Class Notes (1,100,000)
CA (620,000)
U of S (3,000)
PHSI (100)
PHSI 208 (100)
Lecture 1

PHSI 208 Lecture Notes - Lecture 1: Breathing, Pulmonary Pleurae, Thoracic Cavity


Department
Physiology
Course Code
PHSI 208
Professor
Baillie Landon
Lecture
1

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!PHSI!208.6!–!University!of!Saskatchewan!
Prof:&Landon&Baillie&
!
January'11,'2016'–'Respiratory'1'
!
The!respiratory!system!has!four!primary!functions:!
1. Exchange!of!gases!between!the!atmosphere!and!blood.!
2. Homeostatic!regulation!of!body!pH.!
3. Protection!from!inhaled!pathogens!and!irritating!substances!
4. Vocalization.!
!
Air!exchange!occurs!by!bulk!flow!and!follows!many!of!the!principles!that!govern!bulk!flow!
through!the!cardiovascular!system:!
1. Flow!occurs!from!a!region!of!high!pressure!to!low!pressure.!
2. Muscular!pump!creates!the!pressure!gradients.!
3. Resistance!is!primarily!influenced!by!diameter!of!tubes!through!which!it!is!flowing.!
!
There!are!two!kinds!of!respiration:!cellular&and&external.!
Cellular!respiration!is!the!aerobic!metabolism!of!glucose.!
o Glucose!+!O2!+!ADP!+!Pi!à!CO2!+!H2O!+!ATP!
External!respiration!is!the!movement!of!gases!between!the!environment!and!the!cells!
within!the!body.!The!respiratory!and!circulatory!systems!coordinate!to!move!oxygen!
and!CO2!between!the!atmosphere!and!the!cells.!
!
External!respiration!requires!coordination!between!the!respiratory!and!cardiovascular!systems.!
It!takes!place!in!a!four!step!process:!
1. The!first!exchange!(Exchange!I)!is!atmosphere!to!lung.!This!is!also!called!ventilation.&
Oxygen!is!breathed!in!through!airways!and!sent!to!the!alveoli!of!the!lungs.!
2. The!second!exchange!(Exchange!II)!is!lung!to!blood.!
3. Transport!of!the!gases!in!the!blood!by!pulmonary!circulation!and!systemic!circulation.!
4. Exchange!III!is!blood!to!cells.!This!is!cellular&respiration.!
!
There!are!many!structures!involved!in!ventilation!
and!gas!exchange:!
1. Conducting!system!or!airways.!
2. Alveoli!
3. The!bones!and!muscles!of!the!thorax!
(chest!cavity)!create!the!force!to!move!air!
during!breathing.!
!
The!lungs!are!composed!of!light!spongy!tissue!
whose!volume!is!mostly!occupied!by!air-filled!
space.!The!right!lung!is!slightly!larger!than!the!left!
due!to!the!cardiac!notch.!
!
!
!

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!PHSI!208.6!–!University!of!Saskatchewan!
Prof:&Landon&Baillie&
!
Each!lung!is!surrounded!by!a!double-walled!pleural!sac.!The!pleural!sac!forms!a!double!
membrane!surrounding!the!lung,!similar!to!a!fluid-filled!balloon!surrounding!an!air-filled!
balloon.!
One!layer!is!connected!to!the!outside!surface!of!the!lungs!called!the!visceral!pleura.!
The!other!is!connected!to!the!inside!surface!of!the!thoracic!cavity!known!as!the!parietal!
pleura.!
!
The!pleural!sac!has!two!functions:!
1. Creates!moist!slippery!surface.!
2. Holds!lungs!tight!to!the!thoracic!wall.!
!
Airways!connect!the!lungs!to!the!external!environment.!
Air!enters!the!pharynx!through!the!nasal!cavity!and/or!mouth.!
From!the!pharynx,!air!flows!through!the!larynx!(vocal!cords)!to!the!trachea!(wind!pipe).!
Trachea!is!a!semi-flexible!tube!held!open!with!15-20!cartilage!rings.!
!
The!branching!of!airways!follows!a!similar!branching!of!the!cardiovascular!system,!increase!in!
total!cross-sectional!area!(cm^2).!The!velocity!of!air!flow!is!inversely!proportional!to!total!cross-
sectional!area,!V&=&Q&/&A.&
&
Upper!airways!and!bronchi!play!an!important!role!in!conditioning!air!before!it!reaches!the!
alveoli.!This!role!includes!three!processes:!
1. Warming!air!to!body!temperature.!
2. Adding!water!vapour.!
3. Filtering!out!foreign!material.!
!
These!three!processes!are!more!efficient!with!nose&breathing.&
&
The!nasal!cavity!has!a!large!surface!area,!rich!blood!supply!and!nasal!hair.!The!shape!of!the!
nasal!airway!tends!to!cause!particles!to!embed!in!mucus!in!the!back!of!the!pharynx!and!slide!
down!to!the!esophagus.!
!
Air!is!filtered!in!the!trachea!and!the!bronchi.!
Epithelial!cells!lining!the!airways!and!sub-mucosal!glands!secrete!saline!and!mucus.!
Cilia!move!the!mucus!layer!toward!the!pharynx,!removing!trapped!pathogens!and!
particulate!matter.!
!
Saline!is!produced!by!the!epithelial!cells!and!overtop!of!the!saline!is!a!layer!of!mucus!produced!
by!goblet!cells.!Mucus!contains!immunoglobulins.!The!epithelial!cells!also!contain!cilia,!which!
push!the!mucus!towards!the!pharynx!(mucocillary!escalator).!See!diagram!on!next!page!for!the!
mucocillary!escalator.!
! !
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