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Sonya Mezzina Respiratory (respiratory structures (Bronchi (Main bronchi:…
Sonya Mezzina Respiratory
Steps of Pulmonary Ventilation
Quiet
Inspiration
1) Inspiratory muscles
contract
:
diaphragm
flattens and moves inferiorly,
external intercostals
lift the rib cage
2) Thoracic cavity
volume increases
3) Intrapulmonary volume increases
5) Air moves into the lungs because intrapulmonary pressure is lower than atmospheric pressure (air moves down its pressure gradient)
inspiration continues until intrapulmonary and atmospheric pressure equalize
4) As intrapulmonary
volume increases
, intrapulmonary
pressure decreases
(now lower than atmospheric pressure)
Quiet
Expiration
passive process
3) Intrapulmonary volume decreases
4) As intrapulmonary
volume decreases
, intrapulmonary
pressure increases
(now higher than atmospheric pressure)
2) Thoracic cavity
volume decreases
5) Air moves out of the lungs because intrapulmonary pressure is higher than atmospheric pressure (air moves down its pressure gradient)
expiration continues until intrapulmonary pressure and atmospheric pressure equalize
1) Inspiratory muscles
relax
: diaphragm becomes rounded and moves superiorly, external intercostals cause rib cage to descend
Deep or forced inspiration
uses the addition of
accessory respiratory muscles
(sternocleidomastoid, scalenes, pectoralis minor) in step one
Forced expiration
active process
involves the use of contracting anterior abdominal wall muscles
involves a steeper pressure gradient so air moves more quickly out of the lungs
3 physical factors that can affect pulmonary ventilation
2)
Surface tension of alveolar fluid:
surfactant in the aloveolar fluid reduces surface tension and allows alveoli to remain open as air exits during expiration
3)
Compliance:
refers to stretchiness of the stroma. decreased compliance makes it more difficult for lung inflation, making breathing more difficult.
1)
Airway resistance
: any condition that slows or blocks the flow of air.
The more obstructed passages are, the lower air flow will be.
Transport of respiratory gases by blood
O2 transport
98.5% transported in hemoglobin of RBC's
1.5% dissolved in plasma
CO2 transport
7-10% dissolved in plasma
20% bound to hemoglobin (carbaminohemoglobin)
70% converted to bicarbonate ion
(CO2 + H2O > H2CO3 > H+ + HCO3-)
Changes in CO2 levels in the CSF lead to changes in pH of CSF (negative feedback loop affecting rate and depth of respirations)
If CO2
increases
, the pH will
decrease
(stimulus)
Central chemoreceptors in the medulla will activate (receptor)
Sensory nerve fibers (Afferent Pathway)
Respiratory Center (control center)
Somatic nerve fibers (Efferent Pathway)
diaphragm and external intercostals (effectors) will increase the rate and depth of respiration (hyperventilation)
This will enable you to exhale excess CO2 so that pH will increase
If CO2
decreases
, the pH will
increase
(stimulus)
Respiratory Center (control center)
sensory nerve fibers (Afferent Pathway)
Somatic nerve fibers (Efferent Pathway)
Central chemoreceptors in the medulla will activate (receptor)
diaphragm and external intercostals (effectors) will decrease the rate and depth of respiration causing slow and shallow respirations (hypoventilation)
This will enable you to retain CO2 to decrease the pH of CSF
external respiration
occurs at the respiratory membrane
2)
Surface area
of the respiratory membrane: related to the number of alveoli.
Decreased alveoli will decrease rate of external respiration.
3)
Partial pressure gradients
: rate of diffusion is faster when pressure gradients are steeper.
decreased partial pressure gradient will decrease rate of respirations. increased partial pressure gradients will increase rate of respirations
1)
Thickness
of the respiratory membrane: typically <1 micrometer thick makes for efficient diffusion.
Any disorder that increases thickness of the respiratory membrane will slow the rate of external respiration
gas exchange occurs via simple diffusion
Factors that affect external respiration:
respiratory structures
Alveoli
3 separate cell types
Type I Alveolar cells:
simple squamous epithelium. make up alveolar wall
Type II Alveolar cells:
simple cuboidal epithelial cells spaced at irregular intervals. Produces surfactant that coats the alveolar surface.
Alveolar macrophages:
fixed macrophages. continually move over alveolar surface to remove debris and pathogens
Pleura
: thin double layered serous membrane covering the lungs
Parietal pleura:
superficial layer. covers the thoracic wall, superior surface of the diaphragm, heart
Visceral pleura:
deeper layer. covers all external lung surfaces
Pleural cavity
contains
pleural fluid
produced by the pleura. It lubricates the pleural surfaces so the lungs glide over the pleural wall and other surrounding structures during breathing.
Bronchi
Main bronchi:
attached to inferior end of trachea. directs air from trachea into the lungs
Lobar bronchi
: subdivision of main bronchus. Each supplies and individual lobe of a lung
Segmental bronchi:
subdivision of lobar bronchus
As bronchi transition to bronchioles 3 major changes can be noted:
1) bronchi have cartilage, bronchioles DO NOT
2) As passageways get smaller, epithelium thins
3) Bronchi have less smooth muscle than bronchioles
Pharynx
: funnel shaped structure. connects the nasal cavity and mouth to larynx
nasopharynx
: superior section. connects to the nasal cavity. Only part that serves solely as a passageway for air. lined by respiratory mucosa
oropharynx
: middle section. connects to the oral cavity. lined by a mucous membrane
(nonkeratinized stratified squamous epithelium
aka oral mucosa
)
laryngopharynx
: inferior section. connects to the larynx and upper esophageal opening. lined by oral mucosa
Trachea
wall has four layers
mucosa
: areolar connective tissue. cleans and humidifies air. capillary blood warms the air
Submucosa
: loose connective tissue. produce sheets of sticky mucous that line the trachea
Adventitia
: fibrous CT. supports and protects the entire structure
c-shaped rings of hyaline cartilage
: maintain open airway in spite of pressure changes
Larynx
: structure composed mainly of cartilage
3 main functions:
1) provide open airway
: accomplished by the hyaline cartilage portions (thyroid cartilage and cricoid cartilage)
2) Route food/fluids and air into proper passageways:
specifically the
epiglottis
does this. it is composed of elastic cartilage because of its repeated bending.
3) voice production:
this is the function of the vocal cords.