Biology 12
Respiratory System Notes
Oxygen is moved to lungs → CO2 moved away from cells of body→ _______ → outside of body Inhalation— Exhalation— Air is filtered, warmed and hydrated as moves along air passages
throughout the system
A. Nose Made of 2 _______ ________ _________ are openings to nasal cavities Separated by bone or cartilage Inside nasal cavities have hairs and cilia which filter out
contaminants such as dust, pollen, etc. Have sensory receptors in nasal cavities for smell
Nasal cavities connected to sinuses in the head—i.e. bony cavities lined with mucous membrane
Nasal cavities open up into the ___________
Figure 1: Nasal Cavity
B. Pharynx
Composed of ___________, ___________ and _____________ Where ________, _________ and ________ are found
C. Larynx ______ found on top of trachea—Adam’s apple at front of larynx ______ is opening lying above larynx→ moves up and against
____________ when swallowing to block tracheaFigure 2: Larynx
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Larynx contains ________ _______ (mucus membranes and elastic ligaments) which vibrate as air passes them→ sound
More narrow cords→
Figure 3: trachea in relation to esophagus
D.Trachea
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Surrounded with cartilaginous c-shaped rings that help maintain
open airways Lined with cilia that help keep airway clean by sweeping up
contaminants caught in mucus to throat where swallowed ______________—procedure where opening is made in trachea if
blocked At end of trachea are main ___________
Figure 4: Trachea and larynx
Figure 5: Tracheostomy
E. Lungs
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2 lungs— Each divided into lobes R lung has 3 lobes and left has 2→ Lobes are further divided into smaller lobules
F. R & L Bronchus (pl.= Bronchi) Right and Left main __________→ lead into lungs Maintain cartilaginous rings Divide to form smaller and smaller diameter and thinner _____
eventually losing cartilage Eventually, bronchi become structures called bronchioles which
end in small sacs called _________
Figure 6: Lung structure
G.Alveoli
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Thin structures only 1 cell layer thick—simple squamous
epithelium Covered by capillaries Alveoli covered by a thin film of a ____________ __________—
chemical that lowers surface tension—prevents them from collapsing and clinging due to surface tension of water lining alveoli which would cause alveoli to collapse
Infant ___________ ________ __________—where babies do not produce this and have collapse of alveoli—result is trouble breathing; treatment = surfactant replacement therapy
Figure 7: Alveoli
Mechanism of Breathing Overview
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Different kinds of respiration
a) Breathing Expiration (breathing out)
b) External respiration
c) Internal respiration
d) Cellular Respiration ATP production in mitochondria: C6H12O6 + O2 → ATP + CO2 +
H2O
Respiratory Volumes
a) Tidal Volume Volume of air inhaled and exhaled at rest
b) Inspiratory reserve volume
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Forced inspiration 3.0 L
c) Expiratory Reserve Volume About 1.4 L
Note: both inspiratory reserve volume and expiratory reserved volume are used with physical activity
d) Residual Volume Air remaining in lungs even after forced expiration (1.0 L) ____________—residual volume builds & not used for gas
exchange and thereby reducing vital capacity
e) Vital Capacity Sum of tidal volume + inspiratory reserve volume + expiratory
reserve volume (about 4.5 to 5.7 L)
f) Functional Residual Capacity i.e. E.R.V. + R.V. (2.5 L)
g) Dead Space
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E.g. nasal cavities, pharynx, larynx, etc.
Mechanism of Breathing
Air passes from outside to pharynx → alveoli Lungs are in sealed _________ ________ ____ ______ (with intercostals muscles) forms ____ and ______ of
this cavity _____________ (domed muscle) forms lower part of thoracic cavity _________ ___________ is double membrane associated with lungs
and thoracic cavity
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One layer attached to lungs exterior and other layer closely adheres to chest wall and diaphragm
In between 2 pleural membranes is thin layer of fluid (mostly H2O) __________ _________ is about 4mm Hg less than atmosphere—
keeps them together _____________—condition whereby air enters intrapleural space
and causes lungs to collapse
Inspiration
Active process—i.e. requires energy _________ center in medulla senses CO2 and H+ levels in blood
plasma→ automatically causes inspiration Levels of mostly H+ and CO2 as well as O2 are also sensed by _____
bodies (in carotid arteries) and _______ bodies (in aorta) which are _______________ that send signal to respiratory center in medulla via nerves
The more CO2 and H+ in blood, the higher the rate and depth of breathing
_________ nerve → nerve to diaphragm that causes contraction ___________ nerves → send nerve impulses to intercostals muscles
to contract When diaphragm and intercostals muscles contract → expand
volume of thoracic cavity→ lungs expand → negative pressure in lungs → air enters lungs
If inhale deeply → stretch receptors in alveoli → inhibitory nerve impulses to respiratory centre → stops sending signals to diaphragm and intercostals
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Expiration
Respiratory center → stops signal to diaphragm and rib muscles → diaphragm and muscles relax → abdominal organs press against diaphragm → volume of chest cavity decreases → pressure builds up → air is forced out
External Expiration
Gas exchange (CO2, O2 and H20) in alveoli and pulmonary capillaries occurs due to ___________
Internal Respiration
External Respiration and 02 Exchange
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Blood temp. = pH of blood = 7.4 Hb has 4 binding sites for oxygen Oxygen bound to Hb called HbO2 or ______________
Internal Respiration and O2 Exchange
Blood temp = pH of blood = 7.35 (from cell metabolism) Hb-02 → Hb becomes unbound again
Internal Respiration and CO2 Exchange
CO2 + H20 react in red blood cells to give H2CO3 –a reaction catalyzed by enzyme __________ anhydrase
Reaction: CO2 + H20 → H2CO3 → [HCO3-] + H+
H+ ions are bound by Hb to produce HHb or _________ Hb
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Above allows blood to be buffered against changes in pH Some CO2 binds to Hb to give ______________________ (HbCO2) Some very small amount transported as dissolved gas in plasma as
well
External Respiration and CO2 Exchange
At alveolar capillaries:
pH higher and temp. lower than at tissues→ release of CO2 and H+ from Hb
next HCO3 and H+ combine to form carbonic acid by ___________ ______________ enzyme
Reaction: HCO3- + H+ → [H2CO3] → CO2 + H2O
then carbonic acid is converted into H2O and CO2 by enzyme _____ anhydrase
Some CO2 also leaves from HbCO2 as well as dissolved CO2 in plasma
leaving the plasma for the alveoli
Driving Force of Gas Exchange
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Recall that gas exchange occurs by diffusion This gradient is accomplished by partial pressure differences of PCO2
and PO2
Blood in pulmonary capillaries has higher PCO2 and low PO2
concentration Thus, CO2 diffuses out of capillaries into alveoli and O2 diffuses out
from alveoli into capillaries
Effect of PO2/Temperature/pH on Hemoglobin Saturation
a. Oxyhemoglobin Dissociation Curve & PO2
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Notice that as PO2 increases, the oxygen saturation of Hb increases to a point
Notice also that at any given PO2, a rise in temperature or a lowering of pH will result in a lower Hb saturation and therefore more oxygen given off
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