Questions and Answers
What is the origin of the respiratory system?
Endodermal
At what week does the appearance of the respiratory diverticulum (lung bud) occur?
4th week
What does the respiratory primordium develop into?
How many secondary bronchi form on the left side?
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What is the total number of tertiary bronchi on the right side?
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What are the four stages of lung maturation?
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What is formed during the pseudoglandular period?
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What type of cells are responsible for producing surfactant?
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What event occurs during the canalicular period?
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What is established during the terminal sac or primitive alveoli period?
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Study Notes
Formation of Lung Buds
- Lung buds appear during the 4th week of embryonic development as part of the respiratory diverticulum on the ventral wall of the foregut.
- The esophagotracheal septum divides the respiratory diverticulum into ventral (respiratory primordium) and dorsal (esophagus) portions.
Lung Development Overview
- Lung buds continue to form and develop into the trachea and two bronchi (right and left) by the end of the 5th week.
- The right bronchus branches into 3 secondary bronchi, corresponding to 3 lobes.
- The left bronchus forms 2 secondary bronchi for 2 lobes, ultimately leading to the creation of tertiary bronchi (10 on the right, 8 on the left), defining bronchopulmonary segments.
Stages of Lung Maturation
- Maturation of lungs progresses through four distinct periods:
Pseudoglandular Period
- Occurs between 6 and 16 weeks of gestation.
- Formation of terminal bronchioles but no respiratory bronchioles.
Canalicular Period
- Spans from 16 to 26 weeks.
- Type I and Type II alveolar epithelial cells begin to develop; Type II cells produce surfactant.
- Terminal bronchioles divide into smaller canals, leading to the formation of respiratory bronchioles and alveolar ducts.
Terminal Sac (Primitive Alveoli) Period
- Lasts from 26 weeks until birth.
- Involves the formation of terminal sacs (primitive alveoli) and establishment of close contact between alveolar capillaries for effective gas exchange.
Alveolar Period
- This stage is significant for preparing the lungs for functioning at birth, enhancing the capacity for gas exchange.
Key Cell Types
- Type I pneumocytes: Involved in the alveolar structure.
- Type II pneumocytes: Responsible for surfactant production, crucial for reducing surface tension in the alveoli.
Summary of Lung Development Timeline
- 4th week: Appearance of lung buds.
- 5th week: Development of trachea and bronchi.
- 6-16 weeks: Pseudoglandular period, formation of terminal bronchioles.
- 16-26 weeks: Canalicular period, development of surfactant-producing cells.
- 26 weeks to birth: Formation of primitive alveoli and vascular connections.
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Description
Test your knowledge on the formation and development of lung buds during embryonic development. This quiz covers key stages including the pseudoglandular and canalicular periods and the structure of bronchi. Challenge your understanding of respiratory anatomy in early development.
