Overview of the Pulmonary System/Lung Development Flashcards Preview

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Flashcards in Overview of the Pulmonary System/Lung Development Deck (31):

Are humans negative or positive pressure ventilators?



What is a pneumothorax?

A pneumothorax is an abnormal collection of air or gas in the pleural space that causes an uncoupling of the lung from the chest wall.

Like pleural effusion (liquid buildup in that space), pneumothorax may interfere with normal breathing. It is often called collapsed lung, although that term may also refer to atelectasis. One or both lungs may be affected.


What is a pleural effusion?

A pleural effusion is excess fluid that accumulates in the pleural cavity, the fluid-filled space that surrounds the lungs.

This excess can impair breathing by limiting the expansion of the lungs. Various kinds of pleural effusion, depending on the nature of the fluid and what caused its entry into the pleural space, are hydrothorax (serous fluid), hemothorax (blood), urinothorax (urine), chylothorax (chyle), or pyothorax (pus).


How many lobes in each lung?

Right - 3
Left - 2


What is the conducting zone of the lungs?

The first 16 branch points (from trachea => bronchi => bronchioles => terminal bronchioles), are the "conducting zone". These conducting airways are for conducting gas from the atmosphere and do not exchange gas.


What are the transitional and respiratory zones?

Branch points 17-23. This is where gas exchange starts to happen. As you branch further and further, you get less cartilage, more smooth muscle, and more alveoli.

Levels 17-19 have some alveoli.
Levels 20-22 are lined with alveoli.
Level 23 - alveolar sacs


What is the acinus?

Pulmonary acinus: The cluster at the ending of a tiny airway in the lung, where the alveoli (air sacs) are located.


What are Type I Pneumocytes (Type I alveolar cells)?

Type I alveolar cells are squamous (giving more surface area to each cell) and cover approximately 90–95% of the alveolar surface. Type I cells are involved in the process of gas exchange between the alveoli and blood. These cells are extremely thin (sometimes only 25 nm) – the electron microscope was needed to prove that all alveoli are covered with an epithelial lining. These cells need to be so thin to be readily permeable for enabling an easy gas exchange between the alveoli and the blood.


What are Type II Pneumocytes (Type II alveolar cells)?

Type II alveolar cells cover a small fraction of the alveolar surface area. Their function is of major importance in the secretion of pulmonary surfactant, which decreases the surface tension within the alveoli. They are also capable of cellular division, giving rise to more type I alveolar cells when the lung tissue is damaged. These cells are granular and roughly cuboidal. Type II alveolar cells are typically found at the blood-air barrier. Although they only comprise


What is the difference between ventilation and respiration?

Ventilation is the air movement in and out of the lung while respiration is the gas exchange of O2 and CO2 across the alveolar capillary membrane.

Problems with either of these components results in impaired functioning and symptoms of pulmonary insufficiency.


Explain why gas exchange requires integration of several organ systems.

a) the lung, chest wall, and respiratory muscles to provide adequate gas movement
b) the heart and pulmonary circulation to provide adequate blood flow
c) central and peripheral receptors to control and match ventilation and perfusion.


Which embryonic germ layer do the lungs come from?

Embryonic Endoderm


The embryonic endoderm instructs the formation of ______ organs.


The embryonic endoderm instructs the formation of the notochord, heart, and blood vessels.


What is the pleural space?

It is the space in between the parietal pleura (inner lining on the chest wall), and the visceral pleura (outer lining on the lung).


List the conducting airways (3)

Trachea, bronchi, bronchioles


List the gas exchanging airways/units (3)

1. Respiratory bronchioles
2. Alveolar ducts
3. Alveoli


At what level of branching/transition is cartilage lost?

From bronchus to bronchiole


What are the 5 distinct developmental stages in lung embryology?

1. Embryonic Stage
2. Pseudoglandular Stage
3. Canalicular Stage
4. Saccular Stage (or Terminal Sac Stage)
5. Alveolar Stage (or Postnatal Stage)


Do the stages of lung development overlap or do they happen strictly one at a time?

They overlap


True or False: Much of alveolar development happens around the time of birth or after.



What happens during the embryonic stage of lung development? (4)

1. Initially asymmetric branching (to start 3 lobes and 2 lobes)
2. Dichotomous branching pattern
3. Form proximal structures of the tracheobronchial tree to level of segmental bronchi
4. Begins to fill bilateral pleural cavities


What determines the branching pattern of the developing lung?

Mesoderm- the tissue around the invading airway (the lung growing into the mesoderm from the endoderm).


What happens during the pseudoglandular stage? (3)

1. There is differentiation of the conducting airway epithelium. The epithelium starts to have a glandular appearance.
2. Formation of conducting airways is complete. (branch point 16)
3. Development of cartilage, smooth muscle cells, and mucous glands around the airways (these develop from the splanchnic mesenchyme)


What happens during the canalicular stage? (6)

1. Formation of respiratory bronchioles with first delineation of pulmonary acinus.
2. Initial development of pulmonary capillary beds
3. Expansion of airspaces at the expense of mesenchyme
4. Fetal "breathing" starts
5. Epithelial cell differentiation begins
6. Possible to survive but respiratory distress trouble.


What happens in the saccular (terminal sac) stage? (4)

1. Distal growth and branching of terminal saccule
2. Thinning of interstitial space
3. Decrease in cell proliferation
4. Epithelial cell differentiation (Type I and II).

The fetal survival improves from this step as surfactant production is now starting from the type II epithelial cells.


What happens in the alveolar (postnatal) stage? (3)

1. Secondary septal formation (increase in surface area)
2. Presence of true alveoli (90% don't show up until after birth)
3. Type II cells proliferate and differentiate into Type I cells.


The pulmonary arteries develop from which aortic arch?



The pulmonary veins are actually out growths from what structure?

Left Atrium


What are 5 malformations that can happen during development of the respiratory system?

1. Tracheoesophageal fistulas
2. Tracheal or pulmonary atresia
3. Respiratory distress syndrome (premature infants)
4. Gross malformations (generally asymptomatic)
5. Congenital cysts (may be associated with polycystic kidney disease)


What are 3 contributing factors to dyspnea?

1. Increased elastic properties of lung tissue
2. Resistance to airflow in the airways
3. Impaired gas exchange


Name a common obstructive disease

Chronic Obstructive Pulmonary Disease