Respiratory System

Question 1

Embryological derivation of the lungs

Answer 1

Endoderm

Question 2

What is pulmonary surfactant made of?

Answer 2

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

Question 3

Most likely location following aspiration?

Answer 3

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

Question 4

What factors shift the oxygen-hemoglobin curve to the right?

Answer 4

Right shift = reduced affinity = more oxygen is offloaded at a given pO2 ↑ in Cl-, H+, CO2, 2,3-BPG, temperature, altitude, and exercise

Question 5

What factors shift the oxygen-hemoglobin curve to the left?

Answer 5

Left shift = greater affinity = less oxygen is offloaded at a given pO2 ↓ in Cl-, H+, CO2, 2,3-BPG, and temperature

Question 6

Methemeglobinemia

Answer 6

Oxidized hemoglobin (with Fe3+) has reduced affinity for oxygen and increased affinity for cyanide S&S: cyanosis and chocolate-colored blood Tx: methylene blue

Question 7

Cyanide poisoning

Answer 7

Nitrites to oxidize hemoglobin to methemeglobin which binds CN Thiosulfate to bind this cyanide, forming thiocyanate, which is renally excreted

Question 8

Why is the oxygen-hemoglobin curve sigmoidal?

Answer 8

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

Question 9

How far into the bronchial tree do goblet cells, mucous glands, serous glands, cartilage, and cilia go?

Answer 9

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

Question 10

Phrenic nerve

Answer 10

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

Question 11

Hypoxia vs. hypoxemia

Answer 11

Hypoxia = decreased oxygen delivery to tissues Hypoxemia = decreased PaO2 in blood

Question 12

Which muscles are used during inspiration and expiration?

Answer 12

Inspiration: diaphragm (primary) + external intercostals (exercise, respiratory distress) Expiration: usually passive or abdominal muscles + internal intercostals (exercise, increased airway resistance like COPD)

Question 13

Carbon monoxide poisoning

Answer 13

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

Question 14

Triad of aspirin-intolerant asthma?

Answer 14

Asthma Aspirin-induced bronchospasms Nasal polyps

Question 15

Angiofibroma

Answer 15

Benign tumor of nasal mucosa composed of large blood vessels and fibrous tissues Often presents with profuse epistaxis in adolescent males

Question 16

Caplan syndrome

Answer 16

Rheumatoid arthritis and pneumoconioses with intrapulmonary nodules

Question 17

Lobes of the lungs affected by pneumoconioses

Answer 17

Asbestosis –> lung bases Silica and coal –> upper lobes

Question 18

Light’s criteria?

Answer 18

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)

Question 19

Locations of primary lung cancers

Answer 19

Adenocarcinoma, bronchioalveolar, large cell –> peripheral Squamous cell, Small cells –> central

Question 20

Adenocarcinoma

Answer 20

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

Question 21

Squamous cell carcinoma

Answer 21

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

Question 22

Small cell (oat cell) carcinoma

Answer 22

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

Question 23

Large cell carcinoma

Answer 23

Found in periphery Highly anaplastic undifferentiated tumor Less responsive to chemotherapy, removed surgically Pleomorphic giant cells on histology a/w gynecomastia and glactorrhea

Question 24

Bronchial carcinoid tumor

Answer 24

Nests of neuroendocrine cells (chromogranin A +) Excellent prognosis, metastasis rare Symptoms due to mass effect or carcinoid syndrome (5-HT –> flushing, diarrhea, wheezing)

Question 25

Common sites of primary lung cancer metastasis?

Answer 25

Adrenal glands, brain, bone, liver

Question 26

The terrible T’s of a mediastinal mass

Answer 26

Teratoma Thymoma Thyroid cancer Terrible lymphoma

Question 27

Hamartoma of the lung

Answer 27

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

Question 28

Smoking-related vs. A1AT deficiency emphysema

Answer 28

Smoking-related emphysema: centriacinar in the upper lobes A1AT deficiency emphysema: panacinar in the lower lobes

Question 29

Elastin

Answer 29

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

Question 30

Which pneumoconicosis is associated with increased risk of TB?

Answer 30

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

Question 31

Chronic rejection of a lung vs. kidney transplant

Answer 31

Kidney –> inflammation of vasculature Lung –> inflammation of small bronchioles (bronchiolitis obliterans)

Question 32

Causes of deviated trachea

Answer 32

Tension pneumothorax –> trachea deviates away from the collapsed lung Collapsed lung due to bronchial obstruction –> trachea deviates towards the affected side