ANS 331: Respiration
I. Function of Respiratory System
1. To obtain and use oxygen
2. To eliminate carbon dioxide
II. Structure and Function
1. Nostrils
A. Also called nares
B. Paired, external openings
C. Dilatable
a. Species Differences
i Horse--Very Pliable and Dilatable
ii. Pig--Rigid
b. Advantageous
i. More air required (e.g. Running)
ii. Non-mouth Breathing
e.g. Running
2. Nasal Cavities
A. Paired
a. Separated by Nasal Septum, and from mouth
by palate
B. Mucosal-lined Turbinate Bones (Conchae)
a. Form passages called meatuses
C. Functions of Mucosa
a. Warm and humidify air
b. Cool blood to brain
c. Olfaction
3. Pharynx
A. Common pathway for air and food
a. Caudal to nasal cavity
B. Openings
a. Two Posterior Nares
b. Two Eustachian Tubes
c. Oral Cavity (Mouth)
d. Glottis
e. Espophagus
4. Larynx
A. "Voice Box"
B. Organ of Phonation (Sound Production)
C. Sound produced by controlled passage of air which
causes vibration of vocal chords
D. Syrinx
a. Voice Box for Birds
b. Located where trachea divides from bronchi
c. Vibrating Muscles
5. Trachea
A. Primary passage way to Lungs
B. Cartilage Rings prevent collapse of airway
a. Not joined dorsally
b. Allows for dilation
C. Subdivisions
a. Bronchi
b. Bronchioles
c. Alveolar Ducts
6. Alveoli
A. Principle site of gaseous diffusion between air
and blood
B. Alveolar epithelium and capillary endothelium in
direct contact
6. Lungs
A. Principle Organ of Respiratory System
B. Paired, found in Thorax
a. Thorax expansion causes Lung expansion
7. Pleura
A. Serous Membrane attached to C.T.
B. Allows for almost frictionless movement of lungs
in thorax
C. Two Forms
a. Visceral
--Lines Lungs
b. Parietal
--Lines Thorax
D. Mediastinal Space
a. Space between Visceral Pleura
b. Contain Vena Cava, Thoracic Lymph duct,
Esophogus, Aorta, and Trachea
E. Intrapleural Space
a. Space between Visceral and Parietal Pleura
III. Mechanisms of Respiration
1. Respiratory Cycles
A. Inspiration
a. Intake of air
b. Enlargement of thorax and lungs
c. Contraction of Diaphragm and Certain
Intercostals
i. Diaphragm
--Caudal Direction
ii. Intercostals
--Forward and Outward Direction
d. Some abdominal muscles involved
d. Requires greater effort than Expiration
B. Expiration
a. Removal of air
b. Relaxation of diaphragm and some
intercostals (passive)
c. Contraction of other intercostals and
abdominal muscles
--used in active expiration
2. Types of Breathing
A. Abdominal
a. Inspiration
--Abdomen protrude
b. Expiration
--Abdomen recoils
c. Predominant type of breathing
B. Costal
a. Pronounced movement of ribs
b. Used during abdominal pain
(e.g. peritonitis)
3. States of Breathing
A. Eupnea
a. Normal quiet breathing
b. No deviation in frequency or depth
B. Dyspnea
a. Difficult breathing
b. Effort required to breath
C. Hyperpnea
a. Increase depth and/or frequency
b. Caused by physical exertion
D. Polypnea
a. Rapid, shallow breathing
b. Panting
E. Apnea
a. Cessation of breathing
b. Transient cessation
4. Pulmonary Volumes
A. Tidal Volume
a. Amount of air breathed in or out during
a respiratory cycle
b. Can increase or decrease depending on
ventilation requirements
c. Most commonly used volume
B. Inspiration Reserve Volume
a. Amount of air which can still be inspired
after tidal volume
C. Expiration Reserve Volume
a. Amount of air which can still be expired
after tidal volume
D. Residual Volume
a. Air remaining in lungs even after strongest
expiration
b. Remains in lungs even after removal of lungs
E. Total Lung Capacity
a. Sum of all Volumes
F. Vital Capacity
a. Tidal Volume + Reserve Volumes
b. Maximum amount of air that can be
breathed in
after most forceful expiration
G. Inspiration Capacity
a. Tidal Volume + Inspiration Reserve Volume
H. Function Residual Capacity
a. Expiration Reserve Volume + Residual Volume
b. Reservoir of air
5. Respiratory Frequency
A. Number of Respiratory Cycles per minute
B. Factors affecting Respiratory Frequency
a. Species variations
Horse 12
Cow 29
Pig 40
Sheep 25
b. Body Size
--Heavy animals breath heavier
c. Age
--Younger less
d. Exercise
--Increases
e. Excitement
--Increases
f. Environmental Temperature
--Faster in heat (panting)
g. Pregnancy
--Increases
h. Degree of filling of Intestine
--Increases
I. State of health
--Disease increases
6. Respiratory Pressures
A. Concentrations of Gases = Pressure
B. Partial Pressure
a. Pressure (concentration) of a gas in
a mixture of gases
b. PO2, Pco2, PaO2, PvO2, etc.
C. Atmospheric Air
a. 1 atm = 760 mm Hg
b. Components of air
i. 21% O2 (PO2 159 mm Hg)
ii. 0.03% CO2 (PCO2 0.23 mm Hg)
iii. 79% N2 (PN2 600 mm Hg)
c. Humidification (PH2O)
--Dilutes gases
D. Alveolar Air
a. Not the same as Atmospheric Air
i. Does not completely evacuate
ii. 100% Humidification
(PH2O = 47 mm Hg)
b. Gase Pressures
i. PO2 104 mm Hg (159)
ii. PCO2 40 mm Hg (0.23)
iii. PN2 569 mm Hg (600)
IV. Pulmonary Ventilation
1. Definition
A. Process by which gas in closed places is renewed or exchanged
B. Lungs
a. Exchange of gas in the airways and alveoli
with the outside environment.
2. Dead Space Ventilation
A. Part of tidal volume in airways
(bronchi, bronchioles, etc.)
a. No exchange with blood
B. Also alveoli with diminished capillary perfusion
C. Assists in tempering (heat or chill)
and humidifying air
D. Panting is primarily dead space ventilation
a. Alveolar ventilation is constant
3. Pressures that Accomplish Ventilation
A. Intrapulmonic and Intrapleuric Pressures
a. Intrapulmonic
--Pressure within the lungs
b. Intrapleuric
--Pressure outside the lung and inside the
thorax
c. Air flows in the lungs when intrapulmonic
pressure is less than atmospheric pressure
d. Air flows out of the lungs when
intrapulmonic pressure is more than
atmospheric
e. Intrapleuric pressure determines the
amount of air inhaled
B. Generation of Pressure Changes
a. Lungs enlarge because thorax enlarges
i. Causes Vacuum
ii. Intrapleural pressure becomes more
negative
b. Expiration caused by recoil of lung tissue
during passive expiration
i. Elasticity of tissues
ii. Surface tension of alveoli
C. Pneumothorax
a. When intrapleural space is opened to the
atmosphere
b. Lungs don't inflate--no vacuum
c. Usually only one lung involved
c. Remedied by simultaneous closure of hole
and inflation of lungs
D. Mediastinal Pressure
a. Mediastinal pressure is also reduced
during inspiration
b. Decrease in pressure assists in:
i. Movement of blood through vena cava
ii. Movement of lymph through lymph
vessel
iii. Regurgitation in ruminants
V. Diffusion of Respiratory Gases
1. General Characteristics
A. Respiratory Gases diffuse readily throughout body
B. C02 is 20X more diffusible than O2
C. From High Partial Pressure to Low Partial Pressure
--Concentration Gradient
2. Oxygen Transport
A. General
a. Arterial Blood is 20% Oxygen
b. 25% of is consumed at capillaries during
normal activity
--Utilization Coefficient
c. More can be utilized during strenuous
exercise
B. Transport Scheme
a. Alveoli to RBC
i. Interstitial water
ii. Plasma
iii. Erythrocyte water (cytoplasm)
iv. Hemoglobin
b. RBC to Tissue
i. Reverse Process
C. Oxygen in Solution and the Oxygen-Hemoglobin
Dissociation Curve
a. 60X more blood would be needed if
hemoglobin didn't bind O2
b. Arterial blood:
P02 = 100 mm Hg = 97.5% saturation
c. Venous blood:
P02 = 40 mm Hg = 72% saturation
2. Carbon Dioxide Transport
A. General
a. Facilitated by several reactions that
provide other forms of C02 to be
transported
b. CO2 is more soluble than O2
i. Amount produced still exceeds
amount dissolved in
plasma
B. Hydration Reaction
a. Formation of Bicarbonate (HCO3-)
b. Reaction in RBCs
--Carbonic anhydrase
c. 80% of CO2 transport
C. Formation of Carbamino Compounds
a. CO2 binds to terminal amino groups of
protein
b. Plasma Proteins
c. Hemoglobin
D. Loss of Carbon Dioxide at Alveolus
a. Hydration and Carbamino Reactions Reverse
b. CO2 follows concentration gradient from
blood to alveoli
VI. Regulation of Ventilation
1. General
A. Ventilation is regulated by body concentrations
of H+, CO2, and O2
a. If H+ and CO2 increase or O2 decrease,
ventilation increases
b. If H+ and CO2 decrease or O2 increase,
ventilation decreases
c. Changes are in tidal volume and/or frequency
B. Respiratory Centers found in Brain Stem
a. Provides rhythmicity
b. Influenced by vagus and glossopharyngeal
cranial nerves
c. And by Chemoreceptors
2. Neural Control
A. Hering-Bruer Reflex
a. Inflation-sensitive and deflation-sensitive
receptors located in bronchi and bronchioles
b. Signal Respiratory Centers
B. Other Receptors
a. Skin--Newborn stimulation, and Body
Temperature
b. Muscles--Exercise
c. Upper Airways
i. Swallowing
ii. Coughing and Sneezing
d. Pressure receptors in Carotids
and Aortic Arch
e. Pain receptors
C. Voluntary control can alter involuntary breathing
a. Exercise
b. Defecation
c. Urination
d. Parturition
3. Humoral Control
A. Chemoreceptors measure body concentrations
of H+, CO2, and O2
B. Locations
a. H+ and CO2 receptors are located on
ventral surface of brain stem
--Diffuse into Cerebral Spinal Fluid
b. Aortic and Carotid Bodies contain receptors
for O2, H+, and CO2
C. Hormones
VII. Respiratory Clearance
1. The removal of particles that have been inhaled into
the lungs
A. Protective Mechanism
B. Two types
a. Upper respiratory clearance
b. Alveolar clearance
2. Physical Forces of Deposition
A. Deposition
a. Inhaled particles that settle out onto
a membrane of the respiratory tract
B. Physical Forces
a. Gravity
i. Sedimentation
ii. Dependent on mass of particle
--Greater mass sediments faster
b. Inertia
i. Also dependent on mass
ii. Particles continue on path
(inspiration) even though
expiration is happening
c. Brownian Movement
i. Deposition of submicronic particles
(<0.3 µm)
ii. Most significant in small airways
3. Upper Respiratory Tract Clearance
A. Moving blanket of mucous towards pharynx
a. Ciliated epithelium
b. Speed = 15 mm/min
B. Animals usually swallow the fluid and particles
4. Alveolar Clearance
A. Usually small particles involved (<1 um)
B. Possible Fates of Particles
a. Phagocytosis by Macrophages (Dust Cells)
b. Particles enter interstitial space and
enter lymph system
c. Particles in solution may diffuse through
basement membranes and enter blood stream
d. Failure of above mechanisms
i. Stay within lungs
ii. Asbestosis, Silicosis,
and Anthracosis (Black Lung)
VIII. Nonrespiratory Functions of the Respiratory Tract
1. Panting
2. Purring
IX. Descriptive Terms
1. Anoxia
--Without Oxygen
2. Hypoxia
--Reduced O2
3. Hypercapnia
--Excess CO2
4. Hypocapnia
--Reduced CO2
5. Cyanosis
--Bluish or Purplish color of skin or membranes
--Do to inadequate blood supply (Oxygen supply)
6. Asphyxia
--Hypoxia combined with Hypercapnia
--Breathing into a closed space (Suffocation)
7. Pathological Conditions
A. Emphysema
--Destruction of alveolar membranes
--Smaller area of gas exchange
B. Pneumonia
--Inflammation of lungs where alveoli fill
with fluid and debris
C. Atelectasis
--Collapse of alveoli
a. Causes
i. Pneumothorax
ii. Airway Obstruction
iii. Lack of surfactant
--Common in Premature births
~~~~~Revised 10/16/96~~~~~ TAW