1. Respiratory System
Mr O. Tada

2. Functions To obtain and use oxygen To eliminate carbon dioxide
Assisting in the control of acidity (pH) of extra-cellular fluid
Assisting in control of water balance & thermoregulation
Assisting in voice production (phonation)
Protection of the animal against inhaled dust, gases & infectious agents

3. Structure & Function Nostrils Nasal Cavities Pharynx
Paired, external openings
Dilatable
Nasal Cavities
Paired
Separated by Nasal Septum, and from mouth by palate
Pharynx
Common pathway for air and food
Caudal to nasal cavity

4. Structure & Function cont’d
Trachea
Primary passage way to Lungs
Larynx
"Voice Box“
Organ of Phonation (Sound Production)
Sound produced by controlled passage of air, which causes vibration of vocal chords
Syrinx
Voice Box for Birds
Located where trachea divides from bronchi
Vibrating Muscles
Cartilage Rings prevent collapse of airway
Allows for dilation

5. Structure & Function cont’d
Lungs
Principle Organ of Respiratory System
Paired, found in Thorax
Thorax expansion causes Lung expansion

6. Structure & Function cont’d
Pleura
Allows for almost frictionless movement of lungs in thorax
Two Forms
Visceral --Lines Lungs
Parietal --Lines Thorax
Intrapleural Space
Space between Visceral and Parietal Pleura

7. Structure & Function cont’d
Subdivisions
Bronchi
Bronchioles
Alveolar Ducts
Alveoli
Principle site of gaseous diffusion between air and blood
Alveolar epithelium and capillary endothelium in direct contact

8. Mechanism of Respiration
Respiratory Cycles
A. Inspiration
Intake of air
Enlargement of thorax and lungs
Contraction of Diaphragm and Certain Intercostals
Diaphragm --Caudal Direction
Intercostals--Forward and Outward Direction
Some abdominal muscles involved
Requires greater effort than Expiration

9. Mechanism of Respiration
B. Expiration
Removal of air
Relaxation of diaphragm and some intercostals (passive)
Contraction of other intercostals and abdominal muscles
--used in active expiration

10. Mechanism of Respiration
Types of Breathing
A. Abdominal
Inspiration --Abdomen protrude
Expiration --Abdomen recoils
Predominant type of breathing
B. Costal
Pronounced movement of ribs
Used during abdominal pain (e.g. peritonitis)

11. Respiratory Frequency
Number of Respiratory Cycles per minute
Factors affecting Respiratory Frequency
Species variations Horse Cow Pig Sheep 25
Body Size --Heavy animals breath heavier
Age --Younger less

12. Respiratory Frequency
Exercise –Increases
Excitement –Increases
Environmental Temperature
--Faster in heat (panting)
Pregnancy –Increases
Degree of filling of Intestine –Increases
State of health --Disease increases

13. Respiratory Pressures
Concentrations of Gases = Pressure
Partial Pressure
Pressure (concentration) of a gas in a mixture of gases
PO2, PCO2, PaO2, PvO2, etc.
Atmospheric Air
1 atm = 760 mm Hg
Components of air
21% O2 (PO2 159 mm Hg)
0.03% CO2 (PCO mm Hg)
79% N2 (PN2 600 mm Hg)

14. Respiratory Pressures
Humidification (PH2O)
--Dilutes gases
Alveolar Air
Not the same as Atmospheric Air
Does not completely evacuate
100% Humidification (PH2O = 47 mm Hg)
Gas Pressures
PO2 104 mm Hg (159)
PCO2 40 mm Hg (0.23)
PN2 569 mm Hg (600)

15. Pulmonary Ventilation
Process by which gas in closed places is renewed or exchanged
Lungs
Exchange of gas in the airways and alveoli with the outside environment.
Dead Space Ventilation
Part of tidal volume in airways (bronchi, bronchioles, etc.)
No exchange with blood
Also alveoli with diminished capillary perfusion

16. Pulmonary Ventilation
Assists in tempering (heat or chill) and humidifying air
Panting is primarily dead space ventilation
Pressures that accomplish Ventilation
Intrapulmonic and Intrapleuric Pressures
Intrapulmonic
--Pressure within the lungs
Intrapleuric
--Pressure outside the lung and inside the thorax
Air flows in the lungs when intrapulmonic pressure is less than atmospheric pressure

17. Pulmonary Ventilation
Air flows out of the lungs when intrapulmonic pressure is more than atmospheric
Intrapleuric pressure determines the amount of air inhaled
Generation of Pressure Changes
Lungs enlarge because thorax enlarges
Causes Vacuum
Intrapleural pressure becomes more negative
Expiration caused by recoil of lung tissue during passive expiration

18. Diffusion of respiratory gases
General Characteristics
Respiratory Gases diffuse readily throughout body
C02 is 20X more diffusible than O2
From High Partial Pressure to Low Partial Pressure
--Concentration Gradient

19. Oxygen Transport General Transport Scheme Arterial Blood is 20% Oxygen
25% of is consumed at capillaries during normal activity
--Utilization Coefficient
More can be utilized during strenuous exercise
Transport Scheme
Alveoli to RBC
Interstitial water
Plasma
Erythrocyte water (cytoplasm)
Hemoglobin

20. The Flow
60X more blood would be needed if hemoglobin didn't bind O2

21. Gas exchange across capillary and alveolus walls

22. Carbon Dioxide Transport
General
Facilitated by several reactions that provides other forms of C02 to be transported
CO2 is more soluble than O2
Amount produced still exceeds amount dissolved in plasma
Hydration Reaction
Formation of Bicarbonate (HCO3-)
Reaction in RBCs
--Carbonic anhydrase
80% of CO2 transport

23. Carbon Dioxide Transport
Formation of Carbamino Compounds
CO2 binds to terminal amino groups of protein
Plasma Proteins
Hemoglobin
Loss of Carbon Dioxide at Alveolus
Hydration and Carbamino Reactions Reverse
CO2 follows concentration gradient from blood to alveoli

24. Details of gas exchange

25. Regulation of Ventilation
Ventilation is regulated by body concentrations of H+, CO2, and O2
If H+ and CO2 increase or O2 decrease, ventilation increases
If H+ and CO2 decrease or O2 increase, ventilation decreases
Respiratory Centers found in Brain Stem
Provides rhythmicity
Influenced by vagus and glossopharyngeal cranial nerves
And by Chemoreceptors

26. Control cont’d Three Centres
Pneumotaxic center (located in the upper regions of the pons)
Medullary rhythmicity center (the medulla)
Apneumotaxic center (midway of the level pons & apneumotaxic center)

27. Pneumotaxic center

28. Medullary rhythmicity center
Phrenic nerve innervates muscles thru intercostal muscle nerve for mvnt of the rib cage.
Passive expiration then follows while the inspiratory center in under inhibitory control by the pneumotaxic center which allows the maintenance of rhythm of breathing.

29. Apneumotaxic center
The activity of the pulmonary strecth receptors (visceroreceptors) located in the lungs, visceral pleura & bronchioles smooth muscle further re

30. Neural Control Hering-Bruer Reflex
Inflation-sensitive and deflation-sensitive receptors located in bronchi and bronchioles
Signal Respiratory Centers
Other Receptors
Skin--Newborn stimulation, and Body Temperature
Muscles—Exercise
Upper Airways
Swallowing
Coughing and Sneezing
Pressure receptors in Carotids and Aortic Arch
Pain receptors

31. Neural Control Voluntary control can alter involuntary breathing
Exercise
Defecation
Urinating
Parturition

32. Humoral Control
Chemoreceptors measure body concentrations of H+, CO2, and O2
Locations
H+ and CO2 receptors are located on ventral surface of brain stem
--Diffuse into Cerebral Spinal Fluid
Aortic and Carotid Bodies contain receptors for O2, H+, and CO2
Hormones