiration (epiglottis, arytenoid cartilage). Mechanism unknown, making it difficult to breath.

Answer 15

Laryngomalacia

Question 16

Trachea, which is inferior to the larynx, comes from endoderm and splanchnic mesenchyme. What does each form (2 &3)

Answer 16

Endoderm: Epithelium and glands of trachea
Pulmonary epithelium
Splanchnic: Cartilage rings trach, CT, Smooth muscles

Question 17

What congenital abnormality occurs when there is esophageal atresia (blind end esophagus (no passage way)) and tracheoesophageal fistula (abnormal passage between trachea and esophagus)? Patient is cyanotic, gag/difficulty feeding d/t food in airways. Can be dianosed using nasogastric tube: only 12 cm tubing will fit when usually it is 17cm

Answer 17

Tracheoesophageal fistula

Question 18

What embryological disfucntion occurs for tracheoesophageal fistula to occur?

Answer 18

Tracheoesophogeal folds malfunction and did not divide everything appropriately during week 5

Question 19

The lung bud (respiratory diverticulum) forms in week 4. The lung forms into primary bronchial buds during week 5, primary branch into secondary and secondary branch into tertiary bronchial buds during what weeks?

Answer 19

Secondary (three on right, two on left) during week 6

Tertiary (10 right, 9 left) during week 7

Question 20

What does the endoderm for bronchi grow into during formation?

Answer 20

into splanchnic mesoderm, which extends into the pericardial/peritoneal canals (space)

Question 21

What forms in the lungs after 24 weeks gestation, finishing the formation of the conduction system?

Answer 21

Terminal bronchioles are formed (17 orders of branches)

Question 22

What are the four stages of lung development and what weeks do they occur in? (weeks overlap)

Answer 22

Psuedoglandular (5wks-17)
Canalicular (16wks-25)
Terminal sac (Saccular) (24wks-birth)
Alveolar (32wks-8years)

Question 23

Female lungs develop before male lungs. African american lungs develop before caucasian lungs. What about region of the lungs and development?

Answer 23

Superior aspect of lungs develop before inferior aspect of lungs

Question 24

During the pseudoglandular (5-17) region, the terminal bronchioles are formed with terminal sacs. What is it surround by and cant the infant survive if born?

Answer 24

Surrounded by splanchnic CT with capillaries far from the bronchioles, so no gas exchange can occur, infant dies

Question 25

During the canalicular stage (16-25), terminal bronchioles branch to form respiratory bronchioles, which divide to form the primordial alveolar ducts. Can an infant survive if born during this time?

Answer 25

If the infant is born during weeks 22-25 can survive, if weeks 16-19 probably will not survive, due to no gas exchange / gas exchange availible

Question 26

During the terminal sac or saccular stage (24wks-birth), gas exchange occurs more effectively. This occurs due to formation of squamous epithelium which forms __________ and the secretory epithelial cells which form________ which does what?

Answer 26

type I pneumocytes which assist in gas exchange

Type II pneumocytes which provide surfactant to prevent atalectasis (collpased alveoli)

Question 27

During the alveolar stage (32wks - 8years), formation of alveolar capillary membrane consisting of endoderm and mesoderm. There are some primitive alveoli, however when do most of mature alveoli form?

Answer 27

95% of alveoli form after birth til 3 years, this is why it is so important to not be exposed to smoking/chemicals in younger ages because can damage lungs!

Question 28

Fetal breathing movements are essential for lung development. We need three things for normal lung development, what are they?

Answer 28

1. Fetal breathing movements
2. Adequate thoracic space
3. Adequate level of amniotic fluid

Question 29

How is intra alveolar fluid cleared via vaginal birth and c-section?

Answer 29

Vaginal: pressure of vaginal helps expell fluid through mouth and nose
Csection: Fluid goes into pulmonary capillaries,arteries, veins, and lymphatics to be drained

Question 30

What is oligohydramnios? What can it cause?

Answer 30

too little of amniotic fluid, causing malformation of lungs and can result in pulmonary hypoplasia (risk increases prior to 26 weeks)

Question 31

What are some signs and symptoms of respiratory distress? (5)

Answer 31

Tachypnea
Nasal flaring
Suprasternal, intercostal or subcostal retractions
Grunting
Cyanosis

Question 32

What disease is characterized as having diffuse reticulogranular ground glass appearance (fuzzy white where it should be dark for air in lungs)?

Answer 32

Hyaline Membrane Disease (respiratory distress syndrome)

Question 33

What causes hyaline mebrane disease/respiratory distress syndrome?

Answer 33

There is no air due to a lack of surfactant from the type II pneumocytes in the terminal sac stage. (surfactant allows air to be taken up into the lungs)

Question 34

If patient presents with congenital diaphragmatic hernia (foramen of bochdalek) due to failure of the septum transversum/ plueroperitoneal fold to fuse during week 6, what can we expect to see? (4)

Answer 34

Chest will be barrel shaped d/t intestines in left cavity
Abdomen is sunk in
No breath sounds in normal area
No heartbeat in appropriate area

Question 35

Polyhydramnios (too much amniotic fluid), right after birth baby has excissive secretions from mouth, choking coughing and respiratory distress. What defect is present and how?

Answer 35

Tracheoesophageal fistula, due to tracheoesophageal septum and folds not fusing during week 5

Question 36

What are the different types of lung cysts that are though to resolve from a disturbance in bronchial development during late fetal life?

Answer 36

Air and fluid cysts