1 Respiratory System Flashcards
What is the importance of alveoli?
Providing extensive surface area
What is the role of the endocrine function?
Produces hormones
Important in blood pressure control
What is the role of the pleural space?
Has serous fluid, which ensures the lung membranes slide over each other on inhale and exhale
What two circulations do the lungs have, and what are their roles?
Deoxygenated blood from systemic circulation enters heart
Leaves heart via pulmonary arteries to lungs
Oxygenation of blood & release of CO2 in lungs at alveoli
Oxygenated blood re-enters heart via pulmonary veins
Distributed to rest of body by aorta & branches
What is the respiratory system divided into?
Upper and lower respiratory system
Components of upper respiratory system?
Nasal cavity > pharynx
Components of lower respiratory system?
Larynx >trachea > bronchus > lung
What separates breathing and swallowing?
Epitglottis
What is the importance of nose breathing?
Protection of lungs and respiratory epithelium
How is the respiratory epithelium protected by nose breathing?
Mucus secretion
Humidification & warming of air in upper passages
How are the lungs protected by nose breathing?
Mucociliary trapping of foreign matter
Ciliary escalator, wafting mucus out of lungs
Macrophages present in alveoli
Airway reflexes (cough, sneeze, epiglottis closes glottis during swallowing)
Name of the pleura
Parietal = outer
Visceral = inner
What is between the pleura?
Pleural cavity with thin layer of pleural fluid
Are pleural of the lungs connected?
No
Each lung has its own set of parietal and visceral pleural membranes
What is compromised when pleural space is damaged?
Ventilation of patient because pressure and volume are affected
Define conducting zone
The conducting zone consists of all of the structures that provide passageways for air to travel into and out of the lungs: the nasal cavity, pharynx, trachea, bronchi, and most bronchioles.
What role do trachea and bronchi perform?
They both have cartilage for support and keeping airways open (even if they want to close)
What do bronchiole walls contain?
Smooth muscle to facilitate airflow regulation
Define respiratory zone
Respiratory bronchioles leading to alveolar sacs
Where does gas exchange occur?
Exchange of oxygen and carbon dioxide takes place between air in the alveolus and blood
Blood is carried by the capillaries surrounding the alveolus
What type of system is the pulmonary system?
Low pressure because don’t want to burst blood capillaries??? ***
What are the types of cells in alveoli?
Type I alveolar cells = simple squamous epithelium
Type II alveolar cells = surfactant-secreting cells
What is surfactant and its role?
Mixture of proteins and phospholipids
Reduces surface tension from alveolar fluid lining the inner surface of alveolus
Prevents alveolar collapse
Structure of surfactant?
Polar head that interacts with water
Non-polar tail that doesn’t interact with water
What occurs at alveoli-capillary barrier?
Oxygen and carbon dioxide diffuse easily across membrane due to short distance and being lipid soluble
Oxygen crosses over from alveolus into blood
What is the physiological significant of the 0.25s buffering time of full oxygenation?
If it increases because of lung disease, where barrier may be thickened, oxygenation time may increase
What type of binding does oxygen to Hb have?
Cooperative binding = the more oxygen that binds the higher the affinity becomes
Helps get past the initial inertia
How does the partial pressure affect Hb-O2 binding?
In lungs, pO2 is high so oxygen binds to Hb
In tissue, pO2 is low, so oxygen dissociates from Hb
How does cooperative binding work in dissociation?
Dissociation of oxygen molecule from Hb lowers its affinity for other bound oxygen molecules
Further enhances release of oxygen to the tissues
What does the Hb-oxygen saturation curve show?
At high oxygen partial pressure, there is a gentle slope
At low oxygen partial pressure, there is a steep slope
What causes the slope in Hb-oxygen saturation curve?
How does going from sea level to high altitude affect arterial partial pressure and oxygen saturation of Hb?
Sea level has highest pO2 at 100mmHg
High altitude or mild lung condition pO2 = 80mmHg
This causes a drop from 98% to 95% oxygen saturation
What happens to arterial pO2 when going from resting to exercise?
Decrease in arterial pO2 due to oxygen consumption ***
Arterial partial pressure drops from 40mmHg to 20mmHg
What happens to oxygen saturation of Hb when exercising?
Drops from 75% to 35% meaning there is a greater proportion of oxygen dissociated from Hb
In order to meet the oxygen needs of these tissues
What is the threshold of when a patient becomes hypoxic?
At 60mmHg arterial partial pressure the saturation becomes 90%
What 4 factors affect oxygen-Hb affinity?
pH
Temperature
pCO2
BPG
Define oxygen-Hb affinity
How likely oxygen is to bind Hb given the pO2
What can cause a decrease in pH in our body?
Lactic acid when exercising, which will affect oxygen-Hb saturation curve
How does a decrease in pH affect oxygen-Hb affinity?
Decrease in pH (more acidic) shifts saturation curve to the RIGHT
Thus, at given pO2 there is greater oxygen unloading from Hb compared to normal
Facilitates tissues with high oxygen needs
(Examples when exercising muscles need to receive oxygen more efficiently)
How does a decrease in temperature affect oxygen-Hb affinity?
The saturation curve shifts LEFT
Less active muscles/tissues have cooler temperatures
Thus, blood perfusing less active muscles/tissues at lower temps change the Hb conformation to favour binding of O2
What is 2,3-BPG?
Produced inside the RBCs
2,3-BPG binds to hemoglobin and lowers its affinity for oxygen. This is crucial because it helps hemoglobin release oxygen more easily to tissues that need it
What happens to oxygen-Hb affinity when BPG increases in erythrocytes?
BPG competitively binds to Hb against oxygen
Thus, decreasing affinity for oxygen so more oxygen is release from the blood into the tissues
When does an increase in BPG occur?
In chronic hypoxia
Or due to living at high altitudes
How is CO2 transported?
7% dissolved in plasma = giving rise to arteria pCO2
23% carried with Hb
70% converted to bicarbonate ions
Where does carbon dioxide bind on Hb?
Binds the globin (protein) part of Hb to form carbaminohemoglobin
As opposed to the heme part
Why can oxygen and carbon dioxide not bind the at the same time to Hb?
Because of steric hinderance
What happens to carbon dioxide in the tissues?
23% of diffused CO2 from tissues combines with globin portion of Hb
This takes place in regions of high pCO2
What happens to carbon dioxide in the lungs?
Lower pCO2 so CO2 is released from RBCs Diffuses across the respiratory membrane
Is exhaled through the lungs
What happens to the 70% of CO2 in bicarbonate ion form at TISSUES?
High pCO2 so CO2 diffuses out of cells and across capillary to enter RBCs
In RBCs CO2 is converted into carbonic acid via reaction with water = catalyzed by carbonic anhydrase
Carbonic acid dissociates spontaneously to form H+ and bicarbonate ions
H+ combine with Hb and HCO3- are exchanged out of the RBCs with Cl- to maintain electrical neutrality
What happens to the 70% of CO2 in bicarbonate ion form at LUNGS?
At lungs CO2 is exhaled, pCO2 is low
Equation shifts to the left
CO2 + H2O <-> H2CO3 <-> bicarbonate (HCO₃⁻)+ H+
As CO₂ diffuses from the blood into the alveoli to be exhaled, the reaction reverses. Bicarbonate re-enters the RBCs, and the enzyme carbonic anhydrase converts bicarbonate back to carbonic acid, which then dissociates into CO₂ and water.
The CO₂ produced in the RBCs diffuses into the alveoli and is exhaled.
What structures does the respiratory system consist of?
Nose
Pharynx, larynx, trachea
Bronchi and lungs
Which pleura covers the surface of the lungs?
Visceral pleura
What do the parietal pleura cover?
Mediastinum, superior diaphragm and thoracic wall
Where is the respiratory zone found?
End of the terminal bronchiole and consists of alveoli where gas exchange occurs
Where is pO2 high and where is pCO2 high?
High pO2 in lungs
High pCO2 in tissues
How does pH affect oxygen unloading from Hb?
In tissues, high pCO2 means more HCO3- and H+
These two factors promote O2 unloading from Hb = thus shifting HbO2 saturation curve to the right
