Chapter 22
RESPIRATION: THE EXCHANGE OF
GASES
Human Respiratory System
Functions:
 Works
closely with circulatory system,
exchanging gases between air and blood:
 Takes
up oxygen from air and supplies it to blood
(for cellular respiration).
 Removal and disposal of carbon dioxide from blood
(waste product from cellular respiration).
Homeostatic Role:
 Regulates
blood pH.
 Regulates blood oxygen and carbon dioxide
levels.
Blood Transports Gases Between Lungs and Tissues
Human Respiratory System
Components:
Nasal cavity, throat (pharynx), larynx (voice box),
trachea, bronchi, alveoli, and lungs.
Pathway of Inhaled Air:
 Nasal cavity
 Pharynx (Throat)
 Larynx (Voice Box)
 Trachea (Windpipe)
 Bronchi
 Bronchioles
 Alveoli (Site of gas exchange)
Exhaled air follows reverse pathway.
Human Respiratory System
Human Respiratory System
1. Nasal cavity: Air enters nostrils, is filtered by
hairs, warmed, humidified, and sampled for
odors as it flows through a maze of spaces.
2. Pharynx (Throat): Intersection where pathway
for air and food cross. Most of the time, the
pathway for air is open, except when we swallow.
3. Larynx (Voice Box): Reinforced with cartilage.
Contains vocal cords, which allow us to make
sounds by voluntarily tensing muscles.



High pitched sounds: Vocal cords are tense, vibrate fast.
Low pitched sounds: Vocal cords are relaxed, vibrate slowly.
More prominent in males (Adam’s apple).
Larynx or Voicebox Contains the Vocal Cords
Human Respiratory System
4. Trachea (Windpipe): Rings of cartilage maintain
shape of trachea, to prevent it from closing.
Forks into two bronchi.
5. Bronchi (Sing. Bronchus): Each bronchus leads
into a lung and branches into smaller and smaller
bronchioles, resembling an inverted tree.
6. Bronchioles: Fine tubes that allow passage of air.
Muscle layer constricts bronchioles. Epithelium
of bronchioles is covered with cilia and mucus.


Mucus traps dust and other particles.
Ciliary Escalator: Cilia beat upwards and remove trapped
particles from lower respiratory airways. Rate about 1 to 3 cm
per hour.
Human Respiratory System
Alveoli (Sing. Alveolus): Grapelike clusters of tiny
air sacs with very thin elastic walls through
which gas exchange occurs.


Oxygen in air enters blood in capillaries.
Carbon dioxide in blood enters air in alveoli.
There are several million alveoli in the human
lungs, with a total surface roughly equivalent to a
tennis court.
The walls of the alveoli are very delicate.
Alveolar macrophages are phagocytic cells that
swallow inhaled particles (dust, bacteria, etc.)
and digest them.
Structure of Lung Alveoli
Lung Alveoli Are The Site of Gas Exchange
Exchange of Gases Occurs in Alveoli
Breathing Ventilates the Lungs
Breathing: Alternation of inhalation and
exhalation. Supplies our lungs with oxygen rich
air, and expels excess carbon dioxide.
 Inhalation: Diaphragm contracts, moving
downward and causing rib cage, chest cavity, and
lungs to expand. Air rushes in, due to decrease in
internal lung pressure as lungs expand.
 Exhalation: Diaphragm relaxes, moving upwards
and causing rib cage, chest cavity, and lungs to
contract. Air rushes out, due to the increase in
internal lung pressure as lungs contract.
Breathing is controlled by centers in the nervous
system to keep up with body’s demands.
Human Breathing: Inhalation and Exhalation
Human Breathing is Automatically Controlled
Hemoglobin helps transport CO2 and buffer blood
Hemoglobin is found in red blood cells
Functions:
 Transports
oxygen
 Transport carbon dioxide
 Helps buffer blood
As carbon dioxide is picked up from tissues it is
converted into carbonic acid:
CO2 + H2O <-----> H2CO3 <----> H+ + HCO3 Carbon
dioxide
Carbonic acid
Carbonate ion
Hemoglobin picks up most H + ions, so they don’t
acidify the blood.
Blood Transports Gases to Between Lungs and Tissues
Hemoglobin Loading and Unloading of Oxygen
Hemoglobin Transports Gases and Helps Buffer Blood
Diseases of the Respiratory System

Respiratory rate: 10 to 14 inhalations/minute.

In one day, an average human:

Breathes 20,000 times

Inhales 35 pounds of air

Most of us breathe in air that is heavily
contaminated with solid particles, ozone, sulfur
oxide, carbon monoxide, nitrogen oxides, and many
other damaging chemicals.

Breathing contaminated air can cause a number of
diseases including asthma, bronchitis, emphysema,
and lung cancer.
Diseases of the Respiratory System

Cigarette smoke is one of the worse air pollutants.
 Over
1 million people start smoking every year.
 Kills about 350,000 people every year in U.S.
 Contains 4000 different chemicals.
 Each cigarette smoked subtracts about 5 minutes from
life expectancy.
 Cigarette smoke paralyzes cilia in airways, preventing
them from removing debris and from protecting delicate
alveoli.
 Frequent coughing is the only way airways can clean
themselves.
 Cigarette smoke also causes fetal damage, which can
result in miscarriage, premature birth, low birth weight,
and poor development.

Diseases of the Respiratory System
Asthma: Condition in which breathing is
impaired by constriction of bronchi and
bronchioles, cough, and thick mucus secretions.
The severity and incidence of asthma has risen
dramatically in recent years, especially in
children. May be fatal if not treated.
Causes: Attacks may be precipitated by
inhalation of allergens (e.g.: pollen, cats, and
cockroach proteins), pollutants, infection, or
emotional stress.
Treatment: Alleviates symptoms (e.g.: immunosuppressors, bronchodilators), but is not a cure.


Diseases of the Respiratory System
Bronchitis: Inflammation of the mucous
membranes of the bronchi. May present with
cough, fever, chest or back pain, and fatigue.
Causes: Associated with smoking, pollution, and
bacterial or viral infections.
Pneumonia: Acute inflammation of the lungs.
Symptoms include high fever, chills, headache,
cough, and chest pain.
Causes: Bacterial, fungal, or viral infections.
Treatment: Antibiotics or other antimicrobials.

Diseases of the Respiratory System
Emphysema: Permanent and irreversible
destruction of alveolar walls, resulting in loss of
lung elasticity and gas exchange surface.
Symptoms include shortness of breath, difficulty
exhaling, cough, weakness, anxiety, confusion,
heart failure, lung edema (swelling), and
respiratory failure.
Causes: Smoking, pollution, old age, and
infections.
Treatment: Oxygen to help breathing. No cure.

Diseases of the Respiratory System
Lung Cancer: Cancerous growth that invades
and destroys lung tissue. Very high fatality rate.
Symptoms include bloody sputum, persistent
cough, difficulty breathing, chest pain, and
repeated attacks of bronchitis or pneumonia.
Causes: Smoking (50% of all cases) and pollution
(radon, asbestos). Smokers are 10 times more
likely to develop lung cancer than nonsmokers.
Treatment: Surgery is most effective, but only
50% of all lung cancers are operable by time of
detection. Other treatments include radiation
and chemotherapy.
Human Fetus Exchanges Gases with Mother’s Blood
through the Placenta