Embryology 5

Question 1

Broadly speaking, the respiratory system is derived from what embryologic structure?

Answer 1

foregut

Question 2

What are the three primary structures of the upper respiratory system?

Answer 2

nose

nasopharynx

oropharynx

Question 3

Though the respiratory system in general arises from the foregut, the upper respiratory system specifically arises from

Answer 3

the primitive pharynx

Question 4

What are the four primary structures of the lower respiratory system?

Answer 4

larynx

trachea

bronchi

lungs

Question 5

The lower respiratory system develops from

Answer 5

the laryngotracheal groove, an outgrowth of the primitive pharynx

Question 6

Describe the location of the laryngotracheal groove.

Answer 6

laryngotracheal groove lies caudally to the 4th pair of pharyngeal pouches

Question 7

The epithelium and glands of the lower respiratory system are derived from

Answer 7

the endoderm that lines laryngotracheal groove

Question 8

The endoderm of the laryngotracheal groove gives rise to

Answer 8

the epithelium and glands found in the lower respiratory tract

Question 9

Cartilage, connective tissue, and smooth muscle of the lower respiratory system are derived from

Answer 9

the visceral lateral mesoderm that surrounds the foregut

Question 10

The visceral lateral mesoderm of the foregut gives rise to (3)

Answer 10

cartilage

connective tissue

smooth muscle

[all of the lower respiratory system]

Question 11

Describe the fate of the laryngotracheal groove.

Answer 11

laryngotracheal groove → laryngotracheal diverticulum → elongation to become laryngotracheal tube

Question 12

What is the location of the laryngotracheal diverticulum?

Answer 12

located ventrally to the foregut

Question 13

Describe how the primitive pharynx further develops during week 5. (2)

Answer 13

lateral walls of primitive pharynx develop folds called tracheoesophageal folds, which fuse by the end of week 5

ventral laryngotracheal tube is therefore separated from dorsal esophageal tube

Question 14

What is the primordial laryngeal inlet? (2)

Answer 14

the cranial-facing junction of the laryngotracheal tube and esophagus formed during week 5

primordial laryngeal inlet will eventually give rise to larynx

Question 15

What is the tracheoesophageal septum?

Answer 15

the structure that separates the dorsal esophagus from the ventral laryngotracheal tube

Question 16

What causes tracheoesophageal fistulas?

Answer 16

faulty separation of trachea and esophagus

Question 17

Describe the most common manifestation of tracheoesophageal fistulas.

Answer 17

superior part of esophagus ends blind (esophageal atresia), which means that food cannot reach the stomach

Question 18

Describe the milder manifestation of tracheoesophageal fistulas.

Answer 18

patency of trachea and esophagus is preserved, but connections between the 2 tubes cause aspiration of esophageal contents into lungs

Question 19

The epithelium of the larynx develops from

Answer 19

the endoderm of the cranial portion of the laryngotracheal tube

Question 20

Laryngeal cartilages develop from

Answer 20

cartilage portions of pharyngeal arches 4 and 6

[note: does not include epiglottis]

Question 21

The epiglottis develops from

Answer 21

caudal portion of hypobranchial eminence

Question 22

The cranial part of the hypobranchial eminence contributes to

Answer 22

the tongue

Question 23

The laryngeal muscles are derived from

Answer 23

pharyngeal arches 4 and 6

Question 24

The laryngeal muscles are innervated by

Answer 24

laryngeal branches of the vagus nerve (CN X)

Question 25

What gives rise to the respiratory epithelium of the trachea?

Answer 25

endoderm of caudal portion of laryngotracheal tube

Question 26

The endoderm of caudal portion of laryngotracheal tube differentiates into

Answer 26

the respiratory epithelium of the trachea

Question 27

The cartilage, connective tissue, and smooth muscle of the trachea are derived from

Answer 27

the visceral lateral mesoderm that surrounds the endoderm of the laryngotracheal tube

Question 28

The visceral lateral mesoderm that surrounds the endoderm of the laryngotracheal tube gives rise to

Answer 28

the cartilage, connective tissue, and smooth muscle of the trachea

Question 29

Where in the lungs does gas exchange take place?

Answer 29

alveoli

Question 30

Alveoli are derived from

Answer 30

the epithelium of the lung

Question 31

List the pathway from the trachea to the alveoli.

Answer 31

trachea → bronchial tree ( → bronchi → bronchioles → respiratory bronchioles) → alveoli

Question 32

Describe the pathway of lung development.

Answer 32

branching of respiratory buds into 2 bronchial buds bronchial buds expand into pericardioperitoneal cavities in week 5, bronchial buds have formed 2 primary bronchi

Question 33

Differentiate between the right and left bronchus.

Answer 33

right bronchus is more vertically oriented

Question 34

By week 5, the two primary bronchi have formed. How do they develop further?

Answer 34

primary bronchi branch into lobar (secondary) bronchi [3 on right, 2 on left] and then further into segmental (tertiary) bronchi [10 on right, 8-9 on left]

Question 35

Why do aspirated foreign objects tend to lodge in the right bronchus?

Answer 35

because it is more vertically oriented

Question 36

What is the significance of week 26 in embryological lung development?

Answer 36

specialized lung cells start to produce surfactant

Question 37

What is the function of surfactant in the lungs? (2)

Answer 37

reduces surface tension of alveoli essential for efficient gas exchange

Question 38

Babies born prematurely, but after 26 weeks of gestation, may experience

Answer 38

respiratory distress syndrome, because surfactant production has not reached maximum

Question 39

What is a treatment option for babies in respiratory distress due to premature birth and therefore inadequate surfactant production?

Answer 39

corticosteroids

Question 40

(T/F) Lung maturation continues into childhood.

Answer 40

**True**. New alveoli are added until ~8 years of age.

Question 41

The embryological formation of the bronchial tree is typically considered complete at what point of time?

Answer 41

by week 24 (at which point, 17 orders of branching have occurred)

Question 42

What is lung hypoplasia?

Answer 42

poorly developed bronchial tree

Question 43

What is the result of lung hypoplasia?

Answer 43

diminished vital capacity

Question 44

What are the symptoms of lung hypoplasia?

Answer 44

tachypnea (rapid breathing) respiratory distress under stressful conditions (i.e. exercise)

Question 45

What is the cause of lung hypoplasia? (2)

Answer 45

_compression of developing lungs, due to:_ (1) decreased amniotic fluid (2) diaphragmatic hernia