Development Of The Respiratory System

2.

Pulmonary surfactant is produced by

Alveolar epithelial cells
Blood cells
Alveolar macrophages
Endothelial cells
Type II alveolar epithelial cells

Correct Answer

A. Type II alveolar epithelial cells

Explanation

Pulmonary surfactant is a substance that reduces surface tension in the alveoli of the lungs, preventing them from collapsing. Type II alveolar epithelial cells are responsible for producing and secreting this surfactant. These cells are specifically designed to synthesize and release surfactant, which helps to maintain the elasticity and stability of the alveoli. Other cell types mentioned, such as blood cells, alveolar macrophages, and endothelial cells, do not have the same function and do not produce pulmonary surfactant.

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3.

Which is the earliest period of lung maturation to support respiration in a premature fetus?

Alveolar
Terminal saccular
Pseudoglandular
Canalicular
Embryonic

Correct Answer

A. Canalicular

Explanation

The canalicular period is the earliest period of lung maturation to support respiration in a premature fetus. During this stage, which occurs around 16-26 weeks of gestation, the lungs develop a network of capillaries and the airways continue to branch and differentiate. This allows for gas exchange to occur, although the lungs are still not fully mature. The alveolar period, which occurs after the canalicular period, is characterized by the development of alveoli and is the final stage of lung maturation. The other options listed (alveolar, terminal saccular, pseudoglandular, and embryonic) do not accurately describe the earliest period of lung maturation.

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4

4.

Fetal breathing movements

Occur regularly and continuously
Facilitate exchange of oxygen and carbon dioxide between mother and fetus
Decrease as the time of delivery approaches
Are essential for lung development
Prevent aspiration of amniotic fluid

Correct Answer

A. Are essential for lung development

Explanation

Fetal breathing movements are essential for lung development. These movements facilitate the exchange of oxygen and carbon dioxide between the mother and fetus, ensuring that the fetus receives enough oxygen for proper lung development. As the time of delivery approaches, these breathing movements decrease, indicating that the fetus is preparing for birth and will soon be able to breathe on its own. Additionally, these movements also help prevent the aspiration of amniotic fluid, further ensuring the health and development of the fetus's lungs.

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5.

A newborn infant was observed to have continuous coughing and choking. There was an excessive amount of mucous secretion and saliva in the infant’s mouth. The infant showed considerable difficulty breathing. The physician was not able to pass a catheter through the esophagus into the stomach. The most likely diagnosis is

Tracheal stenoisis
Tracheal atresia
Hyaline membrane disease
Duodenal atresia
Esophageal atresia with tracheoesophageal fistula

Correct Answer

A. Esophageal atresia with tracheoesophageal fistula

Explanation

The symptoms described, including continuous coughing and choking, excessive mucous secretion and saliva, difficulty breathing, and the inability to pass a catheter through the esophagus, are indicative of esophageal atresia with tracheoesophageal fistula. In this condition, the esophagus does not develop properly, leading to a gap or blockage, and there is an abnormal connection between the esophagus and the trachea. This can cause food and saliva to enter the lungs, leading to respiratory distress and other symptoms.

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2

6.

Type I pneumocytes are derived from

Splanchnic mesoderm
Neuroectoderm
Endoderm
Neural crest cells
Intermediate mesoderm

Correct Answer

A. Endoderm

Explanation

Type I pneumocytes are derived from the endoderm. The endoderm is one of the three primary germ layers that form during embryonic development. It gives rise to the epithelial lining of various organs, including the respiratory system. Type I pneumocytes are one of the two main cell types found in the alveoli of the lungs. They are responsible for gas exchange and have a thin and flat structure that allows efficient diffusion of oxygen and carbon dioxide. Since the endoderm gives rise to the respiratory system, it is the correct answer for the origin of type I pneumocytes.

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7.

In a four week embryo, the foregut is divided into a dorsal esophagus and a ventral trachea by

Tracheal ridges
Esophageal ridges
A gut septum derived from neural crest cells
Tracheoesophageal ridges
Laryngeal ridges

Correct Answer

A. Tracheoesophageal ridges

Explanation

During the development of a four-week embryo, the foregut undergoes division into a dorsal esophagus and a ventral trachea. This division is achieved by the presence of tracheoesophageal ridges. These ridges form a physical barrier between the developing esophagus and trachea, ensuring their proper separation and formation.

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8.

Which of the following statements regarding lung maturation is correct?

The canalicular period starts at 26 weeks
Surfactant is produced by type II pneumocytes during the pseudoglandular period
Over 600 million alveoli are present at birth
The blood:air barrier forms during the terminal saccular period
Respiratory epithelium is primarily pseudostratified squamous cuboidal

Correct Answer

A. The blood:air barrier forms during the terminal saccular period

Explanation

During the terminal saccular period, the blood:air barrier forms. This refers to the development of the alveolar-capillary membrane, which is responsible for gas exchange in the lungs. This barrier consists of the thin walls of the alveoli and the adjacent capillaries, allowing for the exchange of oxygen and carbon dioxide between the air and the bloodstream. This process occurs towards the end of lung development, specifically during the saccular stage, which is characterized by the formation of terminal saccules.

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9.

Which of the following statements regarding the developing bronchi is correct?

Terminal bronchioles will branch to give respiratory bronchioles
Secondary bronchi are also known as segmental bronchi
Two secondary bronchi develop on the right and three secondary bronchi develop on the left
A bronchopulmonary segment consists of only primary and secondary bronchi
Terminal bronchioles are also known as quaternary bronchi

Correct Answer

A. Terminal bronchioles will branch to give respiratory bronchioles

Explanation

Terminal bronchioles will branch to give respiratory bronchioles. This statement is correct because terminal bronchioles are the smallest branches of the bronchial tree and they further divide into respiratory bronchioles, which then lead to alveolar ducts and alveoli. This branching pattern allows for the exchange of gases in the lungs.

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Development Of The Respiratory System

One-eighth to one-sixth of the adult number of alveoli are present in the lungs at birth. Their number increases after birth for at least _________ years.

Quiz Preview

Pulmonary surfactant is produced by

Which is the earliest period of lung maturation to support respiration in a premature fetus?

Fetal breathing movements

Type I pneumocytes are derived from

In a four week embryo, the foregut is divided into a dorsal esophagus and a ventral trachea by

Which of the following statements regarding lung maturation is correct?

Which of the following statements regarding the developing bronchi is correct?