TBL Knowledge Flashcards
What is the function of the conducting airways?
Passage of air into the body
What are the components of the conducting airways?
Nose, mouth, pharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles
What prevents the walls of the trachea/bronchi from collapsing?
Cartilage in the walls
What is the function of the respiratory airways?
Gaseous exchange
What are the components of the respiratory airways?
Respiratory bronchioles, alveolar ducts, alveolar sacs
What does a single respiratory cycle consist of?
One inspiration and one expiration
Define ventilation
Drop in alveolar pressure causes bulk entry of air during inspiration
What are the pleural sacs and how are they involved in expansion of the lungs?
- Fluid filled sacs surrounding the lungs
- Inner membrane is attached to lung and outer membrane is attached to diaphragm and thoracic wall by connective tissue
- Contraction of the diaphragm and intercostal muscles pulls on the sacs and causes the lungs to expand
What makes up connective tissue?
Collagen and elastic fibres
What makes up the thoracic wall?
Spinal column, ribs and intercostal muscles
What are the additional functions of the conducting airways?
- Speech (larynx)
- Efficient O2/CO2 movement due to warming/moistening of air
- Infection defence (macrophages and mucus)
How does mucus production affect infection control?
- Epithelial cells secrete mucus to trap dust and bacteria
- Mucus wafted towards pharynx by cilia to be swallowed, destroying the pathogens
How does the Cystic Fibrosis Transmembrane Regulator affect mucus movement?
- Allows movement of Cl- out of the epithelial cells
- Watery fluid is secreted as a result which prevents mucus from becoming thick and sticky
What is Cystic Fibrosis?
- Defective CFTR channel
- Decreased fluid secretion results in mucus build up
- More susceptible to infections as pathogens are not removed
What is a pneumothorax?
Air enters the chest cavity due to a breakage in the pleural sac, external pressure causes lung to collapse and chest wall to expand
What adaptation prevents damage to both lungs at any one time?
Pleural cavities isolate each lung, damage to one side is contained
What disease could cause a spontaneous pneumothorax?
- Pneumonia
- Emphysema
How is a pneumothorax treated?
- Let body absorb air and monitor by x-ray
- Remove air from chest using a needle and tube
- Surgically repair lung
- Remove lung if damage is severe
Define:
- Tidal Volume
- Residual Volume
- Vital Capacity
- Tidal Volume: The amount of air inhaled/exhaled in a single breath
- Residual Volume: The amount of air left in the lungs after a forced exhalation
- Vital Capacity: Total vol. - Residual vol.
What is the approximate total volume/volume of inspiration?
- Total volume ~2.5L
- Volume of Inspiration ~0.5L
What are the two different ways of measuring ventilation and what are the equations?
What are the units?
- Minute Ventilation: Tidal vol. x Resp. rate
- Alveolar Ventilation: (Tidal vol. - Dead Space) x Resp. rate
- Units: ml/min
What volume of the airways in anatomical dead space?
About 150ml
Why are there two measurements for ventilation?
Difference between the two can highlight respiratory issues (e.g. air may not actually be reaching respiratory airways)
What are the different lung function tests?
- Spirometry
- Peak Flow
Define FVC and FEV1
- FVC: Forced Vital Capacity, max amount of air exhaled in a forced breath
- FEV1: Forced Expiratory Volume (in 1 sec), max amount of air exhaled in a forced breath in 1 sec
What observations would be seen in obstructive lung disease?
- FEV1 less than 80%, FVC same as normal
- Airways are obstructed so eventually the same volume of air will come out as the lungs can still expand as well
What observations would be seen in restrictive lung disease?
- Reduced FEV1 and FVC
- Lung capacity is reduced (e.g. due to stiffening of the lung or infiltration)
Define lung compliance
Ease of expansion of the lungs and thorax
What does lung compliance depend on?
Transpulmonary pressure (difference between alveolar pressure and intrapleural pressure) and lung volume
What is the equation for working out compliance?
Cl = Change in vol/Change in pressure
What are the observations of normal, high and low compliance?
- Normal: Increase in TP causes increase in volume
- High: Small increase in TP causes big increase in volume
- Low: Big increase in TP causes small increase in volume
What condition causes high lung compliance?
Emphysema
What conditions cause low lung compliance?
Pulmonary oedema, pneumonia, fibrosis
What are the two types of cells of the lungs and what are their functions?
- Type 1 - Adapted for gaseous exchange
- Type 2 - Cuboidal cells, responsible for surfactant production
What is the effect of a lack of surfactant and why?
- Causes alveoli to collapse on expiration
- Surfactant reduces surface tension in the lungs
What is Newborn Respiratory Distress Syndrome?
- Underdeveloped cuboidal cells results in a lack of surfactant, causing lungs to collapse
- Common in premature babies
What other disorders reduce lung compliance?
Disorders affecting rib/spinal column articulation
Why do ventilation and perfusion need to be matched?
Inequality results in reduced O2 entry
What is Emphysema?
What causes it?
How are patients treated?
- Degeneration of the alveolar/bronchiole walls and the surrounding capillaries
- Generally due to protease action
- Caused by smoking
- Results in oxygen treatment because patient cannot get enough oxygen
What is asthma?
Inflammation of conducting airways due to exposure to environmental allergens
What causes the inflammation (physiological)?
Excess mucus production and airway smooth muscle contraction
How are beta agonists used to treat asthma?
- Mimic adrenaline
- Adenylate cyclase enzyme activated, ATP to cAMP
- Causes smooth muscle relaxation
How are phosphodiesterase inhibitors used to treat asthma?
- Prevent breakdown of cAMP
- Smooth muscle relaxation is maintained
How are corticosteroids used to treat asthma?
- Bind to glucocorticoid receptors in cytoplasm of epithelial cells
- Heat shock proteins that hold the receptor in place dissociate so receptor-drug complex moves to nucleus
- In the nucleus it binds to regions of DNA that are responsible for transcribing cytokine molecules
- Cytokines not produced therefore no inflammation
What cytokines cause inflammation in the airways?
- Tumour necrosis factor alpha
- Interleukin 1
Give an example of a corticosteroid used to treat asthma
Beclomethasone
What is the allergic component of asthma?
Overproduction of IgE antibody
How does IgE production cause inflammation?
- Allergen binds to IgE causing it to bind to Fce receptor on mast cells, basophils and dendritic cells
- This causes release of histamine, cytokines, prostaglandins and leukotrienes
How are monoclonal antibodies used as treatment for asthma?
- Antibody binds to Fc region of IgE antibody
- Antibody can’t bind to inflammatory cells so inflammatory markers are not released
Which neurones are involved in breathing control?
Where are they found?
- Inspiratory neurones
- Expiratory neurones
- Mixed neurones
- Pons (brain stem)
How do neurones affect breathing?
Cause contraction of diaphragm and intercostal muscles
What do central chemoreceptors monitor and where are they found?
- pH and pCO2 of cerebrospinal fluid
- Present in brain stem medulla
What do peripheral chemoreceptors monitor and where are they found?
- pH, pCO2 and pO2 of arterial blood
- Found in carotid and aortic bodies
Why is high CO2 dangerous and how is it controlled?
- Toxic, inhibits respiratory neurones of the medulla
- When high CO2 is detected, contraction of intercostal muscles and diaphragm is increased
What is the GI tract specialised for?
Digestion and absorption
What are the components of the GI tract?
Mouth, pharynx, oesophagus, stomach, small intestine (duodenum, jejunum, ileum), large intestine (colon), rectum, anus
What are the functions of the salivary glands?
- Amylase/lipase secretion
- Mucin production (glycoprotein - lubricates for swallowing)
What are the three sets of salivary glands?
- Sublingual
- Submandibular
- Parotid (cheek)