Week 1 - Intro, Histology, Upper Tract Flashcards
Define inspiratory reserve volume
Extra volume that can be breathed in over the tidal volume at rest
Define expiratory reserve volume
Extra volume that can be breathed out over the tidal volume at rest
What is the atmospheric pressure?
101 kPa
How can you use partial pressure to determine the volume of a gas?
The partial pressure of a gas is proportional to the percentage volume of that gas in the mixture
How can you use the pressure of a gas to determine its volume?
The pressure of a gas is inversely proportional to its volume
Explain Boyles law
If temperature is constant, pressure is inversely proportional to volume
- when your lungs expand in inspiration, the volume of air inside the lungs will increase so the pressure inside the lungs will fall. The pressure will fall below atmospheric pressure so air will flow into the lungs from the atmosphere
- when your lungs expand in expiration the volume of air in the the lungs decreases so the pressure rises above atmospheric pressure, hence air flows out of the lungs
How can you use the absolute temperature to determine the pressure of a gas?
If the amount and volume of a gas stays the same, then the pressure is directly proportional to the absolute temperature
- Kinetic energy increases with temperature so molecules will hit the walls more often, hence increasing the pressure
What is ‘vapour pressure’?
The pressure exerted when water molecules enter the gas phase
- On biological systems gas mixtures are always in contact with water
- Gas molecules dissolve and water molecules evaporate, exerting their own partial pressure – vapour pressure
What is ‘saturated vapour pressure’?
The pressure exerted by gas that is saturated by water (it is saturated when the water molecules enter and leave at the same rate - in equilibrium)
- depends on temperature
What is partial pressure in liquids?
Indicates pressure exerted by the dissolved gases in the liquids
- amount of dissolved gas = solubility X tension
- If the gas reacts with a component of the liquid, this reaction must take place before tension and content can be determined
- – Total content = dissolved gas + reacted gas
How is oxygen transported in the blood?
- Bound to haemoglobin
- dissolved in plasma (small amount)
How are the alveoli supplied with blood?
They are surrounded by pulmonary capillaries
- the blood vessels in the pulmonary circulation branch to form a tree like the airways
Describe ‘the bends’ (decompression sickness in divers)
Pressure increases dramatically with depth in water
- as you dive deeper, nitrogen moves from the lungs (high pressure) into the blood (low pressure)
- Swimming up to the surface too quickly doesn’t give the nitrogen enough time to leave the blood (can form painful bubbles)
- A slow return to the surface lets the nitrogen return to the lungs where it is breathed out
Define tidal volume
Volume in and out with each breath during quiet respiration
What is the upper respiratory tract?
The parts of the respiratory system lying outside of the thorax Includes: - Larynx - Pharynx - Nose
What are the functions of the upper respiratory tract?
- Conducting air from atmosphere to lower respiratory tract
- Conditioning (warming, humidifying, trapping particles) inspired air
- Protection of the airway during swallowing
- Smell
- Swallowing
- Speech
What is the lower respiratory tract?
The parts of the respiratory system lying inside the thorax Includes: - Trachea - Main bronchi - Lobar bronchi - Segmental bronchi - Sub-segmental bronchi - Bronchioles - Terminal bronchioles - Alveolar ducts - Alveoli
Describe the structure of the nasal cavity
- Divided into 2 cavities by the nasal septum (made of cartilage and bone and runs in the midline)
- Lateral wall of the nasal cavity has 3 bony projections which are known as conchae
- There are superior, middle and inferior conchae
- The conchae slow the airflow, helping to mix the air
- The space underneath a concha is called a meatus
- Lined by pseudostratified ciliated epithelia
What is the nasal cavity?
A part of the nose (other part is the external nose)
What are the functions of the nose?
- Filter air (nostril hairs filter large particles, mucus traps particles which are then wafted by the cilia)
- Smell
- Warm and humidify the air (vessels just below the epithelium warm the air, watery nasal secretions humidify the air)
- Receives local secretions (sinuses, nasolacrimal duct)
What are the paranasal sinuses?
Air-filled cavities in the skull which open into the nasal cavity
- Lined by respiratory epithelium
- Named for the skull bones within which they are located
- 4: frontal, ethmoidal, maxillary, sphenoidal
Where do the paranasal sinuses drain?
- Frontal: into the middle meatus
- Ethmoidal: anterior and middle parts drain into the middle meatus, posterior part drains into the superior meatus
- Sphenoid: into the sphenoethmoidal recess
- Maxillary: into the middle meatus
What is the function of the paranasal sinuses?
Contribute to the warming and humidification of inhaled air
- Secretions from them drain into the nasal cavity
What is the structure of the pharynx?
Divided into the nasopharynx, oropharynx and laryngopharynx
- Nasopharynx: behind the nose, found above the level of the soft palette, connected to the middle ear cavity by the auditory/Eustachian tube
- Oropharynx: found between the lower border of soft palette and above the upper border of the epiglottis, behind the mouth
- Laryngopharynx: underneath the epiglottis, behind the larynx
Why is it important that the middle ear cavity is connected to the nasopharynx?
Allows air pressure in middle ear cavity to be equal to atmospheric pressure
- URT infections can spread to middle ear
Where is the larynx found?
Between the pharynx and trachea
What is the structure of the larynx?
Has a cartilaginous skeleton
- Made up of 3 unpaired cartilages (epiglottis, thyroid cartilage and cricoid cartilage) and the paired arytenoid cartilages
- The 5 cartilages are linked by ligaments and muscles
- Contains the vocal cords
- – Lined by stratified squamous epithelia
- Has ventricles
- Has ventricular folds
- – Lined by pseudo stratified epithelia
- – Contain mucous glands and numerous lymph nodules
- Ventricles and ventricular folds contribute to the resonance of the voice
What do the vocal cords do?
- Guard the entrance to the trachea (prevent foreign objects reaching the lungs)
- Open during respiration
- Close when swallowing
- Partially close when speaking
- Initially they are closed during cough reflex, then open
What is the glottis?
The 2 vocal cords and the aperture (opening) between them
How are the vocal cords controlled?
By intrinsic laryngeal muscles
- These are controlled by the recurrent laryngeal nerve
What happens if there is laryngeal nerve damage?
Paralysis of the vocal cord of the affected side, which may causes a hoarse voice
- The left side of the recurrent laryngeal nerve extends into the thoracic cavity, so intrathoracic disease can compress/infiltrate the nerve, causing a hoarse voice
Describe the surface marking of the pleural cavity
- Apex of lung and pleural cavity extend about 3cm above the medial 1/3rd of the clavicle, into the root of the neck
- 2nd costal cartilage articulates with the sternal angle
- Both pleural reflections pass vertically down behind the sternum until the 4th costal cartilage
- The right pleura continues vertically down the midline until the 6th costal cartilage
- At the 4th costal cartilage, the left pleura deviates laterally and down towards the 6th costal cartilage (cardiac notch)
- 6th CC: each side turns laterally and passes around the chest wall to cross:
- – 8th rib at the mid-clavicular line
- – 10th rib at the mid-axillary line
- – 12th rib in the scapular line
Describe the surface marking of the lungs
- The lungs fill the pleural cavity except inferiorly
- Most of the inferior space is occupied during inspiration
- Follows the pleura at the apex and anteriorly until the 6th rib
- The left lung also has a cardiac notch, but it is much more marked than the notch in the pleural cavity
- The lower margin of the lung crosses the:
- – 6th rib at the mid-clavicular line
- – 8th rib at the mid-axillary line
- – 10th rib in the scapular line
Describe the surface marking of the lung lobes
- Left lung has 2 lobes: upper and lower
- – Split by the oblique fissure
- Right lung has 3 lobes: upper, middle and lower
- – Upper and middle are split by the horizontal fissure
- – Middle and lower are split by the oblique fissure
- Oblique fissure on either side runs from the T2 spinous process posteriorly round to the 6th costal cartilage anteriorly
- Horizontal fissure on the right runs from the mid-axillary line, anteriorly along the 4th rib, to the anterior edge of the lung
What membranes are found in the respiratory system?
- Mucous membrane: lines the conducting portion of the respiratory tract
- Serous membranes: lines the pleural sacs which envelope each lung
Describe the non-olfactory region of the nasal cavity
Contains:
- Pseudostratified ciliated epithelium
- Mucous glands and venous sinuses in the lamina propria
- Venous plexuses which swell every 20-30 mins, alternating airflow from side to side to prevent overdrying
- Arteries (the arterial blood flow warms inhaled air)
Held open by surrounding cartilage or bone
Describe the olfactory region of the nasal cavity
Located in the posterior, superior region of each nasal fossa
Contains:
- Particularly thick pseudostratified columnar epithelium
- No goblet cells
- Olfactory cells (bipolar neurons)
- Bowman’s glands (serous glands that flush odorants from the epithelial surface)
Where in the respiratory system is pseudostratified ciliated epithelia with goblet cells found?
- Nasal cavity
- Pharynx
- Larynx
- Trachea
- Primary + secondary bronchi
Where in the respiratory system is simple columnar, ciliated epithelia with Clara cells found?
- Bronchioles
- Terminal bronchioles
Where in the respiratory system is simple cuboidal epithelia with Clara cells and sparse cilia found?
- Respiratory bronchioles
- Alveolar ducts
Where in the respiratory system is simple squamous epithelia found?
Alveoli
Describe the structure of the trachea
- C-shaped cartilage rings
- Lined by pseudostratified epithelia
- Has a lamina propria
- Contains seromucous glands
Describe the structure of the primary bronchi
- Similar to trachea
- Cartilage ring completely encircles the lumen
Describe the structure of the lobar and segmental bronchi
- Similar to primary bronchi
- Cartilage is arranged as irregular crescent plates or islands
Describe the structure of the bronchus
- Small diameter
- Cartilage is reduced to small islands
- Glands in the submucosa
Describe the structure of the bronchioles
- No cartilage or glands
- – Absence of cartilage can be problematic as it can allow the air passages to constrict and almost close down when smooth muscle contraction becomes excessive
- Surrounding alveoli keep lumen open
- As they get smaller, goblet cells give way to Clara cells, interspersed between ciliated cuboidal cells
What do Clara cells do?
- Produce surfactant lipoprotein which prevents the walls from sticking together during expiration
- Secrete the protein Clara cell 16 (CC16)
- – Measurable marker in bronchoalveolar damage and leakage in the blood-air barrier
- – If CC16 is lowered = lung damage
- – If CC16 is raised = leakage across barrier
What structures are included in the conducting part of the respiratory tract?
- Nasal cavity (e)
- Trachea (e)
- Primary bronchi (e)
- Secondary bronchi (i)
- Bronchioles (i)
- Terminal bronchioles (i)
e = extrapulmonary, i = intrapulmonary
What structures are included in the respiratory part of the respiratory tract?
- Respiratory bronchioles (i)
- Alveolar ducts (i)
- Alveoli (i)
e = extrapulmonary, i = intrapulmonary
What are the terminal bronchioles?
- The last of the conducting airways
- Each is connected to respiratory bronchioles, alveoli and alveolar ducts
- Contain no goblet cells so that an individual doesn’t drown in mucus
Describe the structure of alveoli
- Walls have abundant capillaries
- Supported by basketwork of elastic and reticular fibres
- Have a covering composing mainly of type 1 pneumocytes
- – Simple squamous cells
- – 90% of surface area
- – Allows gas exchange
- Scattering of intervening type II pneumocytes
- – Produce surfactant
- – Simple cuboidal cells
- – Cover 10% of surface area
- Macrophages line alveolar surface
- – Phagocytose particles
Define respiration rate/pulmonary ventilation rate
The number of breaths in a set time, usually 60 secs
- Normal resp rate = 14-16 breaths per min
What is the universal gas law?
Pressure x volume = gas constant x temperature (K)
What is gas tension?
How readily a gas will leave the liquid it is dissolved in
- At equilibrium, tension = partial pressure
