The Respiratory System
Aerobic Organisms
• Require every cell to obtain oxygen and
remove CO₂ to survive
• All aerobic organisms share two
characteristics;
– A large respiratory surface
– Moist environment
Simple Gas Exchange
• Single celled organisms (bacteria, protozoa,
fungi) rely on diffusion- exchange of gases
through a concentration gradient
• To fulfill the moist requirements these
organisms must live in wet, aquatic
environments  either in the environment or
in a host organism
Specialized Breathing
• As animals increase in size, more O₂ is
required to meet their energy needs
• In order to deliver greater amounts of O₂ to
cells, the respiratory membranes of more
complex animals must have an increased
surface area
Specialized Breathing
• Skin Respiration
– Phylum Annelida  Segmented worms
• Skin must be kept moist to allow for diffusion of oxygen
• Skin is lined with capillaries which allow oxygen to
enter the circulatory system and carbon dioxide to exit
Specialized Breathing
• Tracheal Respiration
– Insects use a series of external pores called
spiracles which each lead to an internal series of
tubes called tracheae
– All of the spiracles are controlled by valves to
monitor water loss by the organism and to
facilitate the pressure differential
• Abdomen expands  air pressure drops in tracheae  4 anterior
paired spiracles open  air rushes into tracheae
• Abdomen contracts  4 anterior paired spiracles stay closed but 6
posterior spiracles open  air pressure inside is now high and air
flows out
Specialized Breathing
• Gills
– Extensions of the outer surface of the body
– The extensive folding and branching of the gills
provide increased surface area for the diffusion of
gases
– Water passes over gills, oxygen diffuses into the
blood and carbon dioxide diffuses out
• If gills become dry, the membrane becomes
impermeable to the diffusion of gases
• Fish also use counter-current flow  water
moves over the gills in one direction while the
blood, contained within the capillaries inside
the gill, moves in the opposite direction
Specialized Breathing
• Lungs
– Used by land animals
– Allow the exchange of gases between the air and
blood
– Internal folds inside the lung increase the surface
area for diffusion  the greater the surface area,
the greater amount of oxygen that can be
absorbed
Mammalian Respiratory System
• An organ system that rhythmically takes in air
and expels it from the body
– Supplies the body with oxygen and expels carbon
dioxide
– Air enters the respiratory system either through
the two nasal cavities or the mouth
The Respiratory System
Functions of the Mammalian
Respiratory System
• Provides for oxygen and carbon dioxide exchange between
the blood and air
• Serves for speech and other vocalization (laughing, crying)
• Provides the sense of smell
• By eliminating CO₂ it helps to control the pH of body fluids
• The lungs carry out a step in the synthesis of a
vasoconstrictor called angiotensin II, which helps to
regulate blood pressure
• Breathing creates pressure gradients between the thorax
and abdomen that promote the flow of lymph and venous
blood
• And the list goes on..
Mammalian Respiration
• Respiration is made up of 4 parts:
1) Breathing- inspiration and expiration
2) External Respiration- gas exchange between air
and blood
3) Internal Respiration- gas exchange between
blood and cells of surrounding tissues
4) Cellular Respiration- chemical reactions
Respiratory Tract
• The airway from the nose through the larynx
is called the upper respiratory tract (the
respiratory organs in the head and neck)
• The regions from the trachea through the
lungs compose the lower respiratory tract
(the respiratory organs of the thorax)
Upper Respiratory Tract
• The Nose
– Warms, cleanses and humidifies inhaled air
– Detects odors
– Serves as a resonating chamber that amplifies the
voice
Upper Respiratory Tract
• The Pharynx
– A muscular funnel extending about 5 inches from
the end of internal nasal openings to the larynx
– Has three regions; the nasopharynx, oropharynx
and laryngopharynx
– The nasopharynx passes only air, whereas the
oropharynx and laryngopharynx pass air, food and
drink
Upper Respiratory Tract
• The Larynx (aka voice box)
– Cartilaginous chamber about 1.5 inches long
– Primary function is to keep food and drink out of
the airway, but it evolved the additional role of
sound production in many animals
– The superior opening of the larynx is guarded by a
flap of tissue called the epiglottis which closes the
airway and directs food and drink into the
esophagus behind it
Lower Respiratory Tract
• Trachea (aka windpipe)
– A rigid tube about 4.5 inches long supported by Cshaped cartilaginous rings
– The trachealis muscles contract or relax to adjust
air flow
Lower Respiratory Tract
• The Lungs and Bronchial Tree
– The trachea branches into bronchi, and each
bronchus subdivides into bronchioles
– Each bronchiole ends in a cluster of tiny sacs
known as alveoli
• This is where gas exchange (external respiration) takes
place
Lower Respiratory Tract
• Lungs are enveloped in a tissue called pleura
which contains the lungs but allows them to
expand and contract
• Each lung is divided into lobes
– Right has 3, left has 2 (one less to accommodate
the heart)
– A bronchiole enters each lobe
Mechanics of Breathing
•
Two muscular structures allow ventilation:
1. Intercostal muscles – muscles associated with ventral
surface of rib cage
2. Diaphragm – muscle that separates thoracic cavity
from abdominal cavity
•
Both work in unison to move air in and out of the
lungs to allow ventilation
–
–
As air moves into the lungs, the intercostal muscles
contract; ribcage moves upward and diaphragm
contracts and moves downward
As air moves out of the lungs, the intercostal muscles
relax; ribcage falls and the diaphragm relaxes and moves
upward
Mechanics of Breathing
Lung Capacity
• Different volumes of air can be drawn into the lungs
– Tidal volume – volume of air that is inhaled and exhaled in a
normal breathing movement
– Inspiratory reserve volume – additional volume that can be
taken in beyond tidal volume
– Expiratory reserve volume – additional volume that can be
forced out beyond tidal volume
– Vital capacity – total volume of gas that can be moved in or out
of lungs
• Tidal volume + inspiratory reserve volume + expiratory reserve volume
– Residual volume – amount of gas that remains in lungs after a
full exhalation  ensures collapse does not occur
Gas Exchange and Transport
• Dalton’s law of partial pressure states that each gas in
a mixture exerts its own pressure, or partial pressure
• Gases diffuse from an area of high partial pressure to
an area of lower partial pressure
• The highest partial pressure of oxygen is found in
atmospheric air (101 kPa)  oxygen diffuses from the
air (21.2 kPa) into the lungs (13.3 kPa for the alveoli)
(The partial pressure exerted by oxygen can be calculated
since we know that 21% of the air is oxygen, 21% x 101
kPa = 21.21 kPa)
Disorders of the Respiratory System
• All respiratory disorders share one common
characteristic: they all decrease oxygen delivery
to the tissues
–
–
–
–
–
–
–
–
Asthma
Emphysema
COPD
Bronchitis
Pneumonia
Tuberculosis
Cystic Fibrosis
Lung Cancer
Asthma
• Chronic inflammatory disease of the bronchioles
– The linings of the airways becomes inflamed (red, irritated
and swollen) and may produce more mucous
• Symptoms include;
–
–
–
–
Shortness of breath
Tightness in the chest
Coughing
Wheezing
• Affects 3 million people in Canada
• Can be mild, moderate to severe
• Controlled by use of corticosteroids (puffers) and
strengthening the respiratory tract through exercise
Chronic Obstructive Pulmonary
Disease (COPD)
• Inflammatory lung disease that causes
obstructive airflow from the lungs
• Results in difficulty blowing air out, causing
shortness of breath
• Smoking is by far the most common cause
– Chronic Bronchitis- Form of COPD where the bronchial
tubes are inflamed and produce a lot of mucous.
Causes repeated, frequent episodes of coughing.
Breathing also becomes difficult.
– Emphysema- Form of COPD where the walls between
the alveoli (lung’s air sacs) are damaged, trapping air
in the lungs and making it difficult to breathe.
Smoking
• Cigarettes contain about 600 ingredientswhen they burn they generate more than
7000 chemicals
• Causes cilia paralysation- your lungs lose the
ability to sweep out harmful particles
• Coughing can’t clear out the toxins sufficiently,
so these toxins get trapped in the lungs
• Exposes you to a countless number of
diseases including many forms of cancer