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Chapter 15: Respiratory System
• The lungs are actively ventilated to
ensure that gas exchange can occur
passively.
• Red blood cells are vital in the transport
of respiratory gases.
I. Respiratory System: carry oxygen to the cells and
eliminate carbon dioxide
A. Lungs: site of gas exchange between
atmosphere and blood and located in thoracic
(thorax) cavity (closed to the outside air)
1. Right side has three lobes and left side has two
lobes
2. Inside chest cavity
and surrounding by membranes
called pleura
B. Passage of air
1. Mouth and nose: air enters
and small hairs in the nose filters the
air and mucus warms and moistens
the air
2. Pharynx: tube at the back of the nasal cavities and
mouth and is passageway for air and food
3. Epiglottis: flap of cartilage that covers the opening to
air passage
4. Trachea: air passageway made of cartilage which
contain cilia and mucus to trap particles
5. Larynx: upper end of trachea that contains the vocal
cords
6. Bronchi: two branches that lead to the lungs from
trachea
7. Bronchioles: smaller tubes into the lungs
8. Alveoli: clusters of tiny air sacs surrounded by
capillaries
a) Gases are exchanged between the alveoli and
blood
b) 300 million alveoli per lung alveoli Overview
clip
The Respiratory System
Mouth
Pharynx
Larynx
Trachea
Lung
Epiglottis
Bronchus
Nose
Bronchiole
Alveoli
Bronchioles
Diaphragm
Edge of
pleural membrane
Capillaries
C. Gas exchange and transport
1. Gas exchange in lungs
a) Oxygen crosses two cells: alveolus cell and
capillary wall cell and enters the blood
b) Carbon dioxide crosses capillary wall cell and
alveolus cell and enters the alveoli
c) Concentration gradient of these two gases will
ensure diffusion of each gas in the correct direction
Gas exchange Higher level gas exchange
Gas Exchange in the Lungs
Alveoli
Bronchiole
Capillary
2. Alveoli are composed of specialized cells called
pneumocytes
a) Pneumocytes: cell type that makes up
the single cell layer of the alveolus
b) Type I pneumocytes
i) Very thin
ii) Very large membrane surface area:
well designed for diffusion
iii) If damaged, cannot be replaced by
mitosis
c) Type II pneumocytes
i) Cuboidal in shape and
have little membrane surface area
ii) Produce and secrete a solution that acts as a
surfactant to reduce the surface tension of the
moist inner surface of alveoli and prevents the
sides of the alveoli form sticking together
iii) Can go through mitosis for replacement of
both types of alveolar cells if they are damaged
Pneumocyte cells
D. Mechanism of breathing
1. Breathing: process of moving air into and out of the
lungs
a) Based on the inverse relationship between
pressure and volume
b) Increase in volume will lead to a decrease in
pressure
c) Whatever pressure does, volume will do the
opposite
2. Ventilation: repeated process of filling our lungs with
air and then expelling that air
3. Inspiration: inhaling, is the process of taking air
into the lungs
a) Tissues that makes up the lungs is passive
and not muscular, so lungs are in capable of
purposeful movement
b) Muscles surrounding the lungs
i) Diaphragm: large flat muscle Clip
ii) External intercostal muscles: surround
ribs
iii) Internal intercostal muscles
4. Actions that lead to inspiration
a) Diaphragm contracts and external
intercostal muscles and one set of abdominal
muscles raise the rib cage: Increases the
volume of the thoracic cavity
b) Increased volume in chest cavity results
in the pressure inside the cavity to decrease:
leads to less pressure “pushing on” the
passive lung tissue
c) Lung tissue increases its volume because there
is less pressure exerted on it
d) Leads to a decrease in pressure inside the
lungs: known as partial vacuum
e) Air comes in through your open mouth or
nasal passages to counter the partial vacuum
within the lungs and fills the alveoli
5. Expiration: exhaling, process of expelling air
from lungs
a) Reverse process of inspiration
b) Diaphragm relaxes
c) Volume in chest cavity decreases and air
pressure is greater so air rushes out
Respiration Video pressure
The Mechanics of Breathing
E. Regulation of breathing
1. Rate at which oxygen is used depends
on the activity of the cell
2. Greater activity requires more oxygen
3. Abdominal and intercostal muscles achieve a
greater initial thoracic volume which leads to
deeper breathing and more air moving into the
lungs Clip
II. Causes and consequences of emphysema
A. Emphysema: disease whereby the alveoli in the
lungs are progressively destroyed
1. Chronic, slowly progressive disease that
turns healthy alveoli into large, irregularly
shaped structures with gaping holes
2. Reduces the surface area for gas exchange,
so less oxygen reaches the bloodstream, so
shortness of breath is a symptom and typically
occurs first during strenuous activity
3. COPD (chronic obstructive pulmonary disease):
group of respiratory diseases including emphysema
a) Shortness of breath, especially during
physical activities
b) Wheezing
c) Chest tightness
d) Having to clear your throat first thing in the
morning, due to excess mucus in your lungs
e) A chronic cough that produces sputum that
may be clear, white, yellow or greenish
f) Blueness of the lips or fingernail beds
(cyanosis)
g) Frequent respiratory infections
h) Lack of energy (Mayo Clinic)
4. Causes
a) Smoking
b) Marijuana smoke
c) Fumes from manufactory plants
d) Coal dust
e) Air pollution
5. No cure for emphysema, but the progression of
the disease can be slowed by stopping smoking
or removal of other risk factors
6. Never start smoking and wear protective mask
when working around dust or chemical fumes
Video
III. Causes and consequences of lung cancer
A. Lung cancer: cancerous growth that begins
in the lungs
1. Cancer that is prone to spreading
(metastasizing)
2. Brain, bones, liver, and adrenal glands
are likely targets for lung cancer that has
metastasized
3. Cancerous growth in the lungs takes over
healthy tissues that were bronchioles and
alveoli
4. The larger the growth, the more the lung
tissue becomes dysfunctional and can result
in internal bleeding
B. Causes
1. Carcinogen: substance that is known to
cause cancer
2. Carcinogen enters the lung tissues and
mutates into a cancerous growth
a) Cigarette smoke and other fumes
b) Asbestos: used to be used in building
insulation products and is consider a carcinogen
i) Need a special company to safely remove
the asbestos from older buildings
ii) Asbestos was cheap, durable, fireproof,
and ability to insulate
iii) Appliances, insulation, flooring, toys,
and crayons
C. Treatment
1. Best treatment is achieved when the
disease is diagnosed early
2. Lung cancer has a high mortality rate
3. Data supports a direct correlation between
those countries and cultures that have shown a
decrease in the number of people who smoke
and a corresponding decrease in the incidence of
lung cancer Video Smoking vs. Healthy Lungs
IV. Hemoglobin and gas exchange (Haemoglobin)
A. Hemoglobin: protein molecule found within
erythrocytes that carries most of the oxygen in the
bloodstream
1. Contains 4 polypeptides, each with a heme
group that has an iron atom
2. Each iron can bind to one oxygen molecule
3. Each hemoglobin molecule is capable of
reversibly binding to as many as four oxygen
molecules and one CO2 molecule
4. Erythrocytes is made of cell membrane,
cytoplasm, few organelles, and hemoglobin
(no nucleus)
5. 250 million hemoglobin molecules in each red
blood cell
Hemoglobin
B. Hemoglobin changes shape and affinity when carrying
oxygen
1. Proteins have an ability to change their 3D shape
(enzyme changes shape as substrate enters active site)
2. Hemoglobin has 4 possible shapes, depending on
how many oxygen molecules are bond to the iron
atoms
3. Hemoglobin’s affinity for oxygen: the different
shapes affect the hemoglobin’s ability to bind with O2
a) Greater the tendency to bind with oxygen,
the higher the affinity
4. Hemoglobin molecules that are already carrying 3 O2
molecules have the greatest affinity for oxygen
5. Hemoglobin molecules that are carrying no oxygen
molecules have the least affinity for oxygen
6. Each oxygen molecule that binds to hemoglobin changes
the hemoglobin shape in a way that increases its affinity
for another O2
7. Hemoglobin can carry a maximum of 4 O2, so one that is
already carrying 4 has no affinity for O2
8. Affinity for oxygen from lowest to highest is Hb4,
Hb4O2, Hb4O4, and finally Hb4O6
C. Oxygen dissociation curves: show the tendency of
hemoglobin to bind to O2 (affinity) and separate from
O2 (dissociate)
1. Oxygen dissociation curves are graphs that
show how various forms of hemoglobin or
myoglobin perform under various conditions
2. Partial pressure: pressure exerted from a single
type of gas when it is found within a mixture of gases
a) Air that we breathe and is a mixture of
gases, and O2 is just one part of the mixture
b) Bloodstream and tissues contain a mixture
of different gases including O2
c) Total pressure: pressure exerted by a
mixture of gases
d) Partial pressure of O2: portion of the total
pressure that is caused by oxygen alone
Partial Pressures
3. x-axis measures the partial pressure of
oxygen
4. y-axis shows the percentage saturation of
hemoglobin with O2
5. Hemoglobin is not saturated until it is carrying
4 oxygen molecules
Curve
6. Very steep S-shape is indicative of the affinity
changes for O2 that hemoglobin undergoes when
at least some O2 is already bound to the molecule
a) At the lower end of the graph: little O2 is
already bound
b) At the upper half of the graph:
hemoglobin is already bound to some O2
and has increased its affinity for O2 because
of the change in the protein shape
7. Homeostatic range of oxygen partial pressures
within the body
a) Upper range of normal: 75mmHg or
10kPa is O2 partial pressure in lungs, graph
shows that more than 90% of hemoglobin
becomes saturated with O2 in lungs
b) Lower range of normal: 35mmHg or 5kPa,
only about 50% is still saturated with O2 and
this is partial pressure of O2 in body tissues
undergone cell respiration
c) 40-50% of the hemoglobin has recently been to
the lungs has given up (dissociates) one or
more O2 molecules when it reaches the body
tissues
d) Hemoglobin typically don’t empty their
oxygen load when they reach respiring tissues,
but they release a significant amount of O2
within a narrow range of O2 partial pressures
D. Comparison of hemoglobin and myoglobin
1. Myogloblin: oxygen-binding protein found in
muscles
a) Single polypeptide
b) Heme group and Fe atom
2. Function: store O2 within muscle tissues until
muscles begin to enter an anaerobic situation
when exercising heavily
3. During heavy exercise, myoglobin dissociates
its O2 and thus delays the onset of lactic acid
fermentation
4. Myoglobin has the ability to hold onto its O2
even at low O2 partial pressures in order to
provide a final reservoir of O2 when exercising
5. Graph shows myoglobin to the left of
hemoglobin (except for upper end)
a) Shows that myoglobin is still bound to
its O2 even when hemoglobin has
dissociated its O2 Hemoglobin and
Myoglobin
E. Comparison of adult hemoglobin and fetal hemoglobin
1. Fetus hemoglobin is slightly different in molecular
composition compared with adult hemoglobin
2. Fetus hemoglobin must have a greater affinity for
O2 than an adult
3. In placental capillaries, adult hemoglobin is more
likely to dissociate O2 and fetus hemoglobin is more
likely to bind to that same O2
4. Fetal hemoglobin dissociates its O2 when it reaches
the tissues of the fetus
5. Curve for fetus hemoglobin is always to the
left of the adult hemoglobin
a) Any point on the x-axis shows that adult
hemoglobin binds less O2 at that partial pressure
compared with fetus hemoglobin
F. The Bohr shift: results when CO2 binds to
hemoglobin, causing a shape change that promotes
the release of O2
1. Hemoglobin’s affinity for O2 is reduced in an
environment where CO2 partial pressure is high
a) Found in cells undergoing cell
respiration
b) Hemoglobin is induced to release
(dissociate) O2 within the capillaries of
body tissues
2. Curve on left shows what happens to hemoglobin
passing through the lungs (partial pressure of CO2 is
low): O2 binds easily to hemoglobin
3. Curve on right shows what happens to hemoglobin in
respiring tissues that are giving off CO2 : Some CO2
binds with hemoglobin and O2 will dissociate to the
tissuesClip
G. Carbon dioxide transport in the blood
1. CO2 is a waste product of cellular
respiration and diffuses out of the cell and
into the capillary
2. Three ways CO2 is transported to lungs
a) Small percentage remains as CO2
and dissolves in blood plasma
b) Some CO2 enters erythrocytes and
becomes reversibly bound within
hemoglobin (Bohr shift): each hemoglobin
can carry one CO2
c) About 70% of CO2 enters erythrocytes
and is converted into hydrogen carbonate
ions (HCO3-) which moves into the blood
plasma for transport
H. Formation of HCO31. Carbonic anhydrase: enzyme in the
cytoplasm of erythrocytes that catalyzes the
reaction of CO2 and water to form carbonic acid
(H2CO3)
2. Carbonic acid then dissociates into H+ and
hydrogen carbonate ion (HCO3-)
3. HCO3- exits cell through protein channel in
erythrocyte membrane by facilitated diffusion
a) One HCO3- moves out and one Cl- moves
in
b) Chloride shift: movement of ions to
keep the charges balanced
Video
I. Maintaining a narrow homeostatic range of
pH in the blood
1. pH of blood plasma: 7.35-7.45
2. Requires a buffering system to maintain
pH range due to more H+ when exercising
due to an increased produce of CO2
3. H+ made from dissociation of carbonic
acid can’t stay in solution in the erythrocyte
cytoplasm or blood plasma
4. pH buffering: temporary removal of H+ from
solutions
a) H+ can be bound at various places on
hemoglobin molecules
b) H+ can exit erythrocyte and bind with
proteins circulating as solutes in plasma
Video
Video
V. Rate of ventilation is controlled by the
respiratory control center in the medulla
oblongata
A. Increase in physical activity leads to an
increase demand for ATP in muscles, which means
an increase demand for O2
1. Mechanism needed to ensure the
rate of transport of respiratory
gases meets the needs of the increased
demand
2. Increase the ventilation or breathing rate
B. Ventilation rate is under the control of an area of
the medulla oblongata at the brainstem (respiratory
control center) and has two mechanisms when
ventilation needs to increase
1. Receptor cells: chemosensor
(chemoreceptors)
a) Inner wall of aorta and carotid arties
b) Detect an increase in CO2 and
decrease in blood pH
c) When stimulated they send action
potentials to medulla’s breathing center
2. Medulla: contains same chemosensors
a) Blood passes through capillaries of
medulla, increased CO2 and decreased pH
levels are detected
b) Medulla respiratory control center sends
action potentials to the diaphragm,
intercostal muscles, and abdominal muscles
c) Frequency of breathing is increased
3. Physical exercise decreases
a) Chemoreceptors detect the decrease in
CO2 levels and slight increase in blood
plasma pH
b) Leads to decrease in ventilation rate
VI. Living and breathing at high altitude
A. Common misconception that the air at high
altitudes contains less oxygen by percentage than air
at sea level
1. Percentage of gases in the air does not change as
altitude increases
2. Air pressures changes at different altitudes
a) Air at higher altitudes is at a lower pressure
b) All the molecules in the mixture are more
spread out than in a mixture at sea level
3. When you breathe less dense air, diffusion of
oxygen across the alveoli into the bloodstream is
less efficient and less oxygen enters the blood
B. Symptoms at high altitude
1. Physical activity leads to immediate
fatigue
2. Altitude or Mountain sickness: vision
problems, nausea, high pulse rate,
difficulty in thinking clearly
3. Severe altitude sickness: fluid around
brain or lungs, can become life threatening
and person suffering should be taken to a lower
altitude
C. How the body compensates when reaching a higher altitude
1. Increasing ventilation rate and heart rate: stressful for
the body and not a long term solution
2. Acclimatization occurs over time
a) Increase in the number of erythrocytes and
amount of hemoglobin
b) Increase in the capillaries in both the lungs and
muscles
c) Increase in lung size and surface area
d) Increase in myoglobin within muscle tissue
D. Sport training at high altitudes: some athletes
train at a higher altitude in order to take
advantage of more erythrocytes and
hemoglobin
E. Mountaineers will typically spend time at a
base camp at higher altitudes before a climb in
or to acclimate before climbing
Altitude sickness
Altitude sickness video
VII. Identification of lung tissues with light and
electronmicrographs
A. Alveoli and capillaries are best viewed under an
electron microscope
1. Illustration shows capillary (in section)
running in/out of the page
2. Inside the capillary are portions of 3
erythrocytes, cut in section
3. On either side of capillary are portions of 2
alveoli
4.Nucleus of an alveolar cells is shown just to the
right of the 3 erythrocytes Textbook image