Respiratory System Flashcards
Embryological derivation of the lungs
Endoderm
What is pulmonary surfactant made of?
Lecithins, especially dipolmitoylphosphatidylcholine Lecithin-to-sphingomyelin ration > 2.0 in amniotic fluid indicates fetal lung maturity (usually reached around 35 weeks) Mothers of premature infants should be given a glucocorticoid injection before birth and babies can be given surfactant; adverse effects of oxygen therapy is retinal vessel proliferation
Most likely location following aspiration?
Right mainstem bronchus wider and more vertical than the left While upright –> lower portion of right inferior lobe While supine –> superior portion of right inferior lobe or posterior segments of the right upper lobe
What factors shift the oxygen-hemoglobin curve to the right?
Right shift = reduced affinity = more oxygen is offloaded at a given pO2 ↑ in Cl-, H+, CO2, 2,3-BPG, temperature, altitude, and exercise
What factors shift the oxygen-hemoglobin curve to the left?
Left shift = greater affinity = less oxygen is offloaded at a given pO2 ↓ in Cl-, H+, CO2, 2,3-BPG, and temperature
Methemeglobinemia
Oxidized hemoglobin (with Fe3+) has reduced affinity for oxygen and increased affinity for cyanide S&S: cyanosis and chocolate-colored blood Tx: methylene blue
Cyanide poisoning
Nitrites to oxidize hemoglobin to methemeglobin which binds CN Thiosulfate to bind this cyanide, forming thiocyanate, which is renally excreted
Why is the oxygen-hemoglobin curve sigmoidal?
Positive cooperativity –> binding of O2 increases affinity for each subsequent O2 molecule bound Since myoglobin is monomeric, it doesn’t demonstrate positive cooperativity and doesn’t have a sigmoidal appearance
How far into the bronchial tree do goblet cells, mucous glands, serous glands, cartilage, and cilia go?
Cartilage, goblet cells, and mucous and serous glands end at the tertiary bronchi (bronchioles don’t have these features) Cilia end in the respiratory bronchioles
Phrenic nerve
Derived from C3-5 nerve roots and innervates the diaphragm (motor and sensory) and mediastinal parietal pleura (sensory) C3, 4, and 5 keep the diaphragm alive Irritation to the mediastinal or diaphragmetic parietal pleura can cause pain that is worse on inspiration that may be referred to the base of the neck and over the shoulder
Hypoxia vs. hypoxemia
Hypoxia = decreased oxygen delivery to tissues Hypoxemia = decreased PaO2 in blood
Which muscles are used during inspiration and expiration?
Inspiration: diaphragm (primary) + external intercostals (exercise, respiratory distress) Expiration: usually passive or abdominal muscles + internal intercostals (exercise, increased airway resistance like COPD)
Carbon monoxide poisoning
The affinity of hemoglobin for CO is 200x that of oxygen CO poisoning causes both a decrease in oxygen content in blood and a shift of the Hb-oxygen dissociation curve to the left
Triad of aspirin-intolerant asthma?
Asthma Aspirin-induced bronchospasms Nasal polyps
Angiofibroma
Benign tumor of nasal mucosa composed of large blood vessels and fibrous tissues Often presents with profuse epistaxis in adolescent males
Caplan syndrome
Rheumatoid arthritis and pneumoconioses with intrapulmonary nodules
Lobes of the lungs affected by pneumoconioses
Asbestosis –> lung bases Silica and coal –> upper lobes
Light’s criteria?
Pleural effusion is exudative if: PF/serum protein > 0.5 PF/serum LDH > 0.6 PF LDH > 2/3 upper limit of normal (about 200)
Locations of primary lung cancers
Adenocarcinoma, bronchioalveolar, large cell –> peripheral Squamous cell, Small cells –> central
Adenocarcinoma
Most common lung cancer in nonsmokers and overall Found in periphery A/w k-ras, EGFR, and ALK mutations Bronchioloalveolar subtype (derived from Clara cells) looks like pneumonia on CXR –> good prognosis
Squamous cell carcinoma
Most common lung cancer in male smokers Centrally located as hilar mass from the bronchus a/w cavitation, cigarettes, hypercalcemia (from PTHrP) a/w inactivation of tumor suppressor genes (CDKN2A, TP53, RB) or amplification of FGFR1 Keratin pearls and intercellular bridges on histology
Small cell (oat cell) carcinoma
Centrally located Undifferentiated neuroendocrine cells –> very aggressive May produce ACTH, ADH, antibodies against presynaptic calcium channels (Lambert-Eaton), or anti-Yo, anti-P/Q, anti-Hu (cross-react with Purkinje neurons –> cerebellar degeneration) A/w myc amplification Inoperable, must treat with chemotherapy
Large cell carcinoma
Found in periphery Highly anaplastic undifferentiated tumor Less responsive to chemotherapy, removed surgically Pleomorphic giant cells on histology a/w gynecomastia and glactorrhea
Bronchial carcinoid tumor
Nests of neuroendocrine cells (chromogranin A +) Excellent prognosis, metastasis rare Symptoms due to mass effect or carcinoid syndrome (5-HT –> flushing, diarrhea, wheezing)
Common sites of primary lung cancer metastasis?
Adrenal glands, brain, bone, liver
The terrible T’s of a mediastinal mass
Teratoma Thymoma Thyroid cancer Terrible lymphoma
Hamartoma of the lung
Benign lesion Typicallly a solitary lung nodule (“coin lesion”) with “popcorn” calcifications Often contains islands of mature hyaline cartilage, fat, smooth muscle, and clefts lines by respiratory epithelium
Smoking-related vs. A1AT deficiency emphysema
Smoking-related emphysema: centriacinar in the upper lobes A1AT deficiency emphysema: panacinar in the lower lobes
Elastin
Large polypeptide made up of mostly nonpolar AAs and proline and lysine residues Tropoelastin exported into the extracellular space and arranged over a microfibrillar scaffold Lysyl oxidase (requires copper) deaminates some lysine residues facilitating formation of desmosine cross-linksbetween neighboring polypeptides that are responsible for the rubber-like properties of elastin
Which pneumoconicosis is associated with increased risk of TB?
Silicosis Silica particles internalized into macrophages disrupt phagolysosomes and cause release of the particles and viable mycobacteria limiting the immune system’s ability to combat TB infection
Chronic rejection of a lung vs. kidney transplant
Kidney –> inflammation of vasculature Lung –> inflammation of small bronchioles (bronchiolitis obliterans)
Causes of deviated trachea
Tension pneumothorax –> trachea deviates away from the collapsed lung Collapsed lung due to bronchial obstruction –> trachea deviates towards the affected side
