Respiratory System Development Quiz

During which stage of lung development do we see the formation of terminal bronchioles?

What is the main characteristic of the Pseudoglandular period?

During which stage of lung development do we see the formation of alveoli type 1 and 2?

What is the main characteristic of the Canalicular period?

What forms the trachea and larynx?

At which stage of development do respiratory bronchioles give rise to 2 or more respiratory bronchioles?

What is the main characteristic of the epithelial lining of terminal sacs at 24 weeks?

During which period do capillaries begin to bulge into developing alveoli?

What is the main function of the type II cells in the alveoli?

At which stage of development is the air-blood barrier formed?

What is the difference between the number of tertiary bronchial buds in the right and left lungs?

At which stage of development do the bronchopulmonary segments of the mature lung form?

What is the origin of the visceral pleura?

What is the characteristic of the outgrowth of a tracheal diverticulum?

How many orders of airways develop after birth?

Lung Development

Respiratory diverticulum arises as a ventral outpouching of foregut endoderm at 5th week
Three initial rounds of branching produce primordia of two lungs, lung lobes, and bronchopulmonary segments
Embryonic stage: normal lung at 7 weeks of gestation

Pseudoglandular Period (5-17 weeks)

Respiratory tree undergoes 14 more generations of branching, forming terminal bronchioles
All major elements have formed by 17th week, except those involved with gas exchange
Respiration is not possible; unable to survive

Canalicular Period (16-24 weeks)

Lumina of bronchi and terminal bronchioles become larger
Each terminal bronchiole branches into 2 or more respiratory bronchioles
Respiratory bronchiole branches into 3-6 alveolar ducts
Respiratory vasculature begins to develop
Blood vessels come into close apposition with lung epithelium
Lung epithelium differentiates into specialized cell types

Terminal Sac Period (24-36 weeks)

Respiratory bronchioles branch into terminal sacs (primitive alveoli)
Many more terminal sacs with very thin epithelium
Development of lymphatic capillaries
Capillaries begin to bulge into developing alveoli
Contact between epithelial and endothelial cells: Air Blood Barrier
24 wks: Terminal sacs lined mainly by squamous epithelial cells (type I)
Rounded secretory type II cells
Surfactant production begins in 20 wks, increasing during the last 2 wks
26-28 wks: Sufficient terminal sacs and surfactant for survival

Bronchi and Lungs

Lung is a composite of endodermal and mesodermal tissues
Lung bud → Bronchial buds → Grow into Pericardioperitoneal canals → Bronchi and their ramification in lungs
Early in 5th week: Primordium of the main bronchus
Main bronchi → Secondary or stem bronchi → Tertiary or segmental bronchi → 10 in R lung & 8-9 in L lung

Parietal and Visceral Pleura

Splanchnic mesoderm → Visceral pleura
Somatic mesoderm → Parietal pleura

Test your knowledge on the development of the respiratory system, including the lungs and pleura. Learn about the embryonic stages and formation of lungs.