3.5 Respiratory 1 Flashcards
Volume of pulmonary flow
Same as systemic CO
Pressure of pulmonary blood circulation
LOW
25/8mm Hg
MAP ~14 mm Hg
Why is the MAP of pulmonary blood circulation so much lower than systemic?
Low resistance due to
- Shorter distance / shorter vessels heart to lungs
- Greater total diameter of pulmonary arterioles / capillaries
What is the pleural cavity?
Closed space (airtight) filled with fluid
What do visceral and parietal pleura epithelia do?
Make slippery and tacky pleural fluid to lubricate, yet create surface tension to hold the lungs against chest wall as they inflate and deflate
What draws air in and out of airway?
Pressure changes in pleural cavity
Trachea, bronchi and bronchiole surface is lined with…
Ciliated epithelia and mucus secreting goblet cells
What do goblet cells do?
Catch and remove foreign material, convey it up to esophagus
Anatomy of airways (in order)
Trachea -> Bronchi-> Bronchioles -> Alveoli
Trachea branches about ___ times to terminate as ~____ alveoli
25
300 million
Alveoli
Huge surface area (tennis court)
Lung epithelium immediately adjacent to capillaries, no muscle, just elastic tissue
Boyle’s Gas Law
Increase Volume -> Decrease pressure
Inspiration
Volume INCREASE during diaphragm CONTRACTION decreases alveolar pressure-air enters
Expiration
Volume decrease during diaphragm relaxation increases alveolar pressure-air exits
Do alveoli have elasticity?
Yes! They recoil back to original shape when stretched (expiratory force)
Tendency for alveoli to recoil is balanced by..
Low pressure vacuum in the intrapleural cavity
Alveolar elastic recoil force is due to..
1) Elastic tissue surrounding alveoli
2) Surface tension of alveolar fluid
What is surfactant and what does it do?
A detergent that tries to reduce surface tension
Lung collapse is due to…
A) Loss of vacuum in interpleural cavity
B) Surface tension problems
Pneumothorax
Lung collapses due to hole or air penetration between body wall and inter pleural cavity (no vacuum created)
Infant respiratory distress syndrome
Not enough surfactant in premature infants makes it difficult to expand lungs due to stickiness of fluid within alveoli
What is the role of lymphatic vessels in gas exchange in alveoli?
Prevent fluid build-up at exchange surface, due to blood pressure
Alveolar type II cell
Make surfactant, lowers surface tension of fluid inside alveoli (like a detergent), prevents wall collapse
What is the role of macrophages in alveoli?
Clear debris b/c no cilia in alveoli
Gas exchange
How atmospheric gases enter the alveoli, then diffuse into / out of your RBCs
3 Factors affecting Gas Exchange
1) Respiratory membrane thickness
2) Surface Area (SA)
3) Partial pressure gradient
Respiratory membrane thickness
5 layers, normally very thin
Pulmonary Edema
Pulmonary edema
Interstitial fluid layer expands, increases gas exchange distance, reduced efficiency of exchange
Interstitial space is..
Space between type 1 alveolar cell and endothelial cell
Two things that can lead to pulmonary edema
Congestive heart failure, pneumonia
Emphysema
Loss of alveolar walls (decreases surface area)
Partial pressure
Concentration of a gas in a liquid will equilibrate with or equal to the partial pressure of the gas in contact with the liquid
Partial pressure
Concentration of a gas in a liquid will equilibrate with or equal to the partial pressure of the gas in contact with the liquid
Is there usually equilibrium between blood and air?
No, rarely because of gas usage in cell metabolism
Where does CO2 in blood come from?
Glucose
Is O2 higher in blood or tissues usually?
Blood
Is CO2 higher in blood or tissues usually?
Tissues
Why is oxygen low and carbon dioxide high in systemic tissues?
Cellular respiration (glucose to carbon dioxide and oxygen to water)
Oxygen is carried in the plasma within..
RBCs, bound to hemoglobin
Carbon dioxide is carried as the plasma primarily as…
Bicarbonate (HCO3-)
What is a small amount of CO2 carried by?
Carried bound to amino acids in hemoglobin protein
At rest, _____ of the oxygen bound to hemoglobin is unloaded in the tissues
25%
During exercise, up to _____ oxygen bound to hemoglobin is unloaded in active tissues to drop PO2
65%
X-axis of oxygen-hemoglobin dissociation curve
Partial pressure of oxygen in tissues
Bohr Effect
pH impacts the oxygen-hemoglobin dissociation curve
As blood pH decreases, amount of oxygen bound to hemoglobin…
Also decreases
What does hemoglobin do under acidic conditions?
Gives up O2 more readily
Why does hemoglobin release O2 more readily under acidic conditions?
Increase in H+ ions changes shape of hemoglobin, decreases its affinity for oxygen
Where does the curve shift as pH decreases?
To the right
Hemoglobin “picks up on both…
Oxygen concentration and pH
CO2 +H2O create H2CO3 with the assistance of..
Carbonic anyhydrase
slow reaction when uncatalyzed
What does H2CO3 turn into spontaneously in water?
HCO3- and H+
Carbonic anyhydrase
Very high concentration in RBCs
Catalyzes chemical reaction in BOTH directions
RBCs are CO2 and HCO3- factories
In systemic tissue, CO2..
Is converted to HCO3- by RBCs and delivered to plasma
In the lungs, HCO3-…
Enters RBC (pumped in, Cl- exchanged) Converted to CO2 and H2O and diffuses out to air in lungs
