Download the respiratory system

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Level 3 Diploma in Aromatherapy (ABC)
LEVEL 3 DIPLOMA IN AROMATHERAPY
MODULE 14
KNOWLEDGE OF ANATOMY, PHYSIOLOGY & PATHOLOGY FOR
COMPLEMENTARY THERAPIES
THE RESPIRATORY SYSTEM
MODULE 7
COURSE MANUAL
CHRISTINA LYNE
[email protected]
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THE RESPIRATORY SYSTEM
The respiratory and the circulatory system work together to deliver oxygen to the
body's cells and they also enable the cells to expel carbon dioxide. Breathing is the
most fundamental action of the human body. Cells cannot survive without oxygen.
The organs of the respiratory system are:
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Nose & Paranasal Sinuses
Pharynx (throat)
Larynx (voice box)
Trachea (windpipe)
Epiglottis
Two Bronchi & Bronchioles
Alveoli
Two lungs and their coverings - pleura
Ribs & Intercostal Muscles
Diaphragm
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NOSE
The nose is an organ on the face. It is made of 2 nasal bones and hyaline cartilage,
is covered by skin and lined with mucous membrane which contains mucussecreting goblet cells. It has two entrances, called nostrils that allow air to enter into
the body. The hollow space found inside the external and internal portions of the
nose is called the nasal cavity. It is divided into the right and left sides by a partition
called the nasal septum.
Four functions of the nose are:
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Warming air upon entering the body
Moistening so that it does not have a drying effect on the air passages
Trapping inhaled dust and dirt. Fine nasal hairs coated in sticky mucus called
cilia line the inside walls of the nasal cavity. Larger particles of dust, etc. are
usually expelled from the body by sneezing, coughing or blowing the nose
Smelling odours from the inhaled air (olfactory stimuli)
Air can also be breathed in via the mouth. The two openings – the nose and mouth –
meet at the pharynx, which is situated at the back of the mouth.
PARANASAL SINUSES
There are four paranasal sinuses - the frontal, maxillary, ethmoid and sphenoid
sinuses. These are cavities in the bones of the face and the cranium. They are lined
with mucous membrane. They contain air and their function is to lighten the bones
and to give resonance to the voice.
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PHARYNX
This is more commonly known as the throat. The pharynx connects with the back of
the mouth and nose and divides into the larynx and oesophagus. It is about
12.5cms long and is composed of three layers of tissue:
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Mucous membrane lining which protects the underlying tissues from being
damaged as foodstuff passes through during swallowing.
Submucosa which is rich in lymphoid tissue to help guard against infection.
Skeletal muscles help to keep the pharynx open all the time so that breathing
is not prevented. Constrictor muscles help during swallowing, pushing food
and fluid into the oesophagus.
It has several functions:
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It carries food as well as air. It warms and moistens air as it passes
through
Mucus helps to trap dust particles and cilia move the mucus downwards
Small masses of lymphoid tissue which form the tonsils are found at the
back of the pharynx. These produce antibodies for protection, if needed
It is involved with taste via olfactory nerve endings present in the pharynx
It helps in the hearing process - air can enter the middle ear maintaining
atmospheric pressure either side of the tympanic membrane (eardrum)
LARYNX
The larynx is also called the voice box. It contains the vocal chords. It moves up and
down when swallowing. It lies between the tongue at the back of the mouth and the
trachea. During puberty it grows larger in the male, which produces the deeper
voice and the ‘Adam’s apple‘. It is composed of several irregular shaped cartilages.
Several ligaments and membranes help the cartilages to attach to each other and to
the hyoid bone.
The main cartilages listed below are made of rigid hyaline cartilage:
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1 thyroid cartilage (Adam’s apple)
2 arytenoid cartilages
1 epiglottis cartilage – consists of elastic fibrocartilage
1 cricoid cartilage
The thyroid cartilage lies to the front of the neck. It gives the larynx its triangular
shape and is bound with ligaments to the hyoid bone above and the cricoid cartilage
below.
The arytenoid cartilages lie above the cricoid cartilage. They attach to the vocal
cords and pharyngeal muscles and help with voice production.
The epiglottis cartilage is a large, leaf-shaped piece of elastic cartilage. Its base is
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attached to the thyroid cartilage but the ‘leaf‘ is unattached and is free to move up
and down. It acts like a lid and closes during swallowing thus sealing off the air
passages below it. This allows food and fluids to move into the oesophagus,
preventing them from passing into the larynx.
The cricoid cartilage lies below the thyroid cartilage and connects the larynx to the
trachea. It marks the end of the upper respiratory tract.
The larynx is involved with:
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Production of sound i.e. pitch, volume and resonance
Speech
Ensuring that food passes into the oesophagus and not into the respiratory
passages
Moistening, warming and filtering air as it travels through the larynx
Vocal cords
The larynx also houses the vocal cords. These are two pale folds of mucous
membrane which are attached to the inside of the Adam’s apple, and they run
backwards across the larynx. The upper pair called false vocal cords shut off the
larynx when swallowing. They also do not produce sound. The lower pair, the true
vocal cords, is stretched by muscles to produce sound. The cords vibrate as the air
flows past them. If they are loose, the air vibrates slowly, and produces a sound
with a deep pitch. If the cords are pulled tight, the air vibrates much more rapidly,
and produces a high note.
TRACHEA
The trachea is also called the windpipe. This long tube begins just below the larynx
and divides at its lower part into the right and left bronchi. It lies infront of and adjacent to the oesophagus. The wall of the trachea is made up of three layers of tissue:
1. An outer layer containing fibrous and elastic tissue
2. A middle layer consisting of cartilages and bands of smooth muscle
3. An inner lining made of ciliated columnar epithelium, containing mucussecreting goblet cells
It is reinforced with C-shaped rings of hyaline cartilage stacked one on top of
another. These give rigid support to the trachea, helping to keep it open and to
prevent it from bending as the head moves. The main functions are:
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To form a sturdy passageway to allow air to reach the lungs
Minute hair-like projections called cilia move any mucus up towards the larynx
where it is either swallowed of coughed up
The walls of the trachea are lined with mucus which traps any inhaled dust
To warm, moisten and filter air
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BRONCHI
The bronchi are located in the thoracic cavity. Each lung has a bronchus. The right
bronchus enters the right lung and divides into three branches, each one passing to
a lobe. The right bronchus is also wider and shorter than the left bronchus. The left
bronchus enters the left lung, but there are only two branches, each one passing to
a lobe. They are reinforced by cartilage.
The bronchial walls are made of the same cartilage as the trachea and are lined with
mucous membrane. The main function of the bronchi is to carry air into and out of
the lungs.
BRONCHIOLES
These are the airways that lead from a bronchus to the individual alveoli. Their
function is to transport air to the alveoli of the lungs. As the airways get smaller and
smaller, the cartilage rings become smaller and finer until they disappear completely.
The walls gradually become thinner until the cartilage, muscle and connective tissue
disappear, leaving a single layer of simple squamous epithelial cells in the alveolar
ducts and alveoli.
The bronchioles continue to warm and moisten the air, and will remove any particles
of dust by coughing. Each bronchiole ends with small alveoli.
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ALVEOLI
Alveoli are thin-walled, cup-shaped sacs situated at the very end of the respiratory
passageways. They are composed mainly of a single layer of squamous epithelial
cells. Clusters of alveoli look like tiny bunches of grapes surrounded by a dense
network of pulmonary capillaries. The thin walls of the alveoli and the thin walls of
the pulmonary capillaries together form the respiratory membrane.
An adult's lungs contain over 300 million alveoli. The large surface area that they
create is necessary to supply the body with the oxygen that it needs, and to get rid of
carbon dioxide quickly. Their function is to allow gases to be exchanged in the lungs.
This takes place across the respiratory membrane made up of the alveolar wall and
the capillary wall fused firmly together.
Septal cells that lie between the squamous cells secrete alveolar fluid which prevents the alveoli from drying out and stops the alveolar walls collapsing during expiration. They are supported by a network of elastic connective tissue in which macrophages, fibroblasts, nerves, blood and lymph vessels are embedded.
LUNGS
There are two lungs - each situated on either side of the midline in the thoracic
cavity. They are protected by the ribcage. The right lung has three lobes: a superior,
middle and inferior. The left lung has just two: a superior and inferior as there is less
room because of the heart. Each lobe consists of large numbers of lobules. Lungs
allow the exchange of gases into and out of blood. Cilia in the lungs constantly
sweep impurities and deposits out of the lungs to maintain them and keep them
clear.
Each lung is composed of the bronchi and smaller air passages, alveoli, connective
tissue, blood vessels, lymph and nerve vessels all embedded in an elastic connective tissue matrix.
They are covered with and protected by the pleural membrane. This is a serous
membrane and is made up of two layers:
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parietal pleura which lines the walls of the thoracic cavity
visceral pleura which covers the lungs
PLEURA
The lungs are covered and protected by a pleural membrane. The pleura consist of
a closed sac of serous membrane (one for each lung) which contains a small
amount of serous fluid. The outer membrane (parietal pleura) lines the inside of the
chest wall, while the inner membrane (visceral pleura) covers the lung itself. The
narrow space between the two membranes is called the pleural cavity and is filled
with a small amount of serous fluid, which lubricates the membranes and allows for
smooth movement during breathing. This fluid is secreted by the epithelial walls of
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the membrane. The two layers of pleura protect the lungs by preventing friction and
help them to change shape during respiration.
THE RIBCAGE
The ribcage is found in the thoracic cavity. It is made up of 12 pairs of flat, curved
bones called ribs. The rear end of each rib is attached to a thoracic vertebra. The
front ends of the upper seven pairs - the true ribs - are attached to the sternum by
flexible strips of costal muscle. The next three pairs - the false ribs - are each
connected to the rib above, and the lowest two pairs - floating ribs - are attached
only to the backbone. The spaces between the ribs are occupied by the intercostal
muscles, nerves and blood vessels. These muscles contract during breathing
helping the ribs and sternum to lift upwards and outwards which increases the
capacity of the thoracic cavity. This bony frame allows breathing and protects the
internal organs.
INTERCOSTAL MUSCLES
There are 11 pairs of intercostal muscles that connect the bony arches between the
12 pairs of ribs. They are arranged in two layers - the internal and external intercostal muscles. These muscles aid the diaphragm in respiration.
The external intercostal muscles - they help to raise the ribs and are involved in
inspiration.
The internal intercostal muscles - these muscles are used when exhalation
becomes active, as in exercise. Nerve impulses delivered by the intercostal nerves
tell the muscles when to contract or relax.
THE DIAPHRAGM
The diaphragm is a dome-shaped muscle that separates the chest, or thorax, from
the abdomen. It is the main muscle involved in breathing. It consists of a central
tendon from which muscle fibres from the sternum, ribs and costal muscles radiate.
The upper surface of the diaphragm is covered by parts of the membranous sacs,
which enclose the heart and lungs. The lower surface is covered by part of the lining
of the abdominal cavity and has the liver suspended from it. It has an aortic,
oesophageal and inferior vena cava opening. The diaphragm is supplied by the
phrenic nerves.
THE CYCLE OF RESPIRATION
The average rate for breathing is about 12 - 15 breaths per minute. Each breath
consists of three phases: inhalation, exhalation and a pause.
Taking a deep breath is known as inhalation, or inspiration. During inhalation, the
diaphragm and the external intercostal muscles contract at the same time, pulling
down the central tendon and this increases the volume of the thoracic cavity. This
expands the lungs, the pressure within the alveoli and in the air passages falls,
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producing suction in the thoracic cavity, which draws air into the lungs equalizing the
atmospheric and alveolar air pressures. Energy is needed for muscle contraction.
During exhalation, or expiration, the diaphragm and intercostal muscles relax,
pushing the ribcage down and in, reducing the volume of the thoracic cavity. Elastic
recoil compresses the lungs, squeezing the air inside them. As a result, air flows
from the lungs and out of the body. The lungs still contain some air, and are
prevented from complete collapse by the intact pleura. The diaphragm and thoracic
cavity return to their original shape.
At rest, exhalation lasts about 3 seconds, after which there is a pause. Then the
next cycle begins.
What are the five steps of respiration?
a) pulmonary ventilation b) external respiration c) transport of gases through blood
vessels d) internal respiration e) cellular respiration
What is pulmonary respiration?
It is the movement of air in and out of the lung passages. This is accomplished by
the action of the thorax muscles and diaphragm.
What is external respiration?
It is the exchange of gases between the air and blood at pulmonary capillaries,
happens at the ends of lung passages in the pockets called alveoli.
What does the transport of gases through the blood vessels mean?
O2 and CO2 carried in the red blood cells.
What is internal respiration?
It is the exchange of gases between blood and capillaries and the body cells. It is
where oxygen is take out of the red blood cells into the capillaries and then the body
cells and the where carbon dioxide is transported from the cells into the capillaries
and then into the red blood cells.
What is cellular respiration?
This is the breakdown of molecules at the mitochondria within cells to form ATP, this
uses up oxygen and produces carbon dioxide as a by-product.
PHYSIOLOGICAL VARIABLES AFFECTING BREATHING
Elasticity - this is the term used to describe the ability of the lungs to return to their
normal shape after each breath. Forced expiration and increased effort on
inspiration is needed, when the connective tissue in the lungs lose their elasticity.
Compliance - this is a measure of the ability of the lungs to stretch. Low
compliance is the term used when lungs have to work extra hard to bring in the
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normal volume of air. High compliance indicates that the elastic tissue has been
damaged - usually overstretched. High lung compliance is due to poor elastic recoil
i.e. the lungs have no problems taking in the air, but have extreme difficulties in
exhaling it.
Air flow resistance - more respiratory effort is required when this is increased, e.g.
in a bronchospasm.
EXTERNAL & INTERNAL RESPIRATION
EXTERNAL RESPIRATION - the exchange of gases by diffusion between the
alveoli and blood
This is the mechanism that allows air to enter and exit the body. Air enters and
leaves the body by breathing. The wall of each alveoli is one cell thick. Each alveolus is also surrounded by a network of tiny capillaries (the walls of which are also only one cell thick). Venous blood arriving in the lungs is high in carbon dioxide and
low in oxygen. Carbon dioxide diffuses through the walls of the alveoli and we
breathe it out in the normal way.
In the same way, oxygen diffuses through the walls of the alveoli into the blood. The
slow flow of blood through the capillaries increases the time available for diffusion to
occur.
The exchange of oxygen and carbon dioxide between the alveoli of the lungs and
the blood capillaries takes place. Oxygen is then delivered to the body’s cells so that
internal respiration can take place.
INTERNAL RESPIRATION - the exchange of gases by diffusion between blood
in the capillaries and the body cells
This takes place inside individual cells. As soon as external respiration is
completed, blood saturated with oxygen diffuses through the walls of the alveoli and
enters the blood. It leaves the lungs through the pulmonary veins and returns to the
heart. Here it is pumped around the body. Oxygen diffuses from the bloodstream
through the capillary walls into the tissues. And then reaches the various cells of the
body.
In this kind of respiration, food substances such as glucose are broken down by a
series of chemical reactions, most of which need oxygen. These chemical
reactions release energy which can then be used by the cells.
OXYGEN DEBT - the amount of oxygen needed by the body for recovery after
vigorous exercise
During hard exercise, the lungs cannot supply sufficient oxygen to the muscles to
cope with the level of activity. The muscles break down glucose for more energy.
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This partial breakdown produces lactic acid, which results in a sensation of fatigue.
Once the vigorous exercise stops, the body breaks down the accumulated lactic
acid, using extra oxygen to do so. Once this is done, the muscles can start working
normally again. Panting helps to supply the muscles with the oxygen that they need.
The amount of oxygen needed for this process is called an oxygen debt.
GASEOUS EXCHANGE - the movement of gases between the air and the blood
This occurs in the alveoli of the lungs. Air containing oxygen is breathed into the
lungs and enters the alveoli. Oxygen is filtered through the large pulmonary capillary
network that surrounds the alveoli walls. From here it is carried around the body.
At the same time, carbon dioxide from the tissues is carried back in the blood to the
heart and then to the lungs, where it diffuses into the alveoli and is breathed out of
the body.
Boyle’s Law
Boyle’s Law states that the pressure of a given quantity of gas is inversely
proportional to its volume. If the pressure is greater in the lungs than outside the
lungs, then air rushes out. If the opposite occurs, then air rushes in.
Diffusion
Diffusion is the exchange of gases (Oxygen & Carbon Dioxide) between the alveoli
and the blood occurs by simple diffusion: Oxygen diffusing from the alveoli into the
blood and Carbon Dioxide from the blood into the alveoli.
Diffusion requires a concentration gradient. So the concentration (or pressure) of
Oxygen in the alveoli must be kept at a higher level than in the blood and the
concentration (or pressure) of Carbon Dioxide in the alveoli must be kept at a lower
level than in the blood. This occurs by breathing - continuously bringing fresh air,
with more Oxygen and less Carbon Dioxide into the lungs & the alveoli.
PULMONARY CIRCULATION - the circulation from the heart around the lungs
and back again
This is the system through which blood is oxygenated. Deoxygenated blood is sent
from the heart to the lungs where it gathers oxygen, releases carbon dioxide. The
oxygenated blood then travels from the lungs to the heart via the pulmonary veins,
so that it can then be pumped around the body again.
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HOW IS RESPIRATION CONTROLLED?
Nervous control
The basic pattern of respiration is controlled by groups of neurons in the brain stem.
An area called the respiratory centre sends nerve impulses to respiratory muscles to
set the rate and depth of breathing. Motor impulses leaving the respiratory centre
are sent through the phrenic nerves to the diaphragm and the intercostal nerves
send impulses to the intercostal muscles, and these cause the muscles to contract.
Chemical control
Chemo-receptors respond to changes in the partial pressures of oxygen and carbon
dioxide in the blood and cerebrospinal fluid. When the body takes in more oxygen
(when dancing or exercising) it will also produce more carbon dioxide as a
by-product of cells.
Chemo-receptors are sensitive to the levels of carbon dioxide, so when there is an
excess, they send nerve impulses to the respiratory centre in the brain to increase
the respiratory rate to expel it. Chemo-receptors are located in the medulla
oblongata, the walls of the aorta and carotid arteries.
FACTORS THAT MAY AFFECT THE RATE OF BREATHING
Breathing may be modified by the higher centres in the brain in the following
situations:
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Singing, talking
Display of emotions e.g. when we cry, laugh, are fearful
Taking drugs e.g. stimulants will increase respiratory rate (amphetamines or
caffeine) or decrease it with depressants (opiates or barbiturates).
Smoking can cause shortness of breath, chronic cough and a dry mouth.
Alcohol in large amounts depresses the central nervous system. The heart
rate, blood pressure and respiratory rate all slow down - in extreme cases,
this can be fatal.
Temporary changes in respiration occur when we swallow, sneeze and
cough.
Sleeping - when we are awake, breathing is usually quite irregular, since it is
affected by exercise, speech, emotions, posture, etc. When we sleep, the
respiratory rate slows down and becomes very regular.
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Composition of Inspired and Expired Air
Inspired Air
Expired Air
Oxygen
About 21%
About 16.4%
Carbon Dioxide
About 0.03%
About 4.0%
Nitrogen
About 78.0%
About 78.0%
Water Vapour
Variable
Saturated
Temperature
Variable
About body temperature
Dust Particles
Variable but usually
present
Little if any
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RESPIRATORY ORGANS
Organ
Location
Structure
Function
Warms air on entering the body
Filters out dust + dirt particles
Smelling odours
Moistening air so doesn’t dry out
passages
Nose & Nasal
Cavity
Organ on the face
2 bones + cartilage
2 nostrils
Paranasal
sinuses
Inside nasal bones
Hollow spaces lined with mucous
membrane
Full of air to lighten facial bones
Gives resonance to the voice
Pharynx
Connects with the back
of mouth
12 cms long passage, muscular and fibrous tissue, mucous membrane lining
Carries food and air
Warms and moistens air
Lies between the back of
the tongue and trachea
A short funnel, sides kept rigid by cartilages (attached by membranes + ligaments)
Contains vocal cords, helps produce sound
Filters bacteria
Warms and moistens air
Just below the larynx.
Lower part divides into
right and left bronchi.
Lies in front of and adjacent to oesophagus
Reinforced with rings of cartilage to keep
it open and prevent it from bending.
Walls lined with mucus and cilia
Passageway to allow to enter
lungs
Mucus traps inhaled particles
Cilia move the mucus up and out
of the respiratory tract
In the thoracic cavity
The right bronchus enters the right lung divides into 3 - each end in a lobe.
The left bronchus enters left lung - divides
into 2 - each ends in a lobe. Reinforced
with cartilage.
Bronchi are tubes
(Throat)
Larynx
(Voice Box)
Trachea
(Windpipe)
Bronchi
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To carry air in and out of the lungs
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Organ
Location
Structure
Function
Bronchioles
Joins bronchi to individual alveoli (air sac)
Fine passages made of muscular, fibrous and elastic tissue
To transport air to alveoli
Alveoli
300 million in the lungs
A thin-walled sac with a moist inner
Surface, surrounded by a network of
capillaries
Allows gases (oxygen and carbon dioxide) to
be exchanged between the air and the blood
supply
Lungs
One on either side of the heart
in the thoracic cavity
Cone-shaped mass of spongy tissue
with a rich blood supply. Right lung
has 3 lobes. Left lung has 2 (heart)
Pleura
Covers each lung. Outer
membranes line inside of
chest. Inner membrane covers
lungs.
Tough pleural membrane. The narrow space between the 2 membranes is filled with thin film of pleural fluid
Allows gases (oxygen and carbon dioxide) to
be exchanged between the air and the blood
supply
Pleural fluid lubricates and allows smooth
movement during breathing.
Pleura protect lungs, prevent friction and allow
change of shape during breathing.
Ribs
In the thoracic cavity
12 pairs of flat curved bones called
ribs. Spaces occupied by the intercostal muscles
Diaphragm
Separates the chest (or thorax)
from the abdominal cavity
Muscular dome
Intercostal
Muscles
Between the bony arches of
the ribs
11 pairs (internal & external) elastic
muscles. Nerve impulses to intercostal nerves instruct contraction
and relaxation.
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Bony frame allows breathing
Protects the lungs and other internal organs
Inhalation (contracts), becoming flatter to enlarge thoracic cavity to draw air into lungs.
Exhalation (relax), reducing volume of thoracic
cavity, compressing lungs and forcing air out
Connect the ribs
Aid the diaphragm in respiration