Respiratory System I Flashcards
What is pulmonary ventilation?
Mechanism of breathing in and out
Describe gas exchange between lung air spaces and blood
Thin membrane
Oxygen in
Co2 out
Transportation of O2 and CO2 via
The Bloodstream
Briefly describe the anatomy of the RS
Lungs
Upper airways
Respiratory tract
Describe the upper airways
Allows air passages in head/neck
Nasal cavity and oral cavity
Pharynx - Muscular tube for food/air
Describe the respiratory tract
Larynx (vocal cord) - Glottis (opening to windpipe) and Epiglottis (opening for food/to larynx)
Conducting zone
Respiratory zone - Where GE occurs
Describe structure of conducting zone
Trachea Primary bronchi Secondary bronchi Tertiary bronchi Brionchioles Terminal bronchioles Cartilage and smooth muscle - Supports changes in resistance to air flow
Describe the cartilage of conducting zone and its function
C-shape facing the back of the opening to allow food to GI tract
Contractions of smooth muscle adjusts
The diameter of the cartilage
Describe difference between tertiary and respiratory bronchioles
They’re in different zones (terminal in conducting zone, respiratory in respiratory zone)
Terminal doesn’t have alveolar sacs attached to it
Respiratory does have it attached hence gas exchange can occur
Describe epithelium of conducting zone
Composition of epithelium changes from trachea to terminal bronchiole
Has goblet cells and ciliated cells
Describe goblet cells of epithelium in conducting zone and its function
In the larynx and trachea - secretes mucus via mucins to protect against pollution particles and bacterial pathogens
Describe ciliated cells of epithelium in conducting zone
Give example related to cilia
Throughout epithelium
Cilia propel mucus up to be swallowed/clear airways, goes to GI tract where enzymes break it down
Smokers with smokers cough have reduced cilia
Describe function of conducting zone
Provides pathway for air to enter respiratory zone - Hold ‘dead space’ of 150ml
Adjusts air temp - Water vapour inc so no dry throat
Humidifies air
Describe function of ‘dead space’
Every wasted breath never reaches alveoli so when exercising, breathe deeper not faster gain more O2
Describe structure of respiratory zone
Respiratory bronchioles - terminal bronchiole and alveolar
Alveolar ducts
Alveoli (alveolus)
Alveolar sacs (clustered)
Describe function of respiratory zone
Gas exchange between air and blood
Located in respiratory membrane using simple diffusion
Describe the alveolus
300million - Huge SA inc GE Rich supply of caps Alveolar pores Type I cells Type II cells Alveolar macrophages
Function of rich supply of caps in alveolus
Forms a sheet over alveoli
What are the alveolar pores in alveolus
The space connecting alveolar sac
What are type I cells in alveolus
Single layer of epithelial cells overlapping basement membrane (alveolar wall)
What are type II cells in alveolus
Secrete surfactants which facilitate alveolar expansion
Function of alveolar macrophages
WBCs trap (pollution) particles which aren’t blocked by nose hairs
Describe the respiratory membrane
Where GE occurs
Has 3 layers
Thickness of 0.2um
Describe the 3 layers of the respiratory membrane
Alveolar epithelium (has type I cells) Fused basement membrane Capillary endothelium
What facilitates GE?
Thin respiratory membrane
Large SA (for diffusion)
Lipid solubility of gases (O2/CO2)
Partial pressure gradient between alveoli and caps (through ventilation)
Describe the structure of thoracic cavity
Chest wall
Pleura
Pleural sac
Describe the 3 parts of the chest wall
Bones - Rib cage, Sternum, Thoracic vertebrae
Muscles - Int/Ext intercoastal muscles
Connective tissue - Cartilage
What is the pleura of the thoracic cavity
A membrane made of layer of epithelial cells (split into the visceral and parietal pleura)
Visceral - Attached to lung tissue
Parietal - Attached to chest wall, bones and muscles
Describe the pleural sac
The interpleural space filled with (15ml) intrapleural fluid between visceral and parietal pleura
Why is the fluid sac present?
Allows the layers (of pleura) to not separate but allows the movement/flexibility
Eg Separating glass slides when wet/dry
Describe function of thoracic cavity
Protect lungs
Facilitates ventilation
Describe pulmonary pressure at rest
Chest wall compressed, lungs stretched
Negative pressure in intrapleural space as its being stretched
What ability do the lungs and chest wall have due to their structure?
Both elastic so recoil back to original position
Describe 3 types of pulmonary pressures
Atmospheric pressure (Patm) - 760mmHg Intra-alveolar pressure (Palv) - 0 at rest Interpleural pressure (Pip)
What is pressure gradient?
The driving force for ventilation
Describe inspiration
Using inspiratory muscles Diaphragm contracts (moves down) Ext intercoastal muscles contract (Ribs move up and out)
Is inspiration passive or active and why?
Active because muscles contract under nerve control
Describe expiration
Using expiratory muscles Int intercoastal muscles contract Abdominal muscles contract Diaphragm relaxes (up)
Describe the difference between passive and active expiration
Normal expiration is passive as its relaxation of inspiratory muscles
Forceful expiration involves contraction of expiratory muscles (active)
Define Boyle’s Law
For a given quantity of gas in a container, pressure is inversely related to volume (PV=nRT)
What is intra-alveolar dependent on?
Quantity of air
Volume of air
What is lung compliance?
Change jn lung volume that results from given transpulmonary pressure
What does lung compliance depend on?
Elasticity of lungs (elastic fibres)
Surface tension of fluid lining alveoli (to inc SA)
What is the equation to calculate lung compliance
Change in volume/Change in (Palv -Pip)
What is surface tension?
Property of surface of liquid to resist external force - Caused by cohesion of similar molecules
What are surfactants?
Describe its function
Secreted by type II alveolar cells
Dec surface tension, prevent alveoli collapsing, ease elasticity of lung tissue (eg collagen)
Define airway resistance
Total resistance of airways
Low resistance = Better airway flow
What is airway resistance regulated by?
Smooth muscle in bronchiole walls
Extrinsic (neural/hormonal)
Intrinsic (O2 and CO2)
Diseases eg Asthma/COPD
What happens to asthmatic people?
Have narrow bronchioles so inc resistance, so need double the effort to breathe
What are the effects of airway resistance if increased?
Same change in volume, bigger change in pressure
Same change in pressure, smaller change in volume
What is the equation to calculate air flow?
(Patm - Palv)/ Resistance
What are the 4 types of lung volumes?
Tidal volume (VT)
Inspiratory reserve volume (IRV)
Expiratory reserve volume (ERV)
Residual volume (RV)
What is tidal volume (VT)?
Volume of air that moves in/out of lungs during single forced breath (~500ml)
What is inspiratory reserve volume (IRV)?
Max volume of air inspired from end of normal inspiration (~3000ml)
What is expiratory reserve volume (ERV)?
Max volume of air expired from end of normal expiration (~1000ml)
What is residual volume (RV)?
Volume of air left in lungs after max expiration (~1200ml)
Note: Can’t measure using spirometry
What are the 4 types of lung capacities?
Inspiratory capacity (IC)
Vital capacity (VC)
Functional residual capacity (FRC)
Total lung capacity (TLC)
What is IC?
Max volume of air inspired at end of resting expiration (VT + IRV)
What is VC?
Max volume of air expired after max inspiration (VT + IRV + ERV)
What is FRC?
Volume of air left in lungs after tidal expiration (ERV + RV)
What is TLC?
Volume of air in lungs at end of max inspiration (TLC = VT + IRV + ERV + RV)
What is anatomical dead space?
Non exchanging airways
What is minute ventilation?
Total amount of air that flows in/out of respiratory system in a min
(VT x No. of breaths/min)
What is alveolar ventilation?
Amount of fresh air that reaches alveoli/min (excluding dead space)
(VT x RR) - (DSV x RR)
What are the determinants of alveolar?
Po2/Pco2 of inspired air (assumed constant)
Minute alveolar ventilation
Rate of O2/CO2 consumption
Describe regulation of ventilation
Regulation of minute alveolar ventilation (freq/vol of breaths) - Maintain normal po2/co2
Central regulation
Chemoreceptors
Local regulation - Effects po2/co2 on smooth muscles around arteriole/bronchioles
Describe central regulation of ventilation
Neural control of breathing by motor neurones
Generation of rhythm in brain
Perioheral input to respiratory centres
What are chemoreceptors?
Detect changes in chemical concentrations
What are the 2 different types of chemoreceptors?
Central and peripheral
Describe central chemoreceptors
Neurons in medulla oblongata respond to changes in H+ from CO2 in cerebrospinal fluid around them (not sensitive to Po2)
Describe peripheral chemoreceptors
Specialised sensory cells in carotid bodies near carotid sinus
Respond to changes in arterial Po2 (when it falls below 60mm/pH)
