Respiratory System

Respiratory zone
◦ Site of gas exchange
◦ Consists of bronchioles, alveolar ducts, and alveoli

Conducting zone
◦ Provides rigid conduits for air to reach the sites of gas
exchange
◦ Includes all other respiratory structures (e.g., nose, nasal
cavity, pharynx, trachea)

Respiratory muscles
o
diaphragm and other muscles that promote ventilation
Quiz Picture
p. 701
Figure 22.1
◦ Pulmonary ventilation – moving air into and out of
the lungs (breathing)
◦ External respiration – gas exchange between the
lungs and the blood
◦ Transport of respiratory gases – Oxygen and
Carbon dioxide transport in blood
◦ Internal respiration – gas exchange between
systemic blood vessels and tissues
◦ Providing an airway for respiration
◦ Moistening & warming incoming air
◦ Filtering inspired air
◦ Resonating chamber for speech
◦ Contains olfactory receptors
Quiz Picture
1.
2.
Nasal cavity
Mucous membranes
◦ Olfactory Mucosa◦
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
lines superior region of nose
(olfactory receptors=smell)
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
goblet cells, mucous and serous glands
Secrete 1 qt mucus/day
Respiratory Mucosa- ciliated pseudostratified
columnar epithelial



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Lysozyme – antibacterial enzyme
Traps foreign debris and cilia moves to throat
Mucosa-Have rich vascular supply-warm air
Conchae- makes air turbulent- increases mucosal
surface area
Rhinitis
inflammation of nasal mucosa
- Mucus build up, stuffy nose



Surround nasal cavity
Lighten the skull and help to warm and
moisten the air
Mucus drains into nasal cavity
Sinusitis
inflammation of sinus mucosa, infection of mucus
in sinus
-Swelling prevents movement of mucus out of
sinuses = pressure
-Sinus headache
Quiz Picture
p. 702
Figure 22.2b
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Connects nasal cavity to larynx and
esophagus
Throat (5”)
Skeletal muscle
3 regions
◦ Nasopharynx – Air only
 Goblet cells produce mucus
 Swallowing- uvula closes off nasopharynx
 Contains pharyngeal tonsils
◦ Oropharynx – Food and Air
 Continuous with nasopharynx
 Contains palatine and lingual tonsils
◦ Laryngopharynx – Air and Food
 During swallowing food has priority
Voice Box
Superiorly attaches to hyoid bone, inferiorly with
trachea
Functions:
◦ To provide an opening from pharynx to trachea
◦ To act as a switching mechanism to route air and
food into the proper channels
◦ To make sound

Cartilages (hyaline) of the larynx
◦ Thyroid cartilage with a midline laryngeal
prominence (Adam’s apple)
◦ Cricoid cartilage- below thyroid cartilage


Epiglottis – elastic cartilage (valve) that covers
the entrance to larynx during swallowing
Glottis-opening between vocal cords
◦ Normally open-closed swallowing
True Vocal Cord- sound production – elastic fibers
False Vocal Cords- Closed when swallowing
Figure 21.4a, b
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Speech – intermittent release of expired air while
opening and closing the glottis
Pitch – determined by the length and tension of the
vocal cords
Loudness – depends upon the force at which the air
rushes across the vocal cords
The pharynx resonates, amplifies, and enhances
sound quality
Sound is “shaped” into language by action of the
pharynx, tongue, soft palate, and lips
Figure 21.5
Laryngitis
inflammation of vocal cords
-Swelling prevents movement
-Overuse, dry air, bacteria, pollutants



Flexible and mobile tube
Larynx to the primary bronchi
Composed of three layers
◦ Mucosa – made up of goblet cells and ciliated
epithelium –smoking destroys cilia
◦ Submucosa – connective tissue deep to the
mucosa
◦ Adventitia – outermost layer made of C-shaped
rings of hyaline cartilage- keeps open during
inspiration
Figure 22.6a


Right and left primary bronchi-formed by
division of trachea
Air reaching the bronchi is:
◦ Warm and cleansed of impurities
◦ Saturated with water vapor


Bronchi subdivide into secondary bronchi,
each supplying a lobe of the lungs
Air passages undergo 23 orders of branching
in the lungs


Tissue walls of bronchi mimic that of the
trachea
As conducting tubes become smaller,
structural changes occur
◦ Cartilage support structures change
◦ Epithelium types change
◦ Amount of smooth muscle increases

Bronchioles
◦ Consist of cuboidal epithelium
◦ Have a complete layer of circular smooth muscle
◦ Lack cartilage support and mucus-producing
cells



Presence of alveoli; begins as terminal
bronchioles feed into respiratory bronchioles
Respiratory bronchioles lead to alveolar
ducts, then to terminal clusters of alveolar
sacs composed of alveoli
Approximately 300 million alveoli:
◦ Account for most of the lungs’ volume
◦ Provide tremendous surface area for gas exchange
Figure 22.8a
Figure 22.9b
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Type I cells -simple squamous epithelium,
simple diffusion
Dust cells – alveolar macrophages
Type II cells – secrete surfactant
◦ Reduces alveolar surface tension
◦ Coats membrane
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
1. Alveoli
2. Alveolar sac
3. Simple squamous epithelium
4. Blood vessel
Figure 22.9.c, d
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Surface tension – the attraction of liquid
molecules to one another at a liquid-gas
interface
The liquid coating the alveolar surface is
always acting to reduce the alveoli to the
smallest possible size
Detergent –like lipoprotein
Breaks up water molecules
Increases surface area of alveoli


Left lung – separated into upper and lower
lobes by the oblique fissure
Right lung – separated into three lobes by the
oblique and horizontal fissures
◦ Apex – under clavicle
◦ Base – rests on the diaphragm
◦ Hilum – medial surface of each lung-entrance /exit
point


Pulmonary arteries and veins – supply
systemic venous blood to be oxygenated and
then back to heart
Bronchial arteries – nourish lungs
◦ Arise from aorta
◦ Supply all lung tissue except the alveoli

Bronchial veins – drain lungs

Pleura - Thin, double-layered serosa
◦ Visceral pleura – inner membrane
 Covers external lung surface
◦ Parietal pleura – outer membrane
 Covers the thoracic wall and superior face of the
diaphragm
 Continues around heart and between lungs
Pleura Fluid -serous fluid (lubrication)
 Pleural cavity
Pleurisy



Inflammation of pleural membranes
Friction and sticking of membranes
Feels like heart attack
◦ Inspiration – air flows into the lungs
◦ Expiration – air leaves lungs
Boyle’s Law
Large Volume
Small Volume
High Pressure
Low Pressure
=
Change in
Pressure
=
Gas Flow
to
Equalize
the
Pressure

Atmospheric – exerted by air surrounding the
body
◦ Sea level 760 mm Hg

Intrapulmonary – within alveoli
◦ Equalized with atmospheric pressure

Intrapleural - in pleural cavity
◦ Negative
◦ Less than intrapulmonary pressure-keeps lungs
expanded



Intrapulmonary pressure > Intrapleural
pressure
Atmospheric pressure > Intrapleural Pressure
Causes adhesion of pleural membranes
Homeostatic Imbalance
Intrapleural pressure > Intrapulmonary pressure

Pneumothorax◦
◦
◦
◦
Knife wound, gun shot
Air moves into pleural cavity
May affect only one lung
Treatment: Close hole and draw air out.
1.
2.
3.
4.
Diaphragm and external intercostal muscles
(inspiratory muscles) contract = Rib cage
rises
Lungs are stretched and intrapulmonary
Volume increases
Intrapulmonary pressure decreases below
atmospheric pressure (1 mm Hg)
Air flows in the lungs, down its pressure
gradient, until intrapleural pressure =
atmospheric pressure
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Inspiratory muscles relax and the rib cage
descends due to gravity
Thoracic cavity Volume decreases
Elastic lungs recoil passively =
intrapulmonary Volume decreases
Intrapulmonary Pressure rises above
atmospheric pressure (+1 mm Hg)
Gases flow out of the lungs down the
pressure gradient until intrapulmonary
pressure is equal to atmospheric
Figure 21.13
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Tidal volume (TV) – air that moves into and
out of the lungs with each breath
(approximately 500 ml)
Inspiratory reserve volume (IRV) – air that
can be inspired forcibly beyond the tidal
volume (2100–3200 ml)
Expiratory reserve volume (ERV) – air that
can be evacuated from the lungs after a
tidal expiration (1000–1200 ml)
Residual volume (RV) – air left in the lungs
after strenuous expiration (1200 ml)
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Inspiratory capacity (IC) – total amount of
air that can be inspired after a tidal
expiration (IRV + TV)
Functional residual capacity (FRC) – amount
of air remaining in the lungs after a tidal
expiration
(RV + ERV)
Vital capacity (VC) – the total amount of
exchangeable air (TV + IRV + ERV)
Total lung capacity (TLC) – sum of all lung
volumes (approximately 6000 ml in males)
Large Breath (Max)
Normal Breathing
Total air can use
Air never used
Includes
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Anatomical dead space – volume of the
conducting respiratory passages (150 ml)
Alveolar dead space – alveoli that cease to act
in gas exchange due to collapse or
obstruction
Total dead space – sum of alveolar and
anatomical dead spaces

Alveolar ventilation rate (AVR) – measures the
flow of fresh gases into and out of the alveoli
during a particular time
AVR
(ml/min)

=
frequency
(breaths/min)
X
(TV – dead space)
(ml/breath)
Slow, deep breathing increases AVR and
rapid, shallow breathing decreases AVR

Henry’s Law
Dalton’s Law

Talked earlier-Boyle’s Law

When a mixture of gases is in contact with a
liquid, each gas will dissolve in the liquid in
proportion to its partial pressure
More of the gas and faster process
80% Oxygen
20% Oxygen
Gas
Liquid


The amount of gas that will dissolve in a
liquid also depends upon its solubility
Various gases in air have different solubilities
(into liquid portion of blood):
◦ Carbon dioxide is the most soluble
◦ Oxygen is 1/20th as soluble as carbon dioxide
◦ Nitrogen is practically insoluble in plasma


Total pressure exerted by a mixture of gases
is the sum of the pressures exerted
independently by each gas in the mixture
The partial pressure of each gas is directly
proportional to its percentage in the mixture
78.6 % N2
20.9 % O2
0.04 % CO2
ATMOSPHERE
74.9 % N2
13.7 % O2
5.2 % CO2
ALVEOLI


Familiar Concept - High pressure to low
pressure
Gases move from higher partial pressures to
lower partial pressures.
78.6 % N2
20.9 % O2
0.04 % CO2
ATMOSPHERE
74.9 % N2
13.7 % O2
5.2 % CO2
ALVEOLI
Alveolar Air
PO2=104 mm Hg
PCO2=40 mm Hg
Oxygen
Carbon dioxide
RAPID DIFFUSION OF
OXYGEN
Carbon dioxide leaves
the blood at the lungs
because of its high
solubility.
Ventilation – the amount of gas reaching the
alveoli
Perfusion – the blood flow in pulmonary
capillaries
 Ventilation and perfusion must be tightly
regulated for efficient gas exchange
Figure 22.19
1.
2.
Bound to hemoglobin 98.5%
Dissolved in plasma
Hemoglobin-consists of 4 subunits
The four subunits bind oxygen in a cooperative
manner, so that binding of oxygen to one
subunit makes it easier for the other
subunits to bind to oxygen.


Temperature - increases causes affinity of
hemoglobin for oxygen to decrease
pH - as pH drops, affinity of hemoglobin for
oxygen decreases
Active muscles-produce CO2 (low pH), heat and
lactic acid

Carbon dioxide is transported in the blood
in three forms
◦ Dissolved in plasma – 7 to 10%
◦ Chemically bound to hemoglobin – 20% is carried in RBCs
as carbaminohemoglobin
◦ Bicarbonate ion in plasma – 70% is transported as
bicarbonate (HCO3–) Major Buffer
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As CO2 enters the plasma, it may react with water
to form carbonic acid. Carbonic acid then quickly
dissociates into bicarbonate and protons.
CO2 + H2O  H2CO3  HCO3- + H+
The conversion of CO2 and water to carbonic acid is
generally a very slow reaction. However,
erythrocytes contain an enzyme called carbonic
anhydrase, which greatly speeds up this reaction.
CO2 =
carbonic acid
=
blood pH

Medulla – sets rhythm (Pacemaker)

A. Dorsal respiratory group (DRG) - pacemaker for
breathing

Neurons in the DRG fire - send signals to stimulate
the diaphragm and external intercostals = inspiration

Neurons stop firing- expiration occurs passively.


Normal rate of stimulation by the DRG is about 1215 breaths per minute. Normal respiratory rhythm is
called eupnea.
B. Ventral respiratory group (VRG) role is not so clear,
but it appears to be important during forced
breathing.
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The basic rhythm set by the medulla can be
influenced by the pons:
A. Pneumotaxic center of the pons sends
inhibitory signals to the DRG. This finetunes the duration of inspiration and helps
to prevent over-inflation of the lungs.
B. Apneustic center of the pons stimulates
the DRG. This center works with the
pneumotaxic center in fine-tuning the rate
and depth of breathing.
Factors influencing the rate and depth of
breathing
Medulla = basic respiratory rhythm, the rate and
depth of breathing can be altered by:

A. Irritants, such as smoke and dust, stimulate
bronchoconstriction.
◦ also may stimulate coughing and/or sneezing

B. Stretch receptors in the lungs are stimulated as
the lungs expand. (Hering-Breuer reflex)
◦ Send inhibitory signals to the medullary respiratory centers
that may end inspiration.
◦ Once the lungs recoil, the stretch receptors stop sending
signals, and this inhibition of the medulla ends.
◦ May be important in protecting lungs from over-stretching
◦ Does not appear important to normal breathing.

C. Hypothalamus - strong emotions and
pain (consider a gasp of fear).
◦ Increase in respiratory rate in response to rising
body temperature, and a decrease in rate in
response to cold.

D. The cortex - conscious control over
breathing by directly stimulating motor
neurons that excite the muscles involved in
breathing.
◦ Has limits—you cannot hold your breath long
enough to kill yourself!

E. CO2 - Chemoreceptors in the brain stem monitor the
level of CO2 in the CSF
◦ Hypercapnia (rising levels of CO2) = pH of the CSF,
and decreasing pH stimulates the chemoreceptors.
◦ Chemoreceptors then send signals to the respiratory
centers and stimulate increased rate and depth of
breathing.
◦ A high level of stimulation may result in
hyperventilation. Abnormally low levels of CO2
(hypocapnia) decrease respiratory rate and depth,
possibly leading to hypoventilation and even brief
periods of apnea (cessation of breathing).

F. Concentration of oxygen in the blood is typically
not very important in affecting breathing.
However, if arterial PO2 drops below 60 mm Hg,
then chemoreceptors in the aortic and carotid
bodies stimulate the respiratory centers to increase
ventilation.
Chronic Obstructive Pulmonary Diseases (COPD)
 Smoking
 Dyspnea, coughing, infections and pulmonary
failure
2 examples
Obstructive Emphysema
 Enlarged alveoli, deteriated alveolar walls
Chronic Bronchitis
 Excess fluid in lungs, inflammation, infection
Asthma
 Active immune inflammation of airways
 Not simply irritant inflammation
 Corticosteriods
 Future  antibodies against own antibodies
Tuberculosis
 Mycobacterium tuberculois
 Hard, calcified tubercles
 Body can usually handle trough inflammatory and
immune response
Lung Cancer
1. Squamous cell carcinoma  epithelium of bronchi
get hollow holes which bleed out (cough up
blood)
2. Adenocarcinoma  starts on outer edges of lungs
from alveolar cells
3. Small cell carcinoma  grape cluster on
mediastinum
High pitch
Low pitch
Blood Vessels part of a venous
plexus that provide heat-exchange
to help condition the air.
Epithelium
Lamina propria
Submucosa
Adventitia
Trachea
Primary Bronchus
Tertiary
Bronchus
Type II
cell
Type I
cell
Type II
cell
capillary
RBC
macrophage
Rib cage ventilation