Respiratory Flashcards
Name four functions of the nasal cavity?
- Warms inspired air
- Humidifies air
- Filters inspired air - brush-like hairs/cilia
- Defence function - cilia take inhaled particles backwards to be swallowed
What is the role of turbinates in the nose?
To double the surface area of the nasal cavity
What is found in the superior meatus and what drains here?
The olfactory epithelium is found here - olfactory nerves penetrate into superior meatus through pores in the cribriform plate
Sphenoid sinus drains here - sphenoethmoidal recess
What drains into the inferior meatus?
Nasolacrimal duct
Name the four pairs of paranasal sinuses
Frontal
Maxillary
Ethmoid
Sphenoid
Which nerve innervates the Frontal sinus?
Ophthalmic division (V1) of the trigeminal nerve CN5
Which nerve innervates the maxillary sinuses?
Maxillary division (V2) of the trigeminal nerve
Where is the base, Apex and roof of the maxillary sinus?
Base - lateral wall of the nose
Apex: zygomatic process of the maxilla
Roof: the floor of the orbit
Which meatus do the Maxillary sinuses drain into?
Middle meatus
Describe the position and structure of the ethmoid sinuses
The ethmoid sinuses are between the eyes and are a labyrinth of air cells
Which nerves innervate the ethmoid sinuses?
Ophthalmic (V1) & Maxillary (V2) branches of the trigeminal nerve
Which meatus does the ethmoid sinus drain into?
anterior ethmoid - Middle meatus
posterior ethmoid - sphenoethmoidal recess in superior meatus
Which structures are in close proximity to the sphenoid sinus?
Cavernous sinus
Optic canal
Dura
Pituitary gland
Which meatus does the sphenoid sinus drain into?
Superior meatus through the sphenoethmoidal recess
Which nerve innervates the sphenoid sinus?
The ophthalmic (V1) branch of the trigeminal nerve
What is the role of the pharynx?
To take filtered air from the nose to the larynx
Where does the pharynx extend from and finish
Extends from the skull base to C6 where it becomes continuous with the oesophagus
Name the three parts of the pharynx
nasopharynx, oropharynx, laryngopharynx
What are the functions of the larynx?
Valvular function: prevents liquids and food from entering the lungs
Produces vocal sounds - vocal cords
Name the three double and three single cartilages in the larynx
3 paired (cuneiform, corniculate & arytenoid) and 3 unpaired (epiglottis, thyroid & cricoid)
Which cartilages take part in changing the shape/size of the vocal cords and how do they do this?
Arytenoid cartilages rotate on the cricoid cartilage to change vocal cords
What is the nervous innervation of the larynx?
Innervated by the Vagus nerve (CNX) - Superior laryngeal & Recurrent laryngeal nerve
Name the branches of the superior laryngeal nerve and their functions
internal - sensation ABOVE vocal cords
external - motor innervation to CRICOTHYROID MUSCLE)
Describe the role of the recurrent laryngeal nerve
provides motor innervation for ALL muscles except the
cricothyroid muscle
Sensation below the vocal cords
Describe the route that the left recurrent laryngeal nerve takes
runs laterally to the arch of the aorta, loops under aortic arch, ascends
between the trachea and oesophagus
Describe the route of the right recurrent laryngeal nerve
loops under right subclavian artery, then runs up plane between trachea
and oesophagus
What might a patient with an ulcer/tumour on or near the recurrent laryngeal nerve present with?
Hoarse voice
What is the average minute volume and cardiac output?
Minute volume - approx 5 litres
Cardiac Output - approx 5 litres per minute
At what vertebral level does the trachea start and end?
From larynx to carina (C6 - T5)
Describe the structure of the trachea?
Semicircular hyaline cartilages (C-shaped cartilage increases flexibility of trachea)
connected by tracheal muscle
What is respiratory epithelia?
Pseudo-stratified ciliated, columnar epithelium with goblet cells
Why are inhaled foreign object more likely to enter the right lung?
Right main bronchus is more vertically disposed and shorter
How many lobar bronchi division are there in the right and left lungs?
Right has 3 divisions
Left has 3 division
How many segmental branches does the right and the left lungs have?
Right has 10
Left has 8
What is an Acinus?
Acinus: the tissue supplied with air by one terminal bronchiole
Name the two predominant cells found in the alveoli
Type 1 pneumocytes
Type 2 pneumocytes
What is the role of type 2 pneumocytes?
Secretes surfactant to reduce surface tension
What is the nervous innervation of the lung?
The pulmonary plexus lies behind each hilum - right and left vagus nerve and T2-T4 ganglia of sympathetic trunk
What does sympathetic innervation and parasympathetic innervation cause in the lung?
Sympathetic (from sympathetic trunk) - results in bronchodilation
- Parasympathetic (from vagus) - results in bronchoconstriction
Which trilaminar layer does the pleura arise from?
Mesoderm ( splanchnic lateral plate mesoderm)
Where is the visceral pleura found and describe its innervation
applied to the lung surface - only has autonomic innervation
Where is the parietal pleura found and describe its innervation
applied to the internal chest - has pain sensation via phrenic nerve
Name the different types of blood supply to the lungs
Bronchial and pulmonary circulation
Define transpulmonary pressure
difference in pressure between the inside and
outside of the lung (alveolar pressure - intrapleural pressure)
Define intrapleural pressure
The pressure in the pleural space
Define alveolar pressure
Air pressure in pulmonary alveoli
Which muscle is the most important during inspiration?
Diaphragm
Which muscles contract during inspiration?
Diaphragm and the external intercostals
Which nerve innervates the diaphragm?
Phrenic nerve
which arises form C3,4 & 5 (C3,4,5 keeps the diaphragm alive!):
Briefly describe the process of inspiration
1) Diaphragm contracts - moves down increasing thoracic volume
2) External intercostals contract - ribs move up and out - increasing volume
3) negative pressure in the lungs causes inwards airflow
Briefly describe the process of expiration at rest?
1) Diaphragm and external intercostals relax
2) Elastic recoil - pressure increases as volume decreases
3) lungs passively collapse
4) airflow outwards
Briefly describe the extra processes of forced expiration
1) Internal intercostals and abdominal muscles also contract
2) ribs move down and in
3) abdominal muscles force the diaphragm higher up into the thorax - further reducing volume
4) Greater volume of air expired
Which part of the airways has the greatest resistance?
Trachea - it is a single ( not branched) and long structure which contributes to increased resistance
Define dead space and how much in total?
The volume of air not contributing to gas exchange
150mls anatomical and 25mls alveolar
Define anatomical dead space
The volume of air that cannot reach the alveoli
Does a red blood cell come into contact with just one alveoli?
No, can come into contact with many alveoli
What is V/Q mismatch?
Incorrect proportion of ventilation and capillary perfusion available to each alveolus
What is the main effect of ventilation-perfusion mismatch
Decreased partial pressure of oxygen in systemic arterial blood
Why is there naturally some V/Q mismatch in healthy people
Gravitational effects cause increase filling of blood vessels at the bottom of the lung due to gravity
Describe what occurs when there is a high V/Q ratio and what can it be caused by?
ventilated alveoli but no blood supply at all (known as dead space
or wasted ventilation) due to a blood clot for example
Describe what occurs when there is a low V/Q ratio and what can it be caused by?
There may be adequate blood flow through the areas of the lung but there is no ventilation (this is termed shunt) due to collapsed alveoli
What is the bodies response when there is reduced ventilation to a group of alveoli?
Hypoxic Pulmonary constriction
Vasoconstriction - Diverting blood away from poorly ventilated area
What is the bodies response when there is reduced perfusion in a group of alveoli?
Local bronchoconstriction
diverts airflow away from to areas of the lung with better perfusion
Describe the structure of a Hb molecule
Four subunits - two beta and two alpha chains
Four haem groups each with a single Fe2+
Why is the plateau at higher partial pressures of O2 important of the oxygen dissociation curve?
Safety factor allowing for normal oxygen saturation of Hb in situations such as high altitude, pulmonary disease and other limitations in lung function
Why is the plateau at higher partial pressures of O2 important of the oxygen dissociation curve?
Safety factor allowing for normal oxygen saturation of Hb in situations such as high altitude, pulmonary disease and other limitations in lung function
What changes need to occur for a right shift in the oxygen dissociation curve
- High pH (less acidic)
- Low temp
What does a right shift in the oxygen dissociation curve result in
Decreased Hb affinity for O2 so increased O2 unloading at tissues
What does a left shift in the oxygen dissociation curve result in?
Increased Hb affinity - less O2 unloading at tissue level
What changes need to occur for a right shift in the oxygen dissociation curve
Decreased temp
Increased pH
Does CO have a higher affinity for the oxygen binding sites on Hb
Yes - CO has 200 times higher affinity for binding sites compared to O2.
State the equation to calculate the arterial partial pressure of CO2
PaCO2 = k V̇CO2 / V̇A
What is the normal pH of blood?
7.4 (7.35-7.45)
How does respiratory acidosis arise?
Hypoventilation - Inadequate ventilation of alveoli
CO2 cannot be excreted and expired adequately
Partial pressure of CO2 rises and results in more Carbonic acid production and more H+ conc
How does respiratory alkalosis arise?
Hyperventilation - increased CO2 excretion - decreased PaCO2 - decreased H+ conc in blood
State Henderson-Hasselbalch’s equation
pH=Pka+Log ([A-]/[HA])
Describe Daltons law
total pressure of the mixture
is simply the sum of the individual pressures of gases known as partial pressures which are
directly proportional to its concentration
Describe Boyle’s law
pressure of a fixed amount of gas in a container is inversely
proportional to container’s volume; P1V1 = P2V2
Describe Henry’s law
The solubility of a gas is proportional to the partial pressure of the gas. S1/P1 = S2/P2.
State the alveolar gas equation
PAO2 = PiO2 - PaCO2/R
What equation can we use to calculate pressure
Pressure=flow*resistance
Describe Laplace’s law
describes the relationship between pressure (P), surface tension
(T) and the radius (r) of an alveolus: P = 2T/r
What is the significance of Laplace’s law
It tells us that small alveoli have a greater pressure and so air will move from small alveoli to larger alveoli; uneven aeration. (Surfactant can prevent this).
Define lung compliance
A measure of the lung’s ability to stretch and expand
What might cause a decrease in lung compliance
Loss in elastic connective tissues
Describe the role of surfactant
Reduces surface tension
Increases Lung compliance
Easier to expand lungs
What can we do to increase/stimulate the secretion of surfactant?
Take a deep breath - stretches type 2 pneumocyte - stimulates the secretion of surfactant