Embryology L9: Respiratory System

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Questions and Answers

What is the origin of the epithelium in the internal lining of the larynx, trachea, and bronchi?

Ectoderm

Mesoderm

Splanchnic mesoderm

Endoderm (correct)

Which structures are derived from the mesoderm associated with the respiratory system?

Thyroid cartilage (correct)

Bronchial epithelium

Laryngeal epithelium

Muscles of the larynx (correct)

What separates the lung bud from the foregut during development?

Esophageal muscularis

Tracheoesophageal septum (correct)

Laryngeal orifice

Bronchial ridges

At what week does the lung bud begin to separate from the foregut?

4 weeks Signup and view all the answers

What forms as a result of the rapid proliferation of mesenchyme in the larynx?

Laryngeal orifice Signup and view all the answers

How many secondary bronchi does the right bronchial bud form?

3 Signup and view all the answers

Which cranial nerve innervates all laryngeal muscles?

Tenth cranial nerve Signup and view all the answers

What happens to the lung bud during its development into the respiratory system?

It expands into the thoracic cavity Signup and view all the answers

What is the role of type II alveolar epithelial cells during lung maturation?

They produce surfactant to lower surface tension. Signup and view all the answers

Which structures separate the pericardioperitoneal canals from the peritoneal and pericardial cavities?

Pleuroperitoneal and pleuropericardial folds Signup and view all the answers

What changes in the bronchioles enable respiration towards the end of the prenatal period?

Cuboidal cells transform into flat cells. Signup and view all the answers

What is considered the primary function of the pleural cavity?

To cushion the lungs and facilitate expansion. Signup and view all the answers

What happens to the concentration of surfactant in the fluid before birth?

It increases particularly in the last two weeks. Signup and view all the answers

What are the terminal sacs also referred to as during lung maturation?

Primitive alveoli Signup and view all the answers

What initiates the fetal breathing movements before birth?

Aspiration of amniotic fluid Signup and view all the answers

During what period does sufficient blood capillaries develop to ensure gas exchange in the lungs?

In the seventh month of gestation Signup and view all the answers

Study Notes

Embryology L9: Respiratory System

The respiratory diverticulum, the lung bud, emerges from the ventral wall of the foregut during the fourth week of embryonic development.
The lung bud's formation is linked to rising retinoic acid levels prompted by adjacent mesoderm.
The epithelium lining the larynx, trachea, and bronchi, as well as the lungs, are entirely derived from endoderm.
Cartilage, muscle, and connective tissue components of the trachea and lungs arise from splanchnic mesoderm surrounding the foregut.
Initially, the lung bud is connected to the foregut. Later, tracheoesophageal ridges separate it from the foregut, eventually forming the trachea and esophagus.
The respiratory primordium maintains communication with the pharynx through the laryngeal orifice.

Formation of the Lungs Buds

The respiratory diverticulum (lung bud) originates from the ventral wall of the foregut.
The epithelium lining the larynx, trachea, and bronchi, as well as the lungs, is purely endodermal.
Lung bud growth, shaped by surrounding mesoderm, is crucial for proper development.
Cartilage, muscle, and connective tissues that support the lungs and tracheas are derived from the splanchnic mesoderm that is closely associated with the foregut.
Initially, the lung buds are directly connected to the foregut. The lung buds detach and separate from the foregut as they develop, forming the trachea and esophagus.
A crucial step in formation involves the tracheoesophageal septum development, separating the trachea from the esophagus.
The respiratory primordium maintains its connection to the pharynx through the laryngeal orifice.

Larynx

The larynx's inner lining stems from endoderm.
Cartilages and muscles originate from the fourth and sixth pharyngeal arches' mesenchyme.
Rapid mesenchyme growth transforms the laryngeal opening from a slit to a T-shape.
Mesenchyme change into the thyroid, cricoid, and arytenoid cartilages.
Temporarily, the larynx's lumen gets blocked by rapidly proliferating laryngeal epithelium
The tenth cranial nerve (vagus nerve) innervates all the laryngeal muscles.

Trachea, Bronchi, and Lungs

The lung bud divides to form the trachea and two bronchial buds as it detaches from the foregut.
Two bronchial buds (right and left primary bronchi) branch after the fifth week.
The right branches into three secondary bronchi; the left branches into two.
The lung buds project into the pericardioperitoneal space, effectively filling the area.
The mesoderm that wraps around the lungs develops into visceral pleura.
Somatic mesoderm, which covers the body wall, differentiates into parietal pleura.
The pleural cavity forms between visceral and parietal pleura.

Maturation of the Lungs

Bronchioles continuously divide into even smaller bronchial canals throughout the prenatal period until the seventh month.
Some cells lining the respiratory bronchioles transform from cuboidal to flat, facilitating gas exchange.
Terminal sacs, also called primitive alveoli, develop in the respiratory bronchioles.
Adequate capillary networks are built in the terminal sacs by the seventh month to ensure efficient gas exchange.
The number of terminal sacs steadily increases during the final two months of fetal development.
Type I alveolar epithelial cells become thinner for efficient gas exchange, and capillaries penetrate the alveolar sacs.
Alveoli are fully formed only postpartum.
Type II alveolar cells emerge by the sixth month, producing surfactant, a fluid that reduces surface tension within the alveoli, preventing collapse.

Summary

The summary of the respiratory development in embryo.
Information on the various stages of lung growth and development.

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Description

This quiz covers the developmental aspects of the respiratory system, focusing on the embryonic formation of the lung bud from the foregut. Key concepts include the role of endoderm and splanchnic mesoderm in developing respiratory structures, as well as the separation of the lung bud from the foregut. Test your understanding of embryonic respiratory development!