2. Objectives
Define respiratory system.
Define respiration.
Describe the structure and the function of:
• upper respiratory tract (Nose, Pharynx, Larynx)
• lower respiratory tract (Trachea, Bronchial tree, lungs)
Discuss the physiology of respiration by explaining the
mechanism of:
• Pulmonary Ventilation
• External Respiration
• Internal Respiration
Discuss nervous control of respiration
Briefly discuss the lung volumes & capacities
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3. Respiratory System
• Definition: A system consisting of lungs and air
passages specialized for the intake of oxygen and
exchange of gases with the blood.
• Respiration: The exchange of oxygen and carbon
dioxide between the atmosphere and the cells of the
body.
Respiration includes three things:
1) Ventilation of lungs (inspiration and expiration),
2) External respiration (the exchange of gases
between lungs and blood) and Internal respiration
(between blood and tissues), and
3) The use of oxygen in cellular metabolism.
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4. Functions
Respiratory and Non-Respiratory Functions
Respiratory Functions are:
1. Pulmonary ventilation
2. Diffusion of O2 and CO2 b/w alveoli and blood
3. Transport of O2 and CO2 to and from tissues
4. Regulation of O2 and CO2 in blood and tissues
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5. Functions cont....
Non Respiratory Functions are:
• Air filtration
• Protective/Cleansing Reflexes (SSC reflexes)
• Olfaction
• Vocalization
• Defense mechanism..... Includes leukocytes, NK cells,
macrophages, dendritic cells, mast cells, defensins and
cathelicidins.
• Maintenance of water
• Regulation of body temperature
• Regulation of PH
• Secretion of ACE
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6. Respiratory Division
Respiratory tract is divided into two:
• Upper Respiratory Tract (URT): consists of
nose, pharynx, and larynx.
• Lower Respiratory Tract (LRT): consists of
Trachea, Bronchi, bronchioles and lungs.
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8. Upper Respiratory Tract
Nose:
Apart from olfaction the nose has several functions:
it warms, cleanses, and humidifies the inhaled air.
It serves as a resonating chamber that amplifies the voice.
• nasal cavity
• nasal septum
• mucous membrane
– mucus
– hair
– olfactory receptors
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9. Pharynx:
Is a muscular tube extending about 13 cm (5 inch).
It is divided into three regions:
Nasopharynx
-- Lies dorsal to the soft palate.
-- Receives the eustachian (auditory) tubes.
-- Houses pharyngeal tonsils.
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10. Oropharynx
-- The space between the soft palate and root of the
tongue which extends inferiorly to the hyoid bone.
Means it extends from the Uvula to the level of the
hyoid bone.
-- It contains palatine and lingual tonsils.
Laryngopharynx
It extends from the hyoid bone to the cricoid
cartilage.
Oropharynx and laryngopharynx serve as a common
passageway for both food and air.
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12. Larynx
• The larynx or voice box is a cartilaginous chamber
about 4 cm long.
• Its primary function is to keep food and drink out of
the airway, but it also produces sound.
• The superior opening of the larynx, the glottis (at the
base of the tongue) is guarded by a flap of tissue
called the epiglottis.
• During swallowing, extrinsic muscles of the larynx pull
the larynx upward toward the epiglottis, the tongue
pushes the epiglottis downward, and the epiglottis
directs food and drink into the esophagus dorsal to
the airway.
• The vestibular folds of the larynx also keeps food and
drink out of the airway even if epiglottis is removed.
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14. Larynx
• There are nine cartilages, three unpaired and three paired.
The unpaired cartilages of the larynx are
thyroid, cricoid and epiglottis.
• The paired cartilages of the larynx are
the arytenoids, corniculates, and the cuneiforms.
• Thyroid Cartilage: This forms the Adam's apple. It is usually
larger in males than in females. The thyrohyoid membrane
is a ligament associated with the thyroid cartilage that
connects the thyroid cartilage with the hyoid bone.
• Cricoid cartilage: A ring of hyaline cartilage that forms the
inferior wall of the larynx. It is attached to the top of
trachea.
• Epiglottis: A large, spoon-shaped piece of elastic cartilage.
During swallowing, the pharynx and larynx rise. Elevation of
the pharynx widens it to receive food and drink; elevation of
the larynx causes the epiglottis to move down and form a lid
over the glottis, closing it off.
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15. Larynx cont….
• Paired Arytenoid Cartilage: They are smaller, the
arytenoid cartilages are the most important because
they influence the position and tension of the vocal
folds. These are triangular pieces of hyaline cartilage
located at the posterosuperior border of the cricoid
cartilage.
• Paired Corniculate Cartilage: Horn-shaped pieces of
elastic cartilage located at the apex of each
arytenoid cartilage.
• Paired Cuneiform Cartilage: Club-shaped pieces of
elastic cartilage located anteriorly to the corniculate
cartilages.
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16. • The first three are relatively large and unpaired. The
superior one, the epiglottic cartilage, is a spoon
shaped supportive plate in the epiglottis. The largest,
the thyroid cartilage. It has an anterior peak, the
laryngeal prominence, commonly called Adam’s
apple, which is larger in males due to testosterone.
Inferior to the thyroid cartilage is ring like cricoid
cartilage which connects larynx to the trachea.
• The remaining cartilages are smaller and occur in
three pairs. Posterior to the thyroid cartilage are
paired arytenoid, paired corniculate, and paired
cuneiform cartilages.
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18. Lower Respiratory Tract
Trachea
The trachea or windpipe is a rigid tube 12 cm long
and 2.5 cm wide lying anterior to the esophagus.
It is supported by about 20 C-shaped rings of
hyaline cartilage, some of which we can palpate
between larynx and sternum.
The open part of the C faces posteriorly which
allows room for the esophagus to expand when
the swallowed food passes by.
The cartilages are spanned by trachealis muscles.
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19. Bronchi and Bronchial Tree
At the level of fifth thoracic vertebra, the trachea
divides into a right primary bronchus and left
primary bronchus.
The right primary bronchus is more vertical, shorter,
and wider than the left.
As a result, an aspirated object is more likely to
enter and lodge in the right primary bronchus
than the left.
Like the trachea, the primary bronchi contain
incomplete rings of cartilage and are lined by
ciliated pseudostratified columnar epithelium.
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20. • The point where the trachea divides into right and
left primary bronchi is called carina. The mucous
membrane of the carina is one of the most
sensitive areas of the larynx and trachea for
triggering a cough reflex.
• On entering the lungs, the primary bronchi divide
to form smaller bronchi called secondary bronchi.
Each lobe in the lungs receive one secondary
(lobar) bronchus.
• The secondary bronchi continue to branch,
forming still smaller bronchi, called tertiary
(segmental) bronchi.
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21. Cont…
• These bronchi further divide into bronchioles
(1 mm or less in diameter).
• The portion of the lung ventilated by one
bronchiole is called a pulmonary lobule.
• The bronchioles further divide to form
terminal bronchioles. This extensive
branching from the trachea resembles an
inverted tree and is commonly referred to as
the bronchial tree.
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24. • The larynx, trachea, and bronchial tree are lined mostly
by ciliated pseudostratified columnar epithelium,
which functions as a mucociliary escalator. That is, the
mucous traps the inhaled particles and then the ciliary
beating drives the mucus up to the pharynx where it is
either swallowed or spit out.
• Respiratory unit includes:
• 1. Respiratory bronchioles
• 2. Alveolar ducts
• 3. Alveolar sacs
• 4. Antrum
• 5. Alveoli
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25. Lungs
• Each lung is a somewhat conical shaped organ
with a broad concave base resting on the
diaphragm and a blunt peak called apex faces
upward to clavicles.
The broad costal surface is pressed against the rib
cage, and the smaller concave mediastinal
surface faces medially. The lung receives the
bronchus, blood vessels, and nerves through its
hilum, a slit in a mediastinal surface.
The left lung is a little smaller than the right
because of the heart tilting to the left giving
indentation to the lung called cardiac impression
or Cardiac notch.
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26. The left lung has two lobes as superior and inferior
lobe with a deep fissure between them called
oblique fissure.
The right lung has three lobes as superior, middle,
and inferior lobe. Superior lobe is separated from
the middle lobe by horizontal fissure and the
inferior lobe from the middle one by oblique
fissure.
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27. Alveoli
• An alveolus (plural alveoli) is pouch about 0.2 to 0.5 mm in
diameter.
• It is lined by simple squamous epithelium.
• An alveolar sac consists of two or more alveoli that share a
common opening.
• The surface area of the alveoli is about 70 m2.The walls of
alveoli consist of two types of alveolar epithelial cells.
• Type I alveolar cells which are numerous and form a
continuous layer. They are simple squamous epithelial cells.
Gaseous exchange occurs here.
• Type II alveolar cells also called septal cells, rounded or
cuboidal, which are fewer in number and found between
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28. Alveoli cont….
• They secrete alveolar fluid to keep the surface moist.
• Included the alveolar fluid is surfactant, a mixture of
phospholipids and lipoproteins.
• Surfactant lowers the surface tension of the alveolar
fluid, which reduces the tendency of the alveoli to
collapse.
• Associated with the alveolar wall are alveolar
macrophages (dust cells). They are phagocytes
which remove fine dust particles and other debris
and pathogens from the alveolar surface.
• Alveoli are surrounded by a network of blood
capillaries for gaseous exchange.
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31. Plural Membrane
• The lungs are enclosed and protected by two
layers of serous membrane which are collectively
called plural membrane or pleura. The outer
layer, called parietal membrane, lines the wall of
the thoracic cavity. The inner layer, called the
visceral membrane, covers the lungs themselves.
Between the visceral and parietal membranes
(pleurae) is a small space called pleural cavity.
The plural cavity contains a small amount of
lubricating fluid secreted by the serous
membrane. This pleural fluid reduces the friction
between the membranes when sliding over one
another during breathing.
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34. Diaphragm
• Is a skeletal muscle separating chest and
abdomen
• Inspiration: diaphragm contracts and
increases thoracic space
– air flows in
• Expiration: diaphragm relaxes and decreases
thoracic space
– air flows out
• Innervated by phrenic nerve fibers (C3, C4, C5)
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35. Mechanisms of Breathing:
How do we change the volume of the rib cage ?
Inhalation is ACTIVE process
• Diaphragm
Rib Cage
Contract
Diaphragm
Volume
•External Intercostal Muscles
Intercostals
Contract
to Lift
Rib
Spine
Ribs Volume
Both actions occur simultaneously – otherwise not effective
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36. Functions of Diaphragm
• Diaphragm is the muscle of:
• Inspiration
• Abdominal straining
• Weight-lifting
• Thoracoabdominal pump
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37. Nervous Control of Respiration
Respiration is controlled by the respiratory center in the central
nervous system. The respiratory muscles contract as a result
of nerve impulses transmitted to them from centers in the
brain and relax in the absence of nerve impulses. These nerve
impulses are sent from clusters of neurons located bilaterally
in the medulla oblongata and pones of the brain stem. This
group of neurons, collectively called respiratory center, which
is divided into three areas as:
1. Medullary Rhythmicity Area: It is located in the medulla
oblongata. It controls the basic rhythm of respiration.
• There are inspiratory and expiratory areas. During quiet
breathing, inhalation lasts for about 2 seconds and
exhalation lasts for about 3 seconds.
• Inspiratory area establishes the basic rhythm of breathing
by generating nerve impulses.
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38. Inspiratory area sends impulses to the external
intercostal muscles through intercostal nerves (T1
to T11) and to the diaphragm via the phrenic
nerves (C3 to C5).
When the nerve impulses reach the diaphragm and
external intercostal muscles, the muscles contract
and inhalation occurs.
At the end of 2 seconds, the inspiratory area
becomes inactive and nerve impulses cease.
With no impulses arriving, the diaphragm and
intercostal muscles relax for about 3 seconds,
allowing lungs and thoracic wall to recoil. Then, the
cycle repeats.
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39. Nervous Control of Respiration cont…
• The neurons of the expiratory area remain
inactive during quiet breathing.
• However, during forceful breathing nerve
impulses from the inspiratory area activate
the expiratory area Impulses causing
contraction of the internal intercostal and
abdominal muscles and thus forceful
expiration occurs.
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40. 2. Pneumotaxic Area: (pneumo= air; taxic= arrangement)
In the upper pons, it transmits inhibitory impulses to the
inspiratory area to turn off the inspiratory phase before
the lungs become too full of air. Breathing rate is more
rapid when the pneumotaxic area is more active. It means
that it shortens the duration of inhalation.
3. Apneustic Area:
In the lower pons of the brain stem, the apneustic area
sends stimulatory impulses to the inspiratory area that
activate it and prolong inhalation. It causes a long and
deep inhalation. Thus pneumotaxic and apneustic area
coordinate the transition between inhalation and
exhalation.
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41. Respiratory Volumes
• Tidal Volume (TV): The amount of air normally
inhaled or exhaled with one breath. (500 ml)
• Inspiratory Reserve Volume (IRV): The amount of
(additional) air forcefully inhaled after a normal tidal
volume inhalation. (3000 ml)
• Expiratory Reserve Volume (ERV): The amount of air
forcefully exhaled after a normal tidal volume
exhalation. (1200 ml)
• Residual Volume (RV): The amount of air remaining
in the lungs after maximum expiration. (1300 ml)
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42. Respiratory Capacities
• Vital Capacity (VC): Maximum amount of air expired after a
maximum inspiratory effort. (4700 ml)
VC= TV+IRV+ERV
• Inspiratory Capacity (IC): Maximum amount of air inspired after a
normal tidal expiration. (3500 ml)
IC= TV+IRV
• Functional Residual Capacity (FRC): Volume of air remaining in
the lungs after a normal tidal volume expiration. (2500 ml)
FRC= ERV+RV
• Total Lung Capacity (TLC): The amount of air in lungs after a
maximum inspiratory effort. (6000 ml)
TLC= TV+IRV+ERV+ RV
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43. Clinical Conditions
• Inflammation of the pleural membrane is called
pleurisy or pleuritis and as a result the
accumulation of excess fluid in the pleural cavity
is called pleural effusion.
• The introduction of air into the plural cavity
(either by surgical opening or stab or gunshot) is
called pneumothorax while blood or pus in it is
called hemothorax. The collapse of lungs is
known as atelectasis (ateles = incomplete;
ectasis = expansion).
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44. Clinical terminology of ventilation
• Apnea: Temporary cessation of breathing.
• Dyspnea: Difficulty in breathing. Eg. SOB
• Eupnea: Normal breathing. 12 to 15 b/m
• Hyperpnea: Increased rate and depth of breathing.
• Hyperventilation: Increased pulmonary ventilation
leading to low blood level of CO2
• Hypoventilation: Decreased pulmonary ventilation
leading to increased blood level of CO2
• Orthopnea: Dyspnea that occurs when a person is
lying down.
• Tachypnea: Abnormal quick shallow breathing
• Bradypnea: Abnormal slow breathing.
• Hypoxia: Low oxygen level
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