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Human Physiology
Unit Nine
The
Respirator
y System
Oral
cavity
Larynx
Primary
bronchus
Tertiary
bronchus
Nasal
cavity
Pharynx
Epiglottis
Glottis
Trachea
Secondary
bronchus
The Respiratory System
Bronchiole
Pulmonary
arteriole
Pulmonary
venule
Terminal
bronchiole
Respiratory
bronchiole
Alveoli
Capillary
beds
Inspiration & Expiration
Respiration is divided into three
phases:
+ ventilation
+ external respiration
+ internal respiration
Inspiration & Expiration
Ventilation occurs due to differences
in pressure
Humans mechanically produce an
internal pressure that is less than
the atmospheric pressure
This is called negative pressure
breathing
Inspiration & Expiration
Intrapulmonary pressure - pressure
found inside the lungs (alveoli)
Intrapleural pressure - pressure
found outside the lungs in the
pleural
cavity
Transplumonary pressure -
difference between the two
Inspiration & Expiration
Inspiration & Expiration
Inspiration & Expiration
Compliance - the ability of the lungs
to stretch and distend
Elasticity - lung characteristic
produced by large amounts of
elastin connective tissues
Elastic resistance - the tenancy of
elastic fibers to return to original
position (elastic recoil)
Inspiration & Expiration
Muscles of Inspiration & Expiration
Sternocleidomastoid
Scalenes
External
intercostals
Pectoralis
minor
Internal
intercostals
Internal
intercostals
External
abdominal
obliques
Diaphragm
Rectus
abdominis
Lung Volumes
Ventilation Terminology
Eupnea - normal, relaxed quiet
ventilation
Apnea - temporary cessation of
ventilation
Dyspnea - labored ventilation
Ventilation Terminology
Hyperventilation - ventilation faster
than necessary for metabolic
demands
Hypoventilation - ventilation slower
than necessary for metabolic
demands
Ventilation Terminology
Anoxia - condition in which there is
little or no oxygen
Pneumothorax - presence of air in
the pleural cavity
Atelectasis - collapsed lung
Pulmonary
Disorders
COPD - chronic obstructive
pulmonary disorder
Asthma - obstructive disorder
caused by inflammation, mucus
secretions & constriction of air
passageways
Pulmonary
Disorders
Emphysema - obstructive disorder
caused by destruction of alveolar
tissue
Bronchitis - obstructive disorder
caused by inflammation & the
mucus it causes
Pulmonary
Disorders
Pneumonia - lower respiratory
tract infection that causes the
alveoli to fill with fluids
Tuberculosis
- caused by Mycobacterium
tuberculosis
- stimulates the lungs to form
nodules
Pulmonary
Disorders
Cystic fibrosis - a genetic
disorder that clogs air
passageways by the production of
a thick, heavy mucus
Pulmonary
Disorders
Bronchiogenic carcinoma - lung
cancer that arises from the
bronchial tubes
~ squamous cell carcinoma
~ small cell carcinoma
Lung cancer is the leading cause
of cancer death among both men
and women
Pulmonary
Disorders
Pulmonary fibrosis - reduced
compliance and elasticity due to
the accumulation of fibrous
connective tissues as a result of
lung
Blackdamage
lung - form of pulmonary
fibrosis due to inhalation of
carbon dust
Major Atmospheric Gases
Nitrogen - N2 - 78%
Oxygen - O2 - 21%
Carbon dioxide - CO2 - 0.04%
Dalton’s Law
The total pressure of a gas mixture is the sum of the
partial pressures that each of the gases in the
mixture would exert independently
Respiration
Remember - respiration is
divided into three phases:
+ ventilation
+ external respiration
+ internal respiration
Parti
al
Press
ures
and
Ventilation/P
erfusion
This ratio
indicates the amount
Ratio
of O2 in alveoli with respect to
the blood flow (perfusion)
Richly ventilated alveoli have
increased perfusion
Poorly ventilated alveoli have
decreased perfusion
Ventilation/P
erfusion
Ratio
Poor ventilation in areas of
increased perfusion leads to
reduced Po2
Rich ventilation in areas of
decreased perfusion leads to
reduced Po2
Blood Gas Transportation
Oxygen transport:
* hemoglobin on RBCs - 98.5%
* dissolved in plasma - 1.5%
Carbon dioxide transport:
* hemoglobin on RBCs - 20%
* dissolved in plasma - 10%
* converted to HCO3- - 70%
Hemoglobin and
Blood Gas
Transportation
Hemoglobin and
Blood Gas
Transportation
Formation of oxyhemoglobin
HHb + O2
HbO2 + H+
Carbaminohemoglobin formation
CO2 + Hb
HbCO2
Hemoglobin and
Blood Gas
Transportation
Hemoglobin and
Blood Gas
Transportation
The Oxyhemoglobin
Dissociation Curve
Oxyhemoglobin and
the Unloading Oxygen
pH and temperature will affect the
rate and amount of HbO2
dissociation
The Bohr effect - the increase in
HbO2 dissociation in response to
low pH
Oxyhemoglobin and
the Unloading Oxygen
The decrease in pH is the result of
glucose metabolism in cells
The metabolism results in H+ and
CO2 being passed into the
capillaries, decreasing the pH and
increasing the Pco2
Oxyhemoglobin and
the Unloading Oxygen
HbO2 is induced to give off O2 for
four reasons:
► ambient Po2
► temperature increase
► pH decrease
► BPG (biphosphoglycerate)
The
Oxyhemoglobin
Dissociation
Curve
The Effects of
Temperature
and pH
Acidosis vs. Alkalosis
Respiratory acidosis
- occurs when the blood pH
drops below 7.35
- CO2 increases in the blood
- caused by trauma, illness,
hypoventilation, pulmonary
disease or barbiturate overdose
Acidosis vs. Alkalosis
Metabolic acidosis
- occurs when the blood pH
drops below 7.35
- increased levels of metabolic
acids
- caused by starvation, low
dietary carbohydrates,
diarrhea, strenuous exercise or
excessive alcohol
Acidosis vs. Alkalosis
Respiratory alkalosis
- occurs when the blood pH
rises above 7.45
- CO2 decreases in the blood
- caused by hyperventilation or
aspirin overdose
Acidosis vs. Alkalosis
Metabolic alkalosis
- occurs when the blood pH
rises above 7.45
- decreased metabolic acids in
the blood
- caused by constipation,
prolonged emesis or overdosing
on alkaline drugs
Neural Control of
Respiration
Pontine
respiratory
center
Ventral
respiratory
group
Dorsal
respiratory
group
Neural Control of Respiration
Neural Control of
Respiration
Neural Control of Respiration
Since O2 is carried in such high reserves and saturation,
it has little effect on the rate of ventilation
CO2 concentration and pH do significantly change and
have an immediate effect on ventilation
Neural Control of Respiration
Therefore, ventilation functions to maintain Pco2
within its homeostatic range
Neural Control of Respiration
The Hering-Breuer reflex inhibits respiratory control
centers by way of pulmonary stretch receptors
This reflex prevents over distention of the lungs and
contributes to the smoothness of ventilation
Neural Control of Respiration
Cheyne-Stokes ventilation is a condition that exhibits
a rhythmic waxing and waning of the depth of
ventilation with regular periods of apnea
Neural Control of Respiration
SIDS (sudden infant death syndrome) is caused by
sleep apnea
This syndrome typically occurs in infants under the age
of two
Neural Control of Respiration
Causes are being investigated, with failure of
respiratory control centers and/or failure of carotid
bodies being focused on