23.6-7 External and Internal Respiration

Factors that affect lung compliance

-Connective tissue of lungs -level of surfactant production -mobility of thoracic cage

Respiration

-External respiration -internal respiration

anoxia

Complete lack of oxygen in tissues kills cells very quickly Example: tissue damage from heart attack and stroke

Boyle's Law

Defines the relationship between gas pressure and volume: P = 1/V Air flows into and out of the respiratory tract due to pressure gradients created by volume changes in the thoracic cavity

Atelectasis (lung collapse)

Elastic fibers of the lung are able to fully recoil (alveoli collapse)

pulmonary fibrosis

Excess CT decreases compliance(more force to fill up) (pulmonary fibrosis)

Functional residual capacity (FRC) =

Expiratory reserve volume + residual volume ERV-Additional amount of air capable of being exhaled residual volume-Amount of air in lungs after maximal exhalation

Vital capacity (VC)

Expiratory reserve volume + tidal volume + inspiratory reserve volume ERV- additional amount of air capable of being exhaled VT-Amount of air moved into or out of lungs in a breath IRV-Additional amount of air that can be inhaled

Costal breathing or shallow breathing

External intercostals assist inhalation by increasing thoracic volume when the external intercostals raise the ribs and enlarge the thoracic cavity Contribute 25 percent of normal air movement

Relationships among VT, V̇E and V̇A

For a given respiratory rate, increasing tidal volume increases alveolar ventilation rate o For a given tidal volume, increasing respiratory rate increases alveolar ventilation rate

Active exhalation uses:

Internal intercostal muscle and transversus thoracis -Depress the ribs -Abdominal muscles (external & internal obliques, transversus abdominis, rectus abdominis) Compress abdomen and force the diaphragm upward

At the start of the respiratory cycle

Intrapulmonary pressure = atmospheric pressure AIR DOES NOT MOVE

Quiet Breathing (Eupnea)

Involves active inhalation and passive exhalation During quiet breathing, active inhalation involves only the primary respiratory muscles:

Respiratory Rate

Number of breaths per minute

Anatomic dead space volume (VD)

Only about 70% of inhaled air reaches alveolar exchange surfaces o The rest 30% remains in conducting passages is known as (VD) VD = VT x 0.3

Exhalation can be active or passive

Passive means it does not require the contraction of respiratory muscles

pulmonary ventilation (breathing)

Physical movement of air into and out of respiratory tract provides alveolar ventilation Pulmonary ventilation causes volume changes that create changes in pressure Volume of thoracic cavity changes with expansion or contraction of diaphragm or rib cage

Physical Factors Affecting Pulmonary Ventilation

Resistance and compliance

Resistance in pulmonary ventilation

Resistance to airflow is adjusted with bronchodilation and bronchoconstriction

Measuring respiratory rates and volumes

Respiratory system adapts to changing oxygen demands by varying the respiratory rate and the amount of air moved per breath

Diaphragmatic breathing or deep breathing

The diaphram draws air into lungs by increasing thoracic volume when the diaphragm contracts Contributes 75 percent of normal air movement

Pulmonary volumes

Tidal volume (Vt), Expirtory reserve volume (ERV) residual volume inspiratory reserve volume (IRV)

emphysema

Too little CT increases compliance (not require as much force to fill the lungs)(emphysema)

Level of surfactant production

Too little surfactant increases surface tension causing alveoli to collapse, reducing compliance (hard to fill lungs)

internal respiration

Uptake of O2 and release of CO2 by cells in the body as a result of cellular respiration

Total Lung Capacity (TLC)

Vital capacity + residual volume Expiratory reserve volume + tidal volume + inspiratory reserve volume + Residual volume(Amount of air in lungs after maximal exhalation)

Hypoxia

abnormal external res. Low tissue oxygen levels severely limits the metabolic activities of cells

accessory respiratory muscles

activated when respiration increases significantly (excerise)

primary respiratory muscles

diaphragm and external intercostals

Higher compliance

does not require as much force to fill the lungs

During quiet breathing, passive exhalation uses

elastic rebound of the lung tissue -Elastic components of tissues recoil Elastic fibers in the lungs Elastic tissue in connective tissues of the body wall Stretched skeletal muscles of the body wall -Diaphragm and rib cage return to original positions

Lower compliance requires

greater force to fill lungs

spirometer

instrument used to measure breathing

Compliance of pulmonary ventilation

is a measure of the expandability of the lungs

a respiratory cycle consists of

one inspiration (inhalation) plus one expiration (exhalation)

Minimal volume

the amount of residual air that stays in the lungs even after collapse (in a collapsed lung)

Inspiratory capacity

tidal volume + inspiratory reserve volume TV-amount of air moved into/out of lungs in a breath IRV- additional amount of air that can be inhaled

When the chest cavity expands, so do the lungs because?

visceral pleura and the parietal pleura do not separate from one another Pleural fluid "binds" them together -Prevents the lungs from collapsing despite elastic rebound

An increase in volume

will result in a decrease in pressure

A decrease in volume

will result in an increase in pressure

Forced breathing (hyperpnea)

-Involves active inhalation and active exhalation Active inhalation uses: Primary muscles of respiration PLUS -Accessory muscles of inspiration- Assist the primary muscles of inspiration in elevating the ribs to increase the volume in the thoracic cavity Sternocleidomastoid, scalenes, pectoralis minor, and serratus anterior

Intrapleural pressure

-Pressure in the pleural cavity between parietal and visceral pleurae Remains less than atmospheric pressure throughout respiratory cycle

Atmospheric pressure (atm)

-Weight of Earth's atmosphere Has several important physiological effects Air pressure at sea level = 1 atmosphere (atm) = 760 mm Hg

Lungs expansion is physically limited by

1. the expandability of the thoracic cage 2. the expandability of the respiratory muscles, and 3. the expandability of connective tissues within and around the lungs --Prevents overexpansion of the alveoli

inhalation is always active

Active means it requires the contraction of respiratory muscle

Expiratory reserve volume (ERV)

Additional amount of air capable of being exhaled

Inspiratory reserve volume (IRV)

Additional amount of air that can be inhaled

Air flows into and out of the respiratory tract due to pressure gradients created by volume changes in the thoracic cavity

Air always flows from higher pressure to lower pressure!

pneumothorax

Air enters pleural cavity due to injury to chest wall or rupture of alveoli -Breaks the fluid bond between the visceral and parietal pleura Results in atelectasis

Inhalation begins as inspiratory muscles increase the volume of the thoracic cavity

Air flows from high pressure (atmosphere) to low pressure (intrapulmonary pressure)

Exhalation begins as elastic rebound/accessory muscles of expiration decrease the volume of the thoracic cavity

Air flows from high pressure (intrapulmonary pressure) to low pressure (atmosphere)

enternal respiration

All processes involved in exchange of O2 and CO2 with the external environment Integrated steps in external respiration: A.Pulmonary ventilation (breathing) B. Gas diffusion -Across blood air barrier in lungs -Across capillary walls in other tissues C.Transport of O2 and CO2 -Between alveolar capillaries -Between capillary beds in other tissues

intrapulmonary pressure

Also called (intra-alveolar pressure) -Difference from atmospheric pressure determines direction of airflow -In relaxed breathing, pressure differential is small -Heavy breathing increases the pressure gradient

Residual volume

Amount of air in lungs after maximal exhalation

Tidal volume (VT) (pulmonary volumes)

Amount of air moved into or out of lungs in a breath

Tidal volume (VT)

Amount of air moved per breath

Respiratory minute volume (VE)

Amount of air moved per minute Is calculated by: respiratory rate (f) × tidal volume (VT) VE = f x VT MEASURES PULMONARY VENTILATION

Alveolar ventilation (V̇A)

Amount of air reaching alveoli each minute o Calculated as respiratory rate × (tidal volume - anatomic dead space) VA = f x (VT - VD) Alveoli contain less O2 than atmospheric air because inhaled air mixes with "used" air

Cyclical changes in intrapleural pressure create respiratory pump it assists with?

Assists in the venous return of blood to the heart