Structure And Function Of Airways Flashcards
What kind of branching does the lung have
Dichotomous
Every tube splits into two
What area trachea held open by
C shaped cartilage rings
What property does cartilage provide the airway with
Mechanical stability
Why does the back of the trachea not have cartilage
To allow oesophagus to run down the back to swallow food
What is the name of the point at which the bronchi enter the lungs at?
Hilium
Type I cells alveolus
Facilitate gas exchange
Very thin delicate barrier
Type II cell alveolus
- Replicate to replace type I cells
- Secrete surfactant (reduces surface tension) and antiproteases
- Xenobiotic metabolism (breakdown of drugs and noxious chemicals that enter alveoli)
Explain the distribution of type I and type II alveolar cells in the alveolar region
Type I - Cover ~95% of alveolar surface; lesser in number than type II, but are much larger.
Type II - Greater numbers than type I, but only cover ~5% of surface.
What do macrophages and fibroblasts do
Clean debris and viruses
Produce ECM matrix holding the whole thing together
What part of the alveolar region is where gas exchange takes place?
Alveolar sac
- What is the main function of the respiratory airways?
To conduct O2 to alveoli and CO2 out of the lung (gas exchange)
This is facilitated by cartilage which gives mechanical stability, control of calibre (smooth muscle) and protection + cleaning mechanisms
Pharynx function
Common passageway for food liquid and air
What is the function of conchae
Highly vascular contribute to warming and humidification of intra nasally inhaled air
What do nasal hairs do?
Filter out large particles
What do the conchae, meatuses and paranasal sinuses produce?
Mucous traps debris
Describe the structure of the airway wall
Submucosal gland partially embedded within the contractile smooth muscle ring; goblet cells within the epithelium contribute to the production of mucous, lies superficially above the ciliated epithelial layer
Mucociliary transport to release the pollutants
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What assists in the removal of mucous and debris from the nasal cavity?
Cilia
Lining cells
- Ciliated
- Intermediate
- brush
- basal
Contractile cells
Smooth muscle
Secretory cells
- Goblet (epithelium)
- Mucous
- ## Serous (glands)
Connective tissue
Fibroblasts
Interstitial cell
Neuroendocrine cells
- Nerves
- Ganglia
- Neuroendocrine cells
- Neuroepithelial bodies
Vascular cells
- Endothelial
- Pericyte
- Plasma cell
- Smooth muscle
Immune cells
- Mast cell
- Dendritic cell
- Lymphocyte
- Eosinophil
- Macrophage
- Neutrophil
What do mucin granules contain and how is it hydrated
Mucin granules contain mucin in goblet cells; highly condensed forms of mucin requires hydration, this is hydrated through water absorption in trachea ( Airway liquid comes into granule→ Expansion of mucin generates expansive mucous
Why do the epithelial cells have so many mitochondria?
Cillia need energy to move and waft mucous along surface
Acini
Mucous producing units
What do serous acini secrete?
Anti-bacterial enzymes e.g. lysozyme
Water and salts like Na+ and Cl-
What is the arrangement of ciliary structures?
9+2 microtubule arrangement
What is the rhythm of ciliary beating?
Metachronal- different lines of ciliary hair move at different times to waft mucous down to back of throat
List all the airway epithelium functions
- Secretion of mucin, water and electrolytes (Components of mucous + plasma, mediators)
- Movement of mucus **by cilia - Mucociliary clearance
- Physical barrier against inhaled insult
- Production of regulatory and inflammatory mediators:
List the inflammatory mediators
Nitric oxide secreted by nitric oxide synthase (NOS) which could control cilia beating
Carbon Monoxide by haem oxygenase (HO); enzyme catalyses the degradation of haem to produce biliverdin, Fe2+ (ferrous iron) and CO. Products activate vasodilatory pathways
Arachidonic acid metabolites (COX, prostaglandins)
Chemokine (IL-8)
Cytokines (GM-CSF)
Proteases
- What does brown-staining on a histological section in the human airway show?
Anti-NOS antibody results in brown staining to identify NOS
Significant presence of NO exhibits a regulatory function on ciliary beat - high presence within the epithelium
What does contraction of this smooth muscle lead to?
Contraction of smooth muscle stimulates secretion into epithelial lining
Also closes airway to prevent something going down airways
What are the (3) functions of airway smooth muscle cells?
- Structure of airway- contribute to it
- Tone (airway caliber) and contract + relax
- Secretion of mediators, cytokines, chemokines- normally it is a little
Under inflammation
- Structure- contribute more towards structure via hypertrophy and proliferation e.g. in asthma
- Still contribute to tone
- Secrete a lot more mediators, cytokines, chemokines
- Produce prostaglandins, adhesion + NO molecules
What is the name of the airway vasculature?
Tracheo-bronchial systemic circulation
How does blood return from tracheal circulation?
Systemic veins
How does blood return from bronchial circulation to both sides of the heart?
Bronchial and pulmonary veins
List all the functions of tracheo-bronchial circulation (4)
- Direct gaseous exchange between systemic circulation in the tissue of sub-epithelial micro-vasculature. Highly vascular system facilitates direct gas exchange between tissues and blood
- Direct good gas exchange (directly between airway tissues and blood)
- Contributes to warming and humidification of inspired air
- Clearance of inhaled drugs (Benefit is dependent on the mechanism of delivery of drug)
- Supplies airway tissue and lumen with inflammatory cells; in addition to proteinaceous plasma (mechanism of plasma exudation)
Nerves- what different types of nerves control airway function
- Parasympathetic- cholinergic
- Nitrous oxide sympathetic adrenergic pathway
- Sensory nerves
Outline the parasympathetic ‘motor’ pathway for airway control
Innervation via vagus nerve through corticospinal tract, motor pathway
Secretion of ACh NT via cholinergic synapse of postganglionic fibre and gland
This stimulates the bronchostriction and contraction of smooth muscles within trachea + stimulates submucosal glands to secrete mucous
Outline the “sympathetic” and nitric oxide (NO) pathway for airway control
Sympathetic - Adrenergic reflex causes bronchodilation, smooth muscle relaxes, dilating the airways
Adrenaline is secreted by adrenal gland, and directly relaxes the airways
Nitric Oxide - NO is a NT of neuronal pathway that dilates and opens airways
Adrenaline and the neuronal pathway producing nitric work to relax the airways
We DON’T have sympathetic nervous relaxant pathway which release NA- we have NO secreting nerves instead which causes airway smooth muscle to relax
Name 3 respiratory diseases associated with loss of airway control
Asthma, COPD and cystic fibrosis - all common conditions
(These diseases are associated with abnormalities of airway inflammation and obstruction)
