The respiratory physiology
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The Respiratory Physiology. Respiratory System. Why is our respiratory system so important? We require oxygen for cell growth and repair. The four functions of the respiratory system.

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The Respiratory Physiology

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The respiratory physiology

The Respiratory Physiology

Respiratory system

Respiratory System

  • Why is our respiratory system so important?

    • We require oxygen for cell growth and repair.

  • The four functions of the respiratory system.

    • Moves air through thin membrane material to allow for rapid diffusion (take in oxygen and release carbon dioxide).

    • Provides nonspecific defenses against pathogens

    • Allows for vocal communication

    • Helps control the pH level of body fluid

Parts and functions of the respiratory system

Parts and Functions of the Respiratory System

  • The respiratory tract is divided up into two sections.

  • Conducting portion

    • Begins at the entrance of the nasal cavity to the larynx, pharynx, trachea, bronchi and larger bronchioles

  • Respiratory portion

    • Smallest bronchioles. The site of gas exchange.

The respiratory physiology


  • Most air enters here

  • Cilia and moisture protect from larger particles and pathogens

  • Left and right side is divided by the nasal septum

  • Air comes in turning (turbulence) which allows the air to take longer which causes it to warm and humidify

  • Goblet cells produce mucus and are stimulated by noxious vapors, dust, allergens, etc….



  • Three main parts

    • Nasopharynx

    • Oropharynx

    • Larygpharynx

  • Lined with cells to resist mechanical abrasions, chemical attacks and pathogens



  • Air leaves the pharynx to enter the larynx through the glottis

  • Epiglottis closes during swallowing

  • Thyroid cartilage here may form the Adams apple.

  • Vocal chords are located here.

Vocal cords and sound production

Vocal Cords and Sound Production

  • Vocal chords vibrate as air moves through and sound moves through

  • Shorter chords = higher pitch (kids and women)

  • Longer chords = lower pitch



  • “Windpipe”

  • Tough flexible tube (1 in wide, 11 in long)

  • Branches to form a pair of primary bronchi

  • Supported by 20 tracheal cartridges

  • When this becomes blocked it can be life threatening. If a person can talk or breathe there is no immediate risk.



  • Right and Left primary bronchi to secondary bronchi to tertiary bronchi which branch repeatedly

  • With each branch the tubes get smaller. Eventually they lead to the bronchioles (smallest tubes, 1mm)



  • These are enflamed in an asthma attack

  • They lead to the terminal bronchioles (0.3 – 0.5 mm) which lead to lobules

  • Lobules eventually branch to the gas exchange surfaces of the lungs

Alveolar ducts and alveoli

Alveolar ducts and alveoli

  • Each lung contains approximately 150 million alveoli

  • Air goes from the bronchioles to alveolar ducts to alveolar sacs to individual alveoli

  • Alveolar macrophages protect the alveoli from pathogens, dust and debris

  • Surfacant cells secrete oil to lubricate the alveoli. This reduces surface tension to allow for the pressure required for air intake.

Respiratory membrane

Respiratory Membrane

  • Gas exchange occurs across the respiratory membrane of the alveoli

  • Oxygen and carbon dioxide diffuse across the thin membrane very rapidly

  • Blood is carried into the lungs through the pulmonary artery and is returned by the pulmonary vein

The lungs

The Lungs

  • The right lung has three lobes and the left lung has two lobes

  • Allows for the passage of blood vesselsto traveling to and from the heart

  • Very elastic to be able to change in volume

  • Protected by the ribs

The pleural cavity

The Pleural Cavity

  • The thoracic cavity is cone shaped.

  • The mediastanum divides the thoracic cavity into two pleural cavities…. One for each lung.

Respiratory changes at birth

Respiratory Changes at Birth

  • First breath inflates the entire brachial system and forces the fluid out of the way.

  • The expansion is usually an indication used to determine if a baby took a first breath after being born (used in cases of infant death)

Respiratory physiology

Respiratory Physiology

  • Four steps in the process of respiration

    • Pulmonary Ventilation – physical movement of air in and out of lungs.

    • Gas diffusion across the respiratory membrane.

    • The storage and transport of Oxygen and Carbon-dioxide – this is carried through red blood cells.

    • The exchange of Oxygen and Carbon-dioxide (between the blood and interstitial fluid) Oxygen goes to the tissues and carries out the Carbon-dioxide.

The respiratory physiology

  • Pulmonary Ventilation

    • Inhalation = inspiration

    • Exhalation = expiration

    • The goal is to maintain adequate alveolar ventilation (movement of air into and out of the alveoli)

Pressure and air flow

Pressure and Air Flow

  • Air will flow from a high pressure to a low pressure.

  • When lungs expand it creates a lower pressure and air moves inward (diaphragm contracts)

  • When lungs contract there is a greater pressure and air moves out of the lungs (diaphragm relaxes)

Respiratory volume and rates

Respiratory Volume and Rates

  • Tidal Volume

    • The amount of air moved into and out of the lungs in a single respiratory cycle

  • Expiratory Reserve Volume

    • The amount of air left in your lungs after you have exhaled. Normally we exhale about 500 ml of air. If we force out as much as possible, we would force out about 1000ml of air.

  • Inspiratory Reserve Volume

    • The amount of air that can be taken in over and above the tidal volume (typically 3300ml for men and 1900ml for female)

The respiratory physiology

  • Vital Capacity

    • The total amount of air that can be moved into and out the lungs in a single respiratory cycle (Tidal Volume + Expiratory and Inspiratory reserves)

  • Residual Volume

    • About 1200ml remains after all air has been forced out of the lungs.

  • Minimal Volume

    • If the chest cavity is open there is still air in the lungs due to the surfactant cells preventing total collapse.

Gas exchange at the respiratory membrane

Gas exchange at the respiratory membrane

  • Gas will diffuse across the respiratory membrane to a higher to a lower concentration.

  • Hemoglobin – A protein found in red blood cells which drastically increases the oxygen carrying capacity of RBC

    • If we did not have hemoglobin we would need 300 liters of blood instead of 6 liters of blood to sustain everyday life.

How does hemoglobin work

How does Hemoglobin work

  • A single molecule of hemoglobin simply has multiple attachment sites to which oxygen atoms can combine.

  • Carbon monoxide poisoning occurs when CO enters into the lungs and binds to the hemoglobin, (this is actually a stronger bond than oxygen) taking up “spaces” that are normally reserved for oxygen. So the body basically suffocates internally due to the lack of oxygen.

Control of respiration

Control of Respiration

  • The respiratory rate is the number of breaths per minute

    • Normal adult = 12 – 18 bpm

    • Normal child = 18 – 20 bpm

      The respiratory rhythmicity center is located in the medulla oblongata (stimulus such as emotions and speech patterns can cause the rate of change)

The respiratory physiology

  • The two types of receptors that control breathing automatically are chemoreceptors and mechanoreceptors

  • You can’t die from holding your breath. The increased level of carbon di-oxide will allert the chemoreceptors and your body will force you to breathe.

Aging effects on the respiratory system

Aging effects on the respiratory system

  • Decrease the elasticity of tissues = lower vital capacity.

  • Movements of the chest cage are restricted and therefore it limits pulmonary ventilation (exercising is more difficult)

  • Some degree of emphysema.

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