Structure and function of the airways Flashcards
What type of branching do the airways do?
-dichotomus
What provides the mechanical stability to the lungs?
-cartilage
What are the lobes of the lungs?
3 right lung lobes:
- superior
- middle
- inferior
2 left lung lobes:
- superior
- inferior
What are the different parts of the bronchus?
- primary
- secondary (lobar)
- tertiary (segmental)
Compare Type I and Type II cells in the alveolar unit.
Type I cells:
- very thin, delicate barrier (facilitates gas exchange)
- cover 95% of alveolar surfaces
Type II cells:
- replicate to replace Type I cells
- secrete surfactant (reduced surface tension), antiproteases
- xenobiotic metabolism
- greater in number but only cover 5% of surfaces
What are the basic functions of the respiratory airways and what is this facilitates by?
- getting air efficiently to the gas exchange region
- keeping the pipework clear
- conduit to conduct O2 to alveoli
- conduit to conduct CO2 out of the lung
- gas exchange
Facilitated by:
- mechanical stability (cartilage)
- control of calibre (smooth muscle)
- protection and ‘cleansing’
What is the pharynx?
-common passageway for food, liquids and air
What is the conchae?
- highly vascular- contribute to warming and ‘humidification; of intra-nasally-inhaled air
- nasal hairs filter out large particles
Give the cells types which are lining cells.
- ciliated
- intermediate
- brush
- basal
Give the cells types which are contractile cells.
-smooth muscle (airway, vasculature)
Give the cells types which are secretory cells.
- goblet (epithelium)
- mucous
- serous (glands)
Give the cells types which are found in connective tissue.
- fibroblast
- interstitial cell (elastin, collagen, cartilage)
Give the cells types which are neuroendocrine cells.
- nerves
- ganglia
- neuroendocrine cells
- neuroepithelial bodies
Give the cells types which are vascular cells.
- endothelial
- pericyte
- plasma cell (+ smooth muscle)
Give the cells types which are immune cells.
- mast cell
- dendritic cell
- lymphocyte
- eosinophil
- macrophage
- neutrophil
Which cell secretes mucin?-
-by guinea pig tracheal goblet cell
expansion of intra-granular mucin upon secretion; to ATP, Real Time
Which cell secretes mucin?
-by guinea pig tracheal goblet cell
expansion of intra-granular mucin upon secretion; to ATP, Real Time
What do serous cells secrete?
-anti-bacterial enzymes (e.g lysozyme)
What do the submucosal glands also secrete, other than mucus and enzymes?
-water and salts
What is an axoneme?
-a strand of a cilium
How many cilia are there roughly per ciliated cell?
-about 200 cilia
What are the functions of the airway epithelium?
- secretion of mucins, water and electrolytes, components of ‘mucus’
- movement of mucus by cilia- mucociliary clearance
- physical barrier
- production of regulatory and inflammatory mediators:
- NO via nitrous oxide synthase
- CO
- arachidonic acid metabolites (e.g prostaglandins)
- chemokines
- cytokines
- proteases
What are the functions of the airway epithelium?
- secretion of mucins, water and electrolytes, components of ‘mucus’
- movement of mucus by cilia- mucociliary clearance
- physical barrier
- production of regulatory and inflammatory mediators:
- NO via nitrous oxide synthase NOS
- CO via haemeoxygenase HO
- arachidonic acid metabolites (e.g prostaglandins) via COX
- chemokines
- cytokines
- proteases
What happens to airway smooth muscle during inflammation?
Structure:
- hypertrophy
- proliferation
Tone (airway caliber):
- contraction
- relaxation
Secretion:
- mediators
- cytokines
- chemokines
What are the secretory functions of airway smooth muscle during inflammation?
inflammation
bacterial products
-cytokines stimulate NOS to release NO, COX to release prostaglandins, cytokines, chemokines and adhesion molecules
-the released cytokines, chemokines and adhesion molecules stimulate inflammatory cell recruitment
Tell me about the trachea-bronchial circulation (systemic).
- 1-5% of cardiac output
- blood flow to airway mucosa = 100-150 ml/min/100g tissue
- blood returns from tracheal circulation via systemic veins
- blood returns from bronchial circulation to both sides of heart via bronchial and pulmonary veins
What are the functions of the trachea-bronchial circulation?
- good gas exchange directly between airway tissues and blood
- contributes to warming of inspired air
- contributes to humidification of inspired air
- clears inflammatory mediators
- clears inhaled drugs (good/bad, depending on drugs)
- supplies airway tissue and lumen with inflammatory cells
- supplies airway tissue and lumen with proteinaceous plasm (‘plasma exudation’)
What is the parasympathetic innervation of the airways?
Parasympathetic (cholinergic) ‘motor’ pathway
- ACh neurotransmitter
- nodose ganglion
- vagus nerve
- causes restriction and increased mucous secretion (submucosal glands stimulated)
What is the effect of the sympathetic innervation on the airways?
- results in relaxation to increase amount of airflow
- adrenaline from adrenal gland also has same effect.
-NO release (spinal cord- cervical thoracic ganglion) causes relaxation
What is respiratory disease?
- loss of homeostatic control leads to pathophysiology and clinical symptoms of respiratory disease
- loss of ‘airway’ control
Examples of respiratory diseases?
- asthma (5% of population)
- chronic obstructive pulmonary disease (COPD)
- cystic fibrosis (CF)
What is the 4th cause of death in the UK and USA?
-COPD
What is asthma?
-a clinical syndrome characterised by increased airway ‘responsiveness’ to a variety of stimuli - airway obstruction
- airflow obstruction varies over short periods to time and is reversible (spontaneously or with drugs)
- dyspnoea, wheezing and cough
- airway inflammation- re-modelling
What is the pathology of airway inflammation?
- basement membrane thickening
- epithelial fragility
- mucus plug in lumen
- vasodilation- congested vessels
- cellular infiltration
What is the pathology of asthma?
- excess mucous- goblet cell hyperplasia
- sensory nerve activation, cholinergic reflex- mucus hyper secretion and bronchoconstriction
- subepithelial fibrosis
Inflammatory mediators increase e.g cytokines and Bfs
- mast cells
- eosinophils
- Th2 lymphocyte
- fibroblasts
