The Respiratory System

The Respiratory System

High School

​

Learning Objectives

• Define the respiratory system and understand its main function.

• Trace the path air takes from the nose to the alveoli.

• Explain the mechanics of breathing and the process of gas exchange.

• Describe the different volumes of air the lungs can hold.

• Identify common disorders that affect the human respiratory system.

Key Vocabulary

​

Pharynx

The pharynx is the throat, a tube shared by both the respiratory and digestive systems.

​

Larynx

The larynx, or voice box, connects the pharynx to the trachea and contains vocal cords.

​

Alveoli

Tiny air sacs at the end of the bronchioles where the vital exchange of oxygen occurs.

​

Diaphragm

A large, flat muscle below the lungs that helps to expand and contract the chest cavity.

​

Gas Exchange

This is the essential process of swapping oxygen for carbon dioxide in the lungs and tissues.

​

Surfactant

A fluid secreted by some alveolar cells which serves to prevent the alveoli from collapsing.

​

​

Introduction to the Respiratory System

• The respiratory system is the group of organs responsible for breathing.

• Its primary role is to supply oxygen (O₂) and remove carbon dioxide (CO₂).

• It consists of airways, lungs, blood vessels, and muscles for breathing.

• Air travels from the nose and mouth to the lungs via the airways.

​

​

Solved Example 1
A person has a vital capacity of 4,800 mL and a residual volume of 1,200 mL. Based on this information, what is their total lung capacity?

​

Step 1: Analyze and Sketch the Problem

​

Solved Example 1
A person has a vital capacity of 4,800 mL and a residual volume of 1,200 mL. Based on this information, what is their total lung capacity?

​

Step 2: Solve for the Unknown

​

Solved Example 1
A person has a vital capacity of 4,800 mL and a residual volume of 1,200 mL. Based on this information, what is their total lung capacity?

​

Step 3: Evaluate the Answer

• The total lung capacity must be greater than both the vital capacity and residual volume, which 6,000 mL is.

• The calculation is a simple addition, and 4,800 + 1,200 correctly equals 6,000, so the answer is reasonable and mathematically correct.

Multiple Choice

What is the primary function of the respiratory system and what is the general path air takes?

• To digest food; path is mouth -> esophagus -> stomach.

• To supply oxygen and remove carbon dioxide; path is nose -> pharynx -> larynx -> trachea -> bronchi.

• To pump blood; path is heart -> arteries -> veins.

• To filter waste; path is kidneys -> ureters -> bladder.

​

​

The Upper Respiratory System

• The nasal cavity is lined with cilia and mucus to trap foreign particles.

• The pharynx, or throat, serves as a passageway for both air and food.

• The larynx, or voice box, connects the pharynx and contains the vocal cords.

• The epiglottis is a flap of cartilage that prevents food from entering the trachea.

​

Multiple Choice

What is the primary role of the epiglottis in the upper respiratory system?

• To filter dust and smoke from the air.

• To change the pitch of the voice.

• To prevent food from entering the trachea.

• To separate the nasal cavity into two sides.

​

​

The Lower Respiratory System

• The trachea, a tube with cartilage rings, splits into two primary bronchi.

• Bronchi branch into smaller bronchioles within the lungs, which are protected by pleura.

• The right lung has 3 lobes; the left has 2 to accommodate the heart.

• Alveoli are tiny sacs for gas exchange and are coated in surfactant.

​

Multiple Choice

What is the purpose of the surfactant secreted in the alveoli?

• To prevent the alveoli from collapsing.

• To provide a place for the heart.

• To reduce friction between the lung lobes.

• To prevent the trachea from collapsing.

​

​

The Mechanism of Breathing

• Humans use a tidal breathing mechanism, powered by the diaphragm muscle.

• ​Inhalation is active: the diaphragm contracts, chest volume increases, pulling air in.

• Exhalation is passive: the diaphragm relaxes, chest volume decreases, pushing air out.

• High CO₂ levels trigger breathing, controlled by the pons and medulla.

Multiple Choice

What event triggers inspiration (inhalation)?

• The diaphragm contracts and moves down, increasing chest volume.

• The brain detects low levels of oxygen in the blood.

• The rib cage gets smaller, decreasing chest volume.

• The diaphragm relaxes and moves up, increasing pressure.

​

​

Gas Exchange in the Body

• In the lungs, oxygen diffuses into blood, forming oxyhemoglobin with hemoglobin.

• ​Waste carbon dioxide (CO₂) diffuses out of the blood into the alveoli.

• In tissues, oxyhemoglobin releases oxygen, which diffuses into the body’s cells.

• CO₂ from tissues enters blood and is transported as bicarbonate or carbaminohemoglobin.

Multiple Choice

How is most carbon dioxide transported in the blood from the tissues to the lungs?

• As carbaminohemoglobin

• Directly dissolved in red blood cells

• As bicarbonate ions

• As oxyhemoglobin

Lung Volumes

• Tidal volume is the air breathed normally at rest.

• Vital capacity is the maximum air you can consciously exchange.

• Residual volume is the air that always remains in your lungs.

​

Solved Example 5
A person has a tidal volume of 500 mL, an inspiratory reserve of 3000 mL, an expiratory reserve of 1200 mL, and a residual volume of 1300 mL. Calculate their vital capacity and total lung capacity.

​

Step 1: Analyze and Sketch the Problem

​

Solved Example 5
A person has a tidal volume of 500 mL, an inspiratory reserve of 3000 mL, an expiratory reserve of 1200 mL, and a residual volume of 1300 mL. Calculate their vital capacity and total lung capacity.

​

Step 2: Solve for the Unknown

• First, calculate the vital capacity by adding the tidal volume, inspiratory reserve volume, and expiratory reserve volume.

• VC = 500 mL + 3000 mL + 1200 mL = 4700 mL.

• Next, calculate the total lung capacity by adding the vital capacity and the residual volume.

• TLC = 4700 mL + 1300 mL = 6000 mL.

​

Solved Example 5
A person has a tidal volume of 500 mL, an inspiratory reserve of 3000 mL, an expiratory reserve of 1200 mL, and a residual volume of 1300 mL. Calculate their vital capacity and total lung capacity.

​

Step 3: Evaluate the Answer

• The calculated vital capacity is 4700 mL, and the total lung capacity is 6000 mL.

• The units (mL) are correct and the answers are reasonable for typical adult lung volumes.

Multiple Choice

Which lung volume represents the air that remains in the lungs after a maximal, forced exhalation?

• Expiratory reserve volume

• Residual volume

• Vital capacity

• Tidal volume

​

​

Respiratory System Disorders

Upper Tract Infections

• ​These infections affect the upper parts of the respiratory system, including the nose, sinuses, throat, and larynx.

• ​​Common ailments are Strep Throat, a bacterial infection, and Sinusitis, which is the inflammation of the sinuses.

• ​Other examples are Tonsillitis, the inflammation of tonsils, and Laryngitis, which affects the voice box or larynx.

Lower Tract Diseases

• ​These are often more serious, affecting the airways and lungs, and include Bronchitis, Pneumonia, and Pulmonary Tuberculosis.

• ​​Emphysema is a disease where the alveoli are damaged, reducing the surface area available for effective gas exchange.

• ​Asthma involves the constriction of the bronchioles, the small airways in the lungs, which makes breathing very difficult.

Multiple Choice

A disease that specifically involves the inflammation and constriction of the bronchioles is known as what?

• Laryngitis

• Asthma

• Emphysema

• Pneumonia

​

Common Misconceptions about the Respiratory System

Misconception	Correction
Breathing is a completely voluntary action.	Breathing is mainly an involuntary response to blood CO2 levels.
The lungs actively pull air in by themselves.	The diaphragm and rib muscles change chest volume, moving air.
The voice box (larynx) only controls loudness.	The larynx controls both volume and pitch.
Air goes directly from the windpipe to air sacs.	The trachea leads to bronchi, then bronchioles, and finally alveoli.

Multiple Choice

How does the structure of the alveoli, being tiny, clustered sacs surrounded by capillaries, directly relate to their function in the respiratory system?

• The structure helps to warm and humidify air before it is exhaled.

• The structure allows the lungs to expand and contract without the help of the diaphragm.

• The large surface area created by many small sacs maximizes the efficiency of gas exchange.

• The clustered nature helps in producing sound for speech.

Multiple Choice

Why does an increase in physical activity, which generates more carbon dioxide (CO₂) in the body, lead to an increase in your breathing rate?

• Because the brain's respiratory centers (pons and medulla) detect high CO₂ levels and trigger faster breathing to expel it.

• Because the heart beats faster and pushes more air into the lungs.

• Because the diaphragm muscle gets tired and starts to contract more rapidly.

• Because the body detects low oxygen levels and signals the lungs to breathe faster.

Multiple Choice

A patient is diagnosed with Emphysema, a condition where the walls of the alveoli are damaged and break down. Predict the primary consequence of this disease on the patient's respiratory function.

• The patient will have difficulty speaking.

• The reduced surface area for gas exchange will lead to lower blood oxygen levels.

• The patient will be unable to inhale as deeply due to a rigid diaphragm.

• The patient's trachea will be at risk of collapsing.

Multiple Choice

Analyze the potential consequences if the epiglottis were to fail to close properly during the act of swallowing. How does this relate to the structure of the pharynx?

• The pitch of the voice would become uncontrollably high.

• Gas exchange would stop because the bronchioles would constrict.

• Food or liquid could enter the larynx and trachea, leading to choking, because the pharynx is a shared passage for both air and food.

• The sense of smell would be impaired because the nasal cavity would be blocked.

​

Summary

• The respiratory system's main role is gas exchange, supplying O₂ and removing CO₂.

• Air travels through the pharynx, larynx, trachea, and bronchi to the alveoli.

• Breathing is driven by the diaphragm; gas exchange occurs in the alveoli.

• Lung volumes measure air movement; various disorders can affect the respiratory tract.

Poll

On a scale of 1-4, how confident are you with the concepts covered in today's review?

• 1

• 2

• 3

• 4