Exam 4--lung Flashcards
what is the primary function of the respiratory system?
- gas exchange
- oxygen diffuses from the air into the blood and carbon dioxide diffuses from the air into the blood
- ventilation
- control the pH of blood
where does gas exchange occur?
alveoli
conducting zone
bronchioles
do not participate in gas exchange
alveoli
- where gas exchange occurs
- the epithelial cells that make up this structure come in close contact to the endothelium of the lung capillaries
- the air in the alveoli is separated from the blood in the capillaries only by the epithelial cells of the alveoli, the endothelial cells of the capillary, and the basal lamina that separates the cell layers–respiratory zone
pulmonary artery
-delivers deoxygenated blood from the tissues to the pulmonary arteries and then to the right and left lung
pulmonary veins
drain the lungs and return oxygenated blood to the left atrium and ventricle
trachea
- covered by an epiglottis during swallowing but otherwise open to allow air into the respiratory system
- ringed with hyaline cartilage to give it strength
bronchioles
- smooth muscle wraps around them
- autonomic nervous system controls the diameter of them by controlling the amount of contraction and relaxation in the smooth muscle that is wrapped around them
What controls the lungs muscles?
- smooth muscle contraction is under control of the parasympathetic nervous system
- muscle relaxation is under the control of epinephrine released from the adrenal medulla
Asthma
results when these muscles contract inappropriately and restrict passage of air through these small tubes
ventilation
- the process of moving air in and out
- results from the active (muscle) and passive (elastic) characteristics of the system
boyle’s law
- v1p1=v2p2
- because gas is compressibile the volume that it occupies becomes progressively smaller as the pressure increases
- increasing the volume of the container decreases the pressure within the container
- when the volume of the lungs increase, the pressure decreases
P=RF
P=pressure differential between the inside of the compartment and the outside world
R=resistance to air flow in the lungs
F=flow of air
-expanding the volume of the thoracic cavity reduces the pressure in the lungs and permits air to flow into them
what is the bag that each of the two lungs are contained in?
- the pleura
- plastic bag example
- the surface tension of the water will allow the internal surfaces of the bag to cling to one another –formed by a continuous epithelium
- inside this epithelial bag is the intrapleural cavity or space
intrapleural cavity
-always at a negative pressure compared to the inside of the lung and the atmosphere
intrapulmonary pressure
- the pressure inside the lung
- changes from being more negative then the atmosphere (inspiration) to more positive then the atmosphere (expiration)
inspiration
- results from increasing the volume of the thoracic cavity
- when muscle fibers in the diaphragm contract and shorten the diaphragm flattens, the dome is eliminated and the volume of the cavity increases
expiration
- the lungs are elastic
- compliance–contracting to small volume
- when the diaphragm relaxes and returns to the dome shape and reduces the volume
- equilibrium is reached when the force exerted by the compliance of the lung is equal to the force exerted by the lungs attachments to the pleura
type 2 cells
- secrete surfactant
- similar to detergent and keep the alveoli from sticking together
- phospholipids are a important component of surfactant
- premature babies don’t have type 2 cells
tidal volume
- 500ml of air enters and leaves the lungs
- 150ml remain in the conducting airways of the trachea and bronchi and doesn’t participate in gas exchange
- the remaining 350ml enters the alveoli
- about 150ml of the air remains in the alveoli and is known as the alveolar dead space
- with each cycle 350ml of air that enters the alveoli exchanges with the 150ml in the dead space
air is composed of
79% nitrogen
21% oxygen
0.5% carbon dioxide
to calculate partial pressure multiply the percentage by the total air pressure
dalton’s law
the total pressure exerted by the air is the sum of the pressures exerted by each of the component gases in air
henry’s law
gases go into solution in water in proportion to their partial pressures
the alveolus
- oxygen diffuses from the air in the alveolus across two epithelial layers and into blood
- carbon dioxide diffuses from the blood into the alveolus
gas in the alveolus
- 9% N2
- 7% O2
- 2% H2O
- 2% CO2
- because of the thin seperation between blood and air, the blood gases in the blood adjacent to the alveoli quickly come to a new equilibrium
- this ensures that the erythrocytes will be saturated with O2 when they leave the lung
alveolar macrophage
- cell of the non-specfic immune system
- monitors the alveolus for potential pathogens
what molecule in erythrocytes binds oxygen?
hemoglobin
hemoglobin
- oxygenated with each of its 4 hemoglobin molecules has a molecule of oxygen attached
- said to be deoxygenated when the oxygen leaves the iron atoms
- in areas of the body where oxygen partial pressures are high (like the lung) oxygen binds to the iron atoms
- in regions where its low, oxygen leaves the hemoglobin
- this binding is said to be cooperative–binding of the 1st increases the prob. of binding to the second etc…
- hemoglobin returning to the lungs is still 75% saturated with oxygen
- at about 40mmHg hemoglobin gets rid of its oxygen and it diffuses out of the blood and into the tissues
bohr effect
-the affinity of hemoglobin for oxygen in the presence of lowered pH
carbon dioxide in the tissues
- oxidative phosphorylation by mitochondria produces CO2
- 7-10% plasma
- 20% erythrocytes
- 70% HCO3-
carbonic anhydrase
increases the rate of carbonic acid formation from CO2 and H2O—once H2CO3 is formed it breaks into H+ ions the bind to amino acids in hemoglobin
- binding the H+ is what causes the bohr effect–>shifts the curve to the right
- after the H+ and HCO3- dissociate from one another the HCO3- exits the erythrocyte and enters the plasma to go to the lungs
HCO3-
- in the lungs HCO3- reenters the erythrocyte and is converted to H2CO3 which is acted upon by carbonic anhydrase to convert carbonic acid to CO2 and H2O
- CO2 diffuses from the blood into the air in the alveolus and is subsequently exhaled
CO2
- increased arterial PCO2 are indirect and function through changes in pH
- can easily leave blood and pass into the brain
- in the brain CO2 forms carbonic acid and yields an increase in the hydrogen ion concentration (lower pH) in the cerebral spinal fluid
- largely regulates the waxing and waning of activity in the motor neurons that cause muscle contraction in the diaphragm
neurons and breathing
- the neurons respond to an increased H+ by increasing their rate of action potential generation
- the UMN stimulates the LMN
- the peripheral chemosensory neurons are located in the carotid and aortic bodies–sensitive to changes in O2 and CO2
- the major driving force for changes in respiratory rate is the change in pH that is sensed by neurons in the medulla
