Respiration lecture notes

From Biol557

• started here on 02/24/10.

Contents 1 Respiration 1.1 Respiratory functions 1.2 More requirements for respiration 1.3 Non-respiratory functions 1.3.1 Filter and moisten air 1.3.2 Facilitate olfaction by transporting airborne molecules 1.3.3 Defense against airborne pathogens - mucocilliary elevator 1.3.4 Sound production 1.3.5 Trap small emboli in pulmonary circulation where they are dissolved 1.3.6 Blood reservoir for left ventricle 1.3.7 Biochemical reactions 1.4 Organization of the respiratory system 1.4.1 The mucocilliary elevator 1.4.2 Nose 1.4.3 Palate 1.4.4 Nasopharynx 1.4.5 Oropharynx and laryngopharynx 1.4.6 Larynx functions 1.4.7 Anatomy of larynx 1.4.8 Tracheal cartilages 1.4.9 Primary bronchi 1.4.10 Hilus 1.4.11 Lungs 1.4.12 Lung lobes 1.4.13 Lobules 1.5 Smooth muscle control 1.6 Alveolar organization 1.7 Gas exchange 1.7.1 Respiratory membrane 1.7.2 10 stems to transport 1.8 Air replacement 1.9 Integration of two processes (respiration and circulation) 1.9.1 External respiration 1.9.2 Respiratory laws 1.9.2.1 Dalton's law 1.9.2.2 Henry's law 1.9.2.3 Graham's law 1.9.2.4 Fick's law 1.9.3 Balance 1.9.4 Ventilation perfusion coupling 1.9.5 Never perfect perfusion balance 1.10 Normal and abnormal respiration 1.10.1 Tissue structure on perfusion, etc 1.10.2 Pneumonia 1.10.3 Collapsed lung 1.10.4 Surfactant and surface forces 1.10.5 Compliance 1.10.6 Pleural sac 1.10.7 Musculature 1.10.8 Expriation 1.10.9 Quiet breathing 1.10.10 Pressures of pleural sac 1.10.11 Pressure changes associated with ventilation 1.10.12 Chest wall breach

Respiration

• Respiration requires some stuff:
  • We'll talk about convection system (that is, ventilation and cirulation).
  • We'll also talk about mechanisms for gas transport int he blood.

Respiratory functions

• We're going to talk about ventilation in general and which muscles of the chest wall are used.
• We'll tlak about negative pressure that pulls the air into the lungs.
• We're going to think about ...

More requirements for respiration

• We have to have a way for the air to flow. Ventilation perfusion coupling.
  • We'll look at some problems of this, too.
• We'll look at the CNS's involvement in respiration and circulation.
• Oxygen level is important, but CO2 is the primary regulator of respiration.

Non-respiratory functions

Filter and moisten air

Facilitate olfaction by transporting airborne molecules

Defense against airborne pathogens - mucocilliary elevator

Sound production

Trap small emboli in pulmonary circulation where they are dissolved

Blood reservoir for left ventricle

• Lungs contain 500 ml of blood.
• Two beats can be supplied if pulmonary artery is clamped.

Biochemical reactions

• ACE converts angiotensin I to antiotensin II.
• Some prostaglandins are removed at the lungs.

Organization of the respiratory system

• Can be divided into upper (down to the pharynx) and lower (everything lower).
• We could also look at the system in terms of function instead of structure.
  • The transition of function (from conducting zone to respiratory zone) occurs when alveoli start to occur.
• The tubes branch significantly. There are about 16 divisions before there are any alveoli.
• There is also a change in type of cells found.
  • We transition from columnar at the top to squamous at the bottom.
  • We see a change from more to less (going down) of goblet cells because of the elevator.
  • We see a decrease in cartilage because we have less and less structure.
  • Elasticity goes the entire length. They are important for recoil in the chest wall and the alveoli.

The mucocilliary elevator

• Goblet cells are releasing mucus on surface.
• Cillia are beating upward.
• As we get to the lower region, the size of pathogens is important because the smaller they are the deeper they can get and the better they can get across the endothelial cells when they land.

Nose

• The air enters through the external nairs.
• There is mucus secretion and tears coming through ducts, these help to trap crap.
• Air passes through conchae around the turbanates (an outcropping of bone). This generates turbulance to facilitate smell and moistening.
• We have sinuses (four of them) which connect to the nose through the medemus (?).
  • When this connection is blocked, pressure can build up.

Palate

• Separates nose to mouse.
• Hard and soft palate.
• Cleft can occur which is bad. Usually happens where bones come together in top of mouth.
  • Can happen in hard or soft palate or both.

Nasopharynx

• This is in common with digestive and respiration tracts.
• There are three regions but we won't dwell on them.
• Nasal connection is called the internal nares.
  • This is the location of the adenoid.
  • This is also where the opening to the ear occurs and it is important for good sound conductance and balance.

Oropharynx and laryngopharynx

Larynx functions

• This structure is trying to keep the airway open.
• Behind it is the esophagus.
• Epiglottis sits on the top with some cartilage that allows the epiglottis to cover the glottis (a slit-like opening).
• The vocal cords are on either side of the glottis.
• There is upward movement that helps to close off the glottis.

Anatomy of larynx

• The thyroid cartilage forms the adams apple.

Tracheal cartilages

• Begins at the base of the larynx.
• You can feel the cartilage rings with connective tissue in between.
• The rings are c shaped with the open part in the back.
• There is a muscle and a ligament on the back which are responsible for changing the diameter to change resistance.
• The esophagus is posterior to the trachea.

Primary bronchi

• Our first bifurcation occurs.
• The right and left are not equal.
• The angle of division are not equal.
• The right has a short bronchial tube and left has a straighter angle.
• This is a problem when kids breath something. Most likely it is in the right bronchial tube because the angle isn't as great.
• At the bifurction, the cartilage extends into the airway a little (think shelf).
  • This is covered by endothelium and is very sensitive.
  • This causes the coughing when you inhale something.

Hilus

• The hilus is the midline of the lung (theres one on the kidneys, too).
• This is the location where the major structures enter the organ (think veins, lymphatics, bronchii).
• The whole thing is held together by a mesh-work of connective tissue.

Lungs

• The right lobe is larger than left because the heart is taking up space on left side.
• You can see the fissure that helps separate the middle lobes from the upper lobes.
  • Note that on the left there are only two lobes.
  • Right has a middle lobe.

Lung lobes

• The lobes are divided into segments.
• The segments are able to be isolated by surrounding connective tissue.
  • They can be removed for something like lung cancer or what-not.
• The reason for these sections is that the the lymphatics, respiratory, and circulation all branch together such that all the sections separate systems.

Lobules

• Sections can be divided.
• Can be the size of a penny to an eraser.
• Respiration occurs at the level of the alveoli which are at the base of the lobules.
• Artery, vein, and lymphatics all supply each lobule and each alveoli.

Smooth muscle control

• The cartilage is gone, recall, so we rely on the muscle to keep the airway open.
• Therefore we can change the dilation.
• The sympathetic will open airways to reduce resistance and the parasympathetic will do the opposite.
• Histamine will also restrict to increase resistance.
• This is all further compounded by the fact that we need airpressure from the outside to help hold it open.

Alveolar organization

• There are capillaries that pass through avleolar, which means that we can get oxygen from either capillary.
• There are several cell types at this point: type 1 cells and type 2 cells.
  • Type 1 are long and thin, these do gas exchange.
  • Type 2 are important for generating surfactant.
• There are also macrophages in this space to help with protection.
• Neighboring alveoli have pores that connect them; we do not know the function.
  • Might help to maintain stability; for example, gas may be able to move between alveoli.
• Surface area is very important:
  • It increases significantly as we develop (3 to 75 square meters).
  • Yet the number of alveoli stays about the same.

Gas exchange

• We have to oxygen and co2 across the respiratory membrane.
• We have to diffuse across the epithelial cell and the basement membrane that holds them together, then the interstitial space (not much), then the basal membrane, then the endothelial cells.
• So, there are 10 different diffusion steps that have to occur.
• If the wall is too wide, the time to cross will take too long and we're less likely to oxygenate the blood.
  • We only have about 7/10ths of a second before the opportunity is lost.

Respiratory membrane

• The membrane works well when everything is functional.
• It is important that there is a difference in partial pressure (especially for O diffusion).
• Distance is small, which is good and key.
• Oxygen and Co2 and Co are lipid soluble so we don't have to have transporters but we do have to have a moist surface for efficient exchange.
  • So we have to keep solublility issues in our minds.
• Large surface area is important.
• There must be good stability at the air=water interchange.
• Coordination of flow is important.
• The blood cell membrane must be thin with the blood cell close to the cell wall.

10 stems to transport

• Notice that there are D1-d10 steps.
• Amazing it works at all, really.
• So we go from water-air place to type 1, to interstitial, to endothelial cell, through plasma, through blood cell, onto Hb.

Air replacement

• We don't replace all of our air with each breath.
• Even after 16th breaths, there are still some of the original air molecules before total replacement.

Integration of two processes (respiration and circulation)

External respiration

• Involves:
  • Ventilation (breathing)
  • Diffusion over capillaries
  • Exchange of CO2 and O with Hb.

Respiratory laws

• There are four laws.

Dalton's law

• This is looking at the gas mixture itself.
• There is some total pressure, added to by each individual gas, which is a percentage of the total--the partial pressure.
• Remember that the partial pressure is only calculated from the free molecules of gas.

Henry's law

• Takes dalton one step further.
• Here we look at solubility issues.
• This law is important to respiratory process because we need to think about getting the gas dissolved in the liquid interface on the surface of alveoli.
• There is a different solub coeff for different liquieds

Graham's law

• The rate of diffusion is driven by difference in partial pressure of the gasses.
• There are solublility issues, too, but overall, it's the difference in pp.
• Oxygen gets used up so there is an inward gradient while co2 has an exit gradient because we're generating it.

Fick's law

• Ties everything together.
• The gradient the pp difference, the greater the rate of diffusion.
• The greater the permeability of the membrane the better the diffusion.
• The more surface are the more diffusion.
• The larger the molecule the lower the diffusion.
• The thicker the membrane the less diffusion.

Balance

• We have to have blood and gas flow balance.
• Incoming air is not always equally distributed because of mucus or disease or whatever.
• Therefore, there will be differences in concentration of oxygen in these different areas.
• This can generate hypoxia in a certain area, which will cause vasoconstriction (constriction?).

Ventilation perfusion coupling

• This is how pps of O and CO2 change vasodilation.
• Let's say there's a blockage and a reduction of air coming into a certain lobule.
• So CO2 goes up, O goes down.
• The arterioles will restrict because there's no reason to go there because there is no oxygen.
• On the other hand, you can open the vessels where there is more oxygen.
• So this all balances the air with the blood.

Never perfect perfusion balance

• Gravity has an effect.
• Circulation at the topof the lungs isn't as well as the bottom of the lungs.
• So there is more perfusion at the bottom than at the top.

Normal and abnormal respiration

Tissue structure on perfusion, etc

• A normal lung has nice, open, alveoli.
• With pneumonia, you start to lose openness of alveoli.
• In emphasema, you have coelescing of the alveoli.

Pneumonia

• There is an impedance in the alveoli of the sick lung.
• This causes there to be much lower venous return in terms of saturation. So flow hasn't changed but there is a decrease of oxygen returned to the body because one lung is sucking at diffusion.

Collapsed lung

• Edges are sticky, can't inflate.
• Now the circulation does change along with this problem.
• So circulation will be decreased to bad lung and it will be increased in the good lung such that we can offset the loss of oxygen.
• So, this person actually gets more oxygen returned than the penumonic lung patient.

Surfactant and surface forces

• We want the alveoli to be open, even while we exhale.
• The liquid on the inner interface interact differently as the surface becomes smaller.
• They then become part of the subphase and the surfactant keeps the alveoli from collapsing.
  • More on this next time.

Compliance

• This is an indication of how well the lung is inflating relative to the pressure differences we're imposing.
• If it is highly compliant it won't expand as we expect.
• This can be affected by:
  • Connective tissue of lung (elastic versus structural)
  • amount of surfactant
  • missed third
• Historesis is the difference between lung volume during inspiration and expiration.
  • This won't occur if the lung is filled with saline.
  • So looking at the volumes under some pleural pressure can tell us something about the tissue.
• Normal physiology will give a nice, steady change of volume relative to pressure.
• In emphasema, it will be high in compliance. There will be a huge volume change relative to pressure. That is, it is very easy to inflate. It is easy to inhale. the problem is that it is hard to deflate. They make the last little 'hewh'.
• In low compliance, it is easy to exhale but hard to inhale. These people tend to develop a barrel chest under the struggle to inflate lungs.

Pleural sac

• The lungs are in the pleural sac.
• The pleural space is fluid filled.
• The parietal membrane is right underneath the chest wall.
• The visceral membrane follows the ung proper, including folds.

Musculature

• Diagraphm is main.
  • Contraction means it is coming downward and inhaling.
  • Relaxation causes a dome and exhaling.
• intercostal are between ribs and helps with expansion and reflexion.
• The sternocleidomastoid muscles are also able to help lift he rib cage.

Expriation

• Generally passive.
• In active exercise, we can use muscles that make the chest smaller.
  • REctus abdominus = pulling ndown.
  • Intercostal pull ribs downward.
  • External oblique muscle pull chest inward.

Quiet breathing

• Normal shallow breathing = glutnant.
• Hyperpnia is the use of excessory muscles.

Pressures of pleural sac

• REcall that this is fluid filled.
• This is an area of lower pressure than atmospheric pressure (negative pressure).
• The transpulmonary pressure is that between the lung tissue and the pleural sac.
• We're not normally looking at much pressure change differences, usually just 1-2-3 mmHg changes.
• But when we really exercise hard, we can see big changes like -30 mmHg and +100 mmHg. This may not be a good idea.

Pressure changes associated with ventilation

• When normally inhaling, we decrease the pressure in the pleural space because the space gets larger because of muscle movement.
• So the pressure tissue across the pulmonary space will increase (that is the transpulmonary pressure).
• The negative pressure pulls on the lung tissue which causes it to inflate.
• Then the pressure in the alveoli will drop below atmospheric pressure.
• Air enters lung until reaching atmostpheric pressure.
• So then intrapelural pressure decreases and transpulmonary pressure increases and the lung exhales.

Chest wall breach

• When the pleural space is equal to the atmospheric pressure.
• This can happen from gunshot wound or tear.
• The lung will collapse.
• So we have to close the tear and reinflate the lung.

• stopped here on 02/24/10.