Mechanics of Breathing
This explanation of the physiology of breathing shows how our health improves
through the conscious connected breathing that we do in Transformation Breathwork.
Humans need a continuous supply of oxygen for cellular respiration, and they must get rid of
excess carbon dioxide, the poisonous waste product of this process. Gas exchange supports
this cellular respiration by constantly supplying oxygen and removing carbon dioxide. The
oxygen we need is derived from the Earth's atmosphere, which is 21% oxygen. This oxygen in
the air is exchanged in the body by the respiratory surface. In humans, the alveoli in the lungs
serve as the surface for gas exchange.
Gas exchange in humans can be divided into five steps:
1.
2.
3.
4.
5.
Breathing
External Respiration
Gas Transport
Internal Respiration
Cellular Respiration
Other factors involved with respiration are:
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Adaptations of Diving Mammals
Bohr Shift
Control of Breathing
Partial Pressure
Structure of Respiratory System
Structure of the Human Respiratory System
The Nose - Usually air will enter the respiratory system through the nostrils. The nostrils then
lead to open spaces in the nose called the nasal passages. The nasal passages serve as a
moistener, a filter, and to warm up the air before it reaches the lungs. The hairs existing within
the nostrils prevents various foreign particles from entering. Different air passageways and the
nasal passages are covered with a mucous membrane. Many of the cells which produce the
cells that make up the membrane contain cilia. Others secrete a type a sticky fluid called
mucus. The mucus and cilia collect dust, bacteria, and other particles in the air. The mucus
also helps in moistening the air. Under the mucous membrane there are a large number of
capillaries. The blood within these capillaries helps to warm the air as it passes through the
nose. The nose serves three purposes. It warms, filters, and moistens the air before it
reaches the lungs. You will obviously lose these special advantages if you breath through your
mouth.
Pharynx and Larynx - Air travels from the nasal passages to the pharynx, or more
commonly known as the throat. When the air leaves the pharynx it passes into the larynx, or
the voice box. The voice box is constructed mainly of cartilage, which is a flexible connective
tissue. The vocal chords are two pairs of membranes that are stretched across the inside of
the larynx. As the air is expired, the vocal chords vibrate. Humans can control the vibrations
of the vocal chords, which enables us to make sounds. Food and liquids are blocked from
entering the opening of the larynx by the epiglottis to prevent people from choking during
swallowing.
Trachea - The larynx goes directly into the trachea or the windpipe. The trachea is a tube
approximately 12 centimeters in length and 2.5 centimeters wide. The trachea is kept open by
rings of cartilage within its walls. Similar to the nasal passages, the trachea is covered with a
ciliated mucous membrane. Usually the cilia move mucus and trapped foreign matter to the
pharynx. After that, they leave the air passages and are normally swallowed. The respiratory
system cannot deal with tobacco smoke very keenly. Smoking stops the cilia from moving.
Just one cigarette slows their motion for about 20 minutes. The tobacco smoke increases the
amount of mucus in the air passages. When smokers cough, their body is attempting to
dispose of the extra mucus.
Bronchi - Around the center of the chest, the trachea divides into two cartilage-ringed tubes
called bronchi. Also, this section of the respiratory system is lined with ciliated cells. The
bronchi enter the lungs and spread into a treelike fashion into smaller tubes calle bronchial
tubes.
Bronchioles - The bronchial tubes divide and then subdivide. By doing this their walls
become thinner and have less and less cartilage. Eventually, they become a tiny group of
tubes called bronchioles.
Alveoli - Each bronchiole ends in a tiny air chamber that looks like a bunch of grapes. Each
chamber contains many cup-shaped cavities known as alveoli. The walls of the alveoli, which
are only about one cell thick, are the respiratory surface. They are thin, moist, and are
surrounded by several numbers of capillaries. The exchange of oxygen and carbon dioxide
between blood and air occurs through these walls. The estimation is that lungs contain about
300 million alveoli. Their total surface area would be about 70 square meters. That is 40 times
the surface area of the skin. Smoking makes it difficult for oxygen to be taken through the
alveoli. When the cigarette smoke is inhaled, about one-third of the particles will remain within
the alveoli. There are too many particles from smoking or from other sources of air pollution
which can damage the walls in the alveoli. This causes a certain tissue to form. This tissue
reduces the working area of the respiratory surface and leads to the disease called
emphysema.
Breathing
Breathing consists of two phases,
inspiration and expiration. During
inspiration, the diaphragm and the
intercostal muscles contract. The
diaphragm moves downwards increasing
the volume of the thoracic (chest) cavity,
and the intercostal muscles pull the ribs
up expanding the rib cage and further
increasing this volume. This increase of
volume lowers the air pressure in the
alveoli to below atmospheric pressure. Because air always flows from a region of high
pressure to a region of lower pressure, it rushes in through the respiratory tract and into the
alveoli. This is called negative pressure breathing, changing the pressure inside the lungs
relative to the pressure of the outside atmosphere. In contrast to inspiration, during expiration
the diaphragm and intercostal muscles relax. This returns the thoracic cavity to it's original
volume, increasing the air pressure in the lungs, and forcing the air out.
External Respiration
When a breath is taken, air passes in through the nostrils,
through the nasal passages, into the pharynx, through the
larynx, down the trachea, into one of the main bronchi, then
into smaller bronchial tubules, through even smaller
bronchioles, and into a microscopic air sac called an
alveolus. It is here that external respiration occurs. Simply
put, it is the exchange of oxygen and carbon dioxide
between the air and the blood in the lungs. Blood enters
the lungs via the pulmonary arteries. It then proceeds
through arterioles and into the alveolar capillaries. Oxygen
and carbon dioxide are exchanged between blood and the
air. This blood then flows out of the alveolar capillaries,
through venuoles, and back to the heart via the pulmonary
veins. For an explanation as to why gasses are exchanged
here, see partial pressure.
Gas Transport
If 100mL of plasma is exposed to an atmosphere with a pO2 of 100mm Hg, only 0.3mL of
oxygen would be absorbed. However, if 100mL of blood is exposed to the same atmosphere,
about 19mL of oxygen would be absorbed. This is due to the presence of haemoglobin, the
main means of oxygen transport in the body. The respiratory pigment haemoglobin is made up
of an iron-containing porphyron, haem, combined with the protein globin. Each iron atom in
haem is attached to four pyrole groups by covalent bonds. A fifth covalent bond of the iron is
attached to the globin part of the molecule and the sixth covalent bond is available for
combination with oxygen. There are four iron atoms in each hemoglobin molecule and
therefore four heam groups.
Oxygen Transport In the loading and unloading of oxygen, there is a cooperation between these four haem
groups. When oxygen binds to one of the groups,
the others change shape slightly and their attraction
to oxygen increases. The loading of the first
oxygen, results in the rapid loading of the next three
(forming oxyhemoglobin). At the other end, when
one group unloads it's oxygen, the other three
rapidly unload as their groups change shape again
having less attraction for oxygen. This method of
cooperative binding and release can be seen in the dissociation curve for hemoglobin. Over
the range of oxygen concentrations where the curve has a steep slope, the slightest change in
concentration will cause hemoglobin to load or unload a substantial amount of oxygen. Notice
that the steep part of the curve corresponds to the range of oxygen concentrations found in
the tissues. When the cells in a particular location begin to work harder, e.g. during exercise,
oxygen concentration dips in that location, as the oxygen is used in cellular respiration.
Because of the cooperation between the haem groups, this slight change in concentration is
enough to cause a large increase in the amount of oxygen unloaded.
As with all proteins, hemoglobin's shape shift is sensitive to a variety of environmental
conditions. A drop in pH lowers the attraction of hemoglobin to oxygen, an effect known as
the Bohr shift. Because carbon dioxide reacts with water to produce carbonic acid, an active
tissue will lower the pH of it's surroundings and encourage hemoglobin to give up extra
oxygen, to be used in cellular respiration. Hemoglobin is a notable molecule for it's ability to
transport oxygen from regions of supply to regions of demand.
Carbon Dioxide Transport - Out of the carbon
dioxide released from respiring cells, 7%
dissolves into the plasma, 23% binds to the
multiple amino groups of hemoglobin
(Caroxyhemoglobin), and 70% is carried as
bicarbonate ions. Carbon dioxide created by
respiring cells diffuses into the blood plasma
and then into the red blood cells, where most
of it is converted to bicarbonate ions. It first
reacts with water forming carbonic acid, which
then breaks down into H+ and CO3-. Most of
the hydrogen ions that are produced attach to
hemoglobin or other proteins.
Internal Respiration
The body tissues need the oxygen and have to get rid of the carbon dioxide, so the blood
carried throughout the body exchanges oxygen and carbon dioxide with the body's tissues.
Internal respiration is basically the exchange of gasses between the blood in the capillaries
and the body's cells.
Control of Breathing
The respiratory center is gray matter in the pons and the upper Medulla, which is responsible
for rhythmic respiration. This center can be divided into an inspiratory center and an expiratory
center in the Medulla, an apneustic center in the lower and midpons and a pneumotaxic center
in the rostral-most part of the pons. This respiratory center is very sensitive to the pCO 2 in the
arteries and to the pH level of the blood. The CO2 can be brought back to the lungs in three
different ways; dissolved in plasma, as carboxyhemoglobin, or as carbonic acid. That particular
form of acid is almost broken down immediately by carbonic hydrase into bicarbonate and
hydrogen ions. This process is then reversed in the lungs so that water and carbon dioxide
are exhaled. The Medulla Oblongata reacts to both CO2 and pH levels which triggers the
breathing process so that more oxygen can enter the body to replace the oxygen that has
been utilized. The Medulla Oblongata sends neural impulses down through the spinal chord
and into the diaphragm. The impulse contracts down to the floor of the chest cavity, and at the
same time there is a message sent to the chest muscles to expand causing a partial vacuum
to be formed in the lungs. The partial vacuum will draw air into the lungs.
There are two other ways the Medulla Oblongata can be stimulated. The first type is when
there is an oxygen debt (lack of oxygen reaching the muscles), and this produces lactic acid
which lowers the pH level. The Medulla Oblongata is then stimulated. If the pH rises it begins
a process known as the Bohr shift. The Bohr shift is affected when there are extremely high
oxygen and carbon dioxide pressures present in the human body. This factor causes difficulty
for the oxygen and carbon dioxide to attach to hemoglobin. When the body is exposed to
higher altitudes the oxygen will not attach to the hemoglobin properly, causing the oxygen level
to drop and the person will black out. This theory also applies to divers who go to great
depths, and the pressure of the oxygen becomes poisonous. These pressures are known as
pO2 and pCO2, or partial pressures. The second type occurs when the major arteries in the
body called the aortic and carotid bodies, sense a lack of oxygen within the blood and they
send messages to the Medulla Oblongata.
Adaptations of Diving Mammals
Various
marine mammals have been found to have adapted
special abilities which help in their respiratory processes,
enabling them to remain down at great depths for long periods of
time. The Weddell seal possesses some amazing abilities. It
only stores 5% of its oxygen in its lungs, and keeps the remaining
70% of its oxygen circulating throughout the blood stream.
Humans are only able to keep a small 51% of their oxygen
circulating throughout the blood stream, while 36% of the oxygen
is stored in the lungs. The explanation for this is that the Weddell
seal has approximately twice the volume of blood per kilogram as humans. As well, the
Weddell seal's spleen has the ability to store up to 24L of blood. It is believed that when the
seal dives the spleen contracts causing the stored oxygen enriched blood to enter the blood
stream. Also, these seals have a higher concentration of a certain protein found within the
muscles known as myoglobin, which stores oxygen. The Weddell seal contains 25% of its
oxygen in the muscles, while humans only keep about 12% of their oxygen within the muscles.
Not only does the Weddell seal store oxygen for long dives, but they consume it wisely as well. A
diving reflex slows the pulse, and an overall reduction in oxygen consumption occurs due to this
reduced heart rate. Regulatory mechamisms reroute blood to where it is needed most (brain, spinal
cord, eyes, adrenal glands, and in some cases placenta) by constricting blood flow where it is not
needed (mainly in the digestive system). Blood flow is restricted to muscles during long dives and
they rely on oxygen stored in their myoglobin and make their ATP from fermentation rather then from
respiration.