Summary

PSL301 Respiratory System Summary Notes

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Course
PSL301 (PSL300)

Institution
University Of Toronto (U Of T )

Complete and in-depth Notes for PSL300 for EXAM prep. Kevin has combined notes from his peers and his own work to provide the most complete and comprehensive study guide for all types of students. He has achieved an overall cumulative GPA of 3.95 during his undergrad at the University of Toronto St...

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Uploaded on June 10, 2018
Number of pages 15
Written in 2017/2018
Type Summary

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RESPIRATORY SYSTEM

Overview of Function and Structure
Functions
- transfer of ggases between air and blood
o O2 comes in  cellular respiration  ATP  CO2 expelled
- Regulation of body pH
o CO2 levels infuence pH of the blood
- Defence from inhaled pathogens/foreign paricles
- Vocalization
o Air needed over vocal cords

Structures that make up Respiratory System
- pharynx (where both air and food pass)
- vocal cords
- trachea  bronchus
- diaphragm (needed for letting air in and out)

Respiratory Muscles
- muscles of inspiration:
o sternocleidomastoids – attach to the top
o scalenes – attach from top and to ribs
o external intercostals – in between ribs
o diaphragm – key muscle below rib cage
- muscles of expiration
o internal intercostals – has diferent orientation as the external ones
o abdominal muscles
Lungs
- pleural sacs enclose the lungs
- two pleural membranes and pericardial cavity in between
- the double membrane structure forms the ‘sac’
Airways
- air is relatively dry and cold, thus the pathway makes it get warmer and
humidified
o air warmed to 37’C
o air humidified to 100%
o air filtered through nose and repspiratory cilia
- below larynx (voice cord) is trachea
- the trachea branches into two primary bronchi (left and right)
- primary bronchi then separates to secondary, and 22 more times terminating in a
cluster of alveoli
- filtering action of cilia – cilia beat in one direction and move the mucus to pharynx
side
- mucus layer traps inhaled particles. The particles then can be either coughed or
swallowed
o watery saline layer below mucus allow cilia to push mucus toward pharynx
- goblet cell secretes mucus
- immune cells along the epithelium also secrete antibodies to disable pathogens
o IgA
- Airway break down

, o 1st bifurcation: right and left main bronchi
o 2~4th bifurcation: lobar bronchi
 Cartilage maintains their shape (and smooth muscle)
o 5~11th bifurcation: segmental bronchi
o 12~16th bifurcation: terminal bronchioles
 stabilized by bronchiolar smooth muscles
o all the above are “conducting airways” = no gas exchange
o constitute an anatomical dead space
 air in this region does not exchange anything with cells

Lobules
- Primary Lobule (and below): region of gas exchange
- Approximately 300 million alveoli, each about 300um in diameter
- Total cross-sectional area is very large, about 180cm squared, and air velocity is
virtually zero
- Alveoli are covered with rich blood supply (from pulmonary artery and then back
to heart in pulmonary vein)
- The exchange is between single layer of endothelial
- Type I alveolar cell
o Constitute the wall of the tissue
- Type II alveolar cell
o Produce surfactants  allow lungs expand more easily
- Elastic fibers constitute as part of the connective tissue
- Alveolar macrophages
o Engulf foreign particles
- Alveolar gas exchange occurs via by passive difusion across endothelium
o Basement membranes are fused

Bloor transport to and from lungs
- 10% of the blood volume comes to lungs
- pressure is low: 25/8mmHg
- Heart (right ventricle)  pulmonary trunk  pulmonary arteries  pulmonary
arterioles  capillaries (oxygenated)  pulmonary venules  pulmonary veins 
heart (left atrium)
- Pulmonary metarteriole have many branches of capillaries coming out
o In case of embolus / blockage, others will cover and filter
o Systemic capillaries on the other hand, serve a particular area, so when
blocked, the area gets killed

Defending respiratory system
- filtering action of nose
- mucous and action of cilia lining the airways
- antibodies secreted onto respiratory surfaces
- macrophages in respiratory tract including alveoli

Lung function  must see the wave diagram
- measured by Spirometry
o clinically used often (ex. before an operation)
o person breathes into a tube

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