Download Respiratory System - MIDLANDS STATE UNIVERSITY

Respiratory System
Mr O. Tada
1
Functions






To obtain and use oxygen
To eliminate carbon dioxide
Assisting in the control of acidity (pH) of extracellular fluid
Assisting in control of water balance &
thermoregulation
Assisting in voice production (phonation)
Protection of the animal against inhaled dust,
gases & infectious agents
2
Structure & Function

Nostrils



Nasal Cavities



Paired, external openings
Dilatable
Paired
Separated by Nasal Septum, and from mouth by
palate
Pharynx

Common pathway for air and food

Caudal to nasal cavity
3
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
4
Structure & Function cont’d

Lungs


Principle Organ
of Respiratory
System
Paired, found in
Thorax

Thorax
expansion
causes Lung
expansion
5
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
6
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


7
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
8
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
9
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)
10
Respiratory Frequency


Number of Respiratory Cycles per minute
Factors affecting Respiratory Frequency



Species variations
Horse
12
Cow
29
Pig
40
Sheep
25
Body Size --Heavy animals breath heavier
Age --Younger less
11
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
12
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 (PCO2 0.23 mm Hg)
79% N2 (PN2 600 mm Hg)
13
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)
14
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
15
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
16
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
17
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
18
Oxygen Transport

General


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
19
The Flow

60X more
blood would be
needed if
hemoglobin
didn't bind O2
20
Gas exchange across capillary
and alveolus walls
21
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
22
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
23
Details of gas exchange
24
Regulation of Ventilation


Ventilation is regulated by body concentrations of H+,
CO2, and O2
 If H+ and CO increase or O decrease, ventilation
2
2
increases
 If H+ and CO decrease or O increase, ventilation
2
2
decreases
Respiratory Centers found in Brain Stem
 Provides rhythmicity
 Influenced by vagus and glossopharyngeal cranial
nerves
 And by Chemoreceptors
25
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)
26
Pneumotaxic center
27
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.
28
Apneumotaxic center

The activity of the pulmonary strecth
receptors (visceroreceptors) located in
the lungs, visceral pleura & bronchioles
smooth muscle further re
29
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
30
Neural Control

Voluntary control can alter
involuntary breathing




Exercise
Defecation
Urinating
Parturition
31
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
32