The respiratory system - Physiology Flashcards
Describe the function of the conduction zone
- Passage of air from environment to lungs
- Airway protection
- Air humidification and warming
- Smell
- Speech
conduction zone
a) structure
b) Role of structure
c) Role of structure of trachea
a) Cartilage, muscle
b)
- Allows rigidity but flexibility of the airways
- Resistant to compression and collapse
- Allows expansion during breathing
c) C shaped to allow swallowing
Give the 3 types of airway protection of the conduction zone
Mechanical cellular) - cilia and mucus (mucociliary escalator)
Immunologcial - identification of pathogens
Mechanical (anatomical) - Reflex protection
Describe the mechanical (cellular) protection of the conducting zone
Cilia epithelium - cilia traps mucus up the respiratory tract
Nasal hair - removes larger particle materials
Describe the immunological protection of the conducting zone
Nasopharynx - dense lymphoid tissue in the stroma allowing immune cells direct contact with pathogens
Bronchial epithelial cell secretion - lysozyme, lactoferrin, antiprotenase, IgA and epithelial peroxidase
Give 3 mechanical (anatomical) protection of the conduction zone
- Cough reflex
- Swallow reflex
- Gag reflex
Describe the role of the swallow reflex
Enables the epiglottis to cover the larynx to prevent aspiration
Describe the role of the gag reflex
Prevents foreign bodies entering the upper airways
Describe how airway humidification effects the protection of the conducting zone
Cold dry air causes evaporation of watery mucus from seromucinous glands
This induces thicker mucin
This impairs the mucus-ciliary function and therefore the removal of pathogens is compromised
Describe the structure and function of type 1 pneumocytes
- Flattened nuclei
- Thin for more gas exchange
- Form a barrier to prevent fluid loss
Describe the structure and function of type 2 pneumocyte
- More numerous than type 1 but smaller surface area
- Larger darker nuclei
- Surfactant production - reduces surface tension to calitate lung expansion
Describe the role of the Olfactory mucosa
The mucus dissolves odours to allow detection
Name the 7 ways pressure readings are recorded
Pascal (Pa); Kilopascal (kPa)
Atmosphere (atm)
Millimeters of mercury (mmHg)
Torr
Bar
Pounds per square inch (b/in2 or psi)
Psi
Describe the two types of air movements
Convection - bulk movement of air which is driven by pressure gradients
Diffusion - movement of gases from a high pressure to a lower pressure
Compare the structure of the conducting airways (from bronchi to terminal bronchioles) to the respiratory bronchioles and alveolar ducts including there ability to collapse
Conducting airways (from bronchi to terminal bronchiole) - cartilage, few smooth muscles, collapse rare
Respiratory bronchioles and alveolar ducts - no cartilage, lots of smooth muscle, susceptible to collapse during expiration
Explain how air velocity changes as you go from conducting airways to alveolar airways
Drop in relative air velocity as you go from conducting airways to alveolar airways, as there is a change from convection velocity to diffusion
Describe how the cross-sectional area changes from conduction airways to alveolar airways
Cross-sectional area increases from conduction airways to alveolar airways for gas exchange
Describe the 2 blood supplies to the lungs
Pulmonary arteries - carry deoxygenated mixed venous blood from right ventricle to the alveoli of the lungs
Bronchial arteries - branch from aorta and supply oxygenated blood to conducting airways
Describe the role of the pulmonary veins
Return oxygenated blood to left atrium
Describe the 3 systems that innervate the respiratory tract including the transmitter, receptor and effect on smooth muscle of respiratory bronchioles
- System: Cholinergic
Transmitter: Acetycholine
Receptor: Muscarinic
Effect on smooth muscle of respiratory bronchioles: Constrict - System: Adrenergic
Transmitter: Norepinephrine/epinephrine
Receptor: B2-Adrenergic
Effect on smooth muscle of respiratory bronchioles: Dilate - System: Peptidergic (tachykinins)
Transmitter: Vasoactive intestinal peptide (VIP); substance P
Receptor: VIP; neurokinin
Effect on smooth muscle of respiratory bronchioles: Dilate; constrict
a) What is the inspiratory reserve volume?
b) Name 5 factors that affect the inspiratory reserve volume
a) Extra volume of air that can be inspired over and above normal tidal volume (2500ml)
b)
- Current lung volume
- Lung compliance
- Muscle strength
- Comfort
- Flexibility of the skeleton
- Posture
a) What is alveolar ventilation
b) What does it determine?
a) The rate at which new air reaches the alveolar
b) Alveolar ventilation is one of major factors determining O2 and CO2 concentrations in alveoli
Describe the static properties of the lungs
- The lungs are an elastic structure
- Not attached to chest wall
- Lung floats in thoracic cavity surrounded by thin layer of pleural fluid that acts as lubricant
- Chest wall is all elastic
a) What is the equation for the transpulmonary gradient (TPG)
b) Describe the relationship between TPG and the alveolar size
a) Transpulmonary pressure = Alveolar pressure - intrapleural pressure
b) Transpulmonary pressure determines the alveolar size. The alveoli at the top of the lungs have a greater TPG, before inspiration, and therefore are bigger than the ones at the bottom
Describe the changes in intrapleural pressure and alveolar pressure during inspiration
During inspiration expansion of chest cage pulls pleural cavity outwards and downwards so pleural cavity volume increases –> pressure decreases
–> negative pressure increases to about – neg 7.5cm H20 –> alveoli pressure decrease about -1cm H2O –> air sucked in
Name the 4 most important muscle that raise the rib cage
- External intercostals
- Sternocleidomastoid (loft upward on sternum)
- Anterior serrati (lift many ribs)
- Scaleni (lift first two ribs)
Name the two most important muscles that lower the ribcage
- Abdominal recti
- Internal intercostals
Describe the 2 ways the lungs can be expanded and contracted
- Downwards (inspiration) and upward movement (expiration) of diaphragm to lengthen or shorten chest cavity
- Elevation and depression of the ribs to increase or decrease anteroposterior diameter of chest
What is static compliance?
Static compliance is the extent to which the lungs expand for each unit to increase the transpulomonary pressure
Describe the relationship between the elastance of the lungs (measure of elastic recoil) and the compliance
The elastance of the lungs (measure of elastic recoil) is the reciprocal of compliance (E=1/C). So high compliance means low elastic recoil
Name the 2 elastic forces that affect lung compliance
- Elastic forces of the lung tissue itself
- Elastic forces caused by surface tension of fluid that lines the alveoli
Describe the effect of interstitial lung disease on lung compliance
There is high elastic recoil of the stiff lungs which leads to reduced lung compliance
Resulting in a greater that normal transpulmonary pressure needed to give the same increase in lung volume
What are the different changes in lung volume in interstitial lung disease?
Low RV, low FVC, low TLC, decreased DLCO, poor lung compliance
Describe the effect of emphysema on lung compliance
Poor elastic recoil leads to high lung compliance
Resulting in a less than normal transpulmonary pressure needed to give the same increase in lung volume
What are the changes in lung volume in emphysema?
Increased RV, FRC, TLC, lung compliance
What are the lung volume changes in chronic bronchitis
Increased RV, FRC, TLC, normal compliance
What is surface tension?
A measure of the force acting to pull a liquid’s surface molecules together at an air-liquid interface
b) What is the law of LaPlace
b) How does this apply to the lungs?
a) The pressure (P) within a fluid-lined alveolus is dependent on the surface tension of the fluid (T) and the radius of the alveolus (r) –> P = (2 x T) / r
b) In the lungs, surface tensions results in air flowing from smaller alveoli to larger alveoli, as larger alveoli has a smaller pressure. This allowing the alveoli to collapse.
How do alveoli prevent themselves from collapsing
Type II pneumocytes release surfactant, that lowers surface tension and prevent apolar collapse
What are surfactants made of?
A complex mixture of phospholipids
Describe how surfactant work?
Hydrophilic head inserts into water phase and hydrophilic tail inserts into air phase which breaks up surface water molecules, there is less of a pull of the molecules and reduces surface tension
Name the two types of airflow in the lungs
- Turbulent
- Laminar
Name the 2 mechanical functions of speech
Phonation (achieved by larynx)
Articulation (achieved by structure of mouth)
Describe the structure and function of the larynx
Structure
- Rigid skeleton of several cartilaginous structures: thyroid and circoid cartilage
- Glottis formed by vocal cords (folds)
Function
- Primary function is to protect tracheobronchial tree
- Voice production
- Prevents food and saliva entering respiratory tract by sphincteric action of the cords and epiglottis
What nerve are the following laryngeal regions supplied by?
a) Pharynx
b) Laryngeal muscles
c) Cricothyroid
e) Glottis
a) Pharyngeal plexus
b) Recurrent laryngeal nerve (excel cricothyroid)
c) Branch of superior laryngeal nerve
d) Recurrent laryngeal nerve
e) Superior laryngeal nerve
Describe the movement of the vocal cords during normal breathing and phonation
During normal breathing, vocal cords are wide open to allow air movement
During phonation, cords move together so passage of air between them causes vibration
What is pitch determined by?
Pitch determined by degree of stretch of cords
what are the 3 major organs of articulation?
- Lips
- Tongue
- Soft palate
Describe the importance of a ventilation-perfusion match
Ideally, the amount of ventilation (VA) to a given area of lung should be matched with the amount of blood perfusing (Q) that area for the efficient exchange of oxygen and carbon dioxide
How is the V/Q ratio affected if perfusion excess ventilation?
V/Q ratio < 1
How is the V/Q ratio affected if ventilation excess perfusion?
V/Q ratio > 1
Explain how the effect of VA/q mismatch on gaseous exchange in the lungs is minimised
Localised hypoxia in under-ventilated areas of the lungs causes local vasoconstriction so that blood is diverted to better ventilated area
This allows for gas exchange to be at its most efficient and thus maintain a proper V/Q ratio
Describe how the V/Q ratio varies from apex of the lungs to the base
Because of the variations in perfusion and ventilation, the V/Q ratio varies from 3.3 at the apex of the lungs to 0.6 in the base
Name 3 clinical conditions leading to uneven ventilation
- Asthma
- COPD
- Emphysema
- Pneumothorax
- Pulmonary fibrosis
Give 3 causes of uneven blood flow may arise from
- Anatomica shunts
- Regional destruction to vascular bed by emphysema
- Pulmonary embolism or a tumour preventing blood flow to an area of the lung
a) What is alveolar ventilation?
b) What is the equation for alveolar ventilation rate
a) The rate of exchange of gas between the alveoli and the external environment
b) Va = Freq x (Vt - Vd)
Va = alveolar ventilation rate per min
Freq = frequency of respiration per min
Vt = tidal volume
Vd = dead space
Describe how pulmonary ventilation is distributed in the lungs in inspiration
Ventilation is not uniformly distributed in the lungs due to affects of gravity
Alveoli at top of lung are more expanded (bigger volume) than those at the bottom
Pleural pressure is less (more negative) at apex than base of lung, with inspiration pleural pressure decrease further
As inspiration begins, under inflated (smaller) alveoli at base of lung are more compliant to receive more of a tidal volume
What it the Alveolar-arterial (A-a) gradient
Measures the difference between oxygen concentration in the alveoli and arterial system
