Functions Of Respiratory System, Ventilation, Pneumothorax & Airway Resistance Flashcards
Site & function of conducting portion
From nose to terminal bronchioles
- conduct air at low resistance
- moisten and warm air
- protect alveoli from damage by bacteria/foreign particles
- smell
- phonation
Describe the protective role of conducting portion
Filtration action of nose to remove dust by phagocytes, mucous & cilia, foreign particles stick to mucus then expelled by cough & sneezing reflex.
Site and function of respiratory portion
Respiratory bronchioles to alveoli
Alveoli are the only site for gas exchange between air in the laveoli and blood.
GR: the alveolar-capillary membrane is extremely thin.
To facilitate gas exchange
Mention the main function of respiratory system
Gas exchange, to obtain O2 from atmosphere, & to remove CO2 produced by the cells.
Mention the non-respiratory functions of res system
Acid-base balance, water/heat loss, venous/lymph return, synthesis and removal of some substances, defense against inhaled foreign matter, vocalization & smell, vascular reservoir, air conditioning.
Mention substances synthesized by the respiratory system
Surfactant, some prostaglandins, histamine, angiotensin converting enzyme, tissue plasminogen activator.
Mention function of tPA in lung
Filtering of blood from blood clots and tissue debris before returning back to the systemic circulation
Describe the rsult of capillary recruitment during exercise
Enables them to accomodate large volume of blood 500-1000 ml, instead of 70-100 ml at rest.
Compare internal & external respiration
Internal: the cellular metabolic processes which use O2 to derive energy from food producing CO2 as by-product.
External: exchange of O2 & CO2 between body and external environment.
Mention steps of external respiration
- Ventilation: done by breathing
- Exchange between gases in lung
- Transport of gases between lung and tissues
- Exchange of gases in tissues
Describe the intra-alveolar pressure during quiet inspiration & expiration
- quiet inspiration: less than atm pressure by 1 mm
- quiet expiration: greater than atm pressure by 1mm
GR: the intra-alveolar pressure is equal to the atm at the end of both inspiration & expiration
Because the alveoli are in direct communication with atmosphere and air continues to flow down its pressure gradient until the two pressures equiliberate.
GR: intrapleural doesn’t equiliberate with pressure of other spaces
because there is no direct communication between them
Compare trans-pulmonary & trans-thoracic pressure gradients
P: across the lung wall, +4 mmHg, distending pressure
T: across the thoracic wall, -4 mmHg, compressing pressure
GR: the intrapleural pressure is subatmospheric
- The stretched lung tends to recoil, while the thoracic wall tends to expand causing slight expansion of the pleural cavity.
- The pleural cavity is filled with fluid, so expnasion creates a vacuum , thus pressure drops.
Importance of negativity of IPP
- Pevents collapse of alveoli
- Helps lung expansion
- Helps venous/lymph return
- Index of lung elasticity
Measurement of the IPP is done by …
Intra-esophageal balloon connected to a sensitive manometer
Noraml values of IPP
At the end of quiet inspiration, -6 mmHg
At the end of quiet expiration, -4 mmHg
Deep inspiration, -30 mmHg
Deep expiration, +30 mmHg
Define pneumothorax
It is the presence of air in the pleural sac (air in the chest cavity)
Describe the effects of pneumothorax
Air flows down the pressure gradient, thus intrapleural, intra-alveolar & atmospheric prssures become equal, leading to lung collapse (atelectasis), thoracic wall expands outwards (uncompressed position)
The most important muscle in respiration, its function & nerve supply.
Diaphragm
Increase the vertical diameter of thoracic cavity
Supplied by C3,4,5
Mention the function of external intercostal muscles
Increase in antero-posterior and lateral (transverse) diameters of the thorax
Mention the expiratory muscles and their role
- Abdominal muscles (decrease the vertical diameter)
2. Internal intercostal muscles (decrease the antero-posterior/lateral diameters)
Mention a point of contrast between quiet & forced expiration
Q-passive
F-active
GR: the lungs are always stretched although intrapleural pressure is variable
Because IPP is lower than the intra-alveolar pressure throughout the respiratory cycle.
GR: although IPP exceeds atm pressure during forced expiration the lung doesn’t collapse.
Due to the corresponding increase in intra-alveolar pressure that maintains the trans-pulmonary pressure gradient.
What happens if diaphragm/intercostals are paralyzed
Diaphragm: respiratory paralysis and death
Intercostals: no serious effect
Cutting of spinal cord below fifth segment
Paralysis of all skeletal muscles except the diaphragm
Name the following:
- Normal breathing
- Diffuclty breathing
- Difficulty with recumbent position
- Rapid shallow breathing
- Increase rate/depth matching metabolic needs
- Eupnea
- Dyspnea
- Orthopnea
- Tachypnea
- Hyperpnea
Name the following:
- Increase breathing above metabolic needs, so CO2 falls
- Decrease breathing below metabolic needs, so CO2 rises
- Dec CO2 in arterial blood
- Inc CO2 in arterial blood
- Temporary stoppage of breathing
- Hyperventilation
- Hypoventilation
- Hypocapnia
- Hypercapnia
- Apnea
Name the following:
- Permenant cessation of breathing
- O2 deprivation due to failure to ventilate
- O2 starvation in the tissues
- Respiratory arrest
- Suffocation
- Asphyxia
Mention the factors controlling airway flow
Pressure gradient & airway resistance
Mention the primary factor affecting airflow
Pressure gradient
GR: airway resistance is low in the small airways
Because of the increase of total cross-sectional area and the parallel arrangement of airways
GR: low velocity of air in small airways.
Due to the increase in the total cross-sectional area which gives time for gas exchange to occur.
GR: Although the resistance of a single terminal bronchiole is greater than that of a single lobar bronchus, the first combined is less than the latter combined.
Because the cross-sectional area of all terminal bronchioles combined greatly exceeds that of all lobar bronchi combined.
GR: Airway resistance is increasing in smoking by pipe than by mouth.
Due to increase in the length of respiratory pathway.
GR: Airway resistance in decreased in tracheostomy.
Due to short respiratory pathway and bypass the upper airway which has high resistance.
Highest airway resistance occurs in
Medium sized bronchi
GR: Lowest airway resistance occurs in the smallest airways
Because the combined cross-sectional area of these airways is much larger than that of the medium sized bronchi.
Compare parasympathetic & sympathetic effects on airway reistance
P: bronchoconstriction, in quiet relaxed situations with low O2 demand.
S: bronchodilation, in stressful situations with high O2 demand
Compare the effects of increased and decreased alveolar CO2
I: relaxation of bronchiolar muscles, decrease airway resistance, increased air flow.
D: contraction of bronchiolar muscles, increase airway resistance, decreased air flow.
….. is used in treatment of bronchiolar spasm
Epinephrine
….. release increases airway resistance
Histamine
…. Is the major factor preventing small airway collapse
Transmural pressure
Transmural pressure increased leading to
Increased airway diameter with reduction of airway resistance.
Small airways are kept open by …&…
While large airways are kept open by …
Transmural pressure gradient & elastic lateral (radial) traction
Semicircular cartilage
Mention the two main characters of obstructive lung disease
Increased airway resistance & more difficult expiration
Bronchial asthma causes airway narrowing due to
- severe constriction of airways in response to allergens
- edematous thickening of airways by histamine
- excessive mucus sectretion
Chronic bronchitis leads to increased airway resistance due to
Long-term inflammatory condition, causing airway narrowing by edematous thickening due to histamine & excess mucous secretion.
Emphysema occurs due to increase of …. More than …..
Elastase, alpha-1-antitrypsin
Emphysema can occur due to
Chronic irritation so elastase increases
Genetic deficiency of alpha-1-antitrypsin
What happens when elastase/alpha-1-antitrypsin balance is disrupted?
Destruction of lung tissue, reduction in surface area, impairment of gas exchange & increased airway resistance.
