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Respiratory System (Gas Exchange (Alveolar Exchange/External Respiration…
Respiratory System
Gas Exchange
Alveolar Exchange/External Respiration
partial pressure gradients
O2 crosses to equalize PO2 in blood and alveoli
CO2 diffuses in opposite direction
Systemic Gas Exchange/Internal Respiration
partial pressure gradients
O2 diffuses from capillaries to interstitial fluid
O2 in interstitiail fluid diffuses to systemic cells
CO2 diffuses in opposite direction
Ventilation-Perfusion Coupling
bronchioles regulate airflow, arterioles regulate blood flow simultaneously
ventilation
bronchodilation = increase in PCO2 bronchoconstriction = decrease in PCO2
perfusion
arterioles dilate = increase in PO2, decrease in PCO2 arterioles constrict = decrease in PO2, increase in PCO2
Henry's Law
solubility of gas in a liquid dependent on:
partial pressure of gas in the air
solubility coefficient of the gas in liquid
Dalton's Law
total pressure=sum of all individual partial pressures
Mechanisms of Breathing
Types of breathing
quiet breathing
rhythmic breathing when at rest
forced inspiration
deep inspiration results in increased volume of thoracic cavity
forced expiration
forced expiration decreases volume of thoracic cavity
Muscles used for breathing
quiet breathing
diaphragm
external intercostals
forced expiration
internal intercostals
abdominal muscles
transversus thoracis
serratus posterior inferior
forced inspiration
sternocleidomastoid
scalenes
pectoralis minor
serratus posterior superior
erector spinae
Associated pressures
Intrapulmonary pressure
equal to the atmospheric pressure at rest
less than atmospheric with inspiration
greater than atmospheric pressure with expiration
Intrapleural pressure
remains lower than intrapulmonary pressure to prevent collapse of lungs
Transportation of Gases
98% of O2 transported within erythrocytes
O2 bound to hemoglobin = oxyhemoglobin
hemoglobin without O2 = deoxyhemoglobin
O2 transported from alveoli into systemic capillaries
from alveoli to Pulmonary circulation
from heart to Aorta then to Systemic circulation
CO2 transported in blood via three methods
CO2 dissolved in plasma
CO2 attached to globin portion of hemoglobin
as bicarbonate (HCO3-) dissolved in plasma
Regulation of Breathing
Respiratory Center
Pontine Respiratory Center
located within pons
modifies activity of nuclei in medulla
provides smooth transition of inspiration and expiration by sending impulses to VRG
Medullary Respiratory Center
Ventral Respiratory Group
located in ventrolateral region of medulla
contains inspiratory and expiratory neurons
Dorsal Respiratory Group
posterior to VRG, dorsomedial region of medulla
relays its input to the VRG