Embryology of respiratory system

Question 1

The median outgrowth where the embryological development of the respiratory system start is known as what?

Answer 1

laryngotracheal groove

Question 2

1. The laryngotracheal groove is the primordium for which structures and also where do this groove appear?
2. Name the pharyngeal pouch pair where the laryngotracheal groove is formed.

Answer 2

Primordium of tracheobronchial tree and lungs
Found on the floor caudal end of anterior foregut (Primordial pharynx)
2. 4th pair

Question 3

1. The endodermal lining of laryngotracheal groove forms which structures?
2. The splanchnic mesoderm surrounding foregut forms?

Answer 3

1. Pulmonary (Respiratory) epithelium of trachea, and larynx and bronchi
   - also forms glands for this structures.
2. connective tissue, smooth muscle, cartilage of larynx, trachea and bronchi

Question 4

By end of 4th week
1. Laryngotracheal groove has protruded to form pouch-like —————-
2. Lies ventral to caudal part of ————–
3. Diverticulum elongates and becomes invested with ————-
4. Distal end of diverticulum enlarges to form globular ————-
5. Single bud from which ————— arises
6. Right and left primary bronchial buds First appear as two lateral outpouchings on either side of ——————

Answer 4

1. Laryngotracheal diverticulum
2. Foregut
3. splanchnic mesenchyme
4. respiratory (lung) buds
5. tracheobronchial tree
6. tracheal primordium

Question 5

1. Laryngotracheal diverticulum separates from ——–A———–
   Maintains communication via ———B————-
   Tracheoesophageal folds develop in ——-C———-
   Come together and fuse to form ——–D——
2. All this happen by end of which week.

Answer 5

1.A. Primordial pharynx
B. primordial laryngeal inlet
C. Diverticulum
D. tracheoesophageal septum
2. end of week 5

Question 6

The tracheoesophageal septum divide cranial end of foregut o which parts and explain their primordium

Answer 6

Septum divides cranial end of foregut into:

Ventral part
Laryngotracheal tube
Primordium of larynx, trachea, bronchi, and lungs
Opening into pharynx becomes primordial laryngeal inlet.

Dorsal part
Primordium of oropharynx and esophagus

Question 7

The endoderm of the cranial end of laryngotracheal tube from?/

Answer 7

respiratory epithelium lining.

Question 8

thye laryngeal cartilages are formed from which arch/ arches

Answer 8

4 and 6 pairs of pharyngeal arches

Question 9

the laryngeal cartilages develop from which cells and layer

Answer 9

mesenchyme derived neural crest cells

Question 10

mesenchyme cells at the cranial end of laryngotracheal tube proliferate rapidly to form which structure?

Answer 10

paired arytenoid swelling.
which grow towards the tongue
from T shaped laryngeal inlet
Reduce the developing laryngeal lumen to a narrow slit.

Question 11

what result as a temporal occlusion of laryngeal lumen?

Answer 11

the rapid proliferation of the laryngeal epithelium.

Question 12

by which week does the above recanalization occur?

Answer 12

10 week

Question 13

what structure of the larynx form during the process of recanalization?

Answer 13

laryngeal ventricles

Question 14

what happens to the hypopharyngeal eminence?

Answer 14

it protrusion is produced by the proliferation of mesenchyme in the 3rd and 4th pharyngeal arches
.

Question 15

results of the protruded hypopharyngeal eminence?

Answer 15

caudal/ posterior—- forms epiglottis
ventral/ anterior — forms posterior 1/3 part of the tongue

Question 16

Where does the laryngeal muscle develop?

Answer 16

from the myoblast in the 4th and 6th pairs of the pharyngeal arches

Question 17

innervation of the laryngeal muscle ?

Answer 17

Innervated by laryngeal branches of vagus nerves that supply these arches

Question 18

The high position of the larynx allow the epiglottis too?

Answer 18

come into contact with the soft palate

Question 19

the relationship between the epiglottis and soft palate

Answer 19

provide an almost separate respiratory and digestive tract.

Question 20

What does the splanchnic mesenchyme surrounding laryngotracheal tube form?

Answer 20

cartilage, connective tissue and laryngeal muscle.

Question 21

what develops during the 4th week at the caudal end of the laryngotracheal diverticulum?

Answer 21

respiratory Bud

Question 22

in which canals do primary bronchial buds grow laterally into?

Answer 22

pericardioperitoneal canals

Question 23

pericardioperitoneal canal are primordial of what ?

Answer 23

pleural cavity

Question 24

Bronchial buds (together with surrounding splanchnic mesenchyme) form:

Answer 24

bronchus and their branches in the lungs
early in the fifth week: connection of each bronchi with trachea enlarges to form primordia of main bronchi

Question 25

by which do the segmental bronchus form:

Answer 25

by 7th week.

Question 26

Segmental bronchi (with surrounding mesenchyme) form:

Answer 26

primordia of bronchopumonary segmements

Question 27

Segmental bronchi (with surrounding mesenchyme) form:

Answer 27

primordia of bronchopumonary segmements By 24 weeks: - Approximately 17 orders of branches have formed - Respiratory bronchioles have developed Additional seven orders of airways develop after birth

Question 28

Splanchnic mesenchyme surrounding developing bronchi form:

Answer 28

- Cartilaginous plates of bronchi - Bronchial smooth muscle & connective tissue - Pulmonary connective tissue and capillaries

Question 29

Name the layer acquired by lungs from the splanchnic mesenchyme?

Answer 29

Visceral layer.

Question 30

content of pseudogladnular stage

Answer 30

- Cartilaginous plates of bronchi - Bronchial smooth muscle & connective tissue - Pulmonary connective tissue and capillaries

Question 31

The canalicular stage

Answer 31

16 - 25 Weeks Overlaps pseudoglandular stage - Cranial segments of lungs mature faster than caudal segments Lumina of bronchi and terminal bronchioles become larger Lung tissue becomes highly vascular

Question 32

what happens during the 24th week of the canalicular stage?

Answer 32

By 24 weeks: - Each terminal bronchiole has formed two or more respiratory bronchioles Each respiratory bronchiole will divide into multiple primordial alveolar ducts

Question 33

during which week is the pseudoglandular stage occur?

Answer 33

5th and 17th week Histologically, developing lungs resemble exocrine glands

Question 34

what happens to the 16th week of the pseudoglandular stage?

Answer 34

all major element of the lungs are developed expect the one for respiratory exchange respiration is not possible fetuses born at this stage will not survive

Question 35

The saccule stage

Answer 35

many more terminal sac hat have developed and their epithelium thins capillaries bulge into terminal sacs

Question 36

what is established by close contact of ------------- and ------------cells

Answer 36

close contact between epithelium and endothelium cells establishes a blood-air barrier

Question 37

name the blood-air barrier

Answer 37

alveolar capillary membrane per

Question 38

what lines the terminal sacs at the 26th weeks

Answer 38

mainly lined by type 1 pneumocytes - Squamous epithelial cells of endodermal origin - Gas exchange occurs across these cells Type II Pneumocytes scattered amongst Type I Pneumocytes - Rounded secretory epithelial cells of same endodermal origin - Secrete pulmonary surfactant

Question 39

pulmonary surfactant secreted by the type 2 pneumocyte does what?

Answer 39

counteracts/prevents surface tension forces at the air-alveolar interface. Facilitates expansion of terminal sacs by preventing collapse of sacs during exhalation

Question 40

production of surfactant begins.--------?

Answer 40

at 20-22 week does not reach the needed level till the 24th week -late fetal period.

Question 41

the production of surfactant increase during----------weeks of pregnancy

Answer 41

last 2 weeks

Question 42

alveolar stage

Answer 42

terminal sacs comparable to alveoli are present at 32 weeks -with thin squamous epithelial layer

Question 43

late fetal peroid

Answer 43

Lungs capable of respiration - Alveolocapillary membrane thin enough for effective gas exchange - Although lungs do not perform this function until birth - Well developed to function at/from birth

Question 44

fetal alveolar stage

Answer 44

Primordial alveoli enlarge as lungs expand Greatest increase in size of lungs  increase in number of respiratory bronchioles and primordial alveoli (rather than increase in size of alveoli)

Question 45

AFTER Birth

Answer 45

Lung development during first few months after birth characterized by exponential increase in surface area of the air–blood barrier - Multiplication of alveoli and capillaries Approximately 150 million primordial alveoli (½ adult number) present in full-term neonate Adult number of 300 million alveoli achieved by 8 years

Question 46

name the 3 factors important for normal lung development.

Answer 46

- Adequate thoracic space for lung growth - Fetal breathing movements - Adequate amniotic fluid volume

Question 47

Define Areation of lung

Answer 47

involves rapid replacement of interalveolar fluid with air

Question 48

how is the fluid in lungs cleared?

Answer 48

via mouth and nose by pressure on fetal thorax during vaginal delivery into pulmonary capillaries, arteries and veins

Question 49

respiratory distress syndrome

Answer 49

Results from surfactant deficiency Lungs are underinflated and alveoli contain a fluid that resembles a hyaline membrane Prolonged intrauterine asphyxia (impaired or absent gas exchange) may cause irreversible changes in Type II Pneumocytes  making them incapable of surfactant production Other factors such as sepsis and pneumonia may inactivate surfactant