7 Mammalian Gas Exchange Flashcards
what is the need for a gas exchange system (GES) in multicellular organisms?
low SA:vol ratio
large diffusion distance
high metabolic rate
∴ diffusion rate too low to sustain aerobic respiration
what is the definition of a tissue?
a group of one or more cell types that are specialised and working together for a particular function
what is the definition of an organ?
a group of one or more tissue types that are specialised to carry out specific function(s)
what is the definition of an organ system?
a collection of organs with particular function
what are the component parts of the GES?
lungs, trachea, bronchi, bronchioles, larynx, mouth, diaphragm
why is a rich blood supply required for the lungs?
maintains a steep concentration gradient for gas exchange of O(2) and CO(2)
what is the diameter of an alveolus?
~ 200 - 300 um
what is the purpose of surfactant in the alveoli?
makes the lining moist ∴ reduces surface tension and prevents the alveoli sticking together during exhalation
easier for O(2) to dissolve and diffuse into the blood
what is the purpose of smooth muscle in the bronchi and bronchioles?
to control the diameter of the lumen during inhalation and exhalation
what is the purpose of ciliated epithelial cells?
to keep the airway free of debris by wafting mucus and its contents up the trachea to be swallowed or expelled as sputum
what is the purpose of goblet cells?
to secrete mucus (a glycoprotein) to trap pathogens and other foreign objects
what is the purpose of cartilage in the trachea?
to provide support to keep the airway open during inhalation as the pressure in the thorax decreases
what happens during inhalation?
intercostal muscles: contract
ribcage: up and out
diaphragm: contracts and flattens
thorax pressure: decreases
thorax volume: increases
what happens during exhalation?
intercostal muscles: relax
ribcage: down and in
diaphragm: relaxes and domes
thorax pressure: increases
thorax volume: decreases
name three factors that contribute to lung size
body size (and ∴ gender)
physical activity level
general health
what is roughly the capacity of the lungs?
~ 6 dm^3
what is the definition of tidal volume?
the volume of air that moves in and out of the lungs during a normal breath
what is the definition of vital capacity?
the maximum amount of air that can be forcibly expelled from the lungs following breathing as deeply as possible
~ 3 - 5 dm^3
what is the definition of residual volume?
the volume of air remaining in the lungs after a maximal expiratory effort
what is the definition of dead space?
the volume of non-exchange surfaces in the breathing system
what is definition of pulmonary ventilation?
the amount of air exchanged with the environment per minute
how is pulmonary ventilation calculated?
p.v. = tidal volume x breathing rate
what is FEV(1)?
{forced expiratory volume}
the volume of air that can be breathed out in the first second of forced exhalation
how is FEV(1) calculated?
FEV(1) = (4.3 x height - 0.029 x age) - 2.49
