Respiratory Phys

functions of the respiratory system

• oxygen provision

• CO₂ elimination

• microbial infection protection

• blood pH regulation

respiratory system contributes to phonation, […], and acts a blood reservoir

olfaction

Components of resp system (6)

• upper airways

• trachea

• lungs

• resp muscles

• rib cage

• CNS

upper airways includes

nostril, oral cavity, pharynx, larynx

Trachea and primary bronchi arrangment

• anterior c-shape cartilage

• posterior smooth muscle

bronchi structure

cartilage and smooth muscle

bronchioles structure

smooth muscle

2 zones of larynx

• conducting zone

• respiratory zone

conducting zone

leads gas to gas exchange region of lungs

• no alveoli

• thus, no gas exchange

conducting zone components

• bronchi

• bronchioles

• terminal bronchioles

respiratory zone

where gas exchange occurs

respiratory zone components

• respiratory bronchioles

• alveolar ducts

• alveolar sacs

Terminal bronchioles

smallest airway w/o alveoli

respiratory bronchioles

contains occasional alveoli

where does gas exchange occur?

alveoli

alveoli structure + function

small, thin-walled, capillary rich sac in lungs where the gas exchange occurs

Type I alveolar cell

• most cells

• lined by continuous mono layer of flat epithelial cell

• don’t divide

Type II alveolar cell

• produce surfactant

• act as progenitor cells (can differentiate into type I)

Transfer of O₂ and CO₂ occurs by diffusion through the […]

respiratory membrane

respiratory membrane

incredibly thin tissue barrier inside the lungs where gas exchange occurs

Steps of respiration (general)

• ventilation via bulk flow

• exchange via diffusion

• transport bulk flow

• exchange via diffusion

• cellular utilization of O₂ and CO₂ prod

How is resp airflow produced (general)

• CNS sends rhythmic drive to resp muscle

• resp muscles contract rhythmically

• change in vol and pressure

• air flows in/out

resp muscle categories

• pump muscles

• airway muscles

• accessory muscles

Diaphragm (3)

dome-shaped muscles which flattens during contraction (INS)

• abdominal contents forced down + forward

• widened rib cage

External intercostal muscles

contract and pull ribs upward increasing the lateral volume of the thorax

• bucket handle motion

Parasternal intercostal muscles

contract and pull sternum forward, increasing anterior posterior dimension of the rib cage

Abdominal muscles (4)

• External oblique

• Internal oblique

• transversus abdominis

• rectus abdominis

Abdominal muscle function

involved in deeper, faster breathing

Internal Intercostal Muscles

pull rib cage down + reduce thoracic vol during exercise

Accessory Inspiratory Muscles (2)

Scalenes and Sternocleidomastoids

scalene

elevate upper ribs

Sternocleidomastoids

raise the sternum

What happens to the abdominal muscles during forced expiration?

abdominal muscles contract and push abdominal content + diaphragm up to reduce thoracic vol

obstructive sleep apnea

reduction in upper airway patency during sleep

muco-ciliary escalator

The filtering action in the conducting zone

types of cells that line the surface of the trachea

• goblet cells (prod mucus)

• ciliated cells (apical surface)

Goblet cells form the — layer, trapping inhaled materials, while ciliated cells form the — layer, eliminating particles.

gel; sol

Macrophages in Alveoli

Last defence for eliminating particulates; digest them and eliminate the risk of infection

pulmonary fibrosis

tissue in your lungs becomes scarred and stiff over time (cannot expand)

spirometry

a pulmonary function test that determines the amount and the rate of inspired and expired ai

tidal volume

the volume of air moved IN OR OUT of the respiratory tract (Breathed) during each ventilatory cycle

Expiratory reserve volume

the additional volume of air that can be forcibly exhaled following a normal expiration;

• _{can be accessed by expiring maximally to the Maximum Voluntary Expiration}

Inspiratory reserve volume

the additional volume of air that can be forcibly inhaled following a normal inspiration

• _{can be accessed by inspiring maximally, to the Maximum Possible Inspiration}

Residual volume RV

the volume of air remaining in the lungs after a Maximal Expiration

• RV = FRC - ERV

• _{cannot be measured with a spirometry test}

Vital capacity (VC)

the maximal volume of air that can be forcibly exhaled after a Maximal Inspiration

Inspiratory capacity IC

maximal volume of air that can be forcibly inhaled

• IC = TV + IRV.

Functional Residual Capacity (FRC)

volume of air remaining in the lungs at the end of a normal expiration.

• FRC = RV + ERV

Total Lung Capacity (TLC)

volume of air in the lungs at the end of a Maximal Inspiration.

• TLC = FRC + TV + IRV = VC + RV

Total or minute ventilation

total amount of air moved into the respiratory system per minute

• tidal volume x respiratory frequency

Alveolar ventilation

amount of air moved into the alveoli per minute

• (tidal volume - anatomical dead space) x resp frequency

How do we improve alveoli ventilation?

Deep and slow breathing: Due to the fact that you are breathing in so much air during a single event will increase alveoli ventilation

FEV1

Forced Expiratory Volume in 1 second

FVC: Forced Vital Capacity

total amount of air blown out in one breath after max inspiration as fast as possible

FEV1/FVC

Proportion of the amount of air that is blown out in 1 second

Obstructive Pattern (3)

• difficulty in exhaling all the air from their lungs

• exhaled air comes out more slowly

• FEV1/FVC is reduced

In an obstructive pattern FEV1 is —, while in a restrictive pattern FEV1 is —

significantly reduced; reduced (severity ranges)

Restrictive Pattern (3)

• cannot fully fill their lungs with air.

• lungs are restricted from fully expanding

• FEV1/FVC almost normal

Helium dilution method

measures the amount of air that remains in the lungs at the end of a normal expiration

• measures only communicating gas

Static properties of the lung

Mechanical properties that are present in the lungs when no air is flowing

Static properties of the lung examples

• intrapleural pressure

• static compliance of the lung

• surface tension of the lung

Dynamic properties of the lung

Mechanical properties when the lungs are changing volume and air is flowing in and out

Dynamic properties of the lung examples

• Alveolar pressure (P_ALV)

• Dynamic lung compliance

• Airway and tissue resistance

ventilation

the exchange of air between the atmosphere and the alveoli

Boyle’s Law

for a fixed amount of an ideal gas that is kept at constant temperature, the pressure and the volume are inversely proportional

• P₁V₁ = P₂V₂

A change in —, and then in —, produces airflow

vol; pressure

During the expiratory phase of the lungs, a(n) — in volume will generate an increase in alveolar pressure

reduction

During the inspiratory phase of the lungs, a(n) — in volume will generate a decrease in alveolar pressure

increase

The pleurae (2)

Thin double-layered envelope

• visceral (external surface of lung)

• parietal (thoracic wall + superior face of diaphragm)

Intrapleural fluid

Reduces friction of lung against thoracic wall during breathing

elastic recoil

the lungs’ natural tendency to collapse and deflate following inflation

Intrapleural Pressure (P_IP)

• pressure in pleural cavity

• Acts as a relative vacuum

• always subatmospheric due opposing directions of elastic recoils

Alveolar Pressure (P_ALV)

• dynamic, directly involved in producing air flow

• when the glottis is open + no air flow = all resp pressure are equal to atm pressure

Transpulmonary Pressure (P_TP)

force responsible for keeping alveoli open

• static parameter which does not cause airflow

• determines lung vol

What factors contribute to airway resistance?

• Inertia of the respiratory system

• friction (negligible)

Types of airflow in small airways, bronchial tree, and large airways (respectively)

laminar, transitional, turbulent

lung compliance

a measure of the elastic properties of the lungs and a measure of how easily the lungs can expand

• slope

Static Compliance of the Lung

Represents the lung compliance, or the elastic properties of the lungs, when no air is flowing through

dynamic compliance

Represents the lung compliance during periods of gas flow (inspiration/expiration)

Lung compliance in Pulmonary fibrosis

• low lung compliance

• stiff lungs due to overproduction of collagen

Lung compliance in Emphysema

• high lung compliance

• “floppy” lungs due to lost alveolar tissue

Hysteresis

defines the different behaviour of the inflation and the deflation curves in pathological conditions as well as in physiological conditions

Lung compliance is determined by…

• elastic components

• surface tension (interface of alveoli)

Elastin properties

• low tensile strength

• extensible

Collagen properties

• high tensile strength

• inextensible

Emphysema and elastin

floppy lungs result from elastin destruction

Pulmonary fibrosis and collagen

stiff lungs due to collagen deposition in alveolar walls

How does surface tension affect alveoli?

creates inward recoil by decreases vol of gas inside of alveoli and increasing pressure— leading to alveolar collapse

What is the function of surfactant?

• lowers surface tension so we can breath w/o too much effort

• makes alveoli stable against collapse

• increase compliance

How does surfactant affect the pressures between alveoli of different sizes?

thickness of surfactant varies inversely w/ SA, equalizing pressures between different sized alveoli and preventing collapse

how do regional differences affect ventilation

weight of lungs increases pressures + makes intrapleural pressures less negative.

• Thus alveoli at the bottom have a less negative P_IP leading to a larger increase in lung vol

Dalton’s law

states that in a mixture of gas, such as air, each gas has its specific pressure and the total pressure of this mixture of gas is given by the sum of the individual pressures

Fick’s law

the rate of transfer of a gas (V; L/min) through a sheet of tissue per unit of time is proportional to the surface area of the membrane (A) and depends on the difference in partial pressures between the two environments and inversely proportional to the thickness (T) of the membrane

Henry’s Law

the amount of gas dissolved in a liquid is directly proportional to the partial pressure of gas in which the liquid is in equilibrium

what affects the amount of gas dissolved in a liquid?

partial pressure, solubility

• only a gas that is dissolved contributes to pp

The partial pressure of oxygen — in alveolar air while carbon dioxide —

decreases; increases

How will Increasing alveolar ventilation affect P_O2 and P_CO2?

increase alveolar P_O2 and decrease P_CO2

How will increasing metabolic rate affect PO2 and PCO2?

consuming more oxygen and producing more carbon dioxide thus, this will decrease alveolar P_O2 and increase alveolar P_CO2

characteristics of pulmonary circulatory system

• low pressure system

• low resistance system

• high compliance vessels

— air must be delivered to regions of the lung where the — is going and vice versa

Inspired; blood

The greater the ventilation, the more the PO2 and PCO2 of the alveoli will be — to the atmospheric pressures

similar