The respiratory system
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The Respiratory system. Pulmonary ventilation – Chp 16 Respiration. Outline. Overview of the respiratory system Anatomy Forces for pulmonary ventilation Factors affecting pulmonary ventilation Clinical significance of respiratory volumes and air flows. Outline.

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The Respiratory system

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The respiratory system

The Respiratory system

  • Pulmonary ventilation – Chp 16

  • Respiration


Outline

Outline

  • Overview of the respiratory system

  • Anatomy

  • Forces for pulmonary ventilation

  • Factors affecting pulmonary ventilation

  • Clinical significance of respiratory volumes and air flows


Outline1

Outline

  • Overview of the respiratory system

  • Anatomy

  • Forces for pulmonary ventilation

  • Factors affecting pulmonary ventilation

  • Clinical significance of respiratory volumes and air flows


Overview

Respiration = gas exchange -- Occurs at the levels of the lungs and tissues (external respiration) and cell (internal or cellular respiration).

External respiration:

- Pulmonary ventilation: movement of air in and out

of the lungs

Gas exchange in the alveoli

Gas transport in the blood

Gas exchanges between blood and tissues

Overview


Outline2

Outline

  • Overview of the respiratory system

  • Anatomy

  • Forces for pulmonary ventilation

  • Factors affecting pulmonary ventilation

  • Clinical significance of respiratory volumes and air flows


Airways

Airways


Airways1

Upper airways:

- nose to pharynx

Lower airways:

- Conducting airway:

larynx  bronchioles

- Respiratory airway:

alveoli

Due to the wall structure of the airway: one cell layer (SSE) allows for gas exchange

Airways


Conducting airways

Presence of cartilage in the wall, from larynx to small bronchi prevents airway collapse.

Goblet cells secreted mucus. Ciliated cells help move the mucus out of the airway.

Presence of smooth muscle fibers in the bronchioles (but no cartilage)

Volume of the conducting airway: 150 ml

Conducting airways


Respiratory airway alveoli

Respiratory airway: Alveoli

  • Alveolar wall is formed by simple squamous epithelium = type I cells (SSE)  gas exchange

  • Respiratory membrane: membrane separating alveolus from blood capillary.

  • Large surface area from the numerous alveoli  better gas exchange

  • Presence of elastic fibers between alveoli


Blood supply to the lungs

Blood supply to the lungs


Alveolar structure

Type I cells  gas exchange

Type II cells  secrete surfactant (lipoproteins)  decrease surface tension  allowing for easier alveoli inflation

Surfactants start to be secreted by the 7th month of pregnancy  risk of lung disease in premature babies

Presence of macrophages in alveoli

Alveolar structure


Structure of the thoracic cavity

Structure of the thoracic cavity


The pleura

Formed by 2 layers: the parietal and visceral pleura

Roles:

- prevents friction of the lungs against the rib cage (due to the thin layer of liquid present in the pleural space)

- maintains lung expansion: due to the negative pressure within the pleural space

What is negative pressure? What is its importance?

The pleura


Pleura and negative pressure

Pneumothorax: lung collapse due to air entering in the pleural cavity

(not to be confused with atelectasy  alveoli collapse)

Pleura and negative pressure


Outline3

Outline

  • Overview of the respiratory system

  • Anatomy

  • Forces for pulmonary ventilation

  • Factors affecting pulmonary ventilation

  • Clinical significance of respiratory volumes and air flows


Mechanics of breathing

Boyle’s law: The pressure of a gas in a closed container is inversely proportional to the volume of the container.

Air flow in the lungs is driven by the differences in pressure between the atmosphere and the alveoli

P.atm is constant  changes in P.alv drive ventilation

Mechanics of breathing


Inspiration and expiration

Inspiration: chest wall expands due to muscle contraction (diaphragm and/or other muscles)

Pressure in alveoli ↓  air moves toward alveoli

Expiration: passive process  muscle relax  chest wall return to resting state  alveoli become compressed  ↑ alveolar pressure  move moves out

Inspiration and expiration


Ventilation

Ventilation


Outline4

Outline

  • Overview of the respiratory system

  • Anatomy

  • Forces for pulmonary ventilation

  • Factors affecting pulmonary ventilation

  • Clinical significance of respiratory volumes and air flows


Factors affecting pulmonary ventilation

1- Lung compliance: ease with which lungs can be stretched

- Compliance is a measure of the elasticity of lung tissue and the alveolar surface tension

2- Airway resistance: to changes in airway radius (↓radius  ↑resistance)

Pathology

lung disease resulting in stiffness of tissue

no or ↓ surfactant

Asthma

Airway obstruction

COPD

Factors affecting pulmonary ventilation


Outline5

Outline

  • Overview of the respiratory system

  • Anatomy

  • Forces for pulmonary ventilation

  • Forces affecting pulmonary ventilation

  • Clinical significance of respiratory volumes and air flows


Lung volumes

Lung volumes


Pulmonary function tests

Can help distinguish between obstructive pulmonary disease and restrictive pulmonary disease

Obstructive disease: obstruction in bronchi-bronchioles severely restricts the speed and amount of air movement

Damage to lung tissue prevents full lung expansion and recoil

Pulmonary function tests


Anatomical dead space

Anatomical dead space: space within the conductive airway, about 150 ml.

What will happen to a person who has a tidal volume of 150 ml due to lung disease?

What can be done to help the person?

Anatomical dead space


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