The most important function is to deliver atmospheric O₂ to the Blood [so that the blood can deliver O₂ to the peripheral tissues].

Therefore, what is the functional unit of the respiratory system?
  The respiratory surface area - the ALVEOLI.

How does the function of the Respiratory System differ from the function of Blood?

Why is supplying O₂ to the blood the most important function? Review chapter 3 and 17.
  Hint: What process produces ATP?
     What role does O₂ play in this process?
What is aerobic cellular respiration?
     What is ATP?
         How much ATP is produced by aerobic cellular respiration?
            How much ATP is produced by ANAEROBIC cellular respiration?

How long will a person live if they do not have oxygen?
        Nervous tissues (brain, etc) will sustain irreparable damage within 3-5 minutes;
          death occurs within 5-8 minutes.
    What is the relationship between anaerobic cellular respiration and asphyxiation?
         Anaerobic cellular respiration produces ATP via the process of  'glycolysis' only - it produces a
           total of 2 (two) ATP.  While this tiny amount of energy will keep the person going for several
           minutes - long enough to provide an opportunity to get out of a lethal (anoxic) situation - it is NOT
           enough to sustain life in multicellular organisms.

Other respiratory functions are:

Exhale CO₂
Balance the pH of the body
Voice
Defend against pathogens

The functional unit of the Respiratory system is the Respiratory Membrane - the ALVEOLUS (alveoli).  This is where O2 moves from the air into the blood.
  aka: Respiratory surface area

There are two (2) main parts to the respiratory system:

Conducting portion – carries air to the respiratory membrane - nasal cavity, pharynx,
    larynx, trachea, bronchi, bronchioles and alveolar ducts and sacs. The conducting portion
    is aka 'dead air space' because no actual exchange of O₂ or CO₂ takes place in these
    passageways.

Respiratory membrane - the alveoli - where O₂ enters the blood and CO₂ exits the blood.

What is the functional unit of the Respiratory system?
  Why is this the functional unit?
     What happens at the Respiratory Membrane?

The CONDUCTING portion begins with the Nasal Cavity.  Air enters through the external nares, the openings to the nose, and passes over the turbinates.

The external nares allow external air to enter the nasal cavity.  Vibrissae, large nasal hairs, in the opening filter large airborne particles (insects, etc) from the air. 

The turbinates are also called the Nasal Conchae. They are bony ridges on the Ethmoid bone that protrude into the nasal cavity and are covered with mucous membrane. As air moves into the nasal cavity from outside the body, the air must pass by these protrusions. The conchae impede the flow of the air, causing turbulence and the air swirls and eddies within the nasal cavity. (Picture water in a river flowing around a large rock – the water ‘mounds’ up upstream from the rock and just downstream of the rock, the water forms a ‘pocket’ in which the water swirls and eddies.) The air swirls in the nasal cavity – which has four functions:

-Cleans the air- as it comes in contact with the sticky mucous
-Moistens the air as it comes in contact with the wet mucous
-Warms the air as it picks up warm water molecules
-Carries molecules to the olfactory epithelium so that we can ‘smell’

What are the 4 membranes in the body?  Review Chapter 4, Tissues.
   What is the defining characteristic of each type?
      Where is each found?

The floor of the nasal cavity is comprised of the Hard Palate and the Soft Palate.  The soft palate and the uvula work together to close off the nasal cavity during the swallowing reflex and prevent food from entering the nasal cavity.  A cleft palate is a condition in which the hard palate does not properly develop and the nasal and oral cavities are not separated.

From the Nasal cavity, air passes through the internal nares into the Pharynx.
      There are 3 parts to the Pharynx.
          Nasopharynx - opens from the nasal cavity; receives air from the nasal cavity, passes air
                 to the Oropharynx.
          Oropharynx - opens from the oral cavity, receives air from the nasopharynx,  AND food and
                 liquids from the oral cavity;  passes air, food and liquids to the laryngopharynx.
          Laryngopharynx - opens into the larynx and to the esophagus.  Receives air, food and liquid
                 from the Oropharynx; passes air to the larynx, food and liquid to the esophagus.

List the three parts of the Pharynx, and the materials that pass through each.

The Nasopharynx only passes air - therefore, the surface of the nasopharynx is mucous membrane that is also a simple epithelium.  Air is not very abrasive or corrosive.

The Oropharynx and Laryngopharynx both must be able to withstand food (dry, wet, lumpy, etc) and liquid (hot, cold, acidic, etc) therefore the surface of these is a mucous membrane that is also a stratified squamous epithelium.  Food and liquid can be both abrasive and corrosive.

Compare and contrast the lining of the three regions of the pharynx. (Make a Table)

What is the common pathway shared by the respiratory and digestive system?

The larynx is made of several large hyaline cartilage structures with an opening. The largest and most noticeable cartilage of the larynx is the thyroid cartilage - which protrudes from the anterior side of the throat in what is commonly known as the Adam's Apple.  The cricoid cartilage serves as a base for the larynx.

Glottis is the opening into the larynx.
  The epiglottis covers the glottis during the swallowing reflex.

The thyroid and cricoid cartilages are hyaline cartilage, while the epiglottis is elastic cartilage (like the nose and ears).  Elastic cartilage is able to 'bend'.
How does elastic cartilage support the function of the epiglottis?

Vocal chords form the sides of the glottis.

As air moves past the vocal chords, the moving air causes the chords to vibrate (like the strings on a guitar) which causes ‘noise’ which we control to produce ‘speech’.  Long, thick  vocal cords produce deep, low sounds (bass guitar strings), while short, thin vocal cords produce high pitched sounds (soprano, thinner guitar strings).

What is the Thyroid cartilage also called (the common name)?
Where are the vocal chords located?
  How is sound produced?

From the layrnx, air passes into the Trachea.

The Trachea is about 11 cm long (4 inches) and has tracheal semi-rings connected by irregular dense connective tissue.  The Tracheal rings are made of hyaline cartilage which functions to keep the trachea from collapsing (open) during inhalation (much the same way that the wire spiral in a vacuum hose keeps the hose open when the vacuum cleaner is vacuuming.)
How does hyaline cartilage support the function of the trachea?

The Trachea splits into two primary bronchi, one into the left lung and one into the right lung.  The left bronchus is more horizontal (to pass around the heart), while the right bronchus is more vertical.  This is important because food/liquid that goes into the trachea is more likely to enter the right lung, AND when a patient is being ventilated, the nurse/doctor must take care to place the ventilator in a location that ventilates both lungs.

The bronchi branch into secondary and tertiary bronchi - into progressively smaller diameter tubes.  As the diameter of the tubes decreases, the amount of cartilage in the wall of the tube decreases while the amount of smooth muscle increases. The wall of the bronchioles is made of smooth muscle, which gives the ability to bronchodilate or bronchoconstrict.

Asthma is a condition in which the bronchioles bronchoconstrict, and prevent the flow of air into the lungs.  Asthmatics commonly use bronchodilator drugs to improve breathing.

Why is food more likely to enter the right lung than the left?
What happens to the amount of cartilage in the wall of the bronchi as the diameter decreases?
  What is common in the wall of the smaller bronchi and the bronchioles?

Define bronchodilate and bronchoconstrict.
  What is Asthma?

The bronchioles branch into smaller diameter
   Alveolar ducts, which branch into
      alveolar sacs which are composed of grapelike clusters of
        alveoli - the Respiratory Membrane.  (see the graphics and diagrams in the text)

Alveolar macrophages are phagocytes living IN the alveoli that 'eat' foreign objects that are inhaled and reach the alveolus. 
Remember the 'defense' function of the respiratory system?
  What are WBCs?
    What other systems are WBCs part of?
       Describe the characteristics of WBCs (review Blood).
       Integrate the actions of WBCs with Immunoglobulins (immune system) and defense of the respiratory
          system.

Surfactant cells secrete surfactant, a chemical that decreases the cohesiveness of water, which helps to keep the alveoli open.  The respiratory membrane is so thin that the strength of the hydrogen bonds formed between water molecules is strong enough to 'collapse' the alveolus. Each inhaled breath must therefore be 'strong' enough to open the collapsed alveoli.  This means that every breath must be VOLUNTARY.  After a while, the person becomes fatigued and eventually does not have the strength/energy to inhale and dies.  Respiratory Distress Syndrome is a condition in which the person cannot inhale with enough force to get air to the respiratory membrane and is often caused by 'collapse' of the alveoli. 

List the properties of water. (Chapter 2)
  What is the function of 'surfactant'?
    Why is water adhesive and cohesive?

The Alveoli are the functional unit of the respiratory membrane.

The wall of the alveoli is directly attached to the wall of the pulmonary capillaries - O₂ diffuses directly from the air (gas) in the alveolus into the liquid of the blood, while CO₂ diffuses directly from the liquid of the blood into the air (gas) of the alveolus.

Alveoli are grapelike structures whose wall is one (1) cell layer thick immediately attached to the wall of a pulmonary capillary. The whole structure (2 cells and a basement membrane between them) is only 0.1 micrometers thick! It is VERY THIN! And fragile. Because it is so thin, O₂ and CO₂ move diffuse easily across the membrane.

What is simple squamous epithelium?
   Why is it efficient for diffusion?
Describe the struture of the respiratory membrane.
  What is the characteristic of this membrane that supports the function of the respiratory
          system?

In addition, O₂ and CO₂ are LIPID-soluble.  I.e. they both diffuse easily through the cell membrane, because the CM is a phospholipid bilayer.
  Define hydrophobic, nonpolar, lipid-soluble.  (Review Chapter 2 and 3)
       Give some examples.
  Define hydrophilic, polar, water-soluble.
       Give some examples.
    Compare and contrast the functions of polar molecules and nonpolar molecules with respect to
           diffusion across the cell membrane.
    Interpret the expression "like dissolves like".

The surface area (SA) of the membrane is about 1400 square ft. This large SA allows LOTS of molecules of O₂ and CO₂ to move between the air in the alveoli and the blood.

How big is 1400 ft2? 
   Many homes are about 1500 square ft!  This is a LOT of surface area through which O₂ and CO₂ may diffuse.
Why does the body need so much oxygen?

Emphysema – chronic, progressive destruction of alveolar surfaces, decreased Surface Area for gas exchange, Alveoli expand and merge to form larger NONfunctional air spaces (dead air space increases). Fine particulate matter such as glass particles (silicosis) and toxic vapors such as caustic or acidic chemicals and smoke can damage the respiratory membrane.  Some degree of emphysema is normal in aging persons.

What is emphysema?
  What is the effect of emphysema on absorption of O₂ and excretion of CO₂?

Less O₂ absorbed means LESS aerobic cellular respiration.  I.e. LESS energy available for metabolic processes and homeostasis.  Decreased ability to exhale CO₂ causes problems with controlling the pH of the body.

TB - tuberculosis is caused by mycobacterium tuberculosis.  This bacterium lives in the alveolus, forming a tubercle.  Eventually the alveolus is full of the tubercle and secondary infections fill it with mucus and that section of respiratory membrane is no longer available for gas exchange.
TB reportedly affects 2 BILLION people worldwide!

Pulmonary Edema - fluid/water in the lung tissues.  Water decreases the surface area available for gas
      exchange.
Pneumonia - water or liquid in the alveoli. Fluid/Water decreases the surface area available for gas
      exchange.

Pulmonary Embolism - something (blood clot, gas bubble, very LARGE fat droplet, etc) blocks the
      pulmonary capillaries - therefore blood cannot pass through those capillaries. Leads to not enough
      oxygenated blood going to the systemic tissues AND congestive heart failure.

Describe the Lungs and where they are located.

The lungs, located in the Pleural cavities in the Thoracic cavity, are made up of 5 lobes, 3 on the right lobe and 2 on the left lobe. The medial surface of the left lung has the cardiac notch, into which the heart fits.
Each pleural cavity is lined with the parietal pleura while the visceral pleura is attached to the surface of each lung.

What are the body cavities?
  What are the membranes that line the body cavities? Review chapter 1.
    What is the name of the cavity in which the lungs are located?
                 Describe the lungs: number of lobes, type of tissue, etc.
     Name the membrane that lines this cavity.
       What is the parietal pleura, and the visceral pleura?
         Where are they located?

What are the functions of pleural fluid?
  Pleural fluid has 2 (two) functions:
    1.  reduces friction and allows the lungs to move within the ribcage, rubbing against the walls of
          the pleural cavity without causing damage.
    2.  the adhesive and cohesive properties of water cause the two layers of the pleura to 'stick' to each
          other. When the muscles move the diaphragm and the ribcage, expanding the volume of the
          thoracic cavity, the volume INSIDE the lungs also expands.

The pleural fluid, being mostly WATER molecules sticks to itself and to the wall of the pleural cavity. Since the water sticks to the visceral pleura, to itself, and to the wall of the ribcage – when diaphragm contracts and pulls the bottom of the thoracic cavity downward and the ribs are RAISED during inhalation, the surface of the lungs ‘stick’ to that moving structure (but slide, too, to prevent friction). As the diaphragm and ribs increase the volume of the thoracic cavity, the surface of the lungs sticks to the wall of the cavity and the volume INSIDE THE LUNGS INCREASES, too.

Why does Air move from one place to another?
  Air, like blood, moves from an area of HIGH pressure to an area with lower pressure.

The diaphram is the main muscle for respiration.  The diaphragm is attached to the bottom of the ribcage and when relaxed, forms a bell-shape upward into the thoracic cavity.  When the diaphragm contracts, it flattens and pulls down on the bottom of the lungs, thereby increasing the volume inside the lungs.  When it relaxes, the diaphragm returns to its bell-shape and decreases the volume of the lungs.

The intercostal muscles also are primary respiratory muscles, which change the volume inside the
       thoracic cavity:
  The EXTERNAL intercostals contract and RAISE the ribcage -which increases the volume inside the
        ribcage.
  The INTERNAL intercostals contract and PULL the ribcage DOWN - which forcefully decreases the
         volume inside the ribcage.

What happens when the diaphragm contracts?
  What happens when the diaphragm relaxes?
What happens when the external intercostals contract?
   What happens when they relax?
What happens when the internal intercostals contract?
   What happens when the relax?

Air moves from HIGH pressure to LOW pressure.

Inhale: When you increase the volume of the thoracic cavity/lungs, the air pressure decreases below that of the external air pressure. So, you have a HIGH pressure OUTSIDE the body and a LOW pressure INSIDE the body – what happens to the air? Which way does it move? We call this ‘inhalation’.

Exhale: when the ribcage falls down and the diaphragm relaxes up into the thoracic cavity, the volume of the cavity decreases, and the air pressure inside the lungs increases above that of the external air pressure. So, you have a HIGH pressure INSIDE the body and a LOW pressure OUTSIDE the body – what happens to the air? Which way does it move? We call this ‘exhalation’.

Now, the air in the atmosphere - the air that we 'breath' -
The external air is made up of about
     79% nitrogen
     21% oxygen.
     0.04 % carbon dioxide

What is the role of O₂ in cellular respiration?
In the very last step (the last step of the electron transport system) it accepts the electrons and is fused to H and becomes part of H₂O.

Therefore the concentration of O₂ in the cell is zero (0).
Is the concentration of O₂ higher inside the cell or outside the body?

Describe the concentration gradient of O₂ in terms of diffusion.
Which way does O₂ move?
     Why?
 O₂ is constantly being attached to H to form H₂O, and the concentration of O₂ inside the cell is therefore constantly going to zero (0).  Therefore, the concentration gradient for O₂ is from extracellular toward intracellular.

CO₂ is constantly being produced inside the cell.

Why?

Describe the concentration gradient of CO₂ in terms of diffusion.
   Because CO₂ is constantly being produced INSIDE the cell, the intracellular concentration of CO₂ will always be higher than extracellular.

Now, we will consider external and internal respiration.

External respiration is the movement of the O₂ and CO₂ molecules across the respiratory surface membrane – between the air in the alveoli and the blood in the pulmonary capillaries.

Internal respiration is the movement of the O₂ and CO₂ molecules across the capillary wall – between the blood and the interstitial spaces in the peripheral tissues.

O₂ diffuses into the blood from the alveoli (why?). Once in the blood, the O₂ diffuses into the RBCs and attaches to the hemoglobin (Hb). When the O₂ attaches to the Hb, the O₂ no longer is part of the O₂ concentration, which decreases the O₂ concentration in the RBC/blood and causes MORE O₂ to diffuse into the blood from the alveolar air. This process continues until all the Hb is full of O₂ and no more O₂ can diffuse into the blood.

99% of the O₂ is transported in blood, bound to the hemoglobin molecule.

When the blood reaches the systemic capillaries – the O₂ concentration in the interstitial space is lower than that in the blood and O₂ diffuses out of the blood into the interstitial space.

CO₂ is produced inside the Cell during the process of aerobic cellular respiration.

This creates a high concentration of CO₂ INSIDE the cell and CO₂ diffuses out into the interstitial fluid, and then into the blood/capillaries.

CO₂ is carried in the blood:
      7% diffuses into the plasma and stays dissolved in the plasma
    23 % diffuses into the RBCs and attaches to Hb - forming carbaminohemoglogin
    70% (seventy percent!) combines with a water molecule and is converted to
         H₂CO₃, carbonic acid, which spontaneously dissociates to form H+ cations and HCO₃- anions.

CO₂ + H₂O ß à H₂CO₃ ß à H(+) + HCO3(-)

Carbon dioxide + water form Carbonic Acid which forms H+ and HCO₃ ions.

This is a FREELY REVERSIBLE reaction (see the arrows pointing both ways?) which stays in equilibrium for each of the three components. When you increase the concentration of CO₂ on the left side – the concentration of H+ ions on the right side increases, too! It makes the body (blood) more acidic (more H+ ions = more acidic).

When you decrease the CO₂ concentration on the Left side, the concentration of H+ ions (on the right side) decreases, too!  It makes the body (blood) less acidic (more basic).

When you increase the concentration of H+ ions on the right side, the concentration of CO₂ on the left increases, too!

When you hold your breath –what happens to the CO₂ concentration in your blood?
      It INCREASES – therefore the concentration of H+ ions increases and the blood (and body)
        become MORE acidic (less basic/alkaline).
Why?
  Look at the equation above.  Increasing CO₂  in the blood results in an increase in H+ in the blood - i.e. the number of H+ means the blood is more acidic.

When you breath rapidly – what happens to the CO₂ concentration in your blood?
    It decreases – therefore the concentration of H+ ions decreases and the blood (and body) becomes LESS acidic ( more basic/alkaline).

Because the rate of breathing controls the rate of CO2 exhaled which has an immediate effect on the number of H+ in the blood, the respiratory system is the FASTEST way to control pH of the body.

The set point for pH in the body is 7.4 
The range for pH in the body is 7.35 to 7.45
      NOTE: anything below 7.35 is considered too ACIDIC pH in humans!

Acidosis - a condition in which the body is TOO acidic.  The patient is said to be 'acidotic'.
    Respiratory acidosis - the body is too acidic due to a malfunction of the respiratory
       system.
    Metabolic acidosis - the body is too acidic due to a malfunction of the Metabolic
       processes.

Alkalosis - a condition in which the body is TOO basic.  (basic = alkaline).  The patient is
      said to be 'alkalotic'.
    Respiratory alkalosis - the body is too basic (alkaline) due to a malfunction of the
       respiratory system.
    Metabolic alkalosis - the body is too acidic due to a malfunction of the Metabolic
       processes.

Acidotic - a person whose fluids are too acidic due to either respiratory or
        metabolic acidosis
Alkalotic - a person whose fluids are to basic due to either respiratory or
        metabolic alkalosis.

Remember - in the human body, the SET POINT for pH is 7.4; and the RANGE is 7.35 to 7.45. 
  A person with pH = 7.2 is ACIDOTIC because the pH is on the acid side of the range (and set point).
  A person with pH = 7.5 is ALKALOTIC because the pH is on the basic side of the range (and set point).

Define Acidosis, acidotic, alkalosis, alkalotic, respiratory acidosis and respiratory alkalosis, and metabolic acidosis and metabolic alkalosis.

Compare the 'benchmark' for neutral pH and acidic vs. basic in a chemical solution with the benchmark for 'normal' pH and acidic vs. alkalotic in the human body.

Chemoreceptors in the carotid sinuses, the aorta, and the CNS sense O₂ and CO₂ concentration and pH. This sensory information is sent to the brain stem. The respiratory control centers in the Brainstem regulate the respiratory rate to maintain O₂ and pH levels in the body.

The average respiratory rate in adults is about 17 breaths per minute.
The range of respiratory rate is 12 to 20 breaths per minute.

Respiratory changes at birth

Fetal lungs are fluid filled - the fetus gets it's oxygen from the mother's blood via the placenta. The trachea, bronchi, bronchioles and alveolar structures are all collapsed - saving volume in the mother's abdomen.

The first breath inflates the respiratory structures and they remain inflated for the rest of the individual’s life.  The first breath is called the 'heroic' breath because it requires lots of energy to open the collapsed conducting portion and alveoli.  The first breath opens 50 to 80% of the lungs.  The next breaths usually inflate (open) much more of the lungs - but the STILL DEVELOPING neonatal respiratory system can require up to 2 months to achieve full functioning.

Before first breath, lungs filled with H2O and baby in water will sink.  After first breath even the collapsed lungs contain enough air to float the baby.

Tuberculosis: 2 *9 folks infected worldwide.  Leading cause of death from infectious disease worldwide.   Bacteria (Mycobacterium tuberculosis) colonize respiratory passages, interstitial spaces and alveoli - Casual contact. 

The lungs become less elastic and do not stretch and return to their normal shape as readily, This makes breathing more difficult.

Arthritis of the ribcage and costal cartilage makes expanding and contracting the ribcage painful, therefore old folks may not willingly breath.

Simple aging of the tissues causes emphysema - loss of respiratory surface area.  Exposure to environmental chemicals such as pesticides, acids, caustic chemicals, smoke and cigarette smoke all cause emphysema.

List all the ways that emphysema affects the body.
   Include oxygen and carbon dioxide concentrations, pH, cellular respiration, tissue repair, metabolism, etc.

Remember – all the systems have to work together to maintain homeostasis.
  Why is O₂ so important to homeostasis?

Define each of the following terms and explain what part of the respiratory system is affected:

Asthma
Bronchitis
Emphysema
Pneumonia
Respiratory distress
Surfactant cells
Tuberculosis (TB)
Cystic fibrosis
Alveolar macrophages

LAB

• Nose
  • External nares
  • Nasal conchae or turbinates
  • Internal nares

   

• Pharynx
  • Nasopharynx
  • Oropharynx
  • Laryngopharynx

   

• Larynx
  • Glottis
  • Epiglottis
  • Vocal cords
    • False
    • True
• Trachea
  • Tracheal cartilage

   

• Bronchi
  • Right and Left primary bronchi
  • Bronchial tree
  • Secondary bronchi
  • Tertiary bronchi

   

• Bronchioles
• Alveolar ducts
• Alveolar sacs
• Alveoli

• Alveolar membrane
• Capillaries

• Right Lung
  • Apex
  • Superior lobe
  • Middle lobe
  • Inferior lobe
  • Base
• Left Lung
  • Apex
  • Superior lobe
  • Cardiac notch
  • Inferior lobe
  • Base
• Pleura
  • Parietal
  • Visceral