Respiratory Session 1- Introduction And Upper Respiratory Tract Flashcards
Roughly how many alveoli do you have and what is their combined surface area?
3 million with a combined surface area of 70m^2
How many generations of dividing airways are there between the trachea and alveoli?
23
What is the difference between divisions 1-16 and divisions 17-23?
1-16 are conducting airways and do not take part in gas exchange
17-23 make up the respiratory zone and participate in gas exchange
Define ventilation
Process of inspiration and expiration
How is the normal rhythmic involuntary breathing pattern controlled?
Neurones in the respiratory centre in the medulla of the brain generate automatic rhythmic impulses
In terms of pressure changes, how is air forced into the lungs?
As the volume of air in the lungs increases the pressure decreases- when pressure drops below atmospheric pressure air flows into the lungs
How is expiration achieved?
Neurones cease generating impulses, inspiratory muscles relax, chest returns to original size- compressing inflated lungs. Air pressure in lungs increases, air flows out
How does oxygen move from the alveoli into the blood?
Diffuses across the air-blood interface down its partial pressure gradient
What is the universal gas law? (Equation)
PV=nRT
P=pressure, V=volume, n=amount of gas, R=gas constant, T=temperature
What is Boyle’s law?
Pressure is inversely proportional to volume for a fixed quantity of gas at a constant temperature
What is Dalton’s law?
In a mixture of gases, the molecules of each type behave independently so each gas exerts a partial pressure. Each component of a gas mixture exerts a partial pressure in proportion to its volume percentage in the mixture
What 2 things happen if a gas mixture is in contact with water?
- Gas molecules enter the liquid to dissolve
2. Water molecules evaporate to enter the gas phase
What is the partial pressure of a gas in liquid and how is it caused?
When gas and liquid are in contact, gas molecules will enter the liquid until an equilibrium is established between rate of solution and dissolution of gas- collision of dissolved gas molecules generates a pressure within the liquid
Define the solubility coefficient of a gas
Amount of the gas that will dissolve in a litre of plasma at 37 degrees when exposed to a given partial pressure
What is the equation to work out the amount of a gas that is dissolved?
Amount of gas dissolved= solubility coefficient of that gas x the partial pressure it is exposed to
Why is the oxygen content of whole blood greater than just plasma?
Haemoglobin in RBC binds large amounts of oxygen in addition to the dissolved
Define saturated vapour pressure
The pressure exerted by the water vapour when the gas mixture is saturated at equilibrium
What is the total pressure of humidified air in the airways and why?
101kPa because this gas is continuous with outside air, and pressure will equilibrate to atmospheric pressure
At 37 degrees what is the SVP of water and what is its relevance?
6.28kPa- this must be taken away from 101kPa when looking at air within the respiratory system as this air is saturated. Then can use the same gas proportions as are in dry air
What structures does the upper respiratory tract comprise of?
Nose and paranasal sinuses
Pharynx
Larynx
What are the respiratory functions of the URT?
- Conducting air from the atmosphere to lower respiratory tract
- Conditioning (warming, humidification and trapping of particles) inspired air
- Protection of the airway during swallowing (larynx)
What are some of the other functions of the URT?
- Swallowing (oropharynx and laryngopharynx)
- Smell (olfactory epithelium in nose)
- Speech (larynx)
What 2 structures does the nose consist of?
External nose and nasal cavity
What makes up the borders of the nasal cavity?
Median- median nasal septum
Anterior- nostril (anterior nares)
Posterior- posterior nares (posterior choanae)
Lateral- wall containing superior, middle and inferior conchae and meatus
Floor- hard and soft palates (also form roof of mouth)
Name all the paranasal sinuses
Frontal
Ethmoidal
Maxillary
Spheroidal
What are the main functions of the nose?
Filtering
Warming
Humidification
How does the structure of the nose contribute to its functions?
Vascular mucosa and large surface area of turbinates cause turbulence and slow down airflow so increase time for warming and humidification
Nostril lined with coarse hairs to trap almost all particles and cilia waft it to oropharynx to be swallowed
How is humidification achieved in the nose?
Transduction of fluid through epithelium (and mucus secretion)
Where is an infection of URT involving the nasal cavity likely to spread?
The paranasal sinuses
Pharynx and larynx
Middle ear
Eye
What are the 3 parts of the pharynx and where are they?
Nasopharynx- behind the nose and above the level of the soft palate
Oropharynx- behind the mouth, between soft palate and tip of epiglottis
Laryngopharynx- behind the larynx, between tip of epiglottis and lower border of cricoid cartilage
How is the nasopharynx connected to the middle ear and why is this important?
Eustachian tube allows air pressure in the middle ear cavity to be equalised to atmospheric pressure
Which 2 structures does the larynx connect?
Pharynx and trachea
Name the cartilages that make up the cartilagenous skeleton of the larynx
Epiglottis, thyroid cartilage and cricoid cartilage
Paired arytenoid cartilages
What is the glottis?
The vocal cords and aperture between them
What is the Rima glottides?
The aperture between the 2 vocal cords
What are the movements of the vocal cords?
Adduction- closing aperture
Abduction- opening aperture
When are the vocal cords adducted or abducted and why?
Abducted during respiration for free movement of air
Partially abducted during speech- sound produced by vibration of vocal cords, air moving through narrowed aperture
Adducted during swallowing to prevent inhalation of food
Adducted voluntarily during straining
Which muscle controls the vocal cords and what is its innervation?
Intrinsic laryngeal muscles innervated by recurrent laryngeal nerve
What can cause the larynx to narrow?
Laryngeal/vocal cord tumour
Laryngeal oedema due to allergic reaction or severe infections
Bilateral vocal cord paralysis
What can cause obstruction of the pharynx?
Tongue of unconscious person falling back and obstructing oropharynx
Sleep apnoea- loss of tone in pharyngeal muscles so become floppy and obstruct airways during sleep
What structures form the conducting part of the respiratory system?
Nose, nasopharynx, larynx, trachea, bronchi and bronchioles
What lines the conducting part of the respiratory system?
Pseudostratified ciliated columnar epithelium with mucus secreting goblet cells (no goblet cells in the pharynx and parts of the larynx)
What is the function of the incomplete bony/cartilagenous framework in the conducting part?
Provides rigidity and patency
What do the walls of the trachea and beyond contain?
Smooth muscles and elastic fibres external to the cartilage
What does the respiratory part consist of?
Respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli
What type of epithelium is the respiratory part lined with?
Respiratory bronchioles and alveolar ducts- simple cuboidal
Alveoli- simple squamous
What lines the olfactory regions of the nasal cavities?
Thick pseudostratified columnar epithelium without goblet cells in posterior superior region of each nasal fossa
How do venous plexuses prevent over drying in non olfactory regions or nasal cavities?
Venous plexuses swell every 20-30 minutes alternating air flow from side to side
What are olfactory cells?
Bipolar neurones- one dendrite extends to the surface to form a swelling from which non motile Silvia extend parallel with the surface to increase surface area and respond to odours. Found in epithelium
What do serous glands do and where are they found?
Flush odorants from the epithelial surface- found in lamina propria
What does each vocal cord contain?
A vocal ligament and vocalis muscle
Lined by stratified squamous epithelium
Where does the trachea divide into 2 primary bronchi?
Mid thorax
Why are foreign objects more likely to lodge in the right bronchus?
Path is more vertical than the left
Where are Clara cells found and what is their purpose?
Found in bronchioles- secrete surfactant lipoprotein to prevent the walls sticking together during expiration
What are the main features of alveolar walls?
Abundant capillaries
Supported by elastic and reticular fibres
Covered with type I pneumocystis (squamous)
Have a scattering of intervening type II pneumocytes (cuboidal)
What is emphysema?
Destruction of alveolar walls and permanent enlargement of air spaces. Alveoli normally hold bronchioles open so bronchioles collapse and air can’t escape
What is pneumonia?
Inflammation of the lung caused by bacteria- lung consolidates as alveoli fill with inflammatory cells
