Anatomy Flashcards
What is the diaphragm innervated by?
Phrenic nerve (C3, 4, 5)
What structures perforate the diaphragm at T8? T10? T12?
T8: IVC
T10: esophagus
T12: aorta, thoracic duct, azygos vein
What favors the taut/low affinity form of Hb over the relaxed/high affinity form?
increased Cl-, H+, CO2, 2,3-BPG and temperature
all shift dissociation curve to the right, increasing the unloading of O2
(decreases affinity for O2)
What is methemoglobin? What causes methemoglobinemia? What is the treatment?
Methemeglobin - oxidized form of Hb (ferric, Fe3+) that does not bind O2 as readily, but has a high affinity for cyanide
Iron is normally in a reduced ferrous, Fe2+ state
Caused by nitrites (poisoning causes oxidation of Fe2+ to Fe3+)
Treated with methylene blue
Why is cyanide toxic? What is the treatment and mechanism?
CN binds to iron-containing enzymes (most important is the cytochrome a-a3 complex critical for e- transport during ox-phos in mitochondria - inhibits aerobic metabolism in minute amounts!)
Treatment is nitrates and sodium thiosulfate.
Nitrates - oxidize Hb into methemoglobin which binds CN with high affinity (binds and sequesters CN in blood and away from mito)
Sodium thiosulfate - combines with CN to form less toxic thiocyanate (excreted in urine)
What are the perfusion-limited gases? What are the diffusion-limited gases?
Perfusion-limited: O2 in normal people, CO2, N2O
Diffusion-limited: CO, O2 in pts with emphysema or fibrosis
Where in the lung is ventilation greatest? Perfusion? What is the V/Q ratio at the apex vs. base of the lung?
Ventilation and perfusion is greatest at the base of the lung vs. apex.
apex V/Q = 3 (wasted ventilation; low ventilation/very low perfusion)
base V/Q = 0.6 (wasted perfusion; high ventilation/very high perfusion)
What are the 3 forms in which CO2 is transported from tissues to the lungs?
- HCO3- (90%)
- Carbaminohemoglobin / HbCO2 (5%)
CO2 bound to N-terminus of globin (not heme) and favors taut Hb - dissolved CO2 (5%)
What is pulmonary surfactant comprised of? Which is the most important?
Pulmonary surfactant is a complex mix of lecithins,
the most important of which is dipalmitoylphosphatidylcholine.
How is fetal lung maturity measured?
Lecithin to sphingomyelin ratio > 2.0 in amniotic fluid indicates fetal lung maturity
What type of organisms are responsible for aspiration pneumonia? What species are common?
most often due to anaerobic bacteria in the oropharynx
- Bacteroides
- Fusobacterium
- Peptococcus
What kind of pneumonia is Legionella associated with? What is the best way to visualize it?
Atypical/interstitial pneumonia
Intracellular organism, best visualized by silver stain