MODULE 09 Gas Conditioning
Gases entering the lungs need to be conditioned, or
TAKE A DEEP BREATH & JUMP RIGHT warmed and cleansed, in order to prevent damage to the
lungs.
IN! THE RESPIRATORY SYSTEM
The conditioning of gases occurs
in the nasal cavities and
paranasal sinuses (discussed later
SECTION 01: RESPIRATORY OVERVIEW AND in this module), where air is
swirled around to become
FUNCTION
warmed and humidified. Inhaled
air is cleansed of particulate
The respiratory system facilitates matter through contact with the
breathing and allows the body to mucosal lining of respiratory
acquire oxygen, a molecule epithelium.
necessary for metabolic function and
cell survival, from the air. This complex
system is made up of many organs
contributing to the conduction of air Sound Production
to and from the lungs, as well as gas Production of sound, such as singing or speech, occurs by
exchange within the lungs. forceful expiration of air through the vocal cords in the
larynx, causing them to vibrate.
Breathing involves two cyclic phases: Different tensions of the
vocal cords produce
1. Inspiration (inhalation): draws oxygen rich air into the different sounds with help
lungs from the teeth, lips, and
tongue.
2. Expiration (exhalation): forces oxygen poor air out of the
lungs
FUNCTIONS OF THE RESPIRATORY SYSTEM
The respiratory system not only provides the structures for
mechanical breathing (inspiration and expiration), but also Olfaction
contributes to the functional mechanisms of respiration and The olfactory epithelium covers the top of the nasal cavity.
immunity. The receptors for the sense of smell are located within this
epithelium.
Gas Exchange
Gas exchange involves the movement of gases across When air is inhaled into the nasal
membranes. cavity, airborne molecules dissolve
in the mucus which lines the cavity
External respiration refers to the exchange of gases and stimulates the receptors.
between the air and blood. Inspired oxygen (O2) moves Signals from these receptors travel
across the cellular membranes of the alveolus of the lung to the brain through the olfactory
and its associated capillaries into the blood, while waste, nerve (C N I), resulting in a sense of
carbon dioxide (C O2), moves in the opposite direction and smell.
out of the body through expiration.
Internal respiration is a similar mechanism that exchanges
gases (O2 and C O2) between the blood and cells of the Defense
body. There are many airborne molecules and microbes that can
cause disease. As such, the respiratory system has a line of
defense against these molecules that can cause infection.
The coarse hairs of the
nostrils, the ciliated
cells of the respiratory
epithelium, and the
mucus lining help to
trap particles and
microorganisms from
entering the nose and
the respiratory system.
, FUNCTIONS OF THE RESPIRATORY SYSTEM Goblet Mucus Cells
Goblet cells can be found interspersed throughout the
Description Function pseudostratified epithelium. These cells produce mucus,
Humidify the air. Conditioning causing them to stain lightly in a histological image.
Oxygen moves across a Gas Exchange
membrane. The mucus from goblet
Mucus traps foreign Defense cells forms a protective
debris. layer over the epithelium
Forceful expiration of air. Sound Production and traps particulate
Sensory signalling/ Olfaction matter or microorganisms
that may be inhaled. It
also provides moisture to
CONNECT YOUR KNOWLEDGE humidify the air before it
reaches the lungs.
The respiratory system and cardiovascular system are
closely linked, as deoxygenated blood is pumped from the
heart to the lungs, where the air is oxygenated and
returned to the heart. IDENTIFYING EPITHELIUM
What chamber of the heart does the deoxygenated blood
exit from to enter the lungs?
right ventricle
What chamber of the heart does oxygenated blood re-
enter after exiting the lungs?
left atrium
RESPIRATORY TRACT EPITHELIUM
As you have learned, the R T E is ciliated, with small finger
As you have learned, the respiratory system has many like projections on the apical surface.
important functions, including defense. The structure of the Briefly explain the consequences if a human body did not
respiratory tract epithelium (R T E) plays a large part in the have ciliated respiratory epithelium.
defense of this system and lines most of the surfaces from The cilia permits the upward movement of mucus with
the nasal cavity down to the terminal bronchi. trapped dirt particles like an escalator toward the pharynx,
where it is swallowed. Without the ciliated epithelium, the
Pseudostratified Ciliated Columnar Epithelium body would lose an aspect of immunity, allowing more
The epithelium of the respiratory tract is pseudostratified, debris and potentially harmful pathogens into the
meaning that all cells are attached to the basal lamina but respiratory system. Therefore, without ciliated R T E as a
only some reach the surface. defense mechanism, a person would be more susceptible
to respiratory tract infections (R T I).
The apical surface of the epithelium is covered in cilia,
which are small fingerlike projections extending from the
cell that provide an increased surface area for REGIONS OF THE RESPIRATORY SYSTEM
conditioning air (filtering, humidifying, moistening). These The respiratory system is made up of many structures that
cilia also function to trap inhaled particles and differ in their contribution to the flow of air to and from the
microorganisms caught in mucus, and sweep them back lungs. These structures can be divided into two regions: the
up the respiratory tract and out through the nose and conducting portion and the respiratory portion.
mouth.
THE CONDUCTING PORTION
The conducting portion of the respiratory system functions
to transfer or ‘conduct’ inhaled air from the outside world
to the lung tissue. This portion also conducts air from the
lungs to the outside world.
This is where humidification and trapping of debris occurs.
No oxygen is absorbed into the blood in this region as the
walls of the organs are too thick.
The structures of the conducting portion include:
• Nose and nasal cavity
• Paranasal sinuses
• Pharynx
Pseudostratified: This epithelium appears stratified (multi- • Larynx
layered) as only some of the cells reach the surface. • Trachea
However, all of the cells are attached to the basal lamina, • Primary, secondary and tertiary bronchi
therefore making it a single-layered epithelium. • Terminal bronchioles
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