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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