The Respiratory system: Anatomy Flashcards
Upper respiratory tract components
Nose , pharynx and larynx
Upper respiratory tract functions
Humidify and warm air
defence-mucus and cilia
sensory, speech
Lower respiratory tract components
Trachea, lungs and primary bronchi (first 2 branches from trachea)
Lower respiratory tract functions
GE
defence
metabolic
Trachea
Rings of cartilage surrounding it interspersed by smooth muscle which can constrict trachea and shut off air supply to lung- incr velocity flow with constriction
Parenchyma
Part of lungs involved in GE: alveoli, alveolar ducts and terminal ad respiratory bronchioles, pulmonary arteriole and vein
ie respiratory bronchioles down
Conducting zone
air passages
top of trachea to start of respiratory bronchioles
Lung branches
Tube divides up to 23x till get to terminal part of the lung
1st 15 or so just to get tubes to right place
Change from psuedostratified columnar in bronchi to cuboidal in terminal and respiratory bronchioles
LArge incr in volume for respiratory bronchioles
What type of blood supply do respiratory bronchioles have
Pulmonary
Airway resistance mathematically
1/resistance
1/radius^4
why is conduction summative
small airways make a small contribution to total resistance
Many respiratory bronchioles
What bronchioles have the largest influence over conduction
conducting zone ones
What happens in diseases
airway resistance increases
inflammation/thickening of airway wall eg in asthma
Tightened smooth muscles constrict airway
Obstruction with mucus
All these factors narrow airway
Get smooth muscle growth and fibrosis (thickening and scarring of connective tissue)
lung epithelium
lining cells in the airway
Bronchi epi
ciliated, goblet and glandular (good diagram)
Bronchioles epi
ciliated, non-ciliated, goblet , club cells (secretory)
Alveoli
Squamous, cuboidal
Airway innervation (conducting airways)- to and from CNS
Sensory afferent nerves from airway epithelium and smooth muscles signal to brain
Autonomic fibres to glandular epithelium and smooth muscles from CNS
Innervation parasympathetic/sympathetic?
Parasympathetic nervous system drives contraction
Parasympathetic branches of the vagus nerve
Little sympathetic innervation: B adrenoreceptors on airway smooth muscle stimulated by circulating adrenaline
Parasympathetic NS receptors
muscarinic and nicotinic cholinergic receptors.
Sympathetic NS receptors
alpha, beta 1 and beta 2
Respiratory unit
Massive network of airways and air sacs
Pneumocytes
alveolar epithelial cells
Type I pnuemocytes
Large SA, cover 95% of alveolus but only 10% of cells, squamous
GE
Type II pnuemocytes
Cuboidal mostly
Secretory: surfactant
Precursors for type I- differentiate to produce them
Surfactant
90% lipid, mostly phospholipid
Reduces surface tension and prevents alveolar collapse
Innate immunity function
Infant Respiratory Distress syndrome
Give premature babies surfactant via tubes to help lung function because not fully formed
Beractant (bovine- cow/animal)
Pumactant (synthetic, lipid only)
Lung at birth
Lung epi develops in last trimester of pregnancy: Maturation stimulated by corticosteroids given to premature babies
Lung is fluid filled in foetus- needs to rapidly empty: surge in corticosteroids and catecholamines (circulating adrenaline) at birth, activation of absorptive channels incl ENaCs, pressure changes (squeeze through birth canal)
Caesarian- reduced drive for fluid absorption
2 circulatory systems for blood supply to the lungs
Pulmonary circulation and bronchial circulation
Pulmonary circulation
Artery flows directly from right ventricle
Low O2, high flow, low pressure
Low pressure because huge network, so high flow
Capillaries pass around alveoli and pulmonary vein returns oxy blood to heart
Bronchial circulation
From aorta (left ventricle)
high pressure
supplies O2 and nutrients to the conducting airways
Not involved in respiration
Ventilation
Automatic and controlled by CNS
Neuronal control of breathing
add to this
(see diagram)
Respiratory center in medulla sends nerve impulses down spinal cord to respiratory muscles
Chemoreceptors in blod detect pH, CO2 and O2 changes, signal to respiratory center
Mechanoreceptors in lung and chest wall also signal
Muscle innervation
somatic motor nerves and autonomic nerves
Somatic motor nerves
innervate skeletal muscles in thorax
Phrenic nerve: innervates diaphragm,pulls muscle downwards and draws air into lungs, allowing ventilation
and Intercostal nerves
Autonomic nerves
Bronchial Supply smooth muscle and secretory cells: - branch from vagus -reflex bronchospasm and mucus secretion -important in asthma
Sensory afferent pathways from the lung (myelinated)
send impulses via vagus to medullary centres
Slowly adapting myelinated
stimulated by stretch receptors in airway smooth muscle
Elicit reflexes:
Hering Breuer reflex:
-promotion of expiration following steady inflation
-prevents over inflation of lung
Rapidly adapting stretch receptors
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 BVs
Exogenous, endogenous stimuli
Reflex bronchoconstriction and mucus secretion
Exogenous stimuli
Noxious agents in air
Endogenous stimuli
Inflammatory agents generated by the body
Cough reflex
Stimulation of irritant receptors- sensory nerve conveys signal to medulla
Motor nerves signal to skeletal muscle
Glottis closes
Abdominal and internal intercostal muscles contract rapidly
Intrapulmonary pressure rises
Glottis opens leading to cough
Pleural membrane
double membrane around the lungs
Collapsed lung
only affects one lung, other can still function because anatomically distinct
Pleural fluid
Between 2 membranes, allows them to move along side each other, surface tension holds them together
Lubricant
contraction of diaphragm and external intercostal muscles leads to
incr lung volume
internal pressure falls (Boyle’s Law)
Air drawn into lungs
What is elasticity an indication of
how well performing the lung is
static compliance
at zero flow
end of inspiration or expiration
Dynamic compliance
compliance during active flow
What is compliance altered by
increased by surfactant
incr in emphysema (loss of elastic tissue, easier to stretch)
decr in pulmonary fibrosis (scarring, harder to stretch)
Metabolic function of the lung
club, vascular cells, fibrinolytic
club cells detoxify inhaled substances
Vascular cells inactivate some circulating hormones
Vascular cells activate Angiotensin I, converted to Ang II by Ang converting enzyme
Fibrinolytic function: breakdown of fibrin in blood clots, lung source of fibrinolytic enzymes
What is pulmonary compliance
measure of elasticity of lung
