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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…