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External respiration processes
Ventilation - bring air in to lungs by convection=bulk flow, dep on total P diff
Gas exchange - at alveolar level by diffusion, depend on partial P of each gas
Blood gas transport - from pulmonary to systemic
Convection vs diffusion in external respiration
convection for ventilation and transport of blood gases in blood stream
Depends on diff in total P

Diffusion at alveoli/tissues for gas exchange
Depends on partial P diff of each gas
Respiratory quotient
Ratio of CO2 pdt'd to O2 consumed
Usually 0.8 at rest, so 8 CO2 pdt for 10 O2 consumed
CO2 pdtn/O2 consumtion at rest
Around 200ml/250ml per min
Can be represented by RQ too=0.8 ish
Diaphragm
Thin skeletal muscle that separates thoracic and abdominal cavity
Unlike most skeletal muscles, works constantly
Main components and functions of upper airway
Uvula, epiglottis, vocal cords, nasal cavity, pharynx etc

Passage for air, food, and involved in breathing, digestion, phonation
Uvula
Epiglottis
Vocal cords/ vocal folds
Closes naso-pharynx during swallowing, inhibits nasal regurgitation

Block passage to trachea during swallowing (by movemnt of hyoid bone), directs food to esophagus

Lie across laryngeal openig, allow phonation and prevent aspiration of food
Upper airway muscles
More than 20 muscles control position of 4 structures (soft palate, tongue, hyoid apparatus, pharyngeal wall) to keep airway closed during swallowing or open during breathing=upper airway dilator
Obstructive sleep apnea
activity of genioglossus muscle of tongue leads to tongue falling back to airway during sleep= can die from lack of O2

So tongue impt upper airway dilator
Upper airway mucosal lining
Heats and humidifies inspired air
Inspired air heated and humidified from heat/moisture lost from lning and by time reaches trachea 37C saturated water vapor
Expired air releases heat moisture and partially warm/humidify mucosa, remaining heat/moist recovered from blood supplying the airways
Tracheostomy
Tube inserted at neck to provide air, bypassing trachea
Air is dry and cold
How many lobes does each lung have?
R=3
L=2
Also L slightly smaller bc of heart
Airway generation
Trachea=0, bronchi=2 etc, usually up to 23~24=alveolar sacs
Diameter dec down generation while number inc
Airway classification based on functions
Trachea, bronchi, bronchioles, terminal bronchioles (up to around gen 16) only air conducting function
Respiratory bronchioles, alveolar ducts, and alveolar sacs (gen 17~23/24) are transitional and respiratory zones where gas exchange occur
Airways w/ cartilage
Trachea has U shaped cartilage and "trachealis" smooth muscle completing the ring
Bronchi have cartiage plates interspersed w/in bronchial smooth muscle ring
Provides stability and structure, these don't collapse
Airways w/out cartilage
Can collapse
Bronchioles - composed mainly of smooth muscle
Terminal bronchles - last gen w/ only conducting function
Respiratory bronchles - conduct and gas exchange due to presence of alveoli
Alveolar ducts - walls covered w/ alveoli and terminate in alveolar sacs
Turbulent flow
axial and radial in direction, noisy, rapid speed
Occur in large diameter airways where speed of air molc fast = upper airways i.e. trachea and up to bronchi during exercise
Air flow and air density
Replacing N of air w/ lighter density gas e.g. He can make laminar flow more likely than turbulent flow
Laminar flow
Streamline (parabolic profile) flow, silent and slow
Found in smaller airways (less than 2mm diameter)= periphery of lungs where speed of air molcs slow
Driving pressure (P diff) pushes air straight in latreal direction w/ no axial movement
Can sometimes change turbulent flow to laminar by changing air density to lighter
Transient flow
In between turbulent/laminar flow, prominent thruout most of tracheobronchial tree
Disturbed laminar flow i.e. some axial movemnt tho not as strong as turbulent
Laryngeal tumor case study
Patient has laryngeal cancer, want to improve airflow to lung by changing flow regime to predominantly laminar flow= lowers the work of breathing req'd to overcome resistance to airflow
Can change air density= N to He= more likely to be laminar
Also can inc ext P by tracheostomy, but would inc dependence on machine.. so yeah
Airway wall lining changes from proximal to distal
Large conducting airway (trachea, bronchi) - thick epithelium w/ ciliated cells, smooth muscle, cartilage, mucous gland and goblet cell
Small conducting airways (bronchioles etc) - no cartilage/muc gland/gob cell, thinner epithelial wall w/ shorter cells (ciliated), smooth muscle
Alveolus - no galnds/muscle/cartilage, thin squamous epithelial wall, capillaries to supply blood
Blood supplies to airway
Conducting zone (trachea~bronchioles) by bronchila circulation i.e. systemic
Respiratory zone (alveoli) by pulmonary circulation capillaries
Alveolar genearl structure
300 mill alveoli each in contact w/ 100s of pulmonary capillaries i.e. highly vascularized
Pores of Kohn for colateral ventilation
Pores of Kohn
Holes in walls of adjacent alveoli
Allow colateral ventilation - if access to part of lung blocked by mucus etc then equalize P of adjacent alveoli=prevent lung collapse
Type I pneumocyte
alveolar cell - flat squamous epithelium, makes up 95% of alveolar wall
Thin= 0.1-0.3 microns
Type II Granular pneumocyte
Alveolar cell - secretory cuboidal cell that makes up part of alveolar wall
Has lamellar inclusion bodies that store pulmonary surfactant to reduce surface tension
Pulmonary surfactant
pdt'd by typeII granular pneumocyte cells, stored in lamellar inclusion bodies w/in cell
Reduce alveolar surface tension
Consists of lipids and proteins
DPPC is the key surface tension reducing agent
Type III alveolar macrophage
Not part of alveolar wall= extracellular
migratory, phagocytic, moves along wall to eat foreign particles
Alveolar capillary membrane
Distance air has to travel from inside alveoli to blood
So pulmonary surfactant > alveolar epithelium > interstitium > capillary endothelium > blood plasma > then to RBC and other way around
Very thin (0.5 um) so cross by diffusion (dep on partial P) not bulk flow (total P)
Alveolar interstitium
Space btwn alveolar/capillary epithelium
Contains collage and elastin fibers that join and supports the system i.e. mechanical support
Also fluid space btwn air& blood barrier part of lymphatic sys so excess fluid drainage (high bp=fluid ooze out and taken up by lymphatic sys, but if too high can seep into alveoli=edema
Airway clearance of particles >10um in diameter
Filtered and trapped by nasal hairs
Irritant receptors lining nasal passages initiate sneeze reflex to remove particles
Airway clearance of particles 2-10um in diameter
Mucociliary transport sys lining airways all the way down to terminal bronchioles
- cilia of epithelial cells whip in same way to move particles towards top where coughed out
Irritant receptors in airway lining initiate coughing reflex to remove particles
Mucous blanket
Cover the airways, secretd by gobulet cell and submucosal glands of mucociliary system of the epithelium
Top layer gel= sticky, trap particles
Bottom layer= aquesous, moved by ciliary motion
Impairment of mucociliary transport system
Consequence and causes
Can inc likelihood of infection
Caused by
Smoking - dec ciliary motion and inc mucuous pdtn
Pathogenic microbes - release stuff that paralyze ciliary motion (e.g. pseudonomas)
Primary ciliary dyskinesia - cilia disfunction due to structural defect (inherited)
Cystic fibrosis - defective chloride channels involved in transport of water+sodium across epithelium = viscous mucus hard to clear from lungs (inherited)
Defence against inhaled particles
Particles smaller than 2um can reach alveoli
Type III alveolar macrophages engulf and degrade them, then moved up by mucociliary system to be removed
Non-degradable inhaled particles
Sharp non-degradable particles e.g. asbestos fibers, silica dusts can injure alveolar epithelium and burst macrophages=release enzymes = inflammation, followed by scar formation (collagen deposited) and pulmonary fibrosis
Can change how easily lung inflate/deflate and affect gas exchange bc alveolar capillary memb thicker
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