4- Respiratory Embryology

Question 1

The respiratory system starts as a median outgrowth, called the ________ ________. This is found in the floor of the caudal end of the foregut/primordial pharynx, which is inferior to the 4th pharyngeal arches.

Answer 1

Laryngotracheal Groove

Question 2

The primordium of the _________ _________ develops caudal to the 4th pharyngeal pouches.

Answer 2

Tracheobronchial Tree

Question 3

The endoderm of the Laryngotracheal Groove will give rise to what?

Answer 3

Pulmonary Epithelium
Glands of Larynx
Trachea
Bronchi

Question 4

The Laryngotracheal Groove will evaginate to form the _________ _________ (lung bud).

Answer 4

Laryngotracheal Diverticulum

Question 5

This is what forms the CT, cartilage, and smooth muscle in the structures formed by the endoderm of the Laryngotracheal Groove (Pulmonary Epithelium, Glands of Larynx, Trachea, and Bronchi). It also surrounds the foregut.

Answer 5

Splanchnic Mesoderm

Question 6

The Laryngotracheal Diverticulum elongates and is invested with _______ _______. The distal end then enlarges to form a globular ________ ________, which is the origin of the respiratory tree.

Answer 6

Splanchnic Mesenchyme

Respiratory Bud

Question 7

Tracheoesophageal Folds develop and fuse to form the _________ _________ at the end of the 5th week.

Answer 7

Tracheoesophageal Septum

Question 8

The Tracheoesophageal Septum divides the cranial portion of the foregut into a ventral part and dorsal part. What do each of these parts give rise to?

Answer 8

Ventral Part = Laryngotracheal Tube (Primordium of Larynx, Trachea, Bronchi, and Lungs)

Dorsal Part = Primordium of Oropharynx and Esophagus

Question 9

What makes the epithelial lining of the Larynx?

Answer 9

Endoderm of Laryngotracheal Tube (Cranial End)

Question 10

What makes the cartilages of the Larynx?

Answer 10

Mesenchyme of 4th and 6th pairs of Pharyngeal Arches (NCC derived)

Question 11

In the development of the Larynx, mesenchyme produces paired arytenoid swellings, which convert the primordial glottis into a…

Answer 11

T-shaped Laryngeal Inlet

Question 12

The Laryngeal epithelium proliferates and occludes the Laryngeal lumen, but it recanalizes by the ______ week.

Answer 12

10th

Question 13

Laryngeal _________ form during recanalization, which are bounded by folds of mucous membranes to form _______ _______ and ________ ________.

Answer 13

Ventricles
Vocal Folds (Cords)
Vestibular Folds

Question 14

The Epiglottis develops from the ________ ________, which is produced from mesenchyme of the 3rd and 4th pharyngeal arches.

Answer 14

Hypopharyngeal Eminence

Question 15

What do Laryngeal muscles develop from?

Answer 15

Myoblasts of 4th and 6th Pharyngeal Arches

Question 16

The Larynx is in a (LOW/HIGH) position in the neck of the neonate. Laryngeal (ASCENT/DESCENT) occurs over the first 2 years.

Answer 16

High

Descent

Question 17

The Epiglottis is in contact with the _______ ______, and separates the respiratory and digestive tracts.

Answer 17

Soft Palate

Question 18

This is a rare birth defect, resulting from failure of recanalization of the Larynx. There is an obstruction of the upper fetal airway, or Congenital High Airway Obstruction Syndrome (CHAOS Syndrome).

Answer 18

Laryngeal Atresia

Question 19

In Laryngeal Atresia, the airways become dilated and the lungs are enlarged and filled with fluid. The _________ is flatted or inverted and there is fetal ascites and/or hydrops. Treatment is by ________ _______ of the Laryngeal web.

Answer 19

Diaphragm

Endoscopic dilation

Question 20

In the development of the trachea, the __________ _________ gives rise to the Trachea and two Primary Bronchial Buds.

Answer 20

Laryngotracheal Diverticulum

Question 21

In the development of the trachea, endoderm differentiates into what?

Answer 21

Tracheal Epithelium & Glands

Pulmonary Epithelium

Question 22

In the development of the trachea, the Splanchnic Mesenchyme develops into what?

Answer 22

Tracheal Cartilages
CT
Muscle

Question 23

This is the term for an abnormal connection between the Trachea and Esophagus due to the failure of the foregut endoderm to proliferate rapidly enough in relation to the rest of the embryo. It is the most common congenital anomaly of the lower respiratory tract.

Answer 23

Tracheoesophageal Fistula

Question 24

Tracheoesophageal Fistula occurs in 1 of 3000-5000 births, and 85% of cases are associated with _________ ________, or blind esophagus.

Answer 24

Esophageal Atresia

Question 25

What are symptoms of a Tracheoesophageal Fistula?

Answer 25

– Cannot swallow

– Frequently drool saliva

– Immediately regurgitate food when fed

– GI contents may reflux through fistula into trachea and lungs

– Polyhydramnios (excess amniotic fluid)

Question 26

In a Tracheoesophageal Fistula, Polyhydramnios can occur because…

Answer 26

• • Fluid cannot enter the stomach/intestines for absorption

- - Fluid not transferred for disposal via the placenta

Question 27

During the 4th week, the distal end of the Laryngotracheal Diverticulum enlarges to form the _________ ________.

Answer 27

Respiratory Bud

Question 28

The Respiratory Bud grows ventrocaudally and bifurcates, forming the…

Answer 28

Primary Bronchial Buds

Question 29

The Primary Bronchial Buds grow laterally into…

Answer 29

Pericardioperitoneal Canals

Question 30

The Primary Bronchial Buds branch beginning in the 5th week, and form the _______ _______ _______. These then give rise to _______ _______ _______.

Answer 30

Secondary Bronchial Buds

Tertiary Bronchial Buds

Question 31

The branching pattern of the lung endoderm is regulated by…

Answer 31

Splanchnic Mesenchyme

Question 32

What is the pathway for branching, starting with the Main Bronchi?

Answer 32

Main Bronchi – Secondary Bronchi – Lobar – Segmental – Intrasegmental Branches

Question 33

These develop during the 7th week and consist of segmental Bronchi and mesenchyme.

Answer 33

Bronchopulmonary Segments

Question 34

As lungs develop, they acquire a layer of _______ _______ (from the Splanchnic portion of the Lateral Plate Mesenchyme).

Answer 34

Visceral Pleura

Question 35

The thoracic body wall becomes lined by a layer of _______ _______ (from the Somatic portion of the Lateral Plate Mesoderm).

Answer 35

Parietal Pleura

Question 36

What is the space between the Parietal and Visceral Pleura called?

Answer 36

Pleural Cavity

Question 37

List the periods of lung maturation from least to most developed.

Answer 37

Pseudoglandular
Canalicular
Terminal Sac
Alveolar

Question 38

This period of lung maturation looks like exocrine glands. All major elements of the lung have formed, except those involved with gas exchange. The fetus cannot survive.

Answer 38

Pseudoglandular (5-17 weeks)

Question 39

This period of lung maturation overlaps Pseudoglandular. There is vascularization and Respiratory Bronchioles develop. Primordial alveolar and sacs are present (primitive alveoli). 50/50 chance for survival.

Answer 39

Canalicular (16-25 weeks)

Question 40

This period of lung maturation includes numerous alveoli and a thin epithelium with increased vascularization. There are Type I Pneumocytes, Type II Pneumocytes (Surfactant), and Lymphatic capillaries. Gas exchange can occur and survival is probable.

Answer 40

Terminal Sac (24 weeks - Birth)

Question 41

This period of lung maturation contain an Alveolocapillary Membrane, primitive alveoli (as well as more formed), and mature alveoli.

Answer 41

Alveolar (32 weeks - 8 years)

Question 42

Approximately 95% of mature alveoli develop postnatally and alveolar development is largely completed by age ______. New alveoli are added until year ______.

Answer 42

3

8

Question 43

As the bronchi develop, Splanchnic Mesoderm is critical because it develops what 3 things?

Answer 43

1) Cartilaginous plates (bronchial)
2) Bronchial smooth muscle and CT
3) Pulmonary CT and capillaries

Question 44

These are essential for normal lung development. It is an intermittent pattern that conditions respiratory muscles and is used during fetal monitoring and as a predictor of fetal outcome in pre-term delivery.

Answer 44

Fetal Breathing Movements (FBMs)

Question 45

_________ _________ _________ are forceful enough to cause aspiration of amniotic fluid and helps to stimulate lung development. At birth, aeration of the lungs requires rapid replacement of intra-alveolar fluid with air.

Answer 45

Fetal Breathing Movements (FBMs)

Question 46

At birth, what are the 3 ways intra-alveolar fluid can be cleared (so air can get in)?

Answer 46

1) Released from mouth/nose by pressure on the fetal thorax during vaginal delivery
2) Pulmonary capillaries, arteries, and veins
3) Lymphatics

Question 47

This occurs in 1 out of 15,000 births and is the complete absence of a lung or a lobe and accompanying bronchi, due to Respiratory Bud failure to split into Right and Left Bronchial Buds.

Answer 47

Pulmonary Agenesis

***Unilateral Agenesis refers to just one lung begin absent

Question 48

This is the term for insufficient amniotic fluid production (<500mL). It is typically associated with renal agenesis or failure. If severe or chronic, then it can retard lung development.

Answer 48

Oligohydramnios

Question 49

This occurs in 14 out of 10,000 births and is a restriction of the fetal thorax (from uterine pressure). There is decreased hydraulic pressure on the lungs and affects stretch receptors and lung growth. Risks of this increase significantly with Oligohydramnios at <26 weeks.

Answer 49

Pulmonary Hypoplasia

Question 50

This is the atypical physical appearance of a baby due to Oligohydramnios experienced when in the uterus. It includes clubbed feet, pulmonary hypoplasia and cranial anomalies related to the Oligohydramnios.

Answer 50

Potters Sequence

Question 51

This affects approximately 2% of neonates and accounts for 50-70% of deaths in premature infants. It includes rapid, labored breathing developed shortly after birth. Surfactant deficiency is a major cause.

Answer 51

Respiratory Distress Syndrome

Question 52

Respiratory Distress Syndrome (RDS) can be caused by surfactant deficiency. Lungs are under inflated and alveoli contain a fluid that resembles a “glassy membrane”. This is called ________ ________ _________. There are also irreversible changes in the ________ alveolar cells, making them incapable of producing surfactant.

Answer 52

Hyaline Membrane Disease

Type II

Question 53

What neonatal pathology is being describe by the following symptoms:

• • Tachypnea
• • Nasal Flaring
• • Suprasternal, Intercostal, or Subcostal Retraction
• • Grunting
• • Cyanosis

Answer 53

Respiratory Distress Syndrome

Question 54

These are filled with fluid or air and are thought to be formed by the dilation of Terminal Bronchi. There is a disturbance in Bronchial development during late fetal life. May exhibit wheezing, cyanosis, and difficulty breathing.

Answer 54

Congenital Lung Cysts