Development of The Respiratory System

20 Questions

What is the primary function of the ductus arteriosus during fetal development?

To shunt blood from the pulmonary artery directly to the aortic arch

What is the primary characteristic of type I pneumocytes?

They are basic simple squamous epithelial cells that comprise 90% of the alveolus

During which stage of fetal lung development do the respiratory bronchioles develop?

Canalicular stage

What is the primary function of surfactant in the alveoli?

To reduce the surface tension of the alveoli

What is the prognosis for babies born during the canalicular stage of fetal lung development?

Generally poor, with a low survival rate

What is the characteristic of surfactant that allows it to bind to both water and air within the alveoli?

Amphipathic properties

During which stage of fetal lung development do the alveoli begin to develop?

Terminal sac stage

What is the primary function of type II pneumocytes?

To produce surfactant

Why are the lungs unable to oxygenate blood during fetal development?

Because there are no alveoli

What is the effect of surfactant on the surface tension of the alveoli?

It reduces the surface tension

What is the primary function of the conducting portion of the respiratory system?

To convey, moisten, and warm the air

What is the name of the structure that separates the respiratory diverticulum from the foregut?

Tracheoesophageal septum

During which stage of development do bronchiolar buds branch off from the tertiary bronchi?

Pseudoglandular stage

What is the embryonic structure that gives rise to the respiratory system?

Primitive gut tube

What is the term for the out-pocketing that appears in the proximal part of the primitive gut tube?

Respiratory diverticulum

What is the term for the portion of the respiratory system that includes the trachea, bronchi, and bronchioles?

Lower respiratory system

During which week of development does the respiratory diverticulum appear?

Week 4

What is the term for the segments that will become specific portions of the lung?

Bronchopulmonary segments

What is the term for the process by which the embryo undergoes lateral folding to form the gut tube?

Lateral folding

What is the clinical correlation of premature birth in relation to respiratory development?

Increased risk of respiratory distress

Study Notes

Respiratory System Function

Divided into two parts: conducting portion and respiratory portion
Conducting portion conveys, moistens, and warms the air from outside the body to the lungs
Exchange of gas occurs at the respiratory portion

Respiratory System Structure

Divided into upper and lower respiratory tracts/systems
Upper respiratory system consists of nasal cavity, oral cavity, pharynx, and associated structures
Lower respiratory system consists of trachea, bronchi, bronchioles, and alveoli

Development of Respiratory System

Derived from the primitive gut tube, precursor to the gastrointestinal tract
Gut tube is an endodermal structure formed during early embryonic period
Respiratory diverticulum appears in the proximal part of the primitive gut tube at week 4 of development
Respiratory diverticulum bifurcates into two buds, which become the left and right primary bronchi

Pseudoglandular Stage (Weeks 8-16)

Each bronchopulmonary segment becomes a specific portion of the lung, carrying its own tertiary bronchus and branches of the bronchial and pulmonary arteries
Ducts develop within bronchopulmonary segments
Bronchiolar buds branch off from the tertiary bronchi and begin to proliferate
No gas exchange occurs at this stage due to the absence of alveoli

Canalicular Stage (Weeks 16-26)

Respiratory bronchioles develop, budding off from the terminal bronchioles
No gas exchange membrane, and lungs are not yet functional
Prognosis for babies born during this stage is not high

Terminal Sac Stage (Week 26 onwards)

Alveoli develop, with two types of cells: Type I and Type II pneumocytes
Type I pneumocytes are basic simple squamous epithelial cells (90% of alveolus)
Type II pneumocytes are simple cuboidal cells (10% of alveolus) responsible for producing surfactant
Surfactant is amphipathic, reducing surface tension and allowing alveoli to expand with minimal effort

Learn about the functions and structural divisions of the respiratory system, including the conducting and respiratory portions, upper and lower tracts, and their roles in gas exchange.

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