Physiology Flashcards
Identify the different classes of airways and the two types of alveolar
type 1- allow for gas exchange
type 2- synthesise surfactant- this substance lowers surface tension, which keeps the alveoli from collapsing after exhalation and makes breathing easy
List the functions of the respiratory system
Gas exchange, acid base balance, protection from infection and communication via speech
Know the difference between pulmonary and systemic circulation
Pulmonary- collects oxygen from pulmonary vein and remove carbon dioxide from pulmonary artery
Systemic- delivers CO2 to the heart, from where it is then transported to the lungs via the pulmonary artery.
Identify points of gas exchange between the respiratory and cardiovascular systems
During exercise- rate and depth of breathing speeds up and heart rate and force of contraction speeds up. Lungs obtain oxygen and heart delivers it to muscles. Breathing produces waste carbon dioxide and its removed via blood
Understand why, and how, resistance to air flow varies across the respiratory tree
alveoli have least resistance to airflow as contraction decreases diameter=increases resistance relaxation= increases diameter= decreases resistance
Name and explain the key terms used to describe the different lung volumes
TV- tidal volume (volume breathed in and out of lungs at each breath)
ERV- expiratory reserve volume- maximum volume of air that can be expelled at end of normal expiration
IRV- Inspiratory reserve volume- maximum volume of air which can be drawn into lungs at end of normal inspiration
RV- residual volume- volume of gas in lungs at end of maximal expiration
Describe the anatomy of the pleural cavity
lungs and inferior of thorax are covered by pleural membranes between the surfaces of these are an extremely thin layer of intrapleural fluid
Describe the relationship between the parietal and visceral pleura and why this is important for inflation and deflation of the lung
Visceral lines outer surface of lungs and parietal lines inner surface of ribs
visceral pleura is stuck to the parietal pleura via cohesive forces of the pleural fluid. so lungs are stuck to ribcage
Describe how the muscles of respiration act to increase and decrease thoracic volume
Inspiration uses external intercostal muscles and the diaphragm (contracts)
Expiration is passive at rest but uses internal intercostal and abdominal muscles during severe load
Relate Boyle’s law to the mechanics of breathing, inspiration and expiration
occurs because thoracic cavity changes volume
increased volume= decreased pressure
State the mechanical factors that affect respiratory minute volume.
lateral and anterior- posterior movement of ribcage
Explain why intrapleural pressure is always less than alveolar pressure
State the role of pulmonary surfactant and the Law of Laplace
reduces surface tension on alveolar surface membrane thus reducing tendency for alveoli to collapse. surface tension occurs where ever there is an air-water interface and refers to the attraction between water molecules
P= 2T/r 2 times surface tension divided by radius
Define the term compliance the factors that affect this
change in volume relative to change in pressure. diseases and ages effect compliance
high compliance- means lots of air getting into lungs with only a small pressure
what does the pulmonary artery carry
deoxygenated blood
what does the pulmonary vein carry
oxygenated blood and has low carbon dioxide
pharynx
from nose air moves down pharynx
epiglottis
small flap that folds over trachea and prevents food from entering when you swallow
larynx
voice box
trachea
made up of stiff rings of cartilage
bronchus
air moves from trachea into bronchi
what structures are part of the upper respiratory tract
pharynx, larynx, oesophagus
what structures are part of the lower respiratory tract
trachea, lungs, bronchus and diaphragm
splitting of primary bronchi
right bronchus splits 3 times and the right bronchus splits 2 times
alveolar
Only site of gas exchange and are very thin and have a large surface area
what does anatomical dead space mean
air in airways that isn’t involved in gas exchange e.g trachea and bronchus
lung capacities
VC- vital capacity= tidal volume + IRV + ERV
TLC= total lung capacity
IC- inspiratory capacity= tidal volume + IRV
FRC- functional residual capacity= ERV and RV
alveolar pressure
pressure in the thoracic cavity. Can be negative or positive depending on atmospheric pressure
intra-pleural pressure
pressure inside the pleural cavity. typically negative
transpulmonary pressure
differences between alveolar and intra-pleural pressure. always positive
Describe the structure and function of the diaphragm
Understand the functional difference between pulmonary and alveolar ventilation
pulmonary ventilation- total air movement into/out of lungs
alveolar ventilation- fresh air getting to alveoli and therefore available for gas exchange
Be able to describe the impact dead space has on alveolar ventilation
air in dead space is used first before taking air from alveolar. found in trachea and bronchi
Know the normal values for alveolar and arterial gas partial pressures in different units
alveolar- 100mmHg/13.3kPa of oxygen and 40mmHg/5.3kPa of carbon dioxide
Be able to describe the blood supply to the lungs
bronchial circulation supplies oxygenated blood to the lungs
pulmonary circulation supplies dense network of capillaries surrounding the alveolar and returns oxygenated blood to the left atrium.
Be able to describe the factors that are proportional to diffusion of gases across the alveoli
partial pressure gradient
gas solubility
surface area availability
Know the abbreviations used to describe the partial pressure of gases in the alveoli, systemic arteries and veins
A= alveolar
a= arterial blood
v=mixed venous blood
Outline the basic characteristics of obstructive and restrictive lung diseases.
obstructive- obstruction of air flow, especially on expiration e.g asthma, COPD, chronic bronchitis, emphysema
restrictive- restriction of lung expansion especially inspiration e.g fibrosis, infant respiratory distress syndrome, oedema, pneumothorax
Outline how spirometry can be used to identify abnormal lung function.
static- consideration made about volume exhaled only
dynamic- time taken to exhale a certain volume
FEV1=4L (forced expiratory volume)
FVC=5L (forced vital capacity)
Describe and explain the characteristic results you would observe following lung function tests in patients with obstructive lung diseases
lower FEV1/FVC as rate of air exhaled in much slower
what is hypoventilation
rapid and shallow breathing
hypoventilation- P02 fails to 30 mm Hg and Pc02 rises to 100mm Hg
what is hyperventilation
slow and deep breathing
hyperventilation- Po2 rises to 120mm Hg and Pco2 falls to 20mm Hg
Emphysema
Destruction of alveoli reduces surface area for gas exchange. Less diffusion so less oxygen can enter. inspiration is easier but expiration is harder because no elastic recoil. smoking produces elastase which breaksdown the elastic fibres, increased compliance whihc increases lung volume
Fibrotic lung disease
Thickened alveolar membrane slows gas exchange. Resists stretch and makes lungs not expand during inhalation
pulmonary edema
Fluid in interstiual space increases diffusion distance between alveoli and capillary. increased blood pressure forces plasma out of capillaries and it cools in interstitual space. co2 can be normal as more soluble
Asthma
increased airway resistance decreases airway ventilation and therefore effects alveolar partial pressure of oxygen and carbon dioxide which limits diffusion
differences between obstructive and restrictive diseases
obstructive- obstruction of air flow, especially on expiration e.g asthma, COPD, chronic bronchitis, emphysema
restrictive- restriction of lung expansion e.g fibrosis, infant respiratory distress syndrome, oedema, pneumothorax
Describe and explain the characteristic results you would observe following lung function tests in patients with restrictive lung diseases
FEV1 reduced and FVC reducesd as rate of airflow reduced as lung volume ratio remains normal or increases
State the differences between partial pressure and gas content.
partial pressure describes amount of oxygen in solution in the plasma and not total oxygen concentration in the blood. however partial pressure determines total oxygen content of the blood by determining the saturation of haemogloblin
Compare oxyhaemoglobin dissociation for adult haemoglobin with that of foetal haemoglobin and myoglobin in relation to their physiological roles.
myoglobin and foetal haemogloblin have a higher stauration for oxygen. as myogloblin wants more oxygen to deliver it ot the skeletal and cardiac muscles and foetal wants to take oxygen from mother
Describe the relationship between ventilation and perfusion and its significance in health
Want them to be matched
ventilation is the air getting to the alveoli
perfusion is the local blood flow
Describe the conditions under which there may be an imbalance in the ventilation- perfusion ratio of regions of the ratio of regions of the lung and describe how this affects the O2 and CO2 content of alveolar gas and arterial blood.
Both decrease with height
At base of lung blood flow is higher than ventilation because arterial pressure exceeds alveolar pressure ventinaltion<perfusion<1
At apex of lung blood flow is low becasue arterial pressure is less than alveolar pressure. ventilation>perfusion>1
Define the terms shunt, alveolar dead space, physiologic dead space and anatomical dead space.
Shunt describes passage of blood through areas of lung that are poorly ventilated.
alveolar dead space refers to alveoli that are ventilated but not perfused
physiological dead space- alveolar dead space and anatomical dead space
anatomical dead space- air unable to participate in gas exchange
Define the five different types of hypoxia
Hypoxaemic- reduction in oxygen diffusion at lungs due to decreased partial pressure of oxygen in atmosphere or tissue pathology
anaemic- reduction of oxygen carrying capacity in blood due to anaemia
stagnant- heart disease results in inefficient pumping of blood to lungs and around body
histotoxic- poisining prevents utilising oxygen delivery delivered to them e.g carbon monoxide
metabolic hypoxia- oxygen delivery to tissues does not meet increased oxygen demand by cells
Apply the concept of partial pressure gradients to the movement of O2 and CO2 between the blood and the alveoli
The partial pressure of oxygen is high in the alveoli and low in the blood of the pulmonary capillaries. As a result, oxygen diffuses across the respiratory membrane from the alveoli into the blood. In contrast, the partial pressure of carbon dioxide is high in the pulmonary capillaries and low in the alveoli.
Describe the role of haemoglobin in the transport of O2 in the blood.
oxygen demand of resting tissues is 250ml/min but add haem you get 1000ml/min so only 25% of arterial oxygen is extracted by periheral tissues at rest
The major determinant of the degree to which haemoglobin binds (is saturated with) oxygen is partial pressure of oxygen in the blood.
Explain why the shape of the oxyhaemoglobin dissociation curve aids O2 loading in the lungs and unloading in the tissues.
haem is almost 100% saturated at normal systemic arterial partial pressure of 100mm Hg. even at 60mm Hg its still more than 90% saturated.
Describe the factors that affect the oxyhaemoglobin dissociation curve.
Ph lower pushes curve to the right and oxygen has a lower affintiy so unloads oxygen
increased temp pushes curve to the right and decreases affinity
Pco2 increases pushes curve to right
DPG present pushes curve to the right.
Use anaemia to demonstrate how PaO2 determines, but is independent of, total blood oxygen content
In anemic patients, oxygen delivery decreases and oxygen extraction is increased. partial pressure of oxygen doesn’t change
Identify the forms in which CO2 is carried in the blood.
some dissolves in the plasma and erythrocytes combine with deoxyhemoglobin to form carbonic acid which yields bicarbonate and hydrogen ions. The bulk of carbon dioxide travels in bicarbonate ions because they get pumped back into plasma in exchange for carbon
Explain the action of carbonic anhydrase in CO2 transport
An enzyme present in red blood cells, carbonic anhydrase, aids in the conversion of carbon dioxide to carbonic acid and bicarbonate ions.
Identify the factors which favour CO2 unloading to the alveoli at the lungs.
Explain how respiratory motor movements are affected by the central nervous system.
emotion- limbic system in the brain
voluntary over-ride- via higher centres in the brain
mechanic-sensory input from the thorax
describe the location of the two classes of chemoreceptors and identify the stimuli which activate them.
central- medulla, responds directly to H+ generated as a result of an increased CO2 in CSF in brain, primary ventilatory drive. doesn’t respond to direct changes in hydrogen conc of plasma
peripheral- carotid and aortic bodies, respond to primary to Po2 and plasma H+, secondary ventilation drive
List the factors involved in changing ‘respiratory drive’, rate and depth of breathing.
barbiturates and opioids depress respiratory centre- decreases sensitivity to pH and therefore response to pressure of CO2 also decreases peripheral chemoreceptor response to lower Po2
nitrous oxide blunts response to falling partial arterial pressure of oxygen
Explain how the central chemoreceptors serve to regulate the arterial PCO2 by monitoring the pH of CSF.
Explain how the peripheral chemoreceptors become important during hypoxia and acid-base imbalance.
Peripheral chemoreceptors monitor changes in arterial blood O2, and within seconds after the onset of hypoxia they trigger cardiorespiratory changes (i.e., increase in breathing and blood pressure), which are important for maintaining O2 homeostasis.
Outline the role of the respiratory system in acid-base disturbances.
if plasma pH falls ventilation will be stimulates ventilation and if plasma pH increases ventilation will be inhibited
Explain how CO2 affects acid-base balance
capable of changing ECF pH. hypoventilation causes CO2 retention and leads to increased H+ bringing about respiratory acidosis
hyperventilation (blowing off more CO2) leads to decreased H+ bringing respiratory alkalosis
Outline how the respiratory system can both create, and compensate for, acid-base disturbances.
pH is directly proportional to bicarbonate( controlled by kidneys)/ carbon dioxide (controlled by lungs)
