The Respiratory System Flashcards
Upper Respiratory
System
nasal cavity
pharynx
larynx
function
Humidify & warm air
Defence – mucus and cilia
Sensory
Speech
Lower Respiratory
System
trachea
primary bronchi
lungs
functions
GAS EXCHANGE
Defence
Metabolic
Airway Resistance (= 1/conduction)
Airway resistance is the resistance to the flow of air through the respiratory tract during inhalation and expiration.
Proportional to 1/radius4
But conduction summative
huge numbers of respiratory bronchioles
small airways make a small contribution to total Resistance
Conducting zone bronchioles largest influence
Lung epithelium
Lining cells in airway
Specialisation changes down the airway
Bronchi
ciliated, goblet, glandular
Bronchioles
ciliated, non-ciliated, goblet, club cells
Alveoli
Squamous, cuboidal
Parenchyma
Respiratory Bronchiole (RB)
Alveolar Duct (AD)
Alveoli
Alveolar epithelial cells (pneumocytes)
Type I
Very large surface area
cover 95% of alveolus
10% of cells
squamous
gas exchange
Type II cells
cuboidal
majority of cells
secretory
surfactant
precursors for type I
Surfactant
Produced by type II alveolar epithelial cells
Lipid (90%) – mostly phospholipid
Proteins – SP-A, -B, -C, -D
Reduces surface tension
prevents alveolar collapse (atelectasis)
Innate immunity function
Instilled into babies with Infant Respiratory Distress Syndrome
Beractant (bovine)
Pumactant (synthetic, lipid only)
Lung at Birth
Lung epithelium develops in the last trimester of pregnancy
Maturation stimulated by corticosteroids in premature babies
Lung is fluid filled in foetus - must rapidly empty
Surge in corticosteroids and catecholamines at birth
Activation of absorptive channels
Epithelial Sodium Channels (ENaC)
Pressure changes (squeeze through birth canal)
Caesarian section – reduced drive for fluid absorption
Blood supply to the lungs – two circulatory systems
Pulmonary circulation
Artery flows directly from the right ventricle
LOW oxygen
HIGH flow
LOW pressure
Capillaries pass around the alveoli
Pulmonary vein returns oxygenated blood to left heart
Bronchial circulation
From aorta (left ventricle)
HIGH pressure
Supplies oxygen and nutrients the conducting airways
Not involved systemic respiration processes
Only 2% of cardiac outflow
Sensory afferent pathways from the lung (myelinated)
Send impulses via vagus to medullary centres
Slowly adapting stretch receptors (SAR)
Stimulated by stretch receptors in airway smooth muscle
Elicit reflexes
Shortened inspiration
Hering-Breuer reflex
Promotion of expiration following steady inflation
Prevents over-inflation of lung
Rapidly adapting stretch receptors (RAR)
Stimulated by sudden, sustained inflation
Also by ‘irritant receptors’ among epithelium
Elicit reflexes:
Cough
Bronchoconstriction
Mucus secretion
Sensory afferent pathways – Unmyelinated fibres
Pulmonary and bronchial C fibres
Located close to blood vessels (J receptors)
Exogenous stimuli
Noxious agents in air
Endogenous stimuli
inflammatory agents generated by the body
Reflex bronchoconstriction & mucus secretion
Pleural membranes
Double membrane surrounding the lungs
Left & right pleura anatomically distinct
Collapsed lung (pneumothorax) usually only affects one lung
Normally very small amounts of pleural fluid between membranes (few ml)
Serous fluid
Lubricant
Respiratory muscles
inspiratory
expiratory
internal intercostal muscles
external intercostal muscles
diaphragm
abdominals
