Respiratory Physiology First Episodes

Respiratory Physiology
By
Abubakar N. M.
FIRST EPISODE
Outline
• Respiratory tracts - Structure and function
• Compliance and Elastance
• Surfactant
• Mechanics of respiratory
Introduction
• Respiration is the process by which the body takes in and
utilizes oxygen (O2) and gets rid of carbon dioxide (CO2)
Events of Respiration
• Ventilation (external respiration) VS Internal respiration
• Gas exchange VS Transport of Gas
Functions of Respiratory System
• Respiratory Functions:
– Pulmonary Ventilation
– Diffusion of O2 and CO2 between the alveoli and the blood
– Transportation of O2 & CO2 in the blood & body fluids to &
fro from the body’s tissue cells
– Regulation of Ventilation
• Non-Respiratory Functions:
– Air filter: Nothing >2.5 μm gets to the alveoli (are trapped)
– Blood filter: particles larger than an RBC are trapped (~8 μm
size barrier), which includes clots, tumour cells and other
emboli
– Blood reservoir: lungs contain ≈ 10% of the circulating blood
volume
Functions of Respiratory System
• Drug administration and elimination: Bronchodilators
Steroids, and volatile anaesthetics agents
• Metabolism: conversion of of angiotensin-I
• Acid-base balance regulation: via CO2 elimination
• Modulator of the clotting cascade: Lungs contain
thromboplastin, heparin and tissue plasminogen activator
• Antimicrobial and immune functions: Alveolar
macrophages and sequestered neutrophils, mast cells in
the lung and bronchi, immunoglobulin in the respiratory
mucus (IgA)
• Body temperature regulation: heat loss can occur by
respiration
• Organ of speech phonation : respiratory system permits
communication by sound and language
Respiratory tract - Structure and function
• Upper Airway
• Nose, pharynx,
larynx and
associated
structures
• Lower Airway
• Trachea,
bronchi, lungs
Respiratory tract - Structure and function
• Conducting Zones:
physiological dead
space
• Warms cleans, filters
and humidifies inspired
air
• Respiratory Zone:
alveolar sacs and
respiratory bronchioles
• Region of gas exchange
between air and blood
Respiratory tract – Lung Blood Supply
• Pulmonary
circulation
• Bronchial
circulation
• Physiological
Shunt
Respiratory tract – Innervation
• Smooth muscles via autonomic nervous system
• Para-Sympathetic:
– Muscarinic receptors (Ach)
– Bronchoconstriction
• Sympathetic:
– Beta2 – receptors
– Bronchodilation - mainly to adrenalin
Respiratory units (alveoli) and Membrane
• Units: respiratory bronchiole,
alveolar ducts, alveolar sacs, and
alveoli (≈ 300 million in the two
lungs)
• Alveoli (simple squamous
epithelial cells):
– Alveolar cells type I: Gases
exchange
– Alveolar cells type II: secrete
surfactant, stem cell for type I
cells
– Alveolar macrophages:
Immune response
– Minute pores (pores of Kohn)
are present in the walls
between neighbouring alveoli
for collateral air flow
Respiratory units (alveoli) and Membrane
• Respiratory membrane
(pulmonary membrane)
– Surfactant
– Alveolar epithelium
– Epithelial basement
membrane
– Interstitial space
– Capillary basement
membrane
– Capillary endothelial
membrane
– Membrane of the RBC
Compliance and Elasticity
• Compliance: It means the volume change produced by a
unit change of pressure
• It is the dis-tensibility of the lungs and thoracic cage
structures
• Elasticity: Is the tendency to return to initial size after
distension (Recoil ability- resist distension)
• Due to ↑ content of elastin proteins
• Elastic tension increases during inspiration and is reduced
by recoil during expiration
Compliance and Elasticity
C = DV/DP
• 100 x more distensible than a balloon but it’s reduced by

factors that produce resistance to distension
• Compliance can be Static or Dynamic
• Static Compliance:
• Is the compliance measured under static conditions
• i.e. by measuring pressure and volume when breathing
does not take place
• Dynamic Compliance:
• Is the compliance measured during dynamic conditions
• i.e. during breathing
Compliance and Elasticity (Pressure-volume curve)
Compliance and Elasticity (Pressure-volume curve)
Surface Tension & Surfactant
• Surface tension:
– Generated by Alveolar lining fluid (H₂O)
– Collapsing force → effect is ↓by surfactant
• Surfactant:
– an oily secretion of phospholipids (90%), proteins (8%)
and ions
– ≈ 1 g (1 ml) in the whole adult lungs
– Produced by Type II pneumocytes
– Production is control by (local, Neural and hormonal)
Surface Tension & Surfactant
• Function of Surfactant:
– Reduce the work of breathing (↑ lungs compliance)
– Stabilize alveoli: prevent collapse and sticking of alveoli
– Maintain the dryness of the alveoli: prevent edema of
the alveoli
– Role in the immune defence system of the lung (SP-A,
SP-D)
Respiratory pressures
Mechanics of respiratory
• Inspiration (Active process) • Quiet expiration:
– Diaphragm contracts: ↑
– Simple elasticity of the lungs
thoracic cavity size (superior-
inferior) – ↓ chest volume
– External intercostal muscle – ↑ pulmonary pressure
contract: ↑ lateral & anterior- – Cause movement of air out
posterior size of the lungs
– ↑ volume to ≈ 0.5L, ↓
pulmonary pressure by -1 • Forced expiration:
mmHg – Contraction of abdominal
– Air rushes into lungs to fill wall muscles
alveoli – Further ↓ chest volume
– Deep/forced inspirations
(exercise or pulmonary dxs) – Further ↑ pulmonary
– Accessory inspiratory muscles pressure
are used – More air moves out
Mechanics of respiratory
Pre/post lecture quiz
• Respiration is the process by which the body takes in and utilizes oxygen (O2) and
gets rid of carbon dioxide (CO2) between the lung and the outside world only ?
– True
– False
• Which of the following is common to both external and Internal respiration?
– Get ride of Co2 for O2 delivery
– Delivery of O2 and in exchange for CO2
– Delivery of CO2 for Nitrogen molecules
– None of the above
• After inspiration commences the:
– Intrapleural pressure and intrapulmonary P both fall
– Intrapleural pressure falls and intrapulmonary P rises
– Intrapleural pressure falls and venous return decreases
– Intrapulmonary pressure rises and volume of the alveoli is momentarily
unchanged
– Intrapleural pressure rises and venous return to heart decreases
• All of these statements about surfactant are true except
– Promote stability of alveoli
– Reduce surface tension of alveoli
– It encourage transudation of fluid into capillary
– Assist in avoiding transudation of fluid into capillary
– Produced by Type II pneumocytes
• Lung of premature infant is presented on electronic photomicrography of biopsy

material. Collapse of the alveolar wall caused by the deficiency of surfactant was
revealed. Dysfunction of what cells of the alveolar wall caused it?
– Alveoeytes type I
– Alveolar macrophagcs
– Secretory cells
– Fibroblasts
– Alveolocytes type II
• A patient after pathological process has a thickened alveolar membrane. The direct
consequence of the process will be the reduction of ?
– Diffuse lung capacity
– Reserve expiratory capacity
– Minute respiratory capacity
– Alveolar lung ventilation
– Oxygen capacity of blood
• Work in a mine is known to cause inhalation of large amount of coal dust. Inhaled
coal dust can be detected in the following pulmonary cells:
– Pericapillary cells
– Secretory endothelial cells
– Capillary endothelial cells
– Alveolar macrophages
– Respiratory epithelial cells
• Wasted air refers to air that is not utilized for gaseous exchange and
occupied the?
– Anatomical Dead space
– Physiological dead space
– pathological dead space
– Histological dead space
– All of the above
• All of the following are respiratory functions of pulmonary system?
– Act as Air filter during ventilation
– Blood filter for smaller particles finer than than an RBC
– Blood reservoir ≈ 1.0% of the circulating blood volume
– Act as modulator of respiration
– All of the above
• Which of the following factors have collapsing tendency of Lungs
are:?
– Elastic tissues of lungs and Surface tension
– Compliance and elasticity
– Intrapleural pressure s only
– Intrapleural pressure and Surfactant
– None of the above
• All of the following states decrease lung compliance EXCEPT

– Lung fibrosis
– Increased pulmonary venous pressure
– Long period of time where the lung is unventilated
– Emphysema
– Alveolar oedema
• Write short note of the following
– Non-respiratory functions of the respiratory system (10 marks)
– Surfactant (10 marks)
– Lung compliances and elasticity (10 marks)
– Pulmonary membrane (10 marks)
– Work of respiration (10 marks)
Let’s meet in the next episode

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Respiratory Physiology

• 100 x more distensible than a balloon but it’s reduced by

• Lung of premature infant is presented on electronic photomicrography of biopsy

• All of the following states decrease lung compliance EXCEPT

Let’s meet in the next episode

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