6.4: Structure and function of the airways Flashcards
What is dichotomous branching
Division 2:2:2
Example of dichotomous branching in airway system
Trachea to bronchi then two smaller bronchi
Mechanical stability of lungs
C shaped cartilage in trachea
More cartilage in bronchi
Where does gas exchange occur in the lungs
Alveoli
What cells are inside the alveoli
Macrophages
Type 1 cells
Fibroblasts
Characteristics of Type 1 cells
Very thin -95% of alveolar surface covered
Delicate barrier facilitating gas exchange
Characteristics of type 2 cells
Replicate to replace type 1 cells
Secrete surfactant
Xenobiotic metabolism
Greater in numbers but only cover 5% of surface
Functions of pipes in the airway
Conduct O2 to alveoli
Conduct CO2 out of lung
Airway pipes are facilitated by
Mechanical stability (cartilage)
Control of calibre (smooth muscle)
Protecting and cleansing
Division of nasal passages
Conchae
Pharynx
Characteristics of nasal conchea
Highly vascular, contribute to humidification of intra-nasally-inhaled air
Function of nasopharynx
Common passageway for food, liquids, air
Mucus ciliary transport
Smooth muscle contracts and causes mucus out of the Submucosal gland
Goblet cells produce mucus which lines cilia
Forms first line of defence against infection- traps pathogens
Main cell types of lining cells
Ciliated
Intermediate
Club
Brush
Basal
Main cell types of contractile cells
Smooth muscle
Main cell types of secretory cells
Goblet, mucous, serous (glands)
Main cell types of neuroendocrine
Nerves
Ganglia
Neuroendocrine cells
Neuroepithelial bodies
Main cell types of vascular cells
Endothelial, pericyte, plasma cell
Main cell types of immune cells
Mast cell
Dendritic cell
Lymphocytes
Eosinophil
Macrophage
Neurtophil
Mucous cells secrete
Mucus
Serous cells secrete
Anti-bacterial enzymes e.g lysozomes
Glands also secrete
Water and salts
3 components of mucus
Mucins
Water
Electrolytes
(+ plasma, mediators)
Mucocillary clearance is
Movement of muspcus by cilia
Functions of airway epithelium
Physical barrier
production of regulatory and inflammatory mediators
Movement of mucus by cilia
Secretion if mucins water and electrolytes
What 6 regulatory and inflammatory mediators does the airway epithelium secrete
Nitric oxide
Carbon monoxide
Arachidonic acid metabolites
Chemokines
Cytokines
Proteases
NOS expression in human airway epithelium
Cilia speed up
Lots of nitric oxide synthase which produces NO
Airway smooth muscle functions 3
Structure
Tone - contract and relax
Secretion - mediators, cytokines, chemokines
How can Inflammation of the airway alter structure
Hypertrophy
Proliferation
Following inflammation how does the airway smooth muscle respond
Produce NO, prostaglandins, cytokines, chemokines
Resulting in inflammatory cell recruitment
(Not necessarily a good thing)
What is the airway vasculature
Tracheo-bronchial circulation
Bronchial arteries arise from many sites on
Aorta
Intercostal arteries
And others
Blood returns from tracheal circulation via
Systemic veins
Blood returns from bronchial circulation to both sides of the heart via
Bronchial and pulmonary veins
Functions of tracheo-bronchial circulation
(Good gas exchange)
Warming inspired air
Humidification of inspired air
Clears inflammatory mediators
Clears inhaled drugs
( supplies airway tissue and lumen with inflammatory cells)
(Supplies airway tissue and lumen with proteinaceous plasma)
4 controls of airway function
Nerves
Regulatory and inflammatory mediators
Proteinases
Reactive gas specied
Nerves controlling airway function
Parasympathetic - cholinergic
Sensory
(Sympathetic- cannot open up smooth muscle)
4 regulatory and inflammatory mediators of airway function
Histamine
Aravhidonic acid metabolites
Cytokines
Chemokines
Innervation of the airways (choking response)
Sensory nerves relay information to the brain
Cholinergic reflex - causes smoothmuscle contraction where food is stuck
Cough reflex
Adrenaline secreted and causes airway smooth muscle to relax and open airways
NO also causes smooth muscle relaxation
3 respiratory diseases with loss of airway control
Asthma
COPD
Cystic fibrosis
(Airway inflammation- airway obstruction)
How many mediators do cells produce
More than one mediator; which do more than one thing
What causes the airway to relax
NOS-containing nerves
Adrenaline
What precipitates lung disease
Loss of homeostatic control
