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James Cook University
Medical
Physiology 2
PP2201 Semester 2 2015
TOPICS
1.
2.
3.
4.
5.
RESPIRATORY
GASTROINTESTINAL AND NUTRITION
RENAL ACID BASE
ENDOCRINOLOGY
REPRODUCTION
Jayde Van-Hoff
Biomedical Sciences Second Year - 2015
Respiratory Physiology
“List and briefly describe the four major processes of respiration”
1. Ventilation – Getting air into the lungs by attempting to create the greatest pressure
gradient across the alveolar membrane.
“Ventilation is all about getting the greatest partial pressure gradient at the respiratory
interface”. This just means, having the most amount if gas available for diffusion.
2. Movement of Gas across the respiratory membrane – actual diffusion of respiratory gases
across the alveolar membrane, in order to get into the bloodstream.
“The exchange of gases across the respiratory membrane is directly associated with the
diffusion of these gases”, this is about how well the gases cross the membrane. The partial
pressure gradient is one factor that will help.
3. Transport of Gas in the Blood – getting oxygen into and carbon dioxide out of the cells, lungs
and body.
“Gas transport is all about getting oxygen and Carbon Dioxide out and Oxygen in.
4. Movement of Gas across the cell membrane – diffusion of the gases between the blood and
the cell.
Lung Anatomy
have knowledge of the sequence and structure that the air moves past
understand the reasons underlying the alveolar structure and position
understand the relationship between the lung pleural sac and the thorax
“Identify the organs forming the respiratory passageways in descending order
until the alveoli are reached.”
Nasel/oral cavity => pharynx => Larynx => Trachea => Right and left Bronchi => Bronchioles =>
Respiratory Bronchioles => alveolar ducts => alveoli
“Discuss the role of cartilage in the trachea and bronchioles.”
The trachea is close to the oesophagus
There are rings of cartilage within the trachea and bronchioles. Cartilage is strong and flexible,
holding both the trachea and the bronchioles open, preventing collapse, hence protecting the
individual. They ultimately support the lungs in inflating and deflating.
“Distinguish between conducting and respiratory zone structures.”
The conducting zone, takes the air into your lungs and forms the dead space. There is no transfer of
gas in the conducting zone. Transfer of gas only occurs within the transitional/respiratory zone. The
amount of gas exchange that occurs within the areas, is proportional to the amount of alveoli.
“Discuss the changes in the properties of the bronchioles as you move down the airway.”
As you move down the airway:




surface area increases
smooth muscle increases
cartilage decreases
cilia decrease (these cilia are a bodily defense mechanism)
Remember
Increase in ‘S’
Decrease in ‘C’
“Describe the makeup of the alveoli membrane, and relate structure to function.”
The following structures enable oxygen to diffuse into the blood from the alveoli and the carbon
dioxide to diffuse out of the blood and into the alveoli
-
The alveolar membrane is one cell thick
The space between the capillary membrane and the alveolar membrane is a tiny 0.5
micrometres (interstitial space)
One alveolus is typically 0.1 to 0.2mm in diameter
They are highly vascularised, completely covered by capillaries
The alveoli are abundant in order to dramatically increase surface area – 300 Million of them
The alveolar membrane is made up of type I cells
Type II alveolar cells secrete surfactant (some premature babies have not developed type II
alveolar cells yet
“Describe the gross structure of the lungs and pleurae”
Lungs are found in the thoracic cavity, within the rib cage and on top of the diaphragm. The
thoracic cavity is airtight. The thoracic cavity is bound by the pleural sac. Within the pleural
sac, there is intrapleural fluid, in which the lungs are suspended. The intrapleural fluid helps
to separate the lungs from the thoracic wall, as well as providing lubrication, reducing friction
and therefore providing protection. The pleural sac is bound by the visceral pleura (inner
membrane) and the parietal pleura (outer membrane). The right and left lungs are suspended
within the right and left pleural cavities respectively.
If the pressure in the intrapleural cavity (alveoli) is greater that of the lung, it will be crushed.
The lungs are divided into lobes, with are distinguished using fissures (cracks). The left lung
has upper and lower lobes, separated by the oblique fissure. The right lung has a superior
lobe, a transverse fissure, middle lobe, its own oblique fissure and inferior lobe.
“List the pressure in the atmosphere, alveoli and intrapleural space and discuss the
physiological importance of their relationship with each other with respect to airflow.”
Here, the intrapulmonary pressure and the atmospheric pressure are the same, meaning that
there is no air movement. It must be the time between moving in and out. In order to get air
into the lungs, the intrapulmonary pressure must decrease belong atmospheric pressure, and
in order to get air out, the intrapulmonary pressure must increase above atmospheric pressure.
To increase pressure in the alveoli, we can decrease the volume of the space. How? The
lung’s natural recoil. If you want to get air into the alveoli, decrease the pressure by
increasing the alveolar volume. This is where the intrapleural pressure, which is -4 mmHg, 4
less than atmospheric in order for air to move in. The diaphragm moves down.so there is a
pressure difference between the alveoli and the intrepleural space. This is known as the
Transpulmonary Pressure (0-(-4) = 4mmmHg).
Atmospheric pressure = 760mm Hg, 0 compared to atmospheric pressure/the same as
atmospheric pressure
Intrapleural pressure = -4mm Hg
Intrapulmonary pressure = the pressure within the alveoli = 0 (760) mm Hg
Air will always move from an area of high pressure to an area of low pressure. In order for air
to enter the lungs (inspiration), the intrapulmonary pressure must be less than the
intrapulmonary pressure. The intrapulmonary pressure is decreased by increasing the volume
of the lungs. The diaphragm and the internal intercostal muscles help with this. During
expiration, a passive process, air rushes out of the lungs until in the intrapulmonary pressure
and the atmospheric pressure are equal.
“Explain the importance of the partial vacuum that exists in the intrapleural space.”
Intrapulmonary pressure is the pressure in the alveoli which eventually equalises with
atmospheric pressure. Intrapleural pressure is the pressure in the pleural cavity. It also rises
and falls during respiration, but is always about 4 mm Hg less than intrapulmonary pressure.
The amount of pleural fluid in the pleural cavity must remain minimal in order for the
negative Pintraplu to be maintained. The pleural fluid is actively pumped out of the pleural
cavity into the lymphatics continuously. If it wasn’t, fluid would accumulate in the
intrapleural space (remember, fluids move from high to low pressure), producing a positive
pressure in the pleural cavity.
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Best Wishes,
Jayde