• The Embryonic Period (3–7 Weeks Postconception) ...
• The Pseudoglandular Period (6–17 Weeks Postconception) ...
• The Canalicular Period (16–26 Weeks Postconception) ...
• The Saccular (26–36 Weeks Postconception) and Alveolar Periods (36 Weeks Postconception Through Adolescence)

What are the 5 stages of lung development?

The life of a human lung can be subdivided into five distinct phases: embryonic, pseudoglandular, canalicular, saccular, and alveolar. The embryonic period, during which the lung primordium is laid down as a diverticulum of the foregut, lasts for about seven weeks.

What are the stages of lung development?

The process divides into five stages: embryonic, pseudoglandular, canalicular, saccular, and alveolar stage.

What is the Pseudoglandular period?

The pseudoglandular period (also known as the glandular period) spans weeks six to 16, during which time the developing lung resembles an endocrine gland. By the end of this period, all major lung elements, except those required for gas exchange (e.g. alveoli), have appeared.

What period does lung maturation occur?

The surfactant system, composed of phospholipids that decrease surface tension within the alveoli and prevent alveolar collapse during exhalation, develops in the last trimester, and reaches maturity by approximately 36 weeks. Lung growth continues after birth as alveolar number continues to increase.

Embryology | Development of the Respiratory System

Why is it called Pseudoglandular period?

The first stage of alveolar development, spanning between the fifth and the 16th week of development, is called the pseudoglandular stage. It is so called because of the histological appearance of the primitive alveoli, which resemble glandular tissue.

Which of the period of lung maturation lasts between the 16th to 26th weeks of development?

The pseudoglandular stage takes place between approximately 6 and 17 weeks of GA and is the period when the conducting airways and initial acinar framework develop. The canalicular stage follows from approximately 17–26 weeks GA, during which further development of the lung parenchyma occurs.

What is terminal sac period?

Terminal sac period (24 weeks to birth)

The blood air barrier is formed by the intimate contact between the epithelial and endothelial cells and permits gas exchange. Two types of cells line the terminal sacs at this stage of development, one concerned with gas exchange and the other with the secretion of surfactant.

What are air Saccules?

The exchange of oxygen and carbon dioxide between the alveoli and the blood vessels. The alveoli are the terminal air saccules of the lungs. Fine pulmonary capillaries surround them. Both are lined by layers of extremely thin epithelium and separated by membranes.

What are Endodermal tubules?

The endodermal cells contain abundant endoplasmic reticulum, glycogen and iron-containing material. Various types of tubules in the endoderm are described. The mesenchymal cells vary in appearance; some are stellate with slender cytoplasmic processes, while others are round. A few show signs of phagocytic capacity.

During which trimester of pregnancy do the lungs complete development?

Although it varies, a baby's lungs are not considered fully-functioning until around 37 weeks gestation, which is considered "full-term." However, because conception and development can happen at different rates, this not a hard and fast number.

When does lung surfactant develop?

A baby normally begins producing surfactant sometime between weeks 24 and 28 of pregnancy. Most babies produce enough to breathe normally by week 34. If your baby is born prematurely, they may not have enough surfactant in their lungs. Occasionally, NRDS affects babies that are not born prematurely.

What is lung bud?

Definition. The lung bud sometimes referred to as the respiratory bud forms from the respiratory diverticulum, an embryological endodermal structure that develops into the respiratory tract organs such as the larynx, trachea, bronchi and lungs. It arises from part of the laryngotracheal tube.

When does the prenatal period of development begin?

Prenatal development is the process that occurs during the 40 weeks prior to the birth of a child, and is heavily influenced by genetics. There are three stages of prenatal development—germinal, embryonic, and fetal.

What is alveolar sac?

(al-VEE-oh-ly) Tiny air sacs at the end of the bronchioles (tiny branches of air tubes in the lungs). The alveoli are where the lungs and the blood exchange oxygen and carbon dioxide during the process of breathing in and breathing out.

What happens in the alveolar stage?

In the alveolar phase the alveoli form from the terminal endings of the alveolar sacculi and with time increase their diameter. Already before birth these alveolar sacculi get to be increasingly complex structurally. Thereby, a large number of small protrusions form along the primary septa.

What are the correct pathway of air in respiratory system?

When you inhale through your nose or mouth, air travels down the pharynx (back of the throat), passes through your larynx (voice box) and into your trachea (windpipe). Your trachea is divided into 2 air passages called bronchial tubes. One bronchial tube leads to the left lung, the other to the right lung.

What does the Saccule do?

The saccule is a small membranous sac, paired with the utricle, within the vestibule of the inner ear. It is part of the membranous labyrinth and has an important role in orientation and balance, particularly in vertical tilt ¹.

What are type II pneumocytes?

Type II pneumocytes are larger, cuboidal cells and occur more diffusely than type I cells. They appear foamier than type I cells because of they contain phospholipid multilamellar bodies, the precursor to pulmonary surfactant. Capillaries form a plexus around each alveolus.

When does lung development stop?

The rate of lung development can vary greatly, and the lungs are among the last organs to fully develop – usually around 37 weeks.

What are terminal sacs?

Terminal sacs are thin-walled dilations that develop at the ends of the respiratory bronchioles. During alveolization, the sacs are subdivided by the ingrowth of ridges or crests known as secondary septae.

What is fetal lung maturity?

Fetal lung maturity is established during the 2 to 3 week interval when the L/S ratio increases to 2.2 or more, PI decreases, and PG becomes detectable. Because PG appears later in gestation, it is a good indicator of maturity (positive predictive value >95%).

Which of the following are parts of the lungs?

• lungs.
• trachea (windpipe)
• bronchi.
• bronchioles.
• alveoli.

How many lobes does the left lung have?

The left lung consists of two lobes: the left upper lobe (LUL) and the left lower lobe (LLL). The right lobe is divided by an oblique and horizontal fissure, where the horizontal fissure divides the upper and middle lobe, and the oblique fissure divides the middle and lower lobes.