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Airways Notes

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Lecture 4 Airways

Describe the structure of the airways and alveoli

Trachea

Explain the function of the conducting zone and respiratory zones o Conducting zone
 Made up of

• Nose

• Pharynx

• Larynx

• Trachea o Ciliated Pseudostratified, columnar epithelium o Lamina propria=where immune cells are

• Bronchi

• Bronchioles o No cartilage o Kept open by radial traction (COPD= decreased traction_

• Terminal bronchioles
 Series of interconnecting cavities & tubes both outside and within the lungs
 Function is to filter, warm, and moisten air and conduct it into the lungs o Respiratory zone
 Site of O2 and CO2 exchange with the blood
 Respiratory bronchioles and the alveolar ducts =10% Alveoli = 90%
 Alveoli

• Look same, but functionally very different depending on position Describe the protective reflexes o Sneeze

o Gag

o Cough

Describe the function of Clara cells, type 1 & 2 pneumocytes, alveolar macs &
fibroblasts o Clara cells
 Dome-shaped cells with short Microvilli

 Found in small airways (bronchioles) of lungs
 May secrete glycosaminoglycans to protect bronchiole lining o Type I pneumocytes
 Simple squamous alveolar cells (large, thin)
 Responsible for gas exchange in alveoli
 Cover majority of surface area
 Not as numerous (half) ad type II o Type II pneumocytes
 Granular and cuboidal
 Produce surfactant to reduce tension (Respiratory Distress Syndrome of Newborn in premature babies without it) o Alveolar macrophages
 Eat bacteria, clean off particles such as dust and microorganisms from respiratory surfaces
 Engulf mycobacterium tuberculosis (but bacteria live/thrive in macs) o Fibroblasts

State the relationship between pressure, flow and resistance o Poiseuille's Law R = 8hl pr4

• R Resistance of tube

• h Viscosity

• l Length

• r Radius
 Radius (and therefore resistance) of bronchi depends upon

• Smooth muscle tone

• Lung volume (larger volume pulls open airways by radial traction) Explain why resistance to flow is greater in trachea and medium sized bronchi than terminal bronchioles o Resistance not very high in bronchioles usually (like tying lots of straws together) o Cancer/tumours increases resistance Describe and explain effect s of acetylcholine, adrenaline, histamine & CO2 on bronchial smooth muscle and airflow o Acetylcholine (PSNS)
 Smooth muscle contraction
 Bronchoconstriction
 Muscarinic receptors
 Treat asthma with ANTIMUSCARINICS (e.g. ipratropium) o Adrenaline (SNS)
 Smooth muscle relaxation
 Bronchodilation
 B2-adrenoreceptor
 Salbutamol activates this by binding receptor (ventolin inhaler, also labour) o Histamine
 Bronchoconstriction
 H1 receptors, smooth muscle o CO2
 Bronchodilator

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