Respiratory Physiology Flashcards
What affects the type of respiratory system an animal can have?
The distance to which nutrients and oxygen have to be delivered and dehydration limits diffusion rate, therefore the size of an animal and the habitat of an animal affects the type of respiratory system it has.
What is aerobic metabolism?
It is the conversion of food sources into ATP with oxygen present.
What are the different lobes of the human lungs?
3 lobes in the right and 2 in the left lung.
Right lung - inferior lobe, middle love and superior lobe.
Left lung - inferior and superior lobe.
What are the two main regions of the respiratory system?
The conducting zone (dead space) - not involved in respiratory gas exchange - includes nasal cavities, pharynx and larynx, trachea and primary bronchi.
The respiratory zone - responsible for gas exchange - includes respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli.
What are the components of the nasal cavities?
- Sweat glands
- Sebaceous glands
- Hair follicles - filters inhaled air.
They all protect the airways.
The nasal cavities are lined by mucosa which are epithelial cells (olfactory mucosa and respiratory mucosa).
Olfactory mucosa - sense of smell.
Respiratory mucosa - secretes antibacterial enzymes and mucus.
Ciliates cells sweep material to pharynx.
Surface area of epithelial is increased by scrolled nasal concha (to maximise heat exchange)
What is the general function of the nasal cavities?
They warm, humidify and filter inhaled air.
Why does the nasal cavity warm and humidify the air breathed in?
To make sure that cold, dry air does not get to the respiratory zone which may ‘ shock’ the body.
What are the functions of the pharynx?
Pharynx (between nose and mouth) - involves the nasopharynx, oropharynx and laryngopharynx - it is part of the digestive system and respiratory system.
The epiglottis seals off the trachea during the swallowing reflex to separate the respiratory and digestive system by preventing food from passing to the trachea.
What are the tonsils and what are their function(s)?
They are lymphoid tissues which surround the airways and defend it. They activate immune responses.
What is the function of the larynx?
Larynx/voice box - involved in respiratory and speech. It contains two vocal cords which vibrate with breathing. Laryngeal muscles alter the tension/positioning folds to create different sounds
What are the function(s) of the trachea?
It is a flattened tube connecting upper (nasal) lower (bronchial) airways There are rings of cartilage (c shape cartilage rings) on the trachea that prevent it from collapsing.
It also has submucosal tissue - produce mucus in trachea
Lamino propria - lymphocytes to provide immune response.
Pseudostratified ciliates epithelial cells
Cough reflex in trachea allows expulsion of foreign bodies.
What are the function(s) of the bronchi?
Surrounded by muscle - to drive inspiration
They also have ciliates pseudostratified epithelial tissues.
They help defend the airways - via the mucociliary escalator :
1. Goblet cells produce sticky mucus to grow bacteria.
2. Bronchial epithelial cells - produce anti-microbial peptides to punch holes in bacteria and kill them.
3. Ciliates epithelial cells beat the mucus to the pharynx.
What is the mucociliary escalatory?
This takes place in the bronchi.
Cilia, periciliary fluid and mucus raft on top of the cilia is required.
1. Sticky mucus (made of glycoproteins) traps inhaled particles and bacteria.
2. Cilia project into the periciliary fluid (a liquid layer secreted by epithelial cells).
3. The action of the ciliary beating moves the mucus raft to the back of the throat (where it can be swallowed or removed via the mouth).
What is the difference between the epithelium in the airways of an individual with cystic fibrosis?
- There is an overproduction of thick mucus.
- There is no periciliary fluid for the cilia to ‘beat’ mucus into because the mucus is ‘dehydrated’.
- Dirt laden mucus is trapped and cannot get to the back of the throat and can therefore not be removed - the individual is more vulnerable to infections.
What are alveolar ducts?
They are tiny ducts connecting respiratory bronchioles to alveolar sacs. They are surrounded by smooth muscle, elastin and collagen.
What are alveolar sacs?
Each alveolar sac contains a bunch of alveoli.
Where does the mucociliary escalator take place?
In the bronchi.
Alveoli has type I and type II pneumocytes which are epithelial cells instead of pseudostratified epithelial cells. What are their functions?
Type I pneumocytes - responsible for gas exchange in alveoli - thin membrane which is close to the endothelium. They have tight junctions to create an impermeable barrier to foreign invaders (this is a function of epithelial cells).
Type II pneumocytes:
- involved in defence in alveoli. They are secretory cells produce surfactants which reduce surface tension to prevent the lugs from collapsing.
- they replenish damaged type II pneumocytes.
- they produce a(alpha)1-anti-trypsin which defend and protect the airways.
What are alveolar macrophages?
They are monocytes that provide further protection/defence in the airways. They patrol the tissue for foreign material or dead/damaged cells that may interfere with lung function.
What is the general function of the alveoli?
Type I pneumocytes - gas exchange.
Type II pneumocytes - repair, defence and regulation of surface tension to prevent lungs from collapsing.
Alveolar macrophages - defence.
How is compliance measured clinically?
To measure compliance, changes in pressure and volume need to be measured. It is difficult to measure pressure changes (oesophageal balloon attached to a pressure transducers and different volumes of air are put into the balloon) but spirometry is used to measure volume changes.
Give two conditions which increase and decrease lung compliance.
Emphysema (an obstructive lung disease) increases lung compliance - tissue damage - easier to inflate - lead to higher vital capacity - elastic recoil has been reduced - shifts compliance curve to the left.
Fibrosis (a restrictive lung disease) reduces compliance - increases elastic recoil - more pressure is required to increase volume - shifts compliance curve to the right.
What is elastic recoil?
It is the inverse of compliance.
Stiff lungs have high elasticity but low compliance.
Elastic recoil of the lung is due to the elastic properties of the parenchyma (the functional parts of the lungs) which have elastin (more compliant) and collagen (less compliant).
An increase in collagen in parenchyma means less compliance and vice versa with elastin.
What is alveolar surface tension?
Surface tension is what makes water form droplets (the cohesive forces between water molecules). The ability of the lungs to recoil (elastic recoil) is due to alveolar surface tension.
Why does alveolar surface tension arise?
Alveoli are not all the same size. Small alveoli tend to collapse - so alveoli will empty their air into adjacent alveoli.
What are the two factors that stabilise alveoli and prevent them from collapsing?
- Structural interdependence of the alveoli - alveoli are held open by the chest wall pulling in the outer surface of the lung and they are dependent on each other. A collapsing alveolus causes stress on adjacent alveoli so they tend to hold each other open.
- Pulmonary surfactant (released by type II pneumocytes) which reduces surface tension. It is made of lipids/phospholipids and proteins. It is recycled by type II pneumocytes.
SP-A and SP-D pulmonary surfactant are required for defence. SP-B is required to reduce surface tension.
Give example(s) where the lack of pulmonary surfactant affects the lungs.
Premature babies without functional surfactant have difficult inflating their lungs because elastic recoil is aided by alveolar surface tension - without the surfactant surface tension remains high and alveoli collapse - they can be given exogenous surfactant.
Hypoxia (where parts of the body have inadequate oxygen supply) may reduce surfactant production and can lead to ARDS (acute respiratory distress syndrome which leads to spontaneous lung collapse) - positive-pressure ventilation can be carried out so that alveolar pressure is greater than atmospheric to prevent spontaneous collage.
What is tidal volume?
The volume of air per breath - 500ml per breath for 70kg adults are eupnea (quite breathing).
What is the residual volume (RV)?
It is the volume of air remaining in the lungs after maximum forced expiration - 1.5L it is normally greater in emphysema - due to increased lung compliance which prevents elastic recoil of lungs.
It cannot be measured by spirometry.
What is the exploratory reserve volume (ERV)?
It is the volume expelled during maximum forced expiration starting at the end of normal tidal expiration - 1.5L.
It is also functional residual capacity - residual volume.
What is the inspiratory reserve volume (IRV)?
It is the volume inhaled during maximum forced inspiration starting at the end of normal tidal inspiration.
It is normally 2.5L.
What are lung capacities?
Hey are a sum of the lung volumes.
What is functional residual capacity (FRC)?
It is the volume remaining at the end of normal tidal expiration.
It is the residual volume + expiratory reserve volume. It is usually 3L.
What is the inspiration capacity (IC)?
It is the volume inhaled during maximum inspiratory effort at the end of normal tidal expiration.
It is vital capacity + inspiratory reserve volume. It is usually 3L.
What is the total lung capacity (TLC)?
It is the volume in the lungs after maximum inspiratory effort. It is residual volume + vital capacity + inspiratory reserve volume + expiratory reserve volume. It is about 6L.
What is vital capacity (VC)?
It is the volume expelled during maximum forced expiration after maximum forced inspiration. It is total lung capacity - residual volume. It is about 4.5L.
Apart from pathological states, what other factor(s) alters lung volume?
Physiology - for example when lying down or standing up - vital capacity is lower when lying down.
How can obstructive and restrictive diseases be diagnosed?
By measuring lung volumes.
What is a restrictive disease?
Restrictive diseases (alveolar fibrosis) leads to reduced compliance and increased elastic recoil.
FRC, TLC, VC, IRV and ERV will be reduced. The breathing rate of the individual will increase as they need to increase oxygen supply to tissues.
What is an obstructive disease?
Includes emphysema and chronic bronchitis.
There is increased resistance, increased compliance and decreased elastic recoil.
RV, FRC and TLC increase.
VC and ERV decrease.
Breathing rate decreases.
What is spirometry?
It is a simple way to measure gas volumes. The breathing pattern is traced on the rotating drum.
What are the limitations of spirometry?
Residual volume cannot be measured and functional residual capacity so the total lung capacity can also not be estimated. Spirometry can only be measured if the individual is conscious and cooperative.
How can we measure the other lung volumes that cannot be measured by spirometry?
- Nitrogen wash out technique.
- Helium-dilution technique.
- Body plethysomography
They are used to measure function residual capacity which can be used to estimate residual volume and total lung capacity.
