Airways Notes

Lecture 4

Airways

• Describe the structure of the airways and alveoli

• Explain the function of the conducting zone and respiratory zones

  • Conducting zone

    • Made up of

      • Nose

      • Pharynx

      • Larynx

      • Trachea

        • Ciliated Pseudostratified, columnar epithelium

        • Lamina propria=where immune cells are

      • Bronchi

      • Bronchioles

        • No cartilage

        • 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

  • 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

  • Sneeze

  • Gag

  • Cough

• Describe the function of Clara cells, type 1 & 2 pneumocytes, alveolar macs & fibroblasts

  • Clara cells

    • Dome-shaped cells with short Microvilli

    • Found in small airways (bronchioles) of lungs

    • May secrete glycosaminoglycans to protect bronchiole lining

  • 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

  • Type II pneumocytes

    • Granular and cuboidal

    • Produce surfactant to reduce tension (Respiratory Distress Syndrome of Newborn in premature babies without it)

  • Alveolar macrophages

    • Eat bacteria, clean off particles such as dust and microorganisms from respiratory surfaces

    • Engulf mycobacterium tuberculosis (but bacteria live/thrive in macs)

  • Fibroblasts

• State the relationship between pressure, flow and resistance

  • 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

  • Resistance not very high in bronchioles usually (like tying lots of straws together)

  • Cancer/tumours increases resistance

• Describe and explain effect s of acetylcholine, adrenaline, histamine & CO₂ on bronchial smooth muscle and airflow

  • Acetylcholine (PSNS)

    • Smooth muscle contraction

    • Bronchoconstriction

    • Muscarinic receptors

    • Treat asthma with ANTIMUSCARINICS (e.g. ipratropium)

  • Adrenaline (SNS)

    • Smooth muscle relaxation

    • Bronchodilation

    • B2-adrenoreceptor

    • Salbutamol activates this by binding receptor (ventolin inhaler, also labour)

  • Histamine

    • Bronchoconstriction

    • H1 receptors, smooth muscle

  • CO₂

    • Bronchodilator

    • One of the most potent relaxants of smooth muscles and vasodilator

Lung volumes and capacities

• Define static and dynamic lung volumes

  • Static volumes

    • Ones that DON’T depend on rate they are inspired or exhaled

    • VT, IRV, ERV, VC, IC, RV, TLC, FRC

  • Dynamic volumes

    • Ones that are dependent on the rate at which they happen

    • FVC

• Use spirometer, vitalograph & peak flow meter to measure lung volumes & interpret data

  • Look at physiology practical

• Define given typical values for…

  • Tidal volume

    • Lung volume representing the normal volume of air displaced between normal inspiration and expiration when extra effort is not applied

    • 500ml or 7ml/kg bodyweight

  • Respiratory rate

    • Number of breaths taken within a set amount of time (60 seconds)

    • Healthy adult at rest is usually given as 12-18 breaths per minute

    • Newborns: 30-40 breaths per minute

  • Total lung capacity (TLC)

    • Maximum volume to which the lungs can be expanded with the greatest possible inspiratory effort

    • Equal to the vital capacity (VC) plus the residual volume (RV)

    • Approximately 5800 ml

  • Vital capacity

    • Max amount of air person can expel from their lungs after max inspiration

    • Equal to inspiratory reserve v. plus tidal volume plus expiratory reserve v.

    • Measured by a spirometer

    • Normal adult: between 3 and 5 litres

  • Functional residual capacity (FRC)

    • Air present in lungs (esp. parenchyma tissues) at end of passive expiration

    • Sum of Expiratory Reserve Volume (ERV) and Residual Volume (RV)

    • Approximately 2400 ml in a 70 kg, average-sized male

  • Residual volume

    • Volume of gas remaining in the lung at the end of a maximal exhalation

    • 1.2 litres

  • Inspiratory reserve volume

    • Max. volume of additional gas that can be inhaled through forcible inspiration following a normal inspiration

    • 3.3 litres

  • Expiratory reserve volume

    • Additional volume of gas exhaled with max. effort at end of normal expiration

    • 1.0 litres

S

S

S

S

S

S

Ss

S

S

• State two methods that can be used to determine residual volume

  • Gas dilution test

    • Person breathes from a container containing a documented amount of a gas (either 100% oxygen or a certain amount of helium in air)

    • Test measures how the concentration of the gases in the container changes

  • Body plethysmography

    • Measures the total amount of air the lungs can hold (total lung volume)

    • Person sits inside airtight booth called a plethysmograph &breathes through a mouthpiece while pressure and air flow measurements are collected

• Explain typical changes in FRC and TLC in obstructive and restrictive lung diseases

  • Use vitalograph to distinguish (measure rate at which air forced out)

  • Obstructive lung diseases

    • Example= COPD

      • Barrel chested (loss...

Buy the full version of these notes or essay plans and more in our Respiratory System Notes.