Lp 13 respiratory system 2008

Respiratory System

VTT 235/245 Anatomy &
Pathology Lab

Introduction
 The body’s cells need a constant
supply of oxygen to produce energy.
 Carbon dioxide is a waste product of
these energy-producing reactions and
must be eliminated.

Types of Respiration
 External- occurs in the lungs and is the
exchange of O2 and CO2 between the air in
the lungs and the blood flowing through the
pulmonary capillaries.
 Internal- occurs all over the body.
 It is the exchange of O2 & CO2 between the blood
and the cells & tissues.
 Both types of respiration are constantly
taking place.

Secondary Functions
 **Voice Production- “phonation”
 The process begins in the **larynx (voice
box).
 Vocal cords stretch across the lumen of
the larynx and vibrate as air passes over
them.

Secondary Functions…
 Body Temperature Regulation-
 A network of superficial blood vessels just
under the epithelium of the nasal
passages helps warm inhaled air before it
reaches the lungs.
 The respiratory system prevents over-
heating by panting.

Secondary Functions…
 Acid-base Balance Regulation-
 For normal chemical reactions to occur, the
relative acidity or alkalinity of their environment
must be controlled carefully.
 The unit used to express acidity or alkalinity is
pH.
 The respiratory system uses its ability to
influence the amount of CO2 in the blood.
 The more CO2 there is in the blood, the lower the
blood pH.

Structures

Upper Respiratory System

Nose
 Begins with the nostrils (nares) which lead
to the nasal passages.
 The nasal passages are located between
the nostrils and the **pharynx (throat).
 A midline wall separates the right from the
left nasal passage called the nasal septum.
 The hard & soft palates separate the
nasal passages from the mouth.

Nose
 Turbinates-
 Thin, scroll-like
bones that help
warm and humidify
inspired air.
 They also filter
particulate matter,
such as dust and
pollen, before it can
reach the lungs.

Nose
 Paranasal Sinuses-
 Contained within the spaces of the
maxillary and frontal bones of the
skull.

Pharynx
 The nasal passages lead back into the
pharynx .
 It is the common passageway for the
respiratory and digestive systems.
 The soft palate divides the pharynx
into the dorsal nasopharynx
(respiratory passageway) and the
ventral oropharynx (digestive
passageway).

Pharynx…
 At the caudal end, the
pharynx opens
dorsally into the
esophagus and
ventrally into the
larynx.
 The larynx & pharynx
work together to
prevent swallowing
from interfering with
breathing.

Larynx
 “Voice box”
 A short, irregular
tube that connects
the pharynx with the
trachea.
 The larynx is
supported in place
by the hyoid bone.

Larynx…Contents…
 Vocal folds- the most lateral
structures, located on the lateral edges
of the glottis.
 Epiglottis- a triangular flap of tissue
that covers or protects the glottis when
in the “up” position.
 Glottis- the most ventral opening of
the larynx.

Larynx…Functions
 Voice production
 Keeps foreign material out of the lungs
by the trapdoor action of the epiglottis.
 It controls airflow to the lungs by
adjusting the diameter of the glottis.

Glottis
 Closure of the glottis even aids in non-
respiratory functions that involve
straining such as: urination, defecation,
and parturition.
 Straining begins with the animal holding
the glottis closed while applying pressure
to the thorax with the breathing muscles.

Glottis…
 This stabilizes the thorax and allows the
abdominal muscles to effectively
compress the abdominal organs when
they contract.
 Without the closed glottis, contraction of
the abdominal muscles merely forces air
out of the lungs.

Trachea
 A short, wide tube that extends from
the larynx to the thorax where it divides
into the two main bronchi that enter the
lungs.
 This division is called the bifurcation of
the trachea and it occurs at the level of
the base of the heart.

Trachea
 The trachea is composed of
fibrous tissue and smooth
muscle held open by hyline
cartilage rings.
 If nothing held the trachea open,
it would collapse each time the
animal inhaled as a result of the
partial vacuum created by the
inhalation process.
 Each tracheal ring is C-shaped
with the open part of the C
facing dorsally.
 The gap of each ring is bridged
by smooth muscle.

Structures

Lower Respiratory Tract

Lower Respiratory Tract
 Starts with the bronchi, ends with the
alveoli, and includes all the air
passages in between.
 Most of the structures in the lower
respiratory tract are located within the
lungs.

Bronchial Tree
 The air passages that lead from the
bronchi to the alveoli.
 After it enters the lungs, each main
bronchus divides into smaller and
smaller bronchi until they become
tiny bronchioles.**
 The smallest air passageways are
called alveolar ducts.**

Bronchial Tree…
 The alveolar ducts end in groups of
alveolar sacs.
 The diameter of each bronchi can be
adjusted by smooth muscle-
 Bronchiodilation
 Bronchioconstriction

Alveoli
 External respiration
takes place in the
alveoli.
 They are tiny, thin-
walled sacs that are
surrounded by
networks of capillaries.
 The wall of each alveoli
is composed of thin
epithelium.

Alveoli…
 The capillary walls
are composed of
the same thin
epithelium.
 These two thin
layers allow oxygen
and carbon dioxide
to diffuse back and
forth.

Lungs
 The base of each lung lies directly on top of
the diaphragm.
 Between each lung is an area called the
mediastinum, which contains:
 Heart
 Large blood vessels
 Nerves
 Trachea
 Esophagus
 Lymphatic vessels & lymph nodes

Lungs…
 **The left lung has 2 lobes-
 Cranial and Caudal
 **The right lung has 4 lobes-
 Cranial, middle, caudal, & accessory.
 Each lung has a well-defined area on
its medial side called a hilus where
blood, lymph, and nerves enter and
exit the lung.

Lungs…
 Physically the lungs are very light and
have a spongy consistency.
 If a piece of lung from an animal that
has taken one breath was placed
under water, it would float.

Thorax
 A thin membrane called pleura lines
the thoracic cavity and its organs.
 Organs- visceral pleura
 Cavity- parietal pleura
 The diaphragm is the thin sheet of
skeletal muscle that forms the caudal
boundary of the thorax.

Physiology…
 The process of respiration requires
effective movement of air in and out of
the lungs at an appropriate rate and
sufficient volume.

Negative Intrathoracic Pressure
 The pressure within the thorax is
negative with respect to the
atmospheric pressure.
 A partial vacuum exists within the
thorax.
 That partial vacuum pulls the lungs
against the thoracic wall and aids in
the return of blood to the heart.

Inspiration
 The basic mechanism for inspiration is
enlargement of the thoracic cavity by
the inspiratory muscles.
 The main muscles of inspiration are
the diaphragm and the external
intercostals.

Expiration
 The main muscles of expiration are the
internal intercostals and the abdominal
muscles.
 When abdominal muscles contract, they
push abdominal organs into the diaphragm.
 Expiration does not require as much work
because gravity pulls the ribs down helping
to decrease the thoracic cavity volume.

Respiratory Volumes
 Tidal Volume- the amount of air
inspired and expired in one breath.
 Minute Volume- the amount of
volume inspired and expired in one
minute.

Gas Exchange
 Occurs in the alveoli.
 Gas exchange follows
the laws of simple
diffusion.
 Basically, gas
molecules from areas
of a high concentration
like to move to areas of
low concentration.

Control of Breathing
 Breathing is controlled by an area of the
brain stem known as the respiratory center.
 The body has two main systems that control
breathing:
 Mechanical system
 Chemical system

Sinusitis
 Usually involves the frontal or maxillary sinus
in the dog.
 It can manifest as a collection of pus in the
area, resulting in a swelling over the sinus.
 It can be a result of the openings of the
nasal passages swelling shut or becoming
plugged.
 This results in the fluid from the sinuses having
nowhere to go.

Sinusitis…
 A common cause of this problem is a
tooth root abscess.

Kennel Cough
 Infectious Canine Tracheobronchitis
 Caused by the bacteria Bordatella
bronchiseptica.
 The disease is characterized by a dry,
hacking cough that can be stimulated
by palpating the throat.

Tracheal Collapse
 This defect involves tracheal rings that lose
their ability to remain firm, subsequently
collapsing during respiration.
 ***Obese toy and miniature breeds of dogs
are predisposed.
 The usually narrow space between the ends
of several of the C-shaped tracheal rings is
wider than normal.

Tracheal Collapse…
 When the animals inhales, the widened area of the
smooth muscle gets sucked down into the lumen of
the trachea and partially blocks it.
 This can cause a dry, honking cough and difficulty
breathing (dyspnea).

Tracheal Collapse…
 Therapy includes:
 Weight loss for
obese animals
 Exercise restriction
 Reduction of
excitement & stress
 Surgical therapy

Feline Asthma p. 255
 A disease characterized by
spontaneous bronchioconstriction &
airway inflammation.
 Clinical signs include:
 Coughing
 Wheezing
 Labored breathing

Feline Asthma…
 Airway epithelium may hypertrophy,
goblet cells and submucosal glands
may produce excess mucus, and the
bronchial mucosa can become
infiltrated with inflammatory cells.

Feline Asthma…
 All these changes result in decreased
air flow.
 A 50% decrease in the lumen of the
trachea is possible.

Feline Viral Rhinotracheitis
 A highly contagious disease that is
extremely severe in young kittens.
 Infections occur year-round in both
vaccinated and un-vaccinated cats.
 Transmission occurs through aerosolization
(sneezing) and direct contact.
 Queens may transmit the disease to their kittens
during grooming.

Pleural Effusion
 The build-up of fluid in the pleural
space which results in respiratory
distress.
 Right-sided CHF is the principal cause
of pleural effusion in both canine &
feline patients.

Pleural Effusion…
 As systemic venous hypertension
increases, significant amounts of the
fluid accumulates in the pleural space,
causing respiratory difficulty.

Pleural Effusion…
 All pleural effusions produce symptoms
of respiratory distress, dyspnea,
cough, & circulatory compromise.

Pneumothorax & Lung Collapse p. 258

 Pneumothorax: the presence of free air
in the pleural space.

Pneumothorax & Lung Collapse…
 Without negative intrathoracic
pressure, normal breathing cannot take
place.
 If air leaks into the pleural space, that
negative pressure is lost.
 This results in the lung falling away
from the thoracic wall.

 The dark black region on the right side of this CT
image clearly shows where the lung has separated
from the chest wall.
 Note the difference between the two lungs.
 One is fully expanded and fills up the chest cavity,
the other is shrunken (i.e. collapsed) and only fills up
part of the chest cavity.

 The general cause is the air comes
either from the outside, as in the case
of a penetrating wound, or from the
lung itself due to the rupture of the
alveoli as a result of lung disease or
injury.

 Treatment consists of re-establishing
the partial vacuum within the pleural
space by:
 Sucking out the air with a needle.
 Placement of a chest tube.

Coughs, Sneezes, Yawns, Sighs, & Hiccups
p. 262
 All Are temporary interruptions in the
normal breathing pattern.
 They can be:
 Responses to irritation (coughs &
sneezes)
 Attempts to correct imbalances (yawns &
sighs).
 Or they may occur for unknown reasons
(hiccups).


 A cough is a protective reflex that is
stimulated by irritation of foreign matter
in the trachea or bronchi.
 It consists of a sudden, forceful expiration
of air.


 A sneeze is similar to a cough, but the
irritation originates in the nasal passages.
 The burst of air is directed through the nose and
mouth in an effort to eliminate the irritant.
 A yawn is a slow, deep breath taken
through a wide-open mouth.
 It may be stimulated by a slight decrease in the
oxygen level of blood, or it may just be due to
boredom, drowsiness, or fatigue.


 A sigh is a slightly deeper than normal
breath.
 It may be a mild corrective action when
the blood level of oxygen gets a little low.
 It may also serve to expand the lungs
more than the normal breathing pattern
does.


 Hiccups are spasmodic contractions
of the diaphragm accompanied by
sudden closure of the glottis, causing
the characteristic “hiccup” sound.

Other Respiratory
Pathology
 Aspiration pneumonia (p. 253)-
 An inflammatory condition of the lungs
produced by inhalation of foreign material.
 Reverse Sneeze-
 Asthmatic symptoms, usually from post
nasal drip.

Other Respiratory Pathology…
 Emphysema-
 The alveoli sacs loose elasticity, remain
stretched and full, CO2 bulids up in the
blood and can lead to cardiac arrest.

 Pulmonary Hypertension-
 Left CHF, the left side of the heart can’t
pump fast enough,
 Pressure rises, no gas exchange can
occur.
 Pulmonary Edema-
 Increase in fluid in the alveoli resulting in
compromised gas exchange.

 Diaphragmatic Hernia
 A break in the diaphragm allows the
protrusion of abdominal viscera into the
thorax.

Parasites of the Respiratory
System

Aleurostrongylus abstrusus
 Nematode
 Feline lung worm
 Lives in the
alveolar ducts
 Recovered by
tracheal wash

Capillaria aerophila
 Nematode
 Often confused with
Trichuris (whipworm
found in the
intestine)
 Diagnosed by
standard fecal
floatation

Paragonimus kellicotti
 Trematode
 “Lung fluke” of dogs
 Found in sputum &
feces
 Single operculated

Pleural Fluid

Collection & Analysis

Collection
 By thoracocentesis
 Review in the McCurnin

Indications
 Air or fluid is present in the pleural
space causing the lungs to not expand
completely
 Diagnostic and therapeutic

Analysis
 Volume- subjective
 Color- colorless to straw or yellow
 Turbidity- transparent to slightly turbid
 Odor- none
 Total Nucleated Cell Counts
 Cytologic Examination
 Total Protein- refractometer
 Fibrinogen Concentrations

Tracheal Fluid

Collection & Analysis

Collection- Tracheal Wash
 Orotracheal- directly through an
endotracheal tube
 Nasotracheal-
 Via the nasal passages
 Transtracheal-
 Through the skin and trachea
 Infuse sterile saline as a wash solution
 May collect tracheal, bronchial or
bronchioalveolar washes
 Collect into RRT and LTT

Analysis
 Record cell numbers during smear
evaluation
 Little mucous-
 Decreased cell numbers
 Prepare smear from sediment
 Heavy mucous-
 Increased cell numbers
 Don’t centrifuge, make an impression smear

Lp 13 respiratory system 2008

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