Physiology Flashcards
what are the 4 main functions of the respiratory system?
- gas exchange
- acid-base balance (regulate pH at 7.4)
- protection from infection- mucus traps pathogens. Cilia beats mucus away.
- communication via speech
what is the resp. system responsible for?
acquiring oxygen & removing co2
what is the difference between cellular and external respiration?
cellular- occurs inside cells aka aerobic respiration
external- integration of cardiovascular & respiratory systems
what is the function of the pulmonary artery?
takes deoxygenated blood away from heart, to lungs
what is the function of the pulmonary vein?
takes oxygenated blood from lungs to heart
how do the cardiovascular and resp systems work together to cater for an increased energy demand of working muscle ?
cardio = increased HR& force of contraction- speeds up waste removal via blood respiratory= increased rate & depth of breathing (increased oxygen transport & co2 removal)
what are the two main places where gas exchange takes place?
lungs- alveoli
systemic capillaries- between capillaries and body cells
where does the respiratory system start?
at the nose
where does the trachea bifurcate?
sternal angle
what does the gas we are inhaling have to be like to undergo gas exchange?
has to be in solution
what do the left and right primary bronchi branch into
secondary bronchi which lead in to the lobes of the lung
how many lobes on right and how many on left
right = 3, left = 2
why is breathing through the nose more effective than breathing through the mouth?
because it is more effective at moistening air that we breathe in
where does the devision of URT & LRT occur ?
larynx
what organs does the URT consist of?
larynx, pharynx, nasal cavity, mouth
what organs does the LRT consist of ?
trachea, bronchi, lungs
which lung is marginally larger and why?
right because part of the left is compressed by the heart
what is the function of the epiglottis?
it is a flap which folds over the trachea to prevent food from entering it when you swallow
what are the lungs encased by?
pleural cavity which contains approx 3ml of fluid
what is the main difference between the right main bronchus and left main bronchus and what happens as a cause of this?
right main bronchus- wider and more obtuse - aspirated foreign bodies commonly lodge here
what does a patent airway mean?
means the airway is open & unobstructed
what are important in maintaining patency of airways?
the rings of cartilage surrounding the airway
what are the first airways to lose the rings of cartilage?
bronchioles
how is patency maintained in the bronchioles?
physical forces of the thorax
what does the conducting zone consist of?
upper airways- trachea and bronchi
what does the respiratory zone consist of and what occurs there?
bronchioles and alveoli, gas exchange occurs there
how can airway diameter be altered?
by the activity of bronchial smooth muscle
what decreases the diameter?
contraction of smooth muscle- increases resistance
what increases the diameter?
relaxation of smooth muscle- decreases resistance
when does resistance to flow become greatest?
in larger airways as there is less of them and therefore more molecules will be there and therefore resistance increases
what is the function of the upper airways?
allow transport of air to and from alveoli, no gas exchange
what is the air in these airways called?
anatomical dead space
what are 2 things alveoli covered in?
- elastic fibres–> stretch when you inspire which requires energy and recoil when you expire which releases energy
- capillaries
what is the function of type 1 alveolar cells ?
gas exchange
what is the function of type 2 alveolar cells ?
surfactant production
what type of cell are capillaries directly adjacent to?
type 1 alveolar cells
what are the things which compose the lining of the respiratory tract?
- epithelium (pseudo- stratified ciliated columnar)
- glands
- lymph nodes
- cilia
- mucous
- blood vessels
what changes occur as you progress from nose down the respiratory tract?
- epithelium becomes more squamous
- mucous cells are lost (goblet cells for example)
- cilia lost (even though they are the last things to be lost)
what are 4 features of alveoli?
- surrounded by elastin which helps them recoil
- surrounded by rich capillary network
- site of gas exchange
- thin walled
what are features of type I pneumocytes
- 97% of alveolar cells
- simple squamous epithelium
- gas exchange
what are features of type II pneumocytes
- surfactant production which is a mixture of phospholipids &proteins
- decreases surface tension at alveolar surface due to air-water interface
what are 3 functions of mucous?
- traps particles
- moistens air - helps produce humidity in resp. system
- large surface area for cilia to act on
through where do the main vessels enter/exit the lung ?
hilum of the lung
what membrane lines the internal pleural cavity and which one the external?
internal- visceral
external- parietal
what are the 2 functions of pleural fluid?
- lubrication- on inspiration, the lungs glide over the ribs and therefore pleural fluid helps lubricate this action and make sure it happens smoothly
- adhesion- pleural fluid sticks the the 2 pleura together, which has a cohesive action between the lungs and ribs and therefore if the ribs expand the lungs will expand too
what is intrapleural pressure and why
it is negative (sub atsmospheric) because the lungs have a tendency to recoil and the rib cage to expand and therefore this increases the volume in the pleural cavity which decreases pressure to sub atmospheric
what is the tendency of the ribs and of the lungs and what stops them from doing so?
ribs- to expand
lungs- to recoil
prevented by the cohesive force of the 2 pleural membranes which effectively stick the ribs and lungs together
what muscles are involved in the active process of breathing ?
diaphragm- contracts, flattens, moves down
external intercostals - pull rib cage forwards and up
but also STERNOCLEIDOMASTOIDS & SCALENES
what muscles are involved in the process of forced expiration?
internal intercostals & abdominal muscles (these can also be recruited with an increased energy demand)
what is asthma ?
over-reactive constriction of bronchial smooth muscle
what is pneumothorax?
disruption of relationship between pleural membranes created between thoracic cavity & lungs due to a penetrating wound: equilibrium is destroyed, air flows in and lungs collapse
define intra-thoracic (alveolar) Pressure (PA)
pressure in the lungs (alveoli)- can be positive or negative depending on inspiration/expiration
define intra-pleural pressure (Pip)
pressure inside pleural cavity - always negative, in healthy lungs
define trans-pulmonary pressure (Pt) and how you would calculate it
pressure difference between alveolar pressure and intrapleural pressure. Calculated - PA-Pip
what is pleurisy ?
inflammation of the pleura
what does boyle’s law state?
that a gas’s volume is inversely proportional to its pressure
how does breathing happen?
-diaphragm contracts, flattens & moves down & external intercostals pull ribcage forwards and up: volume of thoracic cavity increases, lungs expand and their volume increases too
-pressure inside lungs decreases
-air flows from high pressure outside to low pressure inside so lungs pull air in
opposite for expiration
what is tidal volume and how much is it approximately
how much air is breathed in/out with every breath - approx 500ml
what is expiratory reserve volume and how much is it approx?
the maximum amount of air that can be breathed out following normal expiration - approx 1L
what is inspiratory reserve volume and how much is it approx?
the maximum amount of air that can be breathed in following normal inspiration -approx 3L
what is residual volume?
the volume that, no matter how hard you squeeze your lungs, will always be there
what are 2 functions of residual volume?
- keep the alveoli in a partially inflated state and stop them collapsing
- provide a reservoir for gas exchange to happen all the time
what is vital capacity?
tidal volume + inspiratory reserve + expiratory reserve
what is total lung capacity?
vital capacity + residual volume
what is inspiratory capacity?
tidal volume + inspiratory reserve volume
what is functional residual capacity and how much is it approx?
the air that is always in your alveoli at the end of a normal expiration - approx 2.3L
why is FRC important?
stops lungs from collapsing
what is the approx volume of anatomical dead space?
150 ML
what is pulmonary (minute) ventilation?
the amount of air coming into/out of the lungs
what is alveolar ventilation?
the amount of air coming into/out of the alveoli
how do you calculate total pulmonary ventilation?
respiratory rate x tidal volume
how do you calculate how much air is going down to the alveoli? (alveolar ventilation)
(tidal volume - anatomical dead space air aka 150ML) x resp rate
what is hypoventilating?
breathing in and out less than normal
What does Dalton’s law state?
the total pressure of a gas mixture is the sum of all the individual pressures of the gases which make up the mixture
What does Dalton’s law state?
the total pressure of a gas mixture is the sum of all the pressures of the individual gases which make up the mixture
what is the partial pressure of oxygen in atmospheric air?
160mmHg
why is the mixture of air we breathe in different to the mixture of air in the alveoli?
- breathing only 70% effective therefore not all air breathed in goes down to alveoli
- residual volume air in the alveoli takes places in gas exchange and dilutes down air coming in
- air gets humidified as it goes down the respiratory tract and therefore becomes more dilute and this creates its own pressure
- air in alveoli is in equilibrium with arterial blood - partial pressure in alveoli same as partial pressure in arterial blood
what happens to the partial pressures of oxygen and co2 in alveoli during hypoventilation?
oxygen - decreases to 30mmHg
co2- increases to 100mmHg
what are 3 functions of surfactant?
- reduce surface tension
- increase compliance (make lungs more stretchable)
- REDUCES LUNG’S TENDENCY TO RECOIL & makes breathing easier
when does surfactant synthesis begin and what happens if babies are born prematurely ?
25th week of gestation - IRDS
what is compliance?
change in volume related to a change in pressure, represents stretchability of lungs
what is low compliance?
small increase in volume for big decrease in pressure
what is involved in passive expiration?
no muscle action
elastic recoil & surface tension pull inward
what is emphysema?
destruction in the elastic fibres around alveoli by elastase enzyme which hinders recoiling of lung in expiration and therefore expiration becomes difficult
where is greatest compliance seen?
base of lung
compare compliance at base and apex of lung
At the apex, the alveoli are just hanging and are in a partially inflated state so can only inflate up to a certain point = low compliance
At the base of the lung, the alveoli are squashed from the rest of the lung on top. This allows them to have a bigger range of inflation/deflation= greater compliance
define obstructive lung disease, give a characteristic of them & 2 examples
obstruction in the air flow, especially on expiration
-increased airway resistance
asthma & COPD
define restrictive lung disease, give a characteristic & 4 examples
restriction in lung expansion
-lung stiffness
fibrosis, IRDS, oedema, pneumothorax
what is spirometry?
method of assessing lung function
what two types of spirometry are there?
dynamic- consider volume exhaled and time taken
static- only consideration is volume exhaled
what does spirometry generate?
FEV1/FVC ratio
what is FEV and how much is it usually
the amount of air expired in one second - usually 4L in fit, healthy males
how much is FVC usually
usually 5L in fit, healthy males
what is FEV1/FVC ratio in normal, healthy lungs?
80%
what ratio is indicative of obstructive lung disease?
reduced FEV1 so reduced ratio overall
what ratio is indicative of restrictive lung disease?
if the ratio stays the same or increases
what is a limitation of spirometry?
you can have a normal ratio even with diseased lungs as for example in restrictive, both values fall so ratio stays much the same
