Respiration
What is the main purpose of respiration?
In other words why do we breathe?
To provide oxygen to the body
To get rid of carbon dioxide
To burn food
To give energy
C6H12O6 + O2
H2O + CO2 + ATP
(energy)
Respiration
Respiration occurs on two levels:
External Respiration (lung level)
It is the process by which oxygen is delivered to
the blood and carbon dioxide is removed.
Internal Respiration (tissue level)
It is the process by which oxygen is delivered to
the cells and carbon dioxide is removed.
Respiration Processes
• Breathing (ventilation): air into and out of
the lungs
• External respiration: gas exchange between
air and blood
• Internal respiration: gas exchange between
blood and tissues
• Cellular respiration: use oxygen to produce
ATP (energy), produce carbon dioxide as
waste
The Respiratory Cycle
(Mechanism of Breathing)
LUNG VOLUMES
1. Tidal Volume: the normal volume of air you breathe in and out
at rest.
2. Inspiratory reserve: the maximum air you can inhale after the
tidal volume.
3. Expiratory Reserve: the maximum amount of air you can exhale
after exhaling your tidal volume.
4. Vital Capacity: the maximum air you can inhale and exhale (Tidal
volume plus inspiratory and expiratory reserves).
5. Residual air: the air in the lungs that cannot be exhaled.
Conditioning of Inhaled Air:
Several things happen to the air on its journey into the alveoli. The air is:
1. Cleansed of debris in a 2 part process. The initial cleaning is by the nose hairs and
mucous in the nasal passageways. The second part of the process occurs in the trachea
and bronchi which are both lined with mucous and cilia. Any material other than the
gases of the inhaled air will get caught in the mucous. The cilia (microscopic protein
filaments) are in constant motion, beating the debris-laden mucous up towards the
pharynx. When this material is detected at the back of the mouth, it is swallowed or
coughed up and expectorated (spit out). *Note: cilia do not filter!
2. Adjusted to body temperature (~37 degrees Celsius). The more contact the air has
with moist tissues at 37o C, the closer the temperature of the inhaled air gets to body
temperature. By the time the air arrives at the alveoli there is no difference in its
temperature than that of the surrounding tissues.
3. Adjusted to 100% humidity. The air in the lungs is saturated with water. One of the
things that happens to inhaled air is that as it passes over the mucous passageways, it
becomes saturated with water.
Respiration
The basic requirements for respiration to take place are:
1. A respiratory surface that is big enough for the exchange
of oxygen and carbon dioxide to occur at a rate sufficient to
meet the organism’s metabolic needs.
2. A moist environment so that the oxygen and the carbon dioxide
would dissolve.
3. Only 2 cell layers separate air in lungs from the blood
Components of the Upper
Respiratory Tract
Upper Respiratory Tract
Functions:
• Passageway for respiration
• Receptors for smell
• Filters incoming air from large foreign
material
• Moistens and warms incoming air
• Resonating chambers for voice
Vocal Cords, Open
Vocal cords, closed
Components of the Lower
Respiratory Tract
Lung pleural membranes
Lower Respiratory Tract
Functions:
• Larynx:
• Maintains an open airway, routes food and
air appropriately, assists in sound production
• Trachea:
• Transports air to and from lungs
• Bronchi: branch into lungs
• Lungs:
• Transport air to alveoli for gas exchange
Gas Exchange & Transport:
A Passive Process
• Gases diffuse according to their partial
pressures
– External respiration: gases exchanged between
air and blood
– Internal respiration: gases exchanged with tissue
fluids
– Oxygen transport: bound to hemoglobin in red
blood cells or dissolved in blood plasma
– Carbon dioxide transport: dissolved in blood
plasma, bound to hemoglobin, or in the form of
plasma bicarbonate
Gas Exchange Between the Blood and Alveoli
Gas transport in the blood
Partial Pressures
Two molecules help the process of gas exchange become
more efficient:
A.Surfactants – these soap-like molecules, consisting of
phospholipids and protein, coat the inner surface of the
alveoli and reduce surface tension. Without them, the
alveolar walls would stick together, making breathing
very difficult. [This is one effect that cystic fibrosis
sufferers have; they produce too much, very thick
mucus.]
B. Haemoglobin – the red oxygen-carrying molecule that
fills RBC’s. Each haemoglobin molecule has four oxygenbinding sites. Most of the oxygen in blood - 98 percent
– is combined with haemoglobin.
Regulation of Breathing:
Nervous System Involvement
1. Respiratory center in the medulla oblongata:
The control of the breathing process is only voluntary to a point. The
medulla oblongata of the brain is sensitive to the concentration of
carbon dioxide and hydrogen ions in the blood. Both of these are
products of cellular metabolism and both need to be excreted. As
CO2 accumulates in the blood, it means that you’re not breathing fast
enough, and therefore, are not getting enough oxygen. When the
concentrations of H+ and CO2 reach a critical level, the breathing
center in the medulla oblongata is stimulated and sends nerve
impulses to the diaphragm and the intercostal muscles (that lie
between the ribs) to initiate their contraction.
2. Carotid and aortic Vessels:
*The aortic arch and carotid arteries also contain
chemoreceptors that are sensitive to the oxygen content
in the blood. If it is critically low, they will help initiate the
inhalation response. Note, however, that this is a
secondary mechanism. The primary mechanism that
triggers inhalation is still an elevated concentration of
carbon dioxide and hydrogen ions.
Diseases of the Respiratory System:
• Asthma narrows the airways by causing allergy-induced
spasms of surrounding muscles or by clogging the airways
with mucus.
• Bronchitis is an inflammatory response that reduces
airflow and is caused by long-term exposure to irritants
such as cigarette smoke, air pollutants, allergens or
infectious agents.
• Cystic fibrosis is a genetic defect that causes excessive
mucus production that clogs the airways, also its thick
nature tends to keep each alveolus sticking on itself.