structure of airways Flashcards
- What are trachea held open by?
- What property does cartilage provide the airway with?
- What is the name of the point at which the bronchi enter the lungs at?
Trachea held open by C-shaped cartilage rings (C-shaped - transport of substrate down oesophagus, with minimum resistance).
Mechanical stability Hilium
- Describe type I and type II alveolar cells and give their function
Type I - Very thin delicate barrier, large and flat in shape. facilitates GE
Type II - Replicate to replace type I; secrete surfactant (reduces surface tension), antiproteases; Xenobiotic metabolism
- 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 is the basic function of the respiratory airways and what are these functions facilitated by?
Conduit to conduct O2 to the alveoli and conduct CO2 out of the lung - Gas Exchange
- Facilitated by
Mechanical stability (Cartilage)
Control of calibre (Smooth muscle)
Protection and cleansing
- What are each of the lateral walls of the nasal cavity called?
Superior, middle and inferior nasal conchae
- What is the purpose of conchae?
Highly vascular - contribute to warming and humidification of intra-nasally-inhaled air
Nasal hairs filter out large particles
- What do the conchae, meatuses and paranasal sinuses produce?
- What assists in the removal of mucous and debris from the nasal cavity?
- What is the pharynx a path for?
Mucous → Trap debris
Cilia
Common passageway for food, liquids and air.
- What is embedded within the smooth muscle ring?
- What does contraction of this smooth muscle lead to?
Inferior portion of submucosal gland
Contraction of smooth muscle stimulates secretion into epithelial lining Also closes airway to prevent something going down airways
- Describe the structure of the airway wall
Smooth muscle at the outside of airway-> basement membrane-> epithelium -> mucociliary
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
blood vessels between basolateral membrane and smooth muscle
List the categories of airway cell types
Life Can Seem Crazy, Not Very Interesting
- Lining cells
Ciliated, intermediate, brush, basal
- Contractile cells
Smooth muscle (airway, vasculature)
- Secretory cells
Goblet (epithelium), mucous, serous (glands) - Connective tissue
Fibroblast, interstitial cell (elastin, collagen, cartilage) - Neuroendocrine
Nerves, ganglia, neuroendocrine cells, neuroepithelial bodies - Vascular cells
Endothelial, pericyte, plasma cell (+ smooth muscle) - Immune cells
Mast cell, DC, lymphocyte, eosinophil, macrophage, neutrophil
- What do mucin granules contain and how is this substance hydrated?
Mucin granules contain mucin in goblet cells
highly condensed forms of mucin requires hydration
hydrated through water absorption in trachea
Expansion of mucin generates expansive mucous
- What are the functional units of the airway’s submucosal glands, what is their function and what are their different types?
Functional unit - Acini (secrete mucous extracellularly into the collecting duct traversing to ciliated duct, the cilia waft the mucous out of gland)
Serous acini - secrete anti-bacterial enzymes (serous cells produce more dilute mucous). more watery to help wash out viscous substance Mucous acini - secrete mucous
Glands also release water and salts
- What is the arrangement of ciliary structures?
9+2 microtubule arrangement
- Briefly explain the process of beating cilia and describe the rhythm at which they beat
Cilia efficiently move mucous
Metachronal rhythm Backwards cilia sequentially move through alternating forward and backward movements
- List all the airway epithelium functions
- Secretion of mucin, water and electrolytes (Components of mucous + plasma, mediators)
- Movement of mucous by cilia - Mucociliary clearance
- Physical barrier against inhaled insult
- Production of regulatory and inflammatory mediators:
- List the inflammatory mediators
NO secreted by nitric oxide synthase (NOS)
CO 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
outline the function of smooth muscle in epithelium airways (secretion)
- Secretion - Smooth muscle cells produce small amounts of secretions eg chemokines, cytokines and mediators. chemokines lead to recruitment of inflammatory cells; smooth muscle subsequently gets involved in the inflammatory process
- In response to cytokines however, NOS is up-regulated (inc no. of receptors on its surface) ; enhancing secretion of NO, accentuating its effect on cilia and inflammation
- COX enzymes produce more prostaglandins;
outline the function of smooth muscle in epithelium airways (tone and structure)
- Tone (airway calibre)Level of relaxed or contracted the airway is
contracts when needed eg if food goes down the wrong way - StructureInflammation and smooth muscle hypertrophy occurs through proliferation of smooth muscle cells, in addition to hyperplasia.
- What % of cardiac output does this system represent and what volume of blood flow goes to airway mucosa?
1-5%
Blood flow to airway mucosa = 100-150 mL/min/100g tissue The tracheo-bronchial systemic circulation blood flow is AMONG THE HIGHEST to any tissue
- How does blood return from tracheal circulation?
- How does blood return from bronchial circulation to both sides of the heart?
Systemic veins
Via bronchial and pulmonary veins
- List all the functions of tracheo-bronchial circulation
- Direct gaseous exchange between systemic circulation in the tissue of sub-epithelial micro-vasculature.
- Contributes to warming and humidification of inspired air
- Clearance of inflammatory mediators and 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)
- 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 NO - NO is a NT of neuronal pathway that dilates and opens airways
- List the regulatory and inflammatory mediators for the control of airway function
Histamine arachidonic metabolites (prostaglandins and leukotrienes) cytokines chemokines proteinases (e.g. neutrophil elastase).
