:  ACTION

Site of gas exchange 

Consists of respiratory bronchioles, alveolar ducts, and alveoli

Consists of the respiratory and conducting zones

To supply the body with oxygen and dispose of carbon dioxide

need a large surface area for this

provide a way to move air in and out for the above to take place

muscles and nerves control

elastic fibers contribute

keeps itself moist, warm, clean by various structures, chemicals

produce sounds

allow smell

help regulate blood volume and pressure

secrete an enzyme 

recall that mucous membrane line passages open to outside

in upper tract – mucous glands

in tubes of lower part of system there are bundles of smooth muscle

epithelial tissue cells vary along the way

pseudostratified, cuboidal, squamous

since the system is a ‘dead end’ unlike the digestive system, debris taken in needs to be removed (or prevented from entering at all)

mucous cells produce sticky mucus

cilia wave mucus away from lungs

alveolar macrophages patrol the final sacs

The only externally visible part of the respiratory system that functions by:

Providing an airway for respiration

Moistening and warming the entering air

Filtering inspired air and cleaning it of foreign matter

Serving as a resonating chamber for speech

Housing the olfactory receptors-your sense of smell

Lies in and posterior to the external nose

Is divided by a midline nasal septum

Opens posteriorly into the nasal pharynx

The floor is formed by the hard and soft palates

Superior, medial, and inferior conchae: shelves

During inhalation the conchae and nasal mucosa:

Filter, heat, and moisten air

During exhalation these structures:

Reclaim heat and moisture

Minimize heat and moisture loss

bones that surround the nasal cavity

Sinuses lighten the skull and help to warm and moisten the air

Funnel-shaped tube of skeletal muscle that connects to the:

Nasal cavity and mouth superiorly

Larynx and esophagus inferiorly

Attaches to the hyoid bone

Continuous with the trachea posteriorly

Some functions of the larynx are:

To provide an open (patent) airway

To function in voice production

Shield-shaped thyroid cartilage with a midline laryngeal prominence (Adam’s apple)

Signet ring–shaped cricoid cartilage

small cartilages

a flap of epithelial tissue covering  cartilage

necessary to protect larynx from food entering trachea

Composed of elastic fibers that form mucosal folds called true vocal cords

The medial opening between them is the glottis

They vibrate to produce sound as air rushes up from the lungs

The pharynx resonates, amplifies, and enhances sound quality

Sound is “shaped” into language by action of the pharynx, tongue, soft palate, and lips

Valsalva’s maneuver

Air is temporarily held in the lower respiratory tract by closing the glottis 

Causes intra-abdominal pressure to rise when abdominal muscles contract

Helps to empty the rectum

Acts as a splint to stabilize the trunk when lifting heavy loads

Flexible and mobile tube extending from the larynx into the mediastinum

Lined with cilia and mucus secreting cells

Warm and cleansed of impurities

Saturated with water vapor

Main bronchi subdivide into lobar (secondary) bronchi, each supplying a lobe of the lungs

Air passages undergo 23 orders of branching

notice that these are short and partly outside of the lung tissue

they enter at the hilum

Bronchioles 

Consist of cuboidal epithelium

Have a complete layer of circular smooth muscle 

no more cartilage or mucus producing cells

right lung has three lobes

left lung has two…. why????

left is slightly

      longer

pleural membrane

    covers each

    separately

note that lungs are divided into sections

smallest is the 

blood and tubing

is anchored ultimately to pleura

Defined by the presence of alveoli; begins as terminal bronchioles feed into respiratory bronchioles

Respiratory bronchioles lead to alveolar ducts, then to terminal clusters of alveolar sacs composed of alveoli

Approximately 300 million alveoli:

Account for most of the lungs’ volume  

Provide tremendous surface area for gas exchange

Are a single layer of type I epithelial cells

Permit gas exchange by simple diffusion

Type II cells secrete surfactant

not involved in respiratory membrane

Alveolar macrophages here

Alveolar cells 

Capillary walls

Their fused basal laminas

This is the barrier that oxygen and carbon dioxide cross 

Interior of alveolus  has a thin layer of water

supply systemic venous blood to be oxygenated

Branch profusely, along with bronchi

Ultimately feed into the pulmonary capillary network surrounding the alveoli

provide systemic blood to the lung tissue

Arise from aorta and enter the lungs at the hilum

Supply all lung tissue except the alveoli

These are not involved in renewing RBCs with oxygen

Thin, double-layered serous membrane

Parietal pleura

Covers the thoracic wall and superior face of the diaphragm

Continues around heart and between lungs

Visceral  pleura

Covers the  lung surface

getting oxygen to the cells

by way of the lungs, RBCs

pulmonary ventilation is BREATHING

gas diffusion across a respiratory membrane and into the blood

transport of oxygen and carbon dioxide to the working cells

this is most of the rest of the chapter

last section is neural control of breathing

pulmonary ventilation, consists of two phases

Inspiration – air flows into the lungs

Expiration – gases exit the lungs

diaphragm

external intercostals

muscles involved in breathing

atmospheric pressure is compressing us

also compressing things around us

liquids tend to resist being squeezed

gases can be compressed easier

their molecules can have less space to move around if you compress them

if you squeeze a plastic bottle into a smaller size – there will be more pressure inside

is due to the weight of the air – that is what moves air into the lungs

At sea level = 760 mm Hg

When respiratory muscles are at rest – the pressures on the inside of the lungs and alveoli are about the same as on the outside of the thoracic wall

just sit with your mouth open- the pressure of the air (760 mm Hg) is the same inside the lungs as out

it has equalized (called intrapulmonary pressure)

if you change the size of your thoracic cavity – change its volume, then pressure will increase or decrease

when you expand your rib cage/thoracic cavity – the outer layer of the membrane is pulled outward also

it is laying up tight to the inside of the rib cage

since the inner layer is right there, almost touching the outer layer (except for a small amount of liquid) it will be pulled outward, too

but the inner layer also lies on lung tissue, which resists being pulled outward – the elastic fibers pull lung tissue together

the newly created slight space between the layers means there is more room for molecules  

so the pressure between the double layered pleural membrane is always a few mm Hg less than in the lungs – this is the --

The two layers of the pleural membrane are separated by a thin layer of liquid

They resist being pulled apart

When the ribs move outward, they pull the parietal layer out with them

BUT THE ELASTIC FIBERS RESIST – pull back

Then a tiny space is created between the two parts of the membrane (less pressure here because of increased space)

That lowered pressure attracts the visceral part of the membrane outward to follow the parietal layer

IN THE HEALTHY LUNG AIR CANNOT ENTER TO EQUALIZE PRESSURE

The lung tissue  itself just follows both of the layers outward

the lungs have lots of elastic fibers that pull them tighter 

plus there is the surface tension  in the alveoli

water molecules in the alveoli try to be cohesive with each other = also pulls tighter

But yet the lungs expand…

Because they are pulled out by the pleural membrane (diaphragm is stronger than water and elastic fibers)

Lungs would collapse if the intrapulmonary and intrapleural pressure were the same

– collapsed lung

how does this happen?

bronchiole is plugged- alveoli absorb all their air and collapse

chest wound

Can also be caused by air between the pleural membranes

pneumothorax

breaks the fluid bond and the elastic fibers recoil the lung tissue

The inward tendency is in opposition to the pulling outward of the thoracic cavity

So in the healthy person

the lungs are pulling back (getting smaller)

and that creates the lesser pressure between the membranes (more space develops between the two layers)

remember that the double membrane RESISTS being pulled apart

The opposing force –movement of the chest wall pulls the thorax outward to enlarge the lungs

The diaphragm moves down when it contracts and the intercostal muscles contract to lift the ribs

The lungs expand (‘grudgingly’) to follow the enlarged space

So now we have the movement of lung tissue because lowered pressure in the intrapleural cavity pulls them out

When they are pulled out they are bigger – have more volume

Lungs are expanding with each breath

There are pressure changes

But the volume of the lung is also changing

Remember that those volume changes will cause pressure changes elsewhere

size of alveoli will changed and ….

Air will flow down its pressure gradient

A mechanical process that depends on volume changes in the thoracic cavity

Volume changes lead to pressure changes, which lead to the flow of gases to equalize pressure

REMEMBER THE GRADIENT MOVEMENT

The diaphragm and external intercostal muscles (inspiratory muscles) contract and the rib cage rises

The lungs are stretched and intrapulmonary volume increases

More space  available

So intrapulmonary pressure drops below atmospheric pressure (1 mm Hg)

Air flows into the lungs, down its pressure gradient, until intrapulmonary pressure = atmospheric pressure

Inspiratory muscles relax and the rib cage descends due to gravity

Thoracic cavity volume decreases

Elastic lungs recoil passively and intrapulmonary volume decreases

more cramped space, so…

Intrapulmonary pressure rises above atmospheric pressure (+1 mm Hg)

Gases flow out of the lungs down the pressure gradient  (and out the trachea and nose)

The liquid coating the alveolar surface is always acting to reduce the alveoli to the smallest possible size

so the surface tension of the water molecules in the alveoli contribute to lung recoil

BUT --Surfactant, a detergent-like complex, reduces surface tension and helps keep the alveoli from  totally collapsing

The ease with which lungs can be expanded

Determined by these factors

Distensibility of the lung tissue

can it be stretched outward?

Surface tension of the alveoli

are fluids or mucus blocking?

How flexible is the thoracic cavity?

is rib cage stiff or reduced?

Scar tissue or fibrosis that reduces the natural resilience of the lungs

Ex.??

Blockage of the smaller respiratory passages with mucus or fluid

Ex. ??

Reduced production of surfactant

Ex. ??

Decreased flexibility of the thoracic cage or its decreased ability to expand

Ex. ??  more in next slide

Examples include:  

Deformities of thorax

Ossification of the costal cartilage

Paralysis of intercostal muscles

diaphragm and external intercostal muscles are most important

when you have to take in more

SCM, pectoralis minor, abdominal muscles

when you want to blow out excess

abdominal muscles, internal intercostal

What about air movement in the healthy person?

Assuming all positive conditions

we can predict how much air will enter and leave and be used and be left inside 

based on age, size, habits

How much air do you move around?

Can be described in ml of air

These are measured as a way to determine disease or its potential

Total pressure exerted by a mixture of gases is the sum of the pressures exerted independently by each gas in the mixture

The partial pressure of each gas is directly proportional to its percentage in the mixture

So with the pressure at 760 mm Hg total at sea level, we can figure out the individual pressures based on what percent is found in the air

Ex. P of oxygen or PO2 = 21% of 760 = 159 mm Hg

When a mixture of gases is in contact with a liquid, each gas will dissolve in the liquid in proportion to its partial pressure

For example - a can of pop has been bottled under conditions where they force carbon dioxide into the bottle under pressure.  Letting it stand for a while, with the top off, coming up to room temperature will cause the gas to leave the liquid

But the temperature and the solvent will effect how much gas can dissolve also

Dalton figured out that each gas IN THE AIR contributes its share to the total pressure of the air – called PARTIAL PRESSURES

Henry saw that at a given temperature the amount of any gas IN SOLUTION was the same proportion as its pressure in the air

What is in the alveoli will not be the same composition of the air outside your body

It is a mix of ‘old’ and ‘new’ air

Plus there is more moisture

And oxygen leaves for the blood and carbon dioxide enters from the blood

What is in the alveoli will not be the same composition of the air outside your body

It is a mix of ‘old’ and ‘new’ air

Plus there is more moisture

And oxygen leaves for the blood and carbon dioxide enters from the blood

if you are at a high altitude – less pressure of oxygen and less diffusion into blood = light-headed 

pneumonia includes excess liquid and some consolidation of that liquid in the alveoli = oxygen has to move farther and through a liquid it doesn’t mix well with

if you are at a high altitude – less pressure of oxygen and less diffusion into blood = light-headed 

pneumonia includes excess liquid and some consolidation of that liquid in the alveoli = oxygen has to move farther and through a liquid it doesn’t mix well with

1. Partial pressure gradients and gas solubilities

2. Short distance to diffuse (not across fluid build up)

3. Respiratory gases are lipid soluble

4. Surface area is large

Factors influencing the movement of oxygen and carbon dioxide across the respiratory membrane

The partial pressure of  oxygen (PO2) in venous blood is 40 mm Hg; the partial pressure in the alveoli is 104 mm Hg

This steep gradient allows oxygen partial pressures to rapidly reach equilibrium (in 0.25 seconds)

oxygen moves from alveoli to nearby capillaries

a single RBC is in the capillary about .75 second

homeostasis at work

Changes in PCO2 in the alveoli cause changes in the diameters of the BRONCHIOLES

Passageways servicing areas where alveolar carbon dioxide is high dilate

so carbon dioxide can LEAVE

Those serving areas where alveolar carbon dioxide is low constrict

So carbon dioxide levels in lungs trigger smooth muscle changes in BRONCHIOLES

your body adjusts these to the best possible usage

oxygen pressure affect the pulmonary ARTERIOLES

Note: previous slide – bronchioles affected by carbon dioxide levels

if oxygen is in short supply (blocked bronchiole) the arterioles constrict – send blood to other areas 

where there is more oxygen and the chance to pick up oxygen is better

Decrease in surface area with emphysema, when walls of adjacent alveoli break through

The factors promoting gas exchange between systemic capillaries and tissue cells ( example – way down in your foot)  are the same as those acting in the lungs

The partial pressures and diffusion gradients are reversed

PO2 in tissue is always lower than in systemic arterial blood

you can’t just dissolve all the oxygen you need in the blood plasma

likewise carbon dioxide

the RBCs do much absorption and transport

and can pick up or release the gases as needed

Ex. when oxygen levels in plasma are high RBCs will take up excess and also reverse

you can’t just dissolve all the oxygen you need in the blood plasma

likewise carbon dioxide

the RBCs do much absorption and transport

and can pick up or release the gases as needed

Ex. when oxygen levels in plasma are high RBCs will take up excess and also reverse

Molecular oxygen is carried in the blood: 

Bound to hemoglobin (Hb) within red blood cells  - most (98%)

Dissolved in plasma

Each hemoglobin can carry 4 molecules of oxygen

called oxyhemoglobin (HbO2) 

hemoglobin picks ups and drops off the oxygen

Each Hb molecule binds four oxygen molecules in a rapid and reversible process

about 250 or more molecules of hemoglobin per RBC

hemoglobin is a shape-changing molecule 

it has a greater ability to bind oxygen after one oxygen molecule has bound

we say hemoglobin is fully saturated – when all the heme groups have an  O2 - HbO2

speed of loading up or off -loading depends on pressure of oxygen, pH, temperature, pressure of carbon dioxide

Normally only 20–25% of bound oxygen is unloaded during one systemic circulation

If oxygen levels in tissues drop:      (exercise) (less oxygen pressure)

More oxygen dissociates from hemoglobin and is used by cells 

Respiratory rate or cardiac output need not increase

This is a backup system

Normally only 20–25% of bound oxygen is unloaded during one systemic circulation

If oxygen levels in tissues drop:      (exercise) (less oxygen pressure)

More oxygen dissociates from hemoglobin and is used by cells 

Respiratory rate or cardiac output need not increase

This is a backup system

Temperature, H+, PCO2, and BPG

hard working muscles give off heat = oxygen released faster

hard working muscles give off lactic acid = oxygen released faster

hard working muscles give off CO2 = oxygen released faster

 the rise in temperature increases BPG synthesis

a wedge-like molecule that binds Hb until it gets to lungs

All these factors ensure oxygen unloading in the vicinity of working tissue 

Temperature, H+, PCO2, and BPG

hard working muscles give off heat = oxygen released faster

hard working muscles give off lactic acid = oxygen released faster

hard working muscles give off CO2 = oxygen released faster

 the rise in temperature increases BPG synthesis

a wedge-like molecule that binds Hb until it gets to lungs

All these factors ensure oxygen unloading in the vicinity of working tissue 

too few RBCs

abnormal or deficient Hb

thrombus or embolism

toxins (cyanide)

carbon monoxide

competes with oxygen to bind and binds much more tightly

signs are not cyanosis, but reddish skin

Carbon dioxide diffuses into RBCs and combines with water to form carbonic acid (H2CO3), which quickly dissociates into hydrogen ions and bicarbonate ions

In RBCs, carbonic anhydrase reversibly catalyzes the conversion of carbon dioxide and water to carbonic acid

The carbonic acid–bicarbonate buffer system resists blood pH changes

If hydrogen ion concentrations in blood begin to rise beyond the resting rate, excess H+ is removed by combining with HCO3–

If hydrogen ion concentrations begin to drop, carbonic acid dissociates, releasing H+

The carbonic acid–bicarbonate buffer system resists blood pH changes

If hydrogen ion concentrations in blood begin to rise beyond the resting rate, excess H+ is removed by combining with HCO3–

If hydrogen ion concentrations begin to drop, carbonic acid dissociates, releasing H+

breathe into a paper bag and accumulate carbon dioxide, does the blood pH go down or up?

down – towards acid

what happens to breathing rate?

what happens to the carbon dioxide concentration of the blood when you hyperventilate?

lowers

what is the major way carbon dioxide is carried in the blood?

bicarbonate ion

breathe into a paper bag and accumulate carbon dioxide, does the blood pH go down or up?

down – towards acid

what happens to breathing rate?

what happens to the carbon dioxide concentration of the blood when you hyperventilate?

lowers

what is the major way carbon dioxide is carried in the blood?

bicarbonate ion

The dorsal respiratory group (DRG), or inspiratory center: 

Appears to be the pacesetting respiratory center

Excites the inspiratory muscles and sets eupnea (12-15 breaths/minute)

Becomes dormant during expiration

outposts or sensors in convenient areas 

they detect chemicals, irritants, stretched tissue

they also respond to emotional conditions and stress

Your DEPTH and RATE of breathing do change  -- WHY?

Changing PCO2 levels are monitored by chemoreceptors of the brain stem

Carbon dioxide in the blood diffuses into the cerebrospinal fluid where it is hydrated

Resulting carbonic acid dissociates, releasing hydrogen ions

but they are not buffered

pH drops and breathing is increased when the chemoreceptors notice

Changing PCO2 levels are monitored by chemoreceptors of the brain stem

Carbon dioxide in the blood diffuses into the cerebrospinal fluid where it is hydrated

Resulting carbonic acid dissociates, releasing hydrogen ions

but they are not buffered

pH drops and breathing is increased when the chemoreceptors notice

Though a rise CO2 acts as the original stimulus, control of breathing at rest is regulated by the hydrogen ion concentration in the brain

special groups of cells in the carotids and in the aortic arch – sense arterial levels of oxygen

levels must drop substantially before this causes a major stimulus for breathing

Example: person with emphysema

arterial carbon dioxide is chronically high

sensors adapt

so declining oxygen is sensed by the peripheral chemoreceptors and THEY ARE THE MAJOR STIMULUS FOR BREATHING – called hypoxic drive

problem arises when EMS administers too much oxygen – breathing slows or stops and carbon dioxide levels rise more

Example: person with emphysema

arterial carbon dioxide is chronically high

sensors adapt

so declining oxygen is sensed by the peripheral chemoreceptors and THEY ARE THE MAJOR STIMULUS FOR BREATHING – called hypoxic drive

problem arises when EMS administers too much oxygen – breathing slows or stops and carbon dioxide levels rise more

carotid and aortic baroreceptors (pressure sensors) also affect respiratory rate

increased depth and rate of breathing that:

Quickly flushes carbon dioxide from the blood

Ventilation can increase 20 fold 

You breath faster to accommodate the exchange rate  HYPERPNEA

Not the same as hyperventilation, which is done at rest

The body responds to quick movement in high altitude (above 8000 ft) with symptoms of acute mountain sickness – headache, shortness of breath, nausea, and dizziness

But over time

Chemoreceptors adapt 

Erythropoiesis occurs

The body responds to quick movement in high altitude (above 8000 ft) with symptoms of acute mountain sickness – headache, shortness of breath, nausea, and dizziness

But over time

Chemoreceptors adapt 

Erythropoiesis occurs

is too little air flow Ex. inflammation

Ex. mucus

Exemplified by chronic bronchitis and obstructive emphysema – can’t get enough air out…..

Patients have a history of:

Smoking

Dyspnea, where labored breathing occurs and gets progressively worse

Coughing and frequent pulmonary infections

COPD victims develop respiratory failure accompanied by hypoxemia, carbon dioxide retention, and respiratory acidosis

chronic = inhaled irritants  cause excessive mucus production

and inflammation 

infections occurs because of static environment of mucus

diagnosis is made when cough is present for more than 3 months during 2 successive years ( with no other diseases)

Characterized by dyspnea, wheezing, and chest tightness

Active inflammation of the airways precedes bronchospasms

Airway inflammation is an immune response caused by release of IL-4 and IL-5, which stimulate IgE and recruit inflammatory cells

Airways thickened with inflammatory exudates magnify the effect of bronchospasms 

Infectious disease caused by the bacterium Mycobacterium tuberculosis 

Symptoms include fever, night sweats, weight loss, a racking cough, and splitting headache

Treatment entails a 12-month course of antibiotics

Accounts for 1/3 of all cancer deaths in the U.S.

90% of all patients with lung cancer were smokers

The three most common types are:

Squamous cell carcinoma (20-40% of cases) arises in bronchial epithelium

Adenocarcinoma (25-35% of cases) originates in peripheral lung area

Small cell carcinoma (20-25% of cases) contains lymphocyte-like cells that originate in the primary bronchi and subsequently metastasize