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.

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

Provides nonspecific defenses against pathogensAllows for vocal communicationHelps control the pH level of body fluid

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 portionSmallest bronchioles. The site of gas

exchange.

Nose 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….

Pharynx

Three main partsNasopharynxOropharynxLarygpharynx

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

Larynx

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 chords vibrate as air moves

through and sound moves through Shorter chords = higher pitch (kids and

women) Longer chords = lower pitch

Trachea

“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.

Bronchi

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)

Bronchioles

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 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

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

Allows for the passage of blood vessels to traveling to and from the heart

Very elastic to be able to change in volume

Protected by the ribs

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

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 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.

Pulmonary VentilationInhalation = inspirationExhalation = expirationThe goal is to maintain adequate alveolar

ventilation (movement of air into and out of the alveoli)

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

Tidal VolumeThe 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 VolumeThe amount of air that can be taken in over and

above the tidal volume (typically 3300ml for men and 1900ml for female)

Vital CapacityThe 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 VolumeAbout 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 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 RBCIf 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 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

The respiratory rate is the number of breaths per minuteNormal adult = 12 – 18 bpmNormal 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 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 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.