mechanics of breathing Flashcards
how many cells do gases have to diffuse across
- 2
- endothelial cells of capillaries
- and epithelial cells of alveoli
what are the two types of respiration
- internal
- external - removing co2, exchange and transports of gases around the body
what is inspiration
- movement of air into the lungs
in order for air to move into the lungs what must the pressure be of the lungs
- lungs must be at a negative pressure compared to the atmospheric pressure
how are the lungs at a negative pressure
- due to active contraction and downward movement of diaphragm
- and the contraction of intercostal muscles causing ribs to move up
- therefore increasing volume of thorax
when does inspiration end
- as lungs inflate the pressure difference between the atmosphere and intrapleural fluid decreases until at equilibrium with elasticity of lungs
what factor determines elasticity of lungs
- surface tension of the alveoli
what cells aid in the expansion of the lungs and what do they secrete
- type 11 cells
- secretes surfactant
what does the fluid surfactant do
- fluid coats the alveoli and reduces the surface tension
what is surfactant composed of
- lipids and proteins
what is expiration
- movement of air out of the lungs
- diaphragm and intercostal muscles relax
- both muscles recoil back to original position
- volume of thorax decreases increasing the pressure
- expiration is a passive process
what is ventilation
- exchange of gas between the atmosphere and alveoli
- airflow = pressure inversely proportional to resistance
during ventilation what is the pressure gradient between
- pressure in alveoli and atmospheric pressure (alv - atm)
where is the basic respiratory rhythm generated by
- centres in medulla
what are two properties of breathing
- automatic
- rhythmical properties
what are two respiratory groups found in the medullary centre
- dorsal respiratory group
- ventral respiratory group
dorsal respiratory group
- controls inspiration by sending signals to the inspiratory muscles
ventral respiratory group
- inactive during quiet respiration
- active during forced inspiration and expiration
where do pons send stimuli to and what do they regulate
- medulla
- rate and depth of breathing
pneumotaxic centre
- increase rate by shortening inspiration
- inhibitory effect
apneustic centre
- decrease rate and increases depth by prolonging inspirations
- stimulates inhibitory centre
purpose of stretch receptors
- control how far lungs expand
- when breathing chest expands
what do chemoreceptors detect
- changes in ph and carbon dioxide
where do central chemoreceptors monitor conditions
- cerbro - spinal fluid
where are peripheral chemoreceptors found
- carotid body
- aortic arch
what muscles does quiet inspiration require
- primary muscles; diaphragm and intercostal muscles
- leads to an increase in thoracic volume
what muscles does forced inspiration require
- primary muscles and
- accessory muscles; scalene, back and neck muscles, upper respiratory tract muscles
what muscles does quiet expiration require
- no primary muscles
- passive process using elastic recoil
what 4 muscles are needed for forced expiration
- abdominal muscles
- neck and back muscles
- accessory muscles
- internal intercostal
what is the purpose of pleural cavity
- prevents lungs from sticking to chest walls
- enables free expansion and collapse of lungs
term used to describe collapsed lung
- pneumothorax
what is compliance
- measure of elasticity - how easy lungs and thorax expand due to pressure changes
how to calculate compliance
- change in volume / change in pressure
what two factors affect airway resistance
- diameter of airway
- whether airflow is laminar or turbulent
how many sub units does haemoglobin contain
- 4 sub units
- each unit consists of a haem unit and globin chain
- depending on hb type different combination of globing chains
what state does iron have to be in for oxygen to bind
- fe2+
what enzyme helps convert fe2+ to fe3+
- enzyme methaemoglobin reductase
what two states does haemoglobin exist in
- tense - low affinity for oxygen
- relaxed - high affinity for oxygen
what four factors result in dissociation of oxygen
- increased temp
- increase co2 production
- decrease in ph
- increase production of 2,3 DPG
what 5 ways does blood carry co2 as
- dissolved co2
- carbonic acid
- bicarbonate
- carbonate
- carbamino compounds
what two things need to match to ensure continuous delivery of oxygen and removal of co2
- alveolar ventilation (air reaching alveolus)
- pulmonary blood flow (blood reaching alveolus in capillaries)
