Respiratory System: Key Concepts from Anatomy to Gas Exchange

Approximately how many times per minute does a person breathe when not exerting themselves?

Approximately 15 times per minute.

About how many breaths does a person take per hour at 15 breaths per minute?

About 900 breaths per hour.

About how many breaths does a person take per day?

About 21,600 breaths per day.

How many alveoli are in each lung?

About 300 million alveoli per lung.

How many total alveoli are in both lungs?

About 600 million alveoli.

What is the total alveolar surface area in an average adult?

About 75 m², or about 807 square feet.

Where does air enter the body?

Through the nose or mouth.

What are the two main jobs of the upper airway?

To warm the air to body temperature and humidify the air.

Why does the respiratory tract need mucus?

Mucus coats the respiratory tract and helps keep the tissues from drying out.

Why is mucus high in water?

So that it can help humidify inhaled air and be coughed up.

How does inhaled air become more humid?

As air crosses surfaces coated with mucus, it picks up water.

Why does the upper airway warm inhaled air?

It helps prepare the air for the deeper parts of the lungs and minimizes the effects of extreme temperatures.

What happens to the normal path of air when a patient has a trache?

Air enters through the trache opening and bypasses the nose and mouth.

Why is humidification important for a patient with a trache?

Because the air bypasses the nose and mouth, so humidifying the air helps the patient as their body becomes accustomed to having a trache.

What do mucus and cilia in the nasal passages do?

They capture matter and particles floating in the air and help move them out of the body.

What happens to particles that make it past the nose hair?

They can be captured by mucus and cilia in the nasal passages.

What are three protective mechanisms of the upper airway?

Warming, humidifying, and removing particles.

What do these protective mechanisms help prevent?

They help prevent damage to the trachea and lungs.

What is the nasal cavity?

The structure labeled #1 in the respiratory pathway.

What is the pharynx?

The throat, labeled #2.

What is the larynx?

The voice box, labeled #3.

What is found in the larynx that vibrates to produce sound or speech?

The vocal cords.

What is the trachea?

The windpipe, labeled #4.

What is another name for the trachea?

The windpipe.

About how long is the trachea?

About 4-5 inches, or 10-12.5 cm.

What is the diameter of the trachea?

Less than 1 inch, or about 2.5 cm.

Why can an object lodged in the trachea become life-threatening?

Because the trachea is relatively small, and a foreign object can block the airway.

Where is the trachea located in relation to the esophagus?

The trachea is in front of the esophagus.

Where does the trachea begin?

Just under the larynx.

Where does the trachea run?

It runs down behind the sternum.

What helps keep the trachea stiff and open?

Incomplete rings of hyaline cartilage and smooth muscle.

What does the trachea divide into?

Two bronchi, one for the right lung and one for the left lung.

What are the primary bronchi?

The larger tubes that branch from the trachea and enter the right and left lungs.

What are secondary bronchi?

Smaller tubes that extend farther into the lung tissue.

What type of cells line the trachea?

Mucus-producing goblet cells and ciliated epithelia.

What does smooth muscle in the trachea do during coughing?

It can contract, decreasing the trachea's diameter and adding force to exhalation.

Why is a strong cough important?

It helps remove mucus, foreign objects, and particles from the airway.

What happens to mucus in the respiratory tract?

It collects particles and is moved upward so it can be removed from the body.

What do cilia do in the trachea?

They move foreign particles trapped in mucus up toward the pharynx.

What can happen to material that reaches the pharynx?

It can be coughed out or swallowed.

What happens to swallowed material after it reaches the stomach?

It can be acted on by gastric acid.

Why is coughing and deep breathing encouraged after surgery?

Because the patient may have been immobile, and coughing and deep breathing help keep the airways open and functioning well.

Are the right and left lungs identical?

No. They are not identical.

Which lung is larger?

The right lung.

How many lobes does the right lung have?

3 lobes.

How many lobes does the left lung have?

2 lobes.

Why is the left lung smaller?

It is smaller to make room for the heart.

What are bronchi?

The larger airway tubes that have cartilage to help keep them open.

What are bronchioles?

The smaller passageways that do not have cartilage.

What is one major difference between bronchi and bronchioles?

Bronchi have cartilage; bronchioles do not.

What helps bronchioles maintain their shape?

Elastic fibers attached to the surrounding lung tissue.

What helps keep bronchioles open?

Inhaled air and the elastic fibers attached to surrounding lung tissue.

What happens to the elastic fibers of bronchioles during breathing?

They expand when filled and become smaller when air is breathed out.

What happens to the size of bronchioles during expiration?

Their volume becomes smaller.

Why do bronchioles have a relatively larger amount of smooth muscle?

Because they are smaller passageways.

What are the two types of bronchioles mentioned?

Terminal bronchioles and respiratory bronchioles.

Which is smaller, terminal or respiratory bronchioles?

Respiratory bronchioles.

What is found around the bronchioles and alveoli where gas exchange happens?

Capillaries.

What structures have smooth muscle in their walls?

The bronchioles have smooth muscle in their walls.

What happens to the walls of the alveoli and terminal bronchioles during inspiration?

They become larger and stretched as air is brought in.

What happens to the volume during expiration?

The volume gets smaller.

What do alveolar sacs look like?

They look like grape-like clusters.

About how many alveolar sacs are attached to the end of the ducts?

About 100 alveolar sacs.

What region contains the alveolar sacs?

The acinar region.

How many alveoli are contained in each alveolar sac?

About 20-30 alveoli.

What is the main function of the alveoli?

Gas exchange.

What are alveoli made of?

Thin-walled parenchymal cells.

How thick is the alveolar wall?

Typically only one cell thick.

Why are alveoli so thin?

Their thin walls allow gas exchange with the capillaries.

Why can alveoli be fragile?

They are only about one cell thick.

What can make breathing difficult when alveoli are affected?

When alveoli fill with fluid, become infected, or become hyperinflated.

What are alveoli in direct contact with?

Capillaries.

What is special about the capillaries around the alveoli?

They have permeable membranes.

How does oxygen move from the alveoli?

Oxygen diffuses from the alveoli into the blood.

Where does carbon dioxide move?

CO₂ diffuses from the blood into the alveoli.

What happens to CO₂ after it enters the alveoli?

It is exhaled.

What happens to oxygen after it enters the capillaries?

It is carried to the tissues.

What is the unique job of the alveoli that does not happen elsewhere in the respiratory tract?

Gas exchange.

How does gas exchange occur in the alveoli?

By diffusion.

What are the three types of alveolar cells mentioned?

Type I pneumocytes, Type II pneumocytes, and macrophages.

Where are Type I and Type II pneumocytes found?

In the alveolar wall.

What do Type I cells look like?

They are long, thin, and elegant-looking.

What do Type II cells look like?

They are more cuboidal, short, and thick.

What type of immune cells are macrophages?

Phagocytic cells.

Where are alveolar macrophages found?

In the lumens of the alveoli and in the connective tissue between them.

What does phagocytic mean?

The cells can absorb/swallow things.

What system are macrophages part of?

The immune system.

Which pneumocyte is responsible for gas exchange?

Type I pneumocytes.

What are Type I cells also called?

Squamous alveolar cells.

Approximately what percentage of the alveolar surface do Type I cells cover?

About 95%.

What are Type I cells responsible for?

Oxygen and carbon dioxide exchange.

What are Type II cells also called?

Granular alveolar cells.

What shape are Type II cells?

Roughly cuboidal.

Approximately what percentage of the alveolar surface do Type II cells cover?

About 5%.

What is the major job of Type II cells?

They secrete pulmonary surfactant.

Which cells produce pulmonary surfactant?

Type II pneumocytes.

What is surfactant made of?

Lipids and proteins.

What does surfactant help maintain?

The structural integrity of the alveoli.

What happens if alveoli lose their structural integrity?

They can collapse.

Why is a collapsed alveolus a problem?

It cannot properly exchange CO₂ and O₂.