Respiratory Anatomy + Physiology Flashcards by Georgia Campbell

describe the main anatomical features of the airways + gross anatomical features of the lung

airways = trachea, bronchi, bronchioles

lungs = fissures + lobes (R - superior, middle + inferior lobes, horizontal + oblique fissures. L - superior + inferior lobes, oblique fissure)

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what structures make up the upper and lower respiratory tracts

upper tract = mouth, nasal cavity, pharynx + larynx

lower tract = trachea, bronchi + lungs
*note lower tract enclosed in thorax + bounded by ribs, diaphragm + spine

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explain the two types of alveolar cells

type I for gas exchange
type II for surfactant production

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list the functions of the respiratory system

gas exchange
acid base balance
protect against infection
communication via speech

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explain the difference between the pulmonary and systemic circulations

pulmonary delivers CO2 and collects O2 from lungs (p. artery carries deoxygenated blood from heart to lungs then p. vein carries oxygenated blood back to heart)

systemic delivers O2 to peripheral tissues and collects CO2

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identify points of gas exchange between the respiratory system + CVS

at lung + peripheral tissue level

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how does resistance to flow vary across the respiratory tree

conduction zone has highest resistance to flow - known as anatomical dead space, doesn’t partake in gas exchange due to thick walls of trachea, bronchi + bronchioles

respiratory zone has lowest resistance to flow due to thin walls of alveoli - site of gas exchange

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what is the main determinant of resistance to air flow

radius of airways

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what is tidal volume (TV)

volume of air breathed in/out each breath

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what is expiratory reserve volume (ERV)

maximum air volume that can be expelled at the end of a normal expiration

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what inspiratory reserve volume (IRV)

maximum air volume that can be drawn into the lungs at the end of a normal expiration

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what is residual volume (RV)

volume of gas in lungs at the end of a maximal expiration

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what is vital capacity (VC)

amount of air exhaled after a maximal inspiration

VC = TV + ERV + IRV

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what is total lung capacity (TLC)

maximum volume of air lungs can hold after a maximal inspiration

TLC = VC + RV

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what is inspiratory capacity (IC)

maximum volume of air that can be inhaled following a normal, quiet expiration

IC = TV + IRV

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what is functional residual capacity (FRC)

amount of air left in lungs after normal expiration (when lung recoil + chest expansion equal)

FRC = ERV + RV

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what is FEV1:FVC

fraction of forced vital capacity expired in 1 second

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what is dead space

volume of air in conducting zone which is unavailable for gas exchange (due to wall thickness)

dead space = 150ml

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describe the anatomy of the pleural cavity

visceral pleura covers outer lung surface
parietal pleura covers inner surface of ribs

both pleura are continuous which each other and are lubricated by pleural fluid in between layers to allow gliding

left and right pleural cavities independent compartments

pleural membranes stick lungs to chest wall and diaphragm

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how do muscles of respiration increase/decrease thoracic volume

thoracic volume is increased by the external intercostals contracting and pulling the ribs upwards (bucket handle) and also pulling the sternum outwards (pump handle). it is also increased by the diaphragm contracting and descending into the abdominal cavity.

thoracic volume is decreased passively during quiet expiration, the lungs + chest wall recoil alongside the diaphragm relaxing and doming into the thorax causing decreased thoracic volume and therefore increased pressure to force air out (Pa > Patmos). in forced expiration the abdominals force the diaphragm up into the thorax and the internal intercostals push down the ribs and sternum.

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why is intrapleural pressure always less than alveolar

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what is the role of pulmonary surfactant

decrease surface tension of alveoli to prevent collapse

increase compliance

reduce tendency for lung recoil (less work to breath)

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define compliance and list any factors affecting it

how much volume changes for any pressure change i.e how stretchy lungs are

(high compliance lungs will have large increase in volume in response to a small decrease in intrapleural pressure but low compliance lungs will have a small increase in volume for large decreases in intrapleural pressure)

altered in disease state + different ages

what is typical total lung capacity

usually work at around half that (2.8L) - tidal volume typically 500ml

what is typical residual volume and why is it important

1.2l stops alveoli collapsing by keeping some level of inflation

what is pulmonary ventilation and how is it calculated

the total movement of air in/out the lungs tidal volume x respiratory rate

what is alveolar ventilation and how is it calculated

the amount of fresh air available for gas exchange getting to the alveoli (tidal volume - anatomical dead space) x respiratory rate typically 4.2l/min

what has the biggest impact on alveolar ventilation

tidal volume (decreased TV = hypoventilation, increased TV = hyperventilation) *note in practise TV generally won't drop enough to affect alveolar ventilation

describe the impact dead space has on alveolar ventilation

dead space decreases the efficiency of breathing - at rest breathing is approx 70% efficient air sitting in dead space is unavailable to alveoli for gas exchange - at end of inspiration 150ml of fresh air will sit in dead space, we then expire 500ml but only 350ml of air from alveoli can be expired due to 150ml sitting in dead space, we then get 150ml of stale air sitting in dead space at end of expiration, then on next inspiration only 350ml of fresh air reaches alveoli and so on

what are the normal values for alveolar partial pressures (in mmHg and kPa)

PAO2 = 100mHg or 13.3kPa PACO2 = 40mmHg or 5.3kPa

what are the normal values for arterial partial pressures (in mmHg and kPa)

PaO2 = 100mmHg or 13.3kPa PaCO2 = 40mmHg or 5.3kPa

what are the normal values for venous partial pressures (in mmHg and kPa)

PvO2 = 40mmHg or 5.3kPa PvCO2 = 46mmHg or 6.2kPa

describe the blood supply to the lungs

what factors influence gas diffusion across alveoli

what are the basic characteristics of obstructive lung disease

what are the basic characteristics of restrictive lung disease

how can spirometry be used to identify abnormal lung function

what results would you expect from lung function tests in a patient with an obstructive lung disease

what results would you expect from lung function tests in a patient with a restrictive lung disease

what are the differences between partial pressure and gas content

describe the role of Hb in transporting O2 in the blood

what factors can affect the oxygen-haemoglobin dissociation curve

why is the shape of oxygen-haemoglobin dissociation curve important for O2 loading and unloading in tissues

how is CO2 carried in the blood

why is the ventilation-perfusion relationship important

what can cause ventilation-perfusion mismatch and how does this affect alveolar and arterial blood O2/CO2 content

what is shunt

what are the differences between anatomical, physiologic and alveolar dead space

define the 5 types of hypoxia

hypoxaemic - most common, reduced O2 diffusion at lungs (due to pathology or atmosphere) anaemic - reduced O2 carrying capacity due to anaemia stagnant - inefficient pumping of blood to lungs/around body histotoxic - poisoning prevents cells utilising delivered O2 metabolic - O2 delivery doesn't meet increased O2 demand

what are the 2 types of chemoreceptors and what stimuli are they activated by

peripheral chemoreceptors - activated by significant fall in PaO2 central chemoreceptors - activated by changes in PaCO2

list the factors which are involved in changing respiratory drive, rate and depth of breathing

emotion via limbic system voluntary over-ride via higher centres mechano-sensory input from thorax (stretch receptors to stop overinflation) chemical composition of blood dorsal and ventral respiratory groups of neurons

how does the CNS affect respiratory motor movements

ventilatory control is entirely dependent on signalling from the brain

how do central chemoreceptors regulate arterial PCO2

by detecting changes in [H+] in the CSF - will cause reflex stimulation of ventilation if PCO2 increases or reflex inhibition of ventilation if PCO2 decreases (note they respond directly to H+ but this directly reflects PCO2) ions cannot cross BBB but gases can, so if PaCO2 increases then CO2 will cross the BBB by diffusion causing an increase in CSF CO2, this CO2 will combine with water to form carbonic acid which dissociates into bicarb + H+ ions so you get an increase in H+ ions in the CSF which stimulates the chemoreceptors

why are peripheral chemoreceptors important during hypoxia and acid-bace imbalance

peripheral chemoreceptors stimulate ventilation when there is a significant fall in PaO2, usually kick in around <60mmHg PaO2 (point on O2-Hb curve where Hb 90% saturated but will start to rapidly fall) peripheral chemoreceptors can respond to changes in plasma [H+], therefore they can stimulate/inhibit ventilation as required

how does CO2 affect acid-base balance

an increase in CO2 means an increase in plasma [H+] which causes acidosis a decrease in CO2 means a decrease in plasma [H+] which causes alkalosis pH usually stable as we eliminate all our CO2 produced in expiration but hypo/hyperventilation causes plasma PCO2 to alter which then varies plasma [H+] (CO2 + H2O <-> H2CO2 <-> HCO3- + H+)

how can the respiratory system create and compensate for acid-base disturbances

hyperventilation causes respiratory alkalosis hypoventilation causes respiratory acidosis changes in plasma pH alter ventilation via peripheral chemoreceptor pathways so if they kidneys are the source of the disturbance the respiratory system can compensate by stimulating or inhibiting ventilation (remember kidneys control bicarbonate levels whilst lungs control CO2 levels and pH is proportional to bicarbonate and CO2 levels)