1. Respiratory System Part II

2. Respiratory Physiology
In order to supply the body with oxygen and get rid of carbon dioxide the process of respiration MUST occur.
Pulmonary ventilation: air is moved in and out of the lungs so that gas is exchanged and refreshed – breathing.
External respiration: gas exchange between pulmonary blood and alveoli must take place.
Respiratory gas transport: Oxygen and CO2 must be transported to and from the lungs and tissue cells of the body through the bloodstream
Internal respiration: at the capillaries, gas exchanges are made between the blood and tissue cells.

3. Mechanics of Breathing
Breathing/Pulmonary Ventilation:
Mechanical process which depends on volume changes occurring in the thoracic cavity.
These changes can lead to pressure changes which lead to the flow of gasses to equalize the pressure within the lungs.
Gas always conforms to the shape of its container filling it completely. In a large volume the gas molecules are further apart and pressure will be low. If the volume is reduced the gas molecules move closer together and pressure will increase.

4. Inspiration – When air flows into the lungs
Diaphragm:
Inspiratory muscles
When the diaphragm contracts it flattens inferiorly and the height of the thoracic cavity increases.
External Intercostals:
Contraction of the external intercostals causes the rib cage to lift and increases the thoracic cavity.
Intrapulmonary volume:
Volume within the lungs
As the intrapulmonary volume increases the gases in the lungs spread to fill this larger space. The decreasing pressure then causes a vacuum effect sucking air into the lungs. Air continues to move into the lungs until the intrapulmonary pressure is equal to the atmospheric pressure.

5. Expiration – Exhaling
Passive process that depends on the natural elasticity of the lungs vs. muscle contraction
When inspiratory muscles relax and resume their normal resting lengths the thoracic and intrapulmonary volumes decrease. When this occurs the gasses in the lungs are forced to move close together and intrapulmonary pressure increases more than atmospheric pressure and causes gasses to flow out in order to equalize the pressures.

6. Expiration – Exhaling
Normally expiration should be effortless but if the respiratory passages are narrowed or clogged expiration can become a forced process. In these cases the internal intercostals and abdominal muscles will be forced to contract in order to exhale the air.

7. Expiration – Exhaling Intrapleural Pressure: Atelactasis:
Pressure within the pleural space
This pressure is always negative protecting the lungs from collapsing
If the intraplueral space becomes equal to atmospheric pressure the lungs will then collapse.
Atelactasis:
Collapse of the lungs
Usually occurs when air enters the pleural space through a chest wound but may occur from a rupture of the visceral pleura allowing air to enter directly from the respiratory tract.
Pneumothorax:
Presence of air within the intrapleural space disrupting the fluid bond between the pleura.
It can be reversed by inserting a tube into the chest to remove the excess fluid and allowing the lungs to attempt to function normally again

8. Non-respiratory Air movements
Situations other than breathing where air moves into and out of the lungs is usually a result of reflex activity but can sometimes be voluntarily controlled.
Coughing & Sneezing: clear air passages of debris or collected mucus
Laughing & Crying: reflect a persons emotions
Hiccups: involuntary reflex
Yawning: involuntary reflex

9. Respiratory volumes and capacities
Factors affecting respiratory capacity:
Persons size
Age
Sex
Physical condition

10. Respiratory volumes and capacities
Tidal Volume (TV):
Normal breathing
Normally approximately 500 ml. of air are moved in and out of the lungs with each breath.
Inspiratory Reserve Volume (IRV):
The amount of air that can be taken in FORCIBLY over the tidal volume.
Normally between ml.
Expiratory Reserve volume (ERV):
The amount of air that can be forcibly EXHALED after tidal expiration.
Approximately 1200 ml.

11. Respiratory volumes and capacities
Residual volume:
1200 ml. of air that remains in the lungs and cannot be voluntarily expelled.
Allows gas exchange to go on continuously even between breaths and keeps the alveoli open/inflated.
Vital Capacity (VC):
Total amount of exchangeable air
The sum of TV + IRV + ERV
Dead Space Volume:
Air enters the respiratory tract and remains in the passageways but never reaches the alveoli.
During normal breathing the dead space volume is usually about 150 ml.

12. Respiratory volumes and capacities
Functional Volume:
Air that actually reaches the respiratory zone.
Approximately 350 ml.
Spirometer:
Device used to measure respiratory capacities
As a person breathes the volumes of air exhaled can be read on an indicator showing the changes in air volume inside the apparatus.
This testing is useful for evaluating losses in the respiratory function after respiratory diseases have been diagnosed.

13. Respiratory Sounds Bronchial Sounds: Vesicular Breathing:
Produced by air rushing through the large respiratory passageways such as the trachea and bronchi.
Vesicular Breathing:
Sounds occurring as air fills the alveoli
Sounds are soft and resemble a muffled breeze
Abnormal sounds:
Results of diseased respiratory tissues, mucus or pus.
Rales: rasping sounds
Wheezing: whistling sounds

14. Laws of Diffusion
All gas exchanges are made by diffusion causing movement toward the area of a lower concentration of the diffusing substance.

15. External Respiration
As dark red blood flows through the pulmonary circuit it is then transformed to a lighter scarlet color as it is returned to the heart.
This color change is due to the oxygen pickup by hemoglobin in the lungs
Carbon dioxide is then removed from the blood equally as fast as the O2 pickup
Body cells continually remove oxygen from the blood but the alveoli continually hold more oxygen in their sacs.

16. How External Respiration occurs
Oxygen moves from the air of the alveoli into the respiratory membrane
From the respiratory membrane oxygen poor blood is then transported to the blood of the pulmonary capillaries
As tissue removes oxygen from the blood during systemic circulation carbon dioxide is released into the blood.
Because the concentration of CO2 is higher in the pulmonary capillaries than in the alveolar air it leaves the blood to pass into the alveoli and is flushed out of the lungs during expiration.
Therefore blood that is draining from the lungs into the pulmonary veins is oxygen rich and carbon dioxide poor and ready for systemic circulation!

17. Gas Transport in the Blood
Oxygen is transported in the blood in two ways:
Oxyhemoglobin (HbO2): oxygen attaches to hemoglobin molecules inside the red blood cells and produces HbO2
Dissolved in the plasma: very small amounts of oxygen are carried this way.

18. Carbon dioxide transport
CO2 is transported by a Bicarbonate Ion (HC03) inside the plasma and bound to hemoglobin.
It binds at different sites from oxygen so that it does not interfere with the oxygen transport.
Before CO2 can diffuse out of the blood into the alveoli it must be released from the bicarbonate form
For this to occur bicarbonate ions must combine with hydrogen ions to form carbonic acid (H2CO3)
The carbonic acid quickly splits for form water and carbon dioxide
The CO2 then diffuses from the blood and enters the alveoli

19. Internal Respiration
The exchange of gases that takes place between the blood and the tissue cells.
Opposite of what occurs in the lungs.
It is the process of unloading oxygen and loading CO2 into the blood.

20. How Internal Respiration Occurs
CO2 diffuses out of the tissue cells and enters the blood.
When it enters blood it combines with water to form carbonic acid
From here it releases bicarbonate ions and diffuses out into the plasma where it is then transported.

21. How Internal Respiration Occurs
At the same time oxygen is released from the hemoglobin and the oxygen diffuses out of the blood to enter tissue cells it causes the exchanges in venous blood to be much more oxygen poor and carbon dioxide rich than the blood leaving the lungs.
Most of this conversion occurs inside the red blood cells
RBC’s also contain carbonic anyhydrase – a special enzyme which speeds up the reaction time!

22. Impaired Oxygen Transport
Hypoxia:
Inadequate oxygen delivery to the body tissues
Skin becomes cyanotic (blue)
Can be the result of anemia, pulmonary disease, impaired or blocked circulation
Carbon Monoxide Poisoning:
Unique type of hypoxia
Because carbon dioxide binds to hemoglobin at the same sites as oxygen it can crowd out or displace the oxygen.
It is the leading cause of death from fire and does not produce typical signs and symptoms of hypoxia
Victims become confused, have throbbing headache and skin can become red in color
They must be given 100% oxygen to breathe until CO2 is cleared from the body.

23. Control of Respiration
Neural Regulation:
Phrenic and Intercostal nerves control the diaphragm and intercostal muscles used during breathing.
Self-Exciting Inspiratory center: located in the medulla and pons. Sets the basic rhythm for breathing. Impulses going between the two centers of the brain maintain a rate of respirations per minute (rpm)
Eupnea: normal respiratory rate & response
Stretch receptors: located in the bronchioles and alveoli. Respond to extreme over inflation. Impulses are then sent from the stretch receptors to the medulla through vegus nerves where they will end inspiration and begin expiration.

24. Factors influencing respiratory rate and depth
Physical factors:
Talking
Coughing
Exercise
Increased body temperature
Increased rate and depth of breathing

25. Factors influencing respiratory rate and depth
Volition:
Voluntary controls of breathing is limited
Respiratory centers ignore messages from the cortex when oxygen supply is getting low or blood Ph is falling
Emotional factors:
Scared
Gasping at touching something cold, clammy or hot
Reflexes initiated by emotional stimuli from the hypothalamus.

26. Factors influencing respiratory rate and depth
Chemical Factors:
Level of O2 and CO2 in the blood
Increased CO2 and decreased blood pH = increase in rate and depth of breathing
Decrease in O2 only become important stimuli when they are critically low
Hyperventilation: Extremely slow or shallow breathing brought on by anxiety dramatically decreases the amount of carbonic acid in the blood – leads to periods of …
Apnea: cessation of breathing until CO2 builds up in the blood. If breathing is stopped for a significant amount of time …
Cyanosis may occur. Cyanosis: insufficient oxygen in the blood