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Specialist Diploma in Sports & Exercise Sciences
SD SES2
Anatomy and Physiology
Continual Assessment 2
Submitted by: (Student’s name has been removed for confidentiality.)
REPORT ON ASTHMA
INTRODUCTION
Asthma is a pathological condition that affects the respiratory system, specifically the breathing
passages of the lungs.
It is a chronic disorder which causes airway inflammation and
intermittent obstruction as well as hypersensitivity to the respiratory system. It causes
obstruction to the air passages and thus resistance to expiration. This obstruction is reversible,
which distinguishes it from chronic obstructive pulmonary disease in which the obstruction is
irreversible. Asthma is a chronic disease whereby one can still live life to the fullest. However,
occasional unexpected attacks do happen. While the exact cause of asthma is not known and
currently incurable, the disease can be controlled1.
SCOPE
This paper covers the anatomy and functions of the respiratory system, effects of asthma on the
structures and functions, as well as current therapies to alleviate the severity of asthma and their
effectiveness.
ANATOMY OF RESPIRATORY SYSTEM AND ITS FUNCTIONS
On the anatomical aspect, the respiratory system is divided into the upper and lower respiratory
tract. The upper respiratory tract comprise nasal cavity, pharynx and larynx, while the lower
respiratory tract comprise trachea, bronchi and lungs. (See Figure 1) From a functional
perspective, the same structures are almost exactly categorised into the conducting zone and the
respiratory zone. The conducting zone consists of the nose, pharynx, larynx, trachea, bronchi
and bronchioles, while the respiratory zone comprise the respiratory bronchioles, alveolar ducts
and alveoli.
1 Asthma Causes, Symptoms, Signs, Diagnosis, Triggers and Treatment Information on eMedicineHealth.com,
http://www.emedicinehealth.com/asthma/article_em.htm
Upper
Respiratory
Tract
Lower
Respiratory
Tract
Figure 1: Respiratory Tracts (Source: Shier, Butler & Lewis, 2009, p. 445)
Nose. The nose serves as an avenue for the exchange of air. It has bone and cartilage with
internal hairs. Internal hairs in the nose act as filters, thus ensuring that the air breathed in are
free of large particles. The nostrils (also known as anterior nares) allow air to enter the nose and
pass into the nasal cavity (open inner chamber of the nose).2 (See Figure 2)
Figure 2: Nose (Source)
Nasal Cavity. The nasal cavity is a large airway, framed and supported by several bones and
cartilages. The lateral walls of the cavity is mainly framed by the maxilla, while the floor (roof
of the mouth) is formed by bones of the hard palate – horizontal plates of the palatine bones and
palatine processes of maxilla anteriorly. The conchae (also known as turbinates), which lines
2 D. Shier, R. Lewis, J. Butler 'Hole's Anatomy & Physiology' 9 th Edition (New York:McGraw Hill), p. 781
the sides of the nasal cavity, divides the cavity into a series of groove-like passageways and is
lined by mucous membranes. The conchae also causes disturbances to the inhaled air, thus
allowing the air to be better warmed, moistened and filtered. A thin vertical fin, known as nasal
septum, divides the nasal cavity into two. Directly posterior to the nostrils is the vestibules,
which consist of stratified squamous epithelium and vibrissae (coarse hair lined with mucus).
The temperature of the inhaled air passing through the nasal cavity will be warmed or cooled to
within a degree of the human body temperature, due to the large surface area of the conchae.
The existence of mucous membranes warms (capillaries), moistens (mucus), cleans and 'sweeps'
debris away (mucus and cilia) the inhaled air before it travels to other parts of the respiratory
tract. Cilia (found on the columnar epithelial cells) actually sweeps the debris filled mucus to the
throat, which will be swallowed and digested away. The roof of the nasal cavity and conchae is
lined with olfactory mucosa which detects odour-producing chemicals, this is because the
epithelium later has millions of olfactory receptors. Surrounding the nasal cavity are several
open, air-filled chambers, known as paranasal sinuses, lined with respiratory mucosa. These
sinuses resonate voice sounds. 3 (See Figure 3)
Figure 3: Nasal Cavity (Source, source)
Pharynx. The pharynx is part of the digestive and respiratory system. Also known as the throat,
it has a wall of skeletal muscle, lined with mucous membranes, conducting air from the nasal
cavity to the larynx. It is the common passageway for air and food, and also the resonant
chamber for speech sounds. The pharynx consists of three parts – nasopharynx (uppermost),
3 D. Shier, R. Lewis, J. Butler 'Hole's Anatomy & Physiology' 9 th Edition (McGraw Hill), p. 781
oropharynx (middle) and laryngopharynx (lowest). The nasopharynx is located posterior of the
nasal cavity, between the internal nare and soft palate. The oropharynx is located behind the base
of the tongue, in the vicinity of the soft palate, epiglottis of the larynx and hyoid bone. The
laryngopharynx (also known as hypopharynx) is posterior to the larynx, in the region of the
epiglottis and cricoid cartilage of the larynx. The same epithelium found in the nasal cavity
continues to clean, warm and moisten incoming air. 4 (See Figure 4)
Figure 4: Pharynx (Source: Shier, Butler & Lewis, 2009, p. 446)
Larynx. The larynx is a short tube located in the throat, below the base of the hyoid bone and
tongue, and anterior to the esophagus. Also known as the voicebox, it consists of 9 pieces of
cartilages – thyroid cartilage (Adam's apple), epiglottis, two pairs of vocal folds, glottis (space
between the folds), cricoid cartilage, arytenoid cartilages (controls length and position of vocal
folds), corniculate cartilages and cuneiform cartilages. The epiglottis closes the airway so that
food is not accidentally swallowed into the lungs. The vocal folds vibrates to produce sound but
it is the other structures that enables recognisable speech.5 (See Figure 5)
4 D. Shier, R. Lewis, J. Butler 'Hole's Anatomy & Physiology' 9 th Edition (McGraw Hill), p. 781
5 D. Shier, R. Lewis, J. Butler 'Hole's Anatomy & Physiology' 9th Edition (McGraw Hill), p. 784 – 785
Figure 5: Trachea (Source: Shier, Butler & Lewis, 2009, p. 447)
Trachea. The trachea is also known as a windpipe, that runs through the lower neck and chest,
mediastinum and is anterior to the esophagus. It conducts air from the larynx to the bronchi.
The wall of the trachea consists of about 16 – 20 hyaline cartilage rings, stiffening the wall so
that the tracheal lumen stays open and airflow is unimpeded. However when food goes down the
esophagus, the trachea is able to partially collapse due to its open rings. It also has mucous
membranes lining, continuing to warm, moisten and filter the air. The trachea then further
divides into two main passage of airway, known as bronchi (extended into the lungs).6 (See
Figure 6)
Lungs. The cone shaped lungs is located in the thoracic cavity and occupies majority of it. The
lungs are not symmetrical, due to the difference in the number of lobes on both sides (2 on the
left and 3 on the right). Inside the five lobes of the lungs (divided by fissures) are a complex
network comprising the bronchi, bronchioles and alveolar ducts (which extends into alveoli and
alveolar sacs). 7 (See Figure 6)
Bronchi. The main bronchi (primary) has two branches – left and right bronchus. Extended
from the trachea and conducting air into the lungs, the main bronchi will run freely for a few
6 D. Shier, R. Lewis, J. Butler 'Hole's Anatomy & Physiology' 9 th Edition (McGraw Hill), p. 786
7 The Lungs – Tutorials and Quizzes,
http://www.getbodysmart.com/ap/respiratorysystem/lungs/menu/animation.html and D. Shier, R. Lewis, J. Butler
'Hole's Anatomy & Physiology' 9th Edition (McGraw Hill), p. 748
centimetres being entering into the respective lung. The right main bronchus, wider, shorter and
more vertical than the left main bronchus. After entering the lung, primary bronchus on both
sides will branch into secondary bronchi (also known as lobar bronchi because each one
conducts air to and from one of the lung's five lobes – i.e. 3 lobar bronchi on the right and 2 lobar
bronchi on the left) and subsequently tertiary bronchi (also known as segmental bronchi because
they conduct air in and out of the bronchopulmonary segments). The segmental bronchi on the
right supplies 10 bronchopulmonary segment, while the left segmental bronchi supplies to 8
bronchopulmonary segment (due to fuse of several segmental bronchi). A bronchopulmonary
segment is separated from the rest of the lung by a connective tissue septum.
This
'compartmentalisation' permits a segment to be surgically removed without affecting other
segments. The lumenal surface of the bronchus wall is lined with a layer of respiratory mucosa.
Goblet cells present in the epithelium secretes mucus. A broken ring of smooth muscle fibres
can be found deep to the mucosa, so that during exhalation, the fibres contract to facilitate the air
out of the respiratory tubes, and relax during inhalation. Plates of hyaline cartilages are also
present around the muscle fibres, supporting the wall and prevent it from collapsing. In the lobar
and segmental bronchi, the plates are thinner and lesser. 8 (See Figure 6)
Figure 6: Trachea and Bronchi (Source: Shier, Butler & Lewis, 2009, p. 449)
8 D. Shier, R. Lewis, J. Butler 'Hole's Anatomy & Physiology' 9 th Edition (McGraw Hill), p. 787
Bronchioles. The segmental bronchi will further branch into bronchioles and subsequently to
terminal and respiratory bronchioles.
Each terminal bronchiole will branch into several
respiratory bronchioles which subdivides into about 2 – 11 alveolar ducts. Each duct has about 5
– 6 alveolar sacs connected with it, amounting to approximately 300 million alveoli and alveolar
sacs in a human body. With extensive branching of the bronchial tree, the amount of hyaline
cartilages decreases, but the amount of smooth muscles increases.
Also the ciliated
pseudostratified columnar epithelium changes to non-ciliated simple cuboidal epithelium in the
terminal bronchioles.
The simple cuboidal epithelium secretes non-sticky proteinaceous
compound, so as to maintain the airway in the smaller bronchioles, easing surface tension to
allow for bronchioles to expand during inspiration and keep the bronchioles from collapsing
during expiration. The number of goblet cells and seromucous glands decrease with each
division of the bronchioles. 9 (See Figure 7)
Alveoli. These are cup shaped cavities found in tiny air chambers. The composition of ducts
and alveoli (squamous epithelium) allows rapid diffusion of oxygen and carbon dioxide. The
alveoli comprise an epithelial layer and extracellular matrix surrounded by capillaries. In the
alveolar wall are two types of epithelial cells (Simple squamous Type I and Septal Type II) and
macrophages. Type II eases surface tension and prevents the alveoli from collapsing during
exhalation. Macrophages remove debris and harmful substances from the alveoli spaces and thus
protect the lung from damage. The thin and moist alveolus are surrounded by several capillaries
where diffusion of oxygen and carbon dioxide occurs. 10 (See Figure 7)
9 D. Shier, R. Lewis, J. Butler 'Hole's Anatomy & Physiology' 9 th Edition (McGraw Hill), p. 787
10 D. Shier, R. Lewis, J. Butler 'Hole's Anatomy & Physiology' 9 th Edition (McGraw Hill), p. 806
Figure 7: Bronchioles and Alveoli (Source: Shier, Butler & Lewis, 2009, p. 449)
RESPIRATORY SYSTEM – PULMONARY VENTILATION
During pulmonary ventilation (breathing), the air inhaled through the nose and mouth enters the
respiratory passages. The nose is the most common opening by which air enters the respiratory
system. Air may also enter the system through the mouth because the mouth and the nasal cavity
converge at the pharynx.
During inspiration, the diaphragm muscle and the intercostal muscles contract, thus increasing
the vertical and front-to-back dimension of the thoracic cavity. This expansion lowers the air
pressure in the lungs, causing air to move into the lungs. Inhaled air will first enter the nose
through the nostrils, followed by nasal cavity, entering into the pharynx then to the larynx, into
the trachea. Air will continue to be channelled to the bronchi before entering into the
bronchioles. Terminating each bronchioles is the alveolar ducts, sacs and finally the alveoli.
The oxygen in the inhaled air in the alveoli is diffused into the arterial blood through the
capillaries, while the waste-rich blood in the veins releases carbon dioxide into the alveoli which
follows the same route out of the lungs.
EFFECTS ON THE RESPIRATORY SYSTEM
In contrast to COPD (which includes chronic bronchitis and emphysema) , the inflammation of
asthma can be reversed. Unlike emphysema that affects the alveoli, asthma affects the bronchi.
Asthma is a disorder of obstruction to breathing, due to the inflammation (reaction to 'triggers')
and narrowing of bronchial tubes.
Symptoms of asthma includes coughing, wheezing, shortness of breath and chest tightness. This
is because during asthma attacks, three things occur.
When the lining of the lungs get irritated by allergens or irritants, inflammation of the bronchial
tubes occur, thickening the wall of the bronchial tube, leading to narrowing of the airways.
Thick mucus is also excessively produced in the bronchi, forming plugs which lead to coughing
and other breathing difficulties. Subsequently, smooth muscle fibres of the bronchi constrict,
further narrowing the airways in the lungs, and not allowing the air to move freely through the
airways (bronchospasm). The result of these is shortness of breath. The effect of breathing
during an asthma attack is analogous to sucking air through the straw after strenuous exercise.
(See Figure 8)
Figure 8: Inflammation and Bronchospasm (Source)
Effect on the Body. When constriction occurs, the air in the alveoli is not able to be released and
the lungs become over-inflated. The asthmatic will cough to force air out of the over-inflated
lungs. Depending on the severity of the condition, if coughing does not alleviate the situation,the
asthmatic will begin to use the accessory breathing muscles, causing the shoulders to hunch and
rise with each attempt of breathing.
The lack of oxygen supply to the alveoli will not allow diffusion of oxygen to the blood, thus the
supply of oxygen to the other parts of the body is also limited. This is a dangerous situation
especially when the brain is deprived of oxygen leading to brain damage or death. Similarly
carbon dioxide (body's waste product) is unable to be expelled from the body. Thus throwing the
concentration of oxygen and carbon dioxide in the body off equilibrium. The effect of breathing
during an asthma attack is analogous to sucking air through the straw after strenuous exercise.
CURRENT THERAPIES AND THEIR EFFECTS
Before discussing about the therapies for asthma, it is essential to know what causes asthma. An
asthma attack is due to the reaction of a trigger, similar to an allergic reaction 11. Mucus
production and bronchospasms are the body's reactions to the triggers. Triggers of asthma and its
severity varies with differing individuals. However the triggers can largely be categorised into
allergens (specific) and non-allergens (irritants). Examples of allergens and irritants include
cigarette smoke, polluted air, deodorant inhalation, molds, dust, dander, flu, sinusitis, cold & dry
weather, stress and sulfites etc.
As mentioned, asthma cannot be cured, but the effects of treatment can lessen the severity of the
attacks and place asthma under control. Two of the common therapy for asthma is medication
(Pharmacotherapy) and Prevention Therapy.
11 An allergic reaction is the body's cellular immune system response, by setting off defensive reactions, against the
invader.
PHARMACOTHERAPY
Asthma medication are usually received best by the body through inhalation, although many
other forms can be provided. This is because the medication is administered to the area which
needed it most (airways). The most common form of administration is the use of pressured
metered dose inhalers (MDIs).
Controller Medication. This class of medication minimises the inflammation of the bronchial
tubes that causes the asthma attack, and is usually taken daily on a longer-term basis. Some of
controller medication will be covered here. Long acting beta-2 agonists and corticosteroids
inhalation relaxes muscles of the airway, reduces inflammation and thus keep the airways
dilated, making breathing easier.
Another type of controller medication is leukotriene12
inhibitors, which block chemicals that promote inflammatory response to triggers and
minimising mucus production. Slightly similar to leukotriene inhibitors, cromolyn sodium also
inhibits the release of chemicals that causes inflammation. This medication is particularly
effective for asthmatics who suffers attacks in response to certain allergens. When cromolyn
sodium is taken before an allergen exposure, it prevents the development of an attack, however it
is ineffective on the onset of one. 13
Rescue Medication. This class of medication is taken only after the onset of an attack, hence
they do not replace the need for controller drugs. Short-acting beta-2 agonists are common
examples of rescue medication.
Inhalation of these quickly dilate the airways and their
effectiveness usually last for hours. Anticholinergics are another type of rescue medication.
Similar to the effects of beta agonist inhalation, inhalation of anticholinergics also helps to keep
the breathing passages open. Although it takes longer to come into effect, however the
12 Leukotrienes are powerful chemicals, promoting inflammation that occur during asthma attacks.
13 Asthma – Mayo Clinic, May 31, 2008, http://www.mayoclinic.com/health/asthma/DS00021
effectiveness do last longer than beta agonists. 14
Medication for Allergy-Induced Asthma. Such medication will lower the sensitivity of the
body's immune system to allergens, or even prevent the reaction of the immune system to the
allergens. Immunotherapy , given in the form of injections, gradually over time, reduces the
reaction of the immune system to specific allergens. A newer type of agent that works with the
body's immune system is omalizumab. For asthmatics with an increased level of
immunoglobulin E (Ig E), given by injection, omalizumab inhibits Ig E from attaching itself to
cells that release chemicals that worsen asthma symptoms. 15
PREVENTION THERAPY
Since the cause for asthma exacerbations may be due to a wide variety of environmental factors,
the effort taken to observe minimal exposure to such triggers may be effective.
Food. Local food reactions may not reflect those that are of true Ig E mediated allergic reactions,
thus the severity of the reactions can be alleviated once asthma is controlled. However when
there are true Ig E mediated allergic reactions to certain foods, though uncommon, should not be
taken lightly as the consequences can be fatal. Hence any severe food allergy must be well
handled by a medical specialist.
Mites. Dust mites is a common allergen for asthmatics, even from different continents. The
efforts taken to minimise the exposure to dust mites will be extensive and is never a single
solution problem. Good hygiene practice such as weekly cleaning of fabric in the house can
minimise the exposure to mites. Dry air (e.g. air-conditioning) helps reduce the exposure to dust
mites. Recent studies have shown that placing of wheat flour in fridges can restrict the breeding
of mites in the wheat flour, thus lowering an asthmatic's exposure to mites especially when food
14 Asthma – Mayo Clinic, May 31, 2008, http://www.mayoclinic.com/health/asthma/DS00021
15 Asthma – Mayo Clinic, May 31, 2008, http://www.mayoclinic.com/health/asthma/DS00021
is made from the flour.
Poor Air Quality. Studies have shown that there is a strong correlation between the onset of
asthma attacks and air pollutants. Hence during bad weather conditions or poor air quality
situations (e.g. working environment), it is advised that asthmatics reduce their exposure and
more importantly, avoid any strenuous activities outdoors. Similarly, asthma sufferers should
definitely avoid smoking and/or avoid places where cigarette smoke is present.
Monitor Lung Function.
Before the onset of an asthma attack, usually lung function will
deteriorate. Hence, by using a peak flow metre, when the lung function decreases by more than
20%, an asthma attack can be anticipated in 2 to 3 days' time.
Lifestyle. The use of air-conditioning, thus the closing of windows, prevents pollen from
entering indoors. If need be, the exposure to pets with fur and feathers should also be observed.
Exercise is able to strengthen heart and lungs, thus alleviating asthma symptoms, hence an
asthma sufferer should not remain inactive. The consumption of vitamins is found to be able to
improve lung function as well.
With the knowledge of the prevention therapy methods and medication, it is important to identify
the triggers and observe the consumption of medication religiously.
ALTERNATIVE THERAPY TECHNIQUE
Other than the usual medication and preventive measures, there have been recent studies into
alternative therapy methods. One of the example is the Buteyko Method, described below.
Buteyko Method16. This treatment, discovered by Russian doctor Kostantin Buteyko, is a
breathing technique that was reported to have improved the quality of life of some asthma
patients as well as reduced their need for intake of medication. The technique teaches sufferers
to breathe shallowly and slowly as Dr Buteyko believed that hyperventilation is the underlying
cause of asthma. The shallow and slow breaths aim to break the rapid and gasping breathing
which result from airway constriction and wheezing.
CONCLUSION
Although asthma is incurable, however with the current discoveries in the medical field in the
areas of medication and preventive measures, an asthma patient can still live life to the fullest,
except with caution in mind.
References:
1.
Shier D., Butler J. & Lewis R. 9th Edition. (New York: McGraw Hill) Hole’s Essentials of
Human Anatomy & Physiology.
2.
MedicineNet.Com http://www.medicinenet.com
3.
Mayo Clinic. http://www.mayoclinic.com
4.
eMedicine Health. http://www.emedicinehealth.com/asthma/article_em.htm
5.
Wikipedia. http://www.en.wikipedia.org/asthma
6.
Get
Body
Smart.
http://www.getbodysmart.com/ap2/respiratorysystem/nose/introduction/tutorial.html
7.
MOH Clinical Practice Guidelines 1/2008. http://www.moh.gov.sg/cpg
8.
Expert Panel Report 3: Guidelines for the Diagnosis and Management of Asthma. National
Heart,Lung, and Blood Institute (NHLBI). 2007.
16 Extracted from The Sunday Times on 8 Nov 09 article 'Breathe and beat asthma'