Transcript The Respiratory System Lab 10

The Respiratory System rev 11-11
• The primary function of the respiratory system is
to deliver oxygen (O2) to and remove carbon
dioxide (CO2) from the blood.
• The respiratory system also plays a role in
maintaining the blood pH (acid-base balance).
• Additionally, in humans and most animals, the
respiratory system also produces sounds.
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Anatomy of the Upper Respiratory Tract:
• Nose, nasal cavities, sinuses and pharynx
(throat) (everything above the Adam’s apple)
– The nose, nasal cavities and sinuses provide a
large area of highly vascularized tissues which
warm, filter and add moisture to air.
– As air comes into contact with the warm, moist
tissue of the nasal passages, it is warmed and
moistened. The sinuses also add moisture to
the air.
– Your nose contains receptors for smell
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– The pharynx (throat) connects the nasal cavity
and mouth to the larynx (voice box).
– The tract provides a resonating chamber that
gives your voice its characteristic tone
Other structures which enter or are located in the
pharynx are:
– 2 tear ducts which carry fluid away from the
eyes (this is why excess tears also make your
nose runny)
– the esophagus--this makes it possible to
breathe through your mouth.
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– The 2 Eustachian tubes that drain the middle
ear and equalize air pressure between the
middle ear and outside air.
– Food
• Below the throat, the air passage crosses in front of
the esophagus. This makes it possible for food or
liquids to be accidentally sucked into the air
passages and can cause us to cough or choke. These
actions attempt to clear the food or liquid.
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– Epiglottis-a flap of cartilage located in the back
of the throat.
• During swallowing, the epiglottis forms a tight seal
over the trachea so food can’t go down it.
– The Uvula-a flap of tissue in the back of the
mouth that hangs from the roof of your mouth.
• This closes the upper air passages so food does not
come out your nose. (This is also the part of the
body that causes snoring when air passes over it.)
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The lower respiratory tract includes
– the larynx, trachea, 2 bronchi, 2 lungs
(including the bronchioles and alveoli)
– the larynx or voice box is below the epiglottis
and pharynx and is protected by the thyroid
cartilage (nicknamed the Adam’s apple).
– Functions of the larynx
• maintains an open airway
• route food and air into their appropriate tubes
• assist in the production of sound
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– The vocal cords consist of 2 folds of
connective tissue that extend across the airway.
The opening of this airway is called the glottis.
• Vocal cords are supported by ligaments.
Sound is produced as we expel air past the
stretched cords causing them to vibrate.
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– The trachea (or windpipe) is a tube below the
larynx and transports air on its way into the
lungs.
• It is about 4 1/2 inches long,
• is composed of C-shaped rings of cartilage
(to ensure that it stays open), and carries air
to the bronchi and through them to the lungs
• The trachea branches into airways which are
called the right and left bronchi
(sometimes called the primary bronchi).
These further subdivide into smaller and
smaller bronchi.
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– The walls of the bronchi contain fibrous connective
tissue and smooth muscle reinforced with cartilage. As
the branches get smaller, the amount of cartilage
declines. When they have no cartilage, their name
changes into bronchioles.
– Surrounding the bronchi are the lungs. These fill the
thoracic cavity and extend from the clavicles to the
diaphragm (a thin sheet of muscle).
– Bronchioles lead to alveoli which are the air sacs of the
lungs. Alveoli are composed of a single layer of flat,
simple squamous cells and this is where gas exchange
takes place.
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• Breathing
– Involves repetitive cycles of getting air into and
out of the lungs.
– This requires muscular effort.
– Since the lungs themselves do not have any
skeletal muscle tissue, expansion and
contraction occurs because the surrounding
bones and muscles expand the size of the chest
cavity.
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• Inspiration:
– As the diaphragm contracts and flattens, the
external intercostal muscles contract and lift
the ribcage. This causes a pressure drop in the
thoracic cavity.
– The scalene and sternocleidomastoid
(SCM) muscles also contract to help expand
the thoracic cavity space.
– As the volume (space) in the thoracic cavity
increases, air rushes in to fill this space.
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• Other things that help inspiration:
– The lungs and chest cavity are surrounded by a
membrane called “pleura”. There is fluid
between the layers of the pleura (pleural
cavity) so the lungs can stretch and contract
with minimum friction.
• There is also a partial vacuum between the 2
pleural layers. This causes the lungs to stick to
the chest wall as it expands.
• Alveolar surfactant, a chemical within the
lungs, decreases the surface tension so the lung
tissue doesn’t stick to itself.
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• Expiration or Exhalation:
– The diaphragm relaxes and intra-abdominal
pressure pushes the diaphragm up. The
internal intercostal muscles and gravity help
to drop the ribcage and thoracic cavity back to
its smaller size. This increases pressure within
the lungs and forces the air out of them.
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Respiratory Volumes
• Tidal volume is the amount of air an individual
normally inhales and exhales.
• Our body's normal breathing strategy is to
ventilate the air sacs and also keep a minimal
residual volume in the lungs. This allows us to
keep some air for the blood passing through the
lungs between breaths. This air is referred to as
dead space volume.
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• The amount of air that can be forcibly inhaled
after a normal inspiration (tidal volume) is called
inspiratory reserve volume.
• The amount of air that can be forcibly exhaled
after a normal expiration (tidal volume) is called
expiratory reserve volume.
• The vital capacity is the maximal volume that you
can forcibly exhale after a maximal inhalation.
• After you forcibly exhale, there is always some air
left in the lungs. This is called the residual
volume.
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• These lung capacities are measured with a
spirometer.
• Gases are transported from the lungs to the body
primarily by hemoglobin. They can also be
dissolved in the plasma. In plasma, carbon
dioxide dissolves and becomes carbonic acid or
bicarbonate.
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Gas Exchange and Transport: A Passive Process
Gases diffuse according to their partial pressures (pressure
exerted by 1 particular gas in a mixture of gases). No ATP is
used.
• External respiration: gases exchanged between air and blood
• partial pressure of O2 is higher in alveoli-- CO2 is
higher in the capillaries, so gases passively diffuse;
– O2 carried to the blood and then to the body, CO2
exhaled
• Internal respiration: gases exchanged with tissue (interstitial)
fluids/space
• partial pressure of O2 is lower in blood and CO2 is
higher in the extracellular space, so gases passively
diffuse;
– O2 goes into the cell, CO2 diffuses into capillaries
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Gas Exchange and Transport: A Passive Process cont’d
• Oxygen transport: either bound to hemoglobin in red blood
cells (primary method or dissolved in blood plasma
– Forms oxyhemoglobin; depends on partial pressure of O2
(when P O2 rises, oxygen attaches to hemoglobin; when
PO2 falls, oxygen detaches), temperature (likes lower
temperature) & pH (likes neutral pH)
• Hemaglobin’s affinity for oxygen is decreased by
carbon monoxide
• Carbon dioxide transport: dissolved in blood plasma in the
form of plasma bicarbonate (primary method by which CO2 is
transported) or bound to hemoglobin
– Carbaminohemoglobin, can dissolve into carbonic acid
or bicarbonate
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Regulation of Breathing: Nervous System Involvement
The nervous system regulates the rate and depth of breathing
in order to maintain homeostasis.
• The respiratory center in the medulla oblongata establishes
basic breathing pattern including the rate at which we
breathe.
Chemical receptors monitor carbon dioxide, hydrogen ions,
and oxygen levels:
• The medulla is sensitive to hydrogen ions in cerebrospinal
fluid as a result of more carbon dioxide in the blood.
• Carotid and aortic bodies in the blood are sensitive to
carbon dioxide, pH, and oxygen levels
• Conscious control of breathing resides in higher brain
centers (primarily the cortex)--ability to modify breath
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Disorders of Respiratory System
Reduced air flow:
• Asthma: chronic inflammatory disorder of the
airways characterized by inflammation, bronchial
hyperresponsiveness and airflow obstruction
– causes constriction of the bronchi, edema and increased
production of mucus with possible mucus plugs.
• COPD-Chronic Obstructive Pulmonary Disease
– Emphysema is caused by damage to the alveoli
due to damage in the connective tissue in the
bronchioles. The airways tend to collapse and this
causes increased pressure in the lungs which
eventually damage the alveoli.
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• Bronchitis is an inflammation of the bronchi which causes
increased mucus which causes coughing.
• Can be acute or chronic
• Chronic bronchitis is considered a form of COPD
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Infections:
• Pneumonia is an infection which causes inflammation of
the lungs. The alveoli secrete excess fluid so gas exchange
is impaired.
• Tuberculosis is a bacterial infection causing lung scars.
• Botulism is a poisoning by bacterial toxin. The toxin
blocks the transmission of nerve signals to the respiratory
muscles.
• Lung cancer
• Congestive heart failure impairs lung functioning.
• Cystic fibrosis is an inherited condition which causes
mucus producing cells in the lungs to produce a very thick,
sticky mucus which causes frequent infections. Other
organs of the body are also involved.
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