nurs 210: chapter 22 - the respiratory system

respiration is:

the exchange of gases between atmosphere, blood, cells

combo of 3 processes is required for respiration to occur:

ventilation (breathing), external (pulmonary) respiration, internal (tissue) respiration

the cardiovascular system assists:

the respiratory system by transporting gases

structurally, components of respiratory system divided into 2 parts:

upper respiratory system, lower respiratory system

functionally, components of respiratory system divided into 2 zones:

conducting zone, respiratory zone

upper respiratory system consist of:

nose, pharynx, associated structures

lower respiratory system consist of:

larynx, trachea, bronchi, lungs

picture of overiew nose, pharynx, larynx, and trachea

pharynx

functions as a passageway for air and food, houses the tonsils, which participate in immunological reactions against foreign invaders

larynx (voice box)

passageway that connects the pharynx and trachea, contains vocal folds which produce sound when they vibrate

trachea

extends from the larynx to the primary bronchi

bronchi

trachea branches into right primary bronchus that enters right lung, and left primary bronchus that enters left lung; upon entering the lungs, primary bronchi further divide to form smalelr diameter branches

terminal bronchioles

end of conducting zone

picture of table bronchi

lungs

paired organs in the thoracic cavity; they’re enclosed and protected by the pleural membrane

alveoli

when conducting zone ends at termina branchioles, respiratory zone begins, which then terminates at the alveoli (“air sacs” found within the lungs)

picture of alveoli in a lobule of a lung

2 kinds of alveoli

type I, type II

type II alveoli secretes:

surfactant, which reduces surface tension in alveoli, which prevents alveoli from collapsing

respiratory membrane is composed of:

1. layer of type I and type II alveolar cells (and associated alveolar macrophages that constitutes the alveolar wall)

2. an epithelial basement membrane underlying the alveolar wall

3. capillary basement membrane that is often fused to epithelial basement membrane

4. capillary endothelium

pulmonary ventilation

air flows between the atmosphere and the alveoli of lungs between of alternating pressure difference created by contraction and relaxation of respiratory muscles; inhalation (inspiration) air moves out to lungs, exhalation (expiration) air moves into lungs

picture of 3 basic steps involved in respiration

boyle’s law

pressure changes that drive inhalation and exhalation are governed by boyle’s law; volume of gas varies inversely with its pressure

intrapulmonary pressure

aka intra-alveolar pressure; in relaxed breathing, difference between atmosphere pressure and intrapulmonary pressure is small (about -1 mmHg on inhalation or +1 mmHg on exhalation)

intrapleural pressure

pressure in space between parietal and visceral pleura; remains below atmospheric pressure throughout respiratory cycle

picture of muscles of inhalation and exhlation

breathing patterns and respiratory movement

eupnea, apnea, dyspnea, tachypnea, bradypnea

eupnea

quiet breathing or resting respiratory rate; adults 12-18 breath/min

apnea

cessation of breathing

dyspnea

labored or difficult breathing

tachypnea

abnormally fast breathing

bradypnea

abnormally slow breathing

picture of spirometry

tidal volume (TV)

amount of air moved into and out of lung with each breath (averages ~500 ml)

inspiratory reserve volume (IRV)

amount of air that can be inspired forcibly beyond the tidal volume (2100-3200)

expiratory reserve volume (ERV)

amount of air that can be forcibly expelled from lungs (1000-1200 ml)

residual volume (RV)

amount of air that always remains in lungs; needed to keep alveoli alive

picture of lung volumes and capacities

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external respiration

oxygen will diffuse from the alveoli into pulmonary capillaries; CO2 moves in opposite direction

internal respiration

oxygen will diffuse from systemic capillaries into tissue; CO2 moves in opposite direction

transport of O2

1.5% of O2 is dissolved in plasma, with 98.5% of O2 being carried by hemoglobin (Hb)

transport of CO2

7% of CO2 is dissolved in plasma, 23% of CO2 is carried by Hb inside red blood cells as carbaminohemoglobin; 70% of the CO2 is transported as bicarbonate ions (HCO3)

formation of bicarbonate involves CO2 combining with:

water to form carbonic acid H2CO3, which quickly associated into bicarbonate and H+, which is part of transport of CO2

transport of CO2 occurs primarily in RBCs, where:

enzyme carbonic anhydrase reversibly and rapidly catalyzes this reaction

for transport of CO2, in systemic capillaries, after HCO3- is created, it:

quickly diffuses from RBC into plasma, which is an outrush of HCO3- from RBCs is balanced as CI- moves into RBCs from plasma, referred to as chloride shift

picture of exchange of O2 and CO2

hypercapnia

a slight increase in P(CO2) and thus H+, stimulates central chemoreceptors

hypoxia

oxygen deficiency at tissue level, caused by low P(O2) in arterial blood due to high altitude, airway obstruction or fluid in lungs

control of respiration

location of areas of respiratory center

picture of normal and forceful breathing

cortical influences

allow conscious control of respiration that may be needed to avoid inhaling noxious gases or water

chemoreceptor

central and peripheral chemoreceptors monitor levels of O2 and CO2 and provide input to respiratory center

central chemoreceptors

located throughout brain stem

peripheral chemoreceptors

found in aortic arch and carotid arteries

control of respiration

changing levels of PCO2 and pH are most important; levels of these chemicals are sensed by chemoreceptors

if blood P(CO2) levels rise (hypercapnia), which CO2:

accumulates in brain and joins with water to become carbonic acid; carbonic acid dissociates, releasing H+, causing a drop in pH (increase acidity); increases H+ stimulates central chemoreceptors of brain stem, which synapse with respiratory regulatory centers, which even also increases depth and rate of breathing, causing act to lower blood PCO2 and pH to rise to normal levels

picture control of respiration w/ brain

hering-breuer reflex (inflation reflex)

stretch receptors in pleurae and airways are stimulated by lung inflation, send inhibitory signals to medullary respiratory centers to end inhalation and allow expiration; may act as protective response more than as a normal regulatory mechanism

picture of neural and chemical influences on brain

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