Respiratory Defence Mechanisms

Front 1

Two kinds of mechanisms are involved in the security of the respiratory system:

Back 1

Protective mechanisms
Defensive mechanisms

Front 2

Protective mechanisms

Back 2

They protect the airways and lungs from invasion and penetration of harmful substances into the respiratory structures

Front 3

Defensive mechanisms

Back 3

Their role is to clean up respiratory system form the noxas which are present inside the system – to expel these harmful stimuli

Front 4

Protective mechanisms involves:

Back 4

Reflex protection
Nonreflex protection

Front 5

Reflex protection

Back 5

Apnoe – from the nasal cavity, stimulation of trigeminal nerve – endings by mechanical, chemical or cold stimuli – effect is the stop of breathing cycle in the phase of the end of expiration, also involves cardiovascular responses – bradycardia, hypertension as a part of the diving response (Kratschmer reflex)
example: cold nasal drops in newborns, infants
laryngeal constriction (apnoe) – sudden closure of the vocal folds with apnea mediated by the branches of vagus nerve
example: spicy or pungent meals – aspiration of the small particles

Front 6

Nonreflex protection

Back 6

Mechanical filtration of the inspired air
Electrostatic filtration electrically charged particles
Air conditioning system – warming, humidification – complete saturation with water vapor

Front 7

Defensive reflex mechanisms include

Back 7

Sneezing
Expiration reflex from the vocal folds
Sniffing
Aspiration reflex

Front 8

Sneezing

Back 8

stimulation of the trigeminal nerve endings by accumulated mucus, chemical stimuli – histamine, capsaicin, prostaglandins etc.

Front 9

Sneezing involves three phases

Back 9

Inspiratory phase –deep inspiration through the mouth prevent the possibility of inhalation of the noxa from the nose to more distal parts
Compresive phase – closure of glottis with simultaneous activity of expiratory muscles – increase of intrapleural pressure
Expulsion – sudden opening of the glottis with subsequent expulsion of the compressed air through the nose – m. levator veli palatini

Front 10

Role of Sniffing

Back 10

The role of sniffing is to identify olfactory stimuli due to redirection of inspired air from the middle nasal meatus to roof of the nasal cavity where the olfactory region is present

But during this maneuver the mucus is removed from the nasal cavity to the more distal parts of nasaopharynx, oropharynx from where this material could be coughed out or swallowed – therefore – this mechanism could be considered to play an important role in cleaning of the nose especially during rhinitis, or common cold.

Front 11

Aspiration reflex and its role:)

Back 11

Could be elicited from the oropharynx by stimulation of the nerve - endings of glossopharyngeal nerve
Powerful inspiratory efforts not interrupted by expiration, their role is to clean up the throat
Aspiration reflex has also very strong auto resuscitating potential in humans and in animals in experiment

Front 12

Expiration reflex from the vocal folds

Back 12

This reflex was explored during experiment in anaesthetized cats accidentally

Prof. Korpaš – from our department was the first scientist who described this reflex process
This reflex could be elicited from the oral side of vocal folds – aditus laryngis. The main role of the reflex is prevention of aspiration of fluids and alien bodies into the respiratory system, with subsequent strong expiratory efforts with the force of eliminating of this hazards out of the respiratory system

Front 13

Other reflex mechanisms

Back 13

Bronchoconstriction
Mucus secretion – through the parasympathetoc nervous system and through NANC system
COUGH

Front 14

COUGH

Back 14

The most important defensive mechanism,
characterized as a powerful expiratory effort
preceded by a deep inspiration.
Has also three phases:
Inspiratory phase, compression and finally expulsion of compressed air from the airways through the mouth

Front 15

Several types of nerve endings in the airways –

Back 15

Mechanosensors – RAR – sensitive to touch, foreign bodies, edema of mucosa, external compression
Chemosensors – C fibers – sensitive to chemical stimuli – capsaicin, histamine, tachykinines, other inflammatory mediators...
No body clearly knows what is the real cough receptor
TRPV1 – molecule is believed to be important in cough mediation

Front 16

ough can be too weak or absent:
:

Back 16

Due to damage of airway mucosa, disturbances of CNS, respiratory muscles fatigue  mucus stagnation in the airways  susceptibility to infection, formation of mucus plugs lead to impairment of alveolar ventilation and thus gas exchange

Front 17

Cough can be too strong:

Back 17

Sleep disturbances, cough syncope, fracture of the ribs, internal pneumothorax, nausea, vomiting, aspiration of food, choking

Front 18

Nonreflex mechanisms

Back 18

Mucociliary transport
Morphological changes of mucosa
Hypercrinia
Changes of cilliary system
Oxidants/antioxidants
Proteases/antiproteases
alpha1 antitrypsin, alpha2macroglobulin

Front 19

alpha1 antitrypsin, alpha2macroglobulin

Back 19

physiologically are in balance
congenital deficit of alpha1 antitrypsin – infant type of emphysema
acquired imbalance due to i.e. smoking – adult type of emphysema
due to damage of structures in the airways and lungs /elastic fibers etc/