3/17/08 pathway of air/ o 2 nose – external nares → nasal cavity → internal nares pharynx...
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3/17/08
Pathway of Air/ O2
Nose – external nares → nasal cavity → internal nares
Pharynx – nasopharynx → oropharynx → laryngopharynx
Larynx – epiglottis → larynx Trachea – trachea Bronchi – primary bronchi → secondary bronchi → tertiary bronchi → bronchioles
Lungs – alveoli → blood stream
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Pathway of Air/ O2
Each component is composed of special tissues which aid in their function
Passageways & accessory structures in the nose and pharynx = upper respiratory system
Nose: external & internal nose♦Outside: cartilage & skin structure with 2 openings =
external nares♦Directs air into nasal passageways♦External = object of “vanity’
•“nose job” = Rhinoplasty – surgery to repair or alter nose structure – involves addition or removal of tissue
•Involves inconspicuous incisions & local anesthesia
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Pathway of Air/ O2 - SkullNostrils lead into 2 chambers separated by the nasal
septumRight and left chambers of the nasal cavityWalls of the nasal septum = ethmoid & vomer bonesProtrusions of the bone = nasal conchae (superior,
middle, inferior)♦Allows air to swirl in the nasal cavity – airborne particles get
trapped in mucus♦Cavity is lined with mucous membrane♦Mucus is secreted by the paranasal sinuses (=air cavity with
epithelium in the skull)Floor of the nasal cavity = hard palate (roof of the
mouth)
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Function of the NoseDirects air into the nasal passagewayWarms air via blood circulationLocation for olfaction sensationTraps particles & microbes = non-specific defense
♦These then get swallowed with mucous
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Pathway of Air/ O2 – Pharynx and on From the nasal cavity, air
enters internal nares then the pharynx (throat)
Pharynx♦Shared by digestive and
respiratory systems♦It is a muscular tube lined with
mucous epithelium Just behind the nasal cavity =
nasopharynx The oropharynx is located right
under the soft palate – base of the tongue at the opening of the throat
♦It is lined with stratified squamous epithelium (b/c it is shared with the digestive system
Fig. 21.3
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Pathway of Air/ O2 – Pharynx and on
Fig. 21.3
Laryngopharynx♦Below oropharynx = cavity♦Opening to esophagus & trachea♦Common area for air & food♦Stratified squamous epithelium
Next air enters the Larynx♦Top of the trachea♦Epiglottis = elastic cartilage
•Allows distinguish food vs. air•It closes the glottis (opening of
the larynx) if food is passing into the pharynx
•The ligaments stretch during swallowing to prevent food from entering the nasal passageway
•Fig. 21.5
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Pathway of Air/ O2 – Larynx (& sound)
Fig. 21.4
Larynx♦Cylinder made of cartilage,
ligaments & skeletal muscle♦Note large pieces of hyaline
cartilage♦The larynx contains 2 ligaments
stretched from cricoid cartilage to thyroid cartilage = vocal ligaments (commonly called “vocal cords”
♦Air brushes against the vocal cords and creates vibrations = sound
The Larynx is important for air passage and speech
Skeletal muscles lengthen and shorten vocal cords – produces different sounds
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Pathway of Air/ O2 – Trachea
Fig. 21.6
aka “windpipe” Tube made of smooth muscle
from larynx to bronchi Supported by cartilage rings
♦C-shaped cartilage – open at back = flexibility & expansion
♦Posterior wall – pseudostratified epithelium
Bifurcation at bottom of trachea (into 2)
Ridge @ the bifurcation =carina
♦Contains the cough reflex center 2 branches = Primary bronchi
(to right and left lung)♦Cartilage rings support the bronchi
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Pathway of Air/ O2 – Bronchi
Fig. 21.9
Primary bronchi Each Primary bronchi branches into
secondary (lobar) bronchi♦These go to individual lobes of the lung
These then branch into the tertiary (segmental) bronchi
♦These are branches within each lobe Branch to bronchioles
♦End in lobules The bronchi regulate the air flow through
the lungs Bronchitis = infection/inflammation of the
bronchi♦Acute bronchitis is usually caused by a virus
(sometimes by bacteria)♦Cough, mild fever, yellow/green mucous
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Pathway of Air/ O2 – Lung
Fig. 21.7
Collection of lobules containing alveoli Air sacs = light consistency Whole lung = paired organ - Right and left side Each lung is divided into lobes
♦Right = divided into 3 lobes by fissures ♦Left = divided into 2 lobes (know names of fissures and lobes for lab)
The shape of the lungs accommodates neighboring organs♦Heart is slightly to left = left lung is less broad & has cardiac notch♦Right side – liver is just below diaphragm = right lung is shorter
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Pathway of Air/ O2 – Lung
Fig. 21.7
Flat base at the bottom, pointed apex at the top Each lung is covered by a pleural membrane on the outside Review characteristics of pleural cavity Medial surface of lungs = surface in middle
♦Entry point for bronchi & blood vessels (Hilus)♦Primary bronchus and pulmonary arteries & veins
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Pathway of Air/ O2 – Lung
Fig. 21.9
Bronchus divides further inside the lungs – to each lobe Divided into segments within each lobe
♦Bronchopulmonary segment Visceral pleura extends into the lung – divides segments into
smaller sections♦Each section = Pulmonary lobule
Each lobule♦Contains a cluster of alveoli♦Receives air from the Bronchioles♦Lymph vessel circulation♦Pulmonary arteries and venules
Each alveolus within each lobule♦Hollow air sac♦Two or more air sacs may share a common opening = alveolar sac♦Recall what you saw in lab…
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Alveoli In Pulmonary Lobule
Fig. 21.9
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Pathway of Air/ O2 – Alveoli Alveoli = location of gas exchange Each alveolus – is confined – consists of a layer of simple
squamous epithelium Epithelium also contains
♦Macrophages- to engulf any escaped pathogens♦Septal cells – special cells that secrete a liquid called surfactant
•A surfactant keeps alveoli from collapsing shut
There is a continuous capillary adjacent to each alveolus These are connected by fused basement membranes of
epithelial cells & endothelial cells
Gas crosses 3 layers CO2 enters alveolus & O2 enters capillary
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Respiratory System
Chapter 21 – Day 3
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Alvioli – Capillary Interface
Fig. 21.11
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Mechanics of RespirationVentilation
♦= mechanical process♦involves the diaphragm and skeletal muscles (intercostal
muscles)
Breathing consists of 2 phases: ♦Inspiration
•air is taken into the lungs
♦Expiration•Air passes out of the lungs
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Mechanics of RespirationAir is moving in & out because of pressure gradientsAir flows from high pressure to low pressure…For air to enter the lungs, pressure should be low in
the lungs♦EXPANSION of lungs lowers pressure♦The Diaphragm contracts – pushed down = opens space in
the lungs♦External intercostal muscles contract – elevates chest
•Pulls on parietal pleura
•Pulls on visceral pleura
•Expands space into the lung
The pressure gradient forces air into the lungs (insp)ACTIVE process – powered by muscle
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Mechanics of RespirationInspiration = ACTIVE process – powered by muscleExpiration = PASSIVE processObjective = increase pressure in lungs to create high
pressure gradient in TO out…♦The diaphragm and intercostals relax♦Pushes against pleura – close in on lungs♦Imagine a full balloon with hands pushing against it♦Increased pressure in lungs forces air out
Process of regular breathingDeep breathing & forced expiration require additional
muscles – abdominal muscles
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Mechanics of RespirationThe amount of air entering during breathing depends
on several factorsCOMPLIANCE – degree of expandability of lungs
♦Large compliance – more air enters♦Elastic fibers surround alveoli & surfactant in alveoli
contribute to compliance & mobility of thoracic cage•Less surfactant – alveoli collapse – decreases comp.•Less elasticity = increases compliance
♦Emphysema•Shortness of breath, weak at exertion•Destruction of alveolar surface = loss of elasticity•Merged alveoli = larger space, but not enough capillary
support, so gas exchange does not support demand♦Skeletal disorders
•Arthritis or rib injuries reduce compliance
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Lung mechanics
Fig. 21.13
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Lung mechanics
Fig. 21.14
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Lung mechanics
Fig. 21.15
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Lung mechanics
Fig. 21.16
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VentilationOccurs at a
programmed rhythm♦Inspiration every
___ seconds
Normal breathing is called Eupnea
This rhythm (a.k.a. your breathing) is controlled by the pons & medulla in the brain
Fig. 21.26
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VentilationMedulla
♦Rhythmicity area♦2 centers♦Control neurons of
diaphragm & intercostals♦Quiet breathing =
Eupnea•inspiration every 5 sec.
♦Centers are activated then inhibited
♦Also involved in forced breathing (hyperpnea) – other controls are also involved here
Fig. 21.26
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VentilationPons
♦Pneumotaxic & apneustic areas
♦Adjust activity of the respiratory centers
♦Adjusts rate & depth of respiration
Fig. 21.26
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VentilationOther, additional controls can change rhythm
♦Conscious control•Cerebrum sends action potential to respiratory centers
♦Stretch receptors in chest♦Chemoreceptors
•Sense change in blood CO2/O2 concentration
♦Autonomic nervous system•Accelerates or slows down breathing
Problems with neural control in ventilation can result in apnea = breathing stops for long periods (sleep apnea)
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Homeostatic controls (response to changes in PCO2)
Fig. 21.27
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Gas ExchangeVery important activity in the lungs = gas exchange
between the alveoli & capillariesO2 enters blood vessel whileCO2 enters alveolus
Driving force = pressure gradient♦Partial pressure of individual gases…♦Know what is high/low
•in lungs vs. tissues
•What will move? which way? where?
O2 & CO2 uptake is different
Fig. 21.19
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Gas ExchangeO2 uptake in the lungs
♦O2 enters blood by simple diffusion because of the concentration gradient & the partial pressure gradient
The next step is transportation♦RBCs contain hemoglobin = high affinity for O2
♦When O2 enters blood:
•98.5% binds to hemoglobin
•1.5% remains in plasma
•Remember each Hb has 4 heme groups ◦ = 4 Fe2+
•Max. of 4 O2 can bind to one Hb protein
•but….
•There are 280 million Hb in one RBC! Fig. 21.24
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SaturationIf all hemoglobin molecules are bound to full capacity
= 100% saturation of O2 in the blood
Partial saturation = not all Hb has O2 ♦Thus the blood is not carrying up to it’s maximum♦Why would that ever happen?
Fig. 21.20
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SaturationPartial pressure of O2
♦Higher PO2, more saturation
♦Even at 60mg Hg
♦At higher altitudes you get low PO2, so the body produces more RBCs to compensate
Fig. 21.18
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SaturationpH of blood
♦High pH – blood is more alkaline
•More O2 binding = more saturation
♦Low pH – blood is more acidic•O2 is released from Hb = less
saturation
Bohr effect♦CO2 makes blood more acidic
♦When CO2 is high, O2 is low
♦O2 goes to tissues as CO2 enters blood
Fig. 21.21
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SaturationTemperature
♦Higher temp. = less saturation•General property of gases in
solution
♦O2 is released to tissues♦If O2 levels are low in the blood
the amount that is released is reduced by vasoconstriction
•This is the response during shock
Reaction products♦O2 is used for glycolysis♦More consumption of O2 =
higher concentration of glycolysis products = lower saturation in blood and more O2 needed in cells
Fig. 21.21
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SaturationExercise
♦Combined effect♦↑ exercise - ↓ saturation♦↑ respiration rate, but…♦Temperature is increased
♦Lactic acid lowers pH – lower pH = less O2 bound to Hb – releasing at tissues
Other influences♦Surface area of alveoli exposed to capillaries♦Rate of respiration (inhaling & exhaling) b/c also affects
blood pH
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CO poisoningHb has a high affinity for O2,BUT it also has a high
affinity for CO (carbon monoxide)Problem is CO binds but cannot be released from Hb
as easily as O2 CO poisoning
♦CO bound to Hb♦Therefore less O2 saturation♦Less O2 delivered♦Condition = HYPOXIA♦Symptoms: headache, dizziness, gasping
Another cause for hypoxia is atelectasis♦Collapsed alveoli♦Blockage (internal) of bronchiole or bronchus (tumor, lymph
node, mucus plug)
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Transport of CO2 in the bloodVery different from O2 transport
♦O2 is mostly bound to Hb
Only 23% of CO2 is bound to hemoglobin
7% is in plasma as CO2 – as dissolved gas
The majority of CO2 (70%) is converted to carbonic acid = H2CO3 …
Fig. 21.23
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Transport of CO2 in the blood
Fig. 21.23
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Transport of CO2 in the bloodThis process alone would create a high “-” charge in
the plasmaTo balance the charge a chloride shift occurs
♦Cl- is exchanged for HCO3-
♦This keeps ions balanced♦KCl is formed = buffer effect
HCO3-, CO2 in plasma, CO2 on Hb are all transported
to the lungsThe H+ in the blood makes it acidic, low pHAt the alveoli
♦HCO3- has to be changed back to CO2 Fig. 21.23
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Transport of CO2 – at the alveoli
HCO3- has to be changed back to CO2
♦HCO3- re-enters the RBC where it reacts with H+ ions
♦CO2 and H2O are produced
♦Cl- splits from K+ - returns to plasma
As a result of all of this♦The pH of the blood increases (= more basic)
♦High pH favors O2 saturation
♦CO2 gas leaves the blood vessel - CO2 in plasma & on HB diffuse out
Good general overview of O2 and CO2 transport♦Fig. 21.24
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HyperventilationHyperventilation =
♦Rapid breathing♦Air is moving in & out of the lungs very fast
♦HCO3- leaves blood faster at the lungs as CO2
♦Results in an increase in pH = Alkalosis, b/c PCO2 is low
♦At a high pH•O2 remains bound to Hb, not released at tissues
♦Can result in dizziness, unconsciousness
So, how does breathing into a bag help?♦Breathing in the bag, you breath in CO2
♦Which decreases blood pH – thus you release O2 at tissues…
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HypoventilationHypoventilation
♦Slow breathing♦Results in low pH = acidosis
♦HCO3- remains in the blood
♦O2 is released before it can be transported to the tissues
♦BECAUSE – high pH = low saturation of O2 on Hb – released and not reaching tissues
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Respiratory DisordersCommon cold
♦Affects upper respiratory region♦Rhinovirus & adenovirus
Pneumonia♦Inflammation of lobules♦Fluid leaks into alveoli
•Constricts bronchi
♦Usually occurs when defense system is weak•Pathogens escape “filtering” process
•Typically caused by bacteria, fungi
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Respiratory DisordersCystic fibrosis
♦Dense, viscous mucus production♦Cannot be moved efficiently through respiratory
passageway♦Respiratory defense is not efficient♦Risk for infection is very high♦It is largely a genetic disorder
Tuberculosis♦Affects a large population globally♦It is a bacterial infection of the lungs (Notes from lab)♦Responsible for many deaths world-wide and once was
quite bad in U.S. – new antibiotic-resistant strains of TB…
Emphysema, Lung cancer – in book, page 649…
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