respiratory system Flashcards
what is the anatomy of the lungs
large, spongy like structures, each contained within its own pleural cavity on each side of the heart. each lung is surrounded by a double layered pleural membrane consisting of parietal and visceral layers separated by space filled with serous fluid. in the lungs, the primary bronchus gives rise to a bronchial tree, a continuously branching system of progressively smaller and smaller bronchii to bronchioles. bronchioles eventually open into alveoli and alveolar clusters which mostly fill the lungs
what is part of the upper respiratory tract
pharynx, nasal cavity and larynx
what is part of the lower respiratory tract
lungs and bronchii and trachea
what does the conducting zone do (1/2 of the functional zones of the respiratory tract)
it conducts air from the external environment towards the respiratory zone. it is lined with the respiratory mucosa which;
- warms air
- cleanses air
- moisturises air
- from nasal cavity to terminal bronchioles
- lined with respiratory mucosa
what does the respiratory zone do (1/2 of the functional zones of the respiratory tract)
the respiratory zone is defined by the presence of alveoli which have the capability of gas exchange.
- includes respiratory bronchioles and alveoli
- lined with the respiratory membrane
- permits gas exchange
nasal cavity (structure of the conducting zone)
divided into left and right sides by the nasal septum. The nasal conchae generates a turbulent air flow to ensure all air comes into contact with the respiratory mucosa. Air enters the nasal cavity via the nostrils and exits into the pharynx via the nasal aperture.
pharynx (structure of the conducting zone)
divided into 3 parts and conducts both food and air
larynx (structure of the conducting zone)
- conducts air to the trachea
- contains the vocal folds which produce sound.
trachea (structure of the conducting zone)
- it is a connective tissue tube that extends from the larynx divides into 2 primary bronchi.
- C shaped cartilages surround the trachea to prevent collapse
- smooth muscle extends down the trachea which can rapidly force air out upon contraction.
bronchial tree (structure of the conducting zone)
- It has 23 branches
- the bronchi are lined with respiratory mucosa surrounded by a layer of smooth muscle with outer cartilage rings
- Smooth muscle layer progressively forms thickened bands around bronchioles
- The increased smooth muscle and lack of supportive cartilage in the smaller bronchioles allows a greater ability for dilation or constriction to control air flow into the respiratory zone.
alveoli (structure of the respiratory zone)
alveoli are thin-walled sacs that contain air. alveoli begin to bud off respiratory bronchioles and alveolar ducts, but the majority of alveoli form clusters at the end of alveolar ducts in close association with extensive capillary beds.
- pores exist between alveoli clusters to permit the spread of air throughout the cluster for optimum aeration and gas exchange
- diffusion of gases between air in the alveoli and blood in the capillaries.
volume-pressure relationships
the increase in one results in a decrease in the other, known as Boyle’s law
what happens during pulmonary ventilation
gases move between the atmosphere and the lungs. this movement occurs due to change in the volume of the lungs which either decreases or increases lung/intrapulmonary pressure compared to atmospheric pressure, driving air in or out of the lungs.
what are the mechanisms of inspiration
- inspiratory muscles contract
- thoracic cavity expands
- lungs stretch
- lung volume increases
- lung pressure decreases
- air moves into lungs
what are the mechanisms of expiration
- inspiratory muscles relax
- thoracic cavity narrows
- lungs recoil
- lung volume decreases
- lung pressure increases
- air moves out of lungs
what drives the movement of air in and out of lungs
the difference between atmospheric and lung/ intrapulmonary pressure
what is airway resistance
it is the friction or drag that air encounters as it flows through the respiratory tract. it is most influenced by the diameter of airways (bronchial tree) or the presence of excess or foreign material (mucus). airway resistance is related to lung volume
what is alveolar surface tension
occurs in alveoli due to the presence of body fluids. the surface tension must be reduced to make it easier for the lungs to expand and fill with air and to prevent alveolar collapse upon expiration.
what substance reduces alveolar surface tension
surfactant
what is lung compliance
the stretchiness of the lungs. compliant lungs require less energy to fill with air, but less compliance makes it harder to fill up with air. lung compliance is determined by 2 factors
- how elastic lung tissue is (distensibility of lung tissue)
- alveolar surface tension- the greater the surface tension, the harder it is for lungs to expand and inflate
what is the tidal volume or air an adult inhales and exhales
500mL of air, a 1mmhg difference allows us to inhale or exhale
what part of the brain controls the rate and depth of pulmonary ventilation
the brainstem (pons and medulla) are where the respiratory centres are
our body relies on oxygen to generate cellular energy and produce carbon dioxide which is toxic and must be removed from the body
yes
what does the medulla oblongata do
it sets the baseline for respiratory rate
what does the pons do
it modifies the baseline rate to fine-tune the pattern of breathing during vocalisation, sleep and exercise
what is the most potent stimuli that affects the rate and depth of pulmonary ventilation
the blood level of carbon dioxide
what are non respiratory air movements that move air in and out of the lungs
coughing, sneezing, crying, laughing, yawning, hiccuping
what is the inspiratory reserve volume
1900ml
what is the expiratory reserve volume
700ml
what is the residual volume
1100ml
what is the inspiratory capacity (includes inspiratory and tidal volume)
2400ml
what is the functional residual capacity (includes expiratory and residual volume)
1800ml
what is the vital capacity (includes inspiratory, tidal and expiratory volume)
3100ml
what is the total lung capacity
4200ml
what is external respiration
- pulmonary gas exchange (breathing)
- O2 moves into blood (gas moves from alveoli to pulmonary capillaries)
- CO2 moves out of blood (gas moves from pulmonary capillaries to alveoli)
- gas exchange between air and blood
what is internal respiration
- tissue gas exchange
- O2 moves out of blood (gas moves from systemic capillaries to tissue)
- CO2 moves into blood (gas moves from tissues to systemic capillaries)
- gas exchange between blood and body tissues
what drives the diffusion of oxygen and carbon dioxide into/out of blood in capillaries due to external and internal respiration
diffusion driven by the difference in partial pressure of gas in the blood and outside the blood. gases move down the concentration gradient
what impacts pulmonary ventilation
- amount of surfactant
- airway diameter
- foreign objects within airway
- elasticity of the lungs
what is the ventilation (V) to perfusion (Q) ratio
there must be a match between the amount of oxygenated air in the alveoli (ventilation) and the amount of blood in the pulmonary capillaries (perfusion). if the volumes are different, then the exchange of gases will not be maximal.
how is the V-Q ratio maintained
local auto regulatory mechanisms result in changes in pulmonary arteriole diameter (vasoconstriction or vasodilation) to regulate the volume of blood passing through pulmonary capillary beds.
vasoactive substances are released in response to local Po2 levels to regulation perfusion
levels of Pco2 control ventilation by changing the diameter of bronchioles
how is oxygen transported through the blood
bound to haemoglobin (98-99%)
dissolved in plasma (1-2%)
how is carbon dioxide transported through the blood
- dissolved in plasma (7-10%)
- bound to haemoglobin (20%)
- within bicarbonate molecules (70%) CO2+H20- H2C03- H+ + HC03- the bicarbonate ion is a base and the hydrogen ion is an acid. the H+ binds to hemoglobin and is therefore buffered. the HC03- ion then forms part of the bicarbonate buffering system that binds metabolic acids until they are removed from the body by the kidneys
how does oxygen and carbon dioxide bind to haemoglobin
oxygen binds to the iron atom at the centre of each heme pigment and the carbon dioxide bind to the sites on the globin chain
