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X. MRCS: Pathophysiology > Lung/Thorax > Flashcards

Lung/Thorax Flashcards

1
Q

Parts of the lung

A 
Apex
Base
Lobes
Surfaces
Borders
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2
Q

Lobes of the lungs

A

Right: superior, middle, inferior. Divided by oblique and horizontal fissure.
Left: Superior, inferior. Divided by oblique.

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3
Q

Surfaces of the lung

A

Mediastinal surface
Daiphragmatic surface
Costal surface

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4
Q

Borders of the lung

A

Anterior border
Inferior border
posterior border

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5
Q

Lung root

A

Collection of structures that suspends lung from mediastinum.
Contains: bronchus, pulmonary artery, two pulmonary veins, bronchial vessels, pulmonary nerve plexus, lymphatics
Structures leave/enter through hilum

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6
Q

Bronchial tree

A

Tracheal bifurcation at level of sternal angle T4/T5 (carina)
Right main bronchus: shorter, wider, more vertical. 3 lobar bronchi. Segmental bronchi for each bronchopulmonary segment.
Left main bronchus: inferior to arch of aorta, anterior to descending aorta/oesophagus. 2 lobar bronchi.

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7
Q

Sternal angle (Angle of Lois)

A 
T4/5
2nd rib articulation
Aortic arch
Azygous vein
Ligamentum arteriosus
Bifurcation of pulmonary trunk
Bifurcation of trachea
L recurrent laryngeal nerve
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8
Q

Blood supply to the lung

A 
Deoxygenated: 
Pulmonary arteries
Oxygenated: 
Trachea: inferior thyroid artery
Bronchi, lung roots, visceral pleura, lung parenchyma: bronchial arteries (branches of descending aorta. Left bronchial: directly of aorta. Right: 3rd posterior intercostal artery)
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9
Q

Venous drainage from the lung

A 
Oxygenated drainage: 
Pulmonary veins (two for each lung)

Deoxygenated:
Trachea: brachiocephalic/ azygos/hemiazygos veins
Right bronchial vein (drains into azygos vein)
Left bronchial vein (hemiazygos vein)

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10
Q

Nerve supply to the lung

A

Pulmonary plexuses
Parasympathetic: vagus nerve. Stimulates secretion of bronchial glands, contraction of bronchial smooth muscle and vasodilation of pulmonary vessels.
Sympathetic: derived from sympathetic trunk: Stimulate relaxation of bronchial smooth muscle, vasoconstriction of pulmonary vessels.
Visceral afferent: pain impulses to sensory ganglion of vagus
Trachea: recurrent laryngeal nerve

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11
Q

Lymphatic drainage of lung

A

Superficial (sub pleural): drains lung parenchyma

Deep: drains structures of lung root

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12
Q

Trachea structure

A

C-shaped cartilaginous rings
Lined with ciliated pseudo stratified columnar epithelium, interspersed with goblet cells. (forms functional mucociliary escalator)

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13
Q

Bronchi structure

A

Main: Cartilage rings completely encircle wall

Smaller lobar/segmental: crescent shaped cartilage

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14
Q

Bronchioles structure

A

No cartilage/mucus secreting goblet cells
Club cells produce surfactant lipoprotein.
Conducting bronchioles –>
terminal bronchioles –>
respiratory bronchioles –> alveoli

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15
Q

Alveoli structure

A

Thin wall of simple squamous epithelium

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16
Q

Muscles of inspiration

A

Inspiratory muscles: diaphragm, external intercostal muscles

Accessory muscles: scalene, sternocleidomastoid, pec major/minor, serratus anterior. lat doors

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17
Q

Muscles of expiration

A

Passive expiration requires only relaxation

Forced expiration: anterolateral abdominal wall, internal intercostal, innermost intercostal

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18
Q

Pressure changes in inspiration/expiration

A

Boyle’s law: volume of gas is inversely proportional to pressure (when temp constant)
Inspiration: volume of thorax increases, pressure decreases, air enters down pressure gradient
Expiration: volume of thorax decreases, pressure increases, air exits down pressure gradient

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19
Q

Determinants of airway resistance

A

Ohm’s law: flow = pressure gradient/resistance
Poiseuille’s law: resistance = resistance is inversely proportional to radius to power of 4.

Airway diameter

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20
Q

Determinants of airway resistance

A

Ohm’s law: flow = pressure gradient/resistance
Poiseuille’s law: resistance = resistance is inversely proportional to radius to power of 4.

Airway diameter

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21
Q

Control of airway diameter

A

Autonomic control:
Sympathetic: B2 relax bronchial smooth muscle
Parasympathetic: muscarinic (M3) constrict bronchial smooth muscle

Pressure: Large amount of elastic tissue in lung to allow expansion. Low intrathoracic pressure (inspiration) means pressure on airways reduced and airways expand. Inverse is true. Forced expiration can lead to pressure increases that collapse airways.

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22
Q

Surfactant and lung function

A

Produced by Type II alveolar cells
Hydrophilic & hydrophobic component
Disrupt hydrogen bonds between water molecules on surface overcoming surface tension.

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23
Q

Factors affecting gas exchange

A

Fick’s law: factors affecting diffusion of gas through a liquid:

  1. Partial pressure difference across barrier
  2. solubility of gas
  3. cross-sectional area of fluid
  4. distance molecules need to travel
  5. Molecular weight of gas
  6. Temperature of fluid
24
Q

Diffusion barrier for gas exchange

A 
Alveolar epithelium
Tissue fluid
Capillary endothelium
Plasma
Red cell membrane
25
Q

Factors affecting rate of diffusion in the lung

A

Membrane thickness (Fluid: pulmonary oedema. Thickening of alveolar membrane: Pulmonary fibrosis).

Membrane surface area (Destruction go alveolar architecture: emphysema)

26
Q

V-Q (ventilation perfusion ratio)

A

Ventilation: volume of gas inhaled and exhaled in a given time (tidal volume x RR. Approx 6L/min)
Perfusion: total volume of blood reaching pulmonary capillaries in a given time

27
Q

V-Q mismatch

A

If ventilation decreases capillary partial pressure of O2 falls and CO2 rises.
Hypoxic vasoconstriction causes diversion of blood to better ventilated parts.

Causes of reduced ventilation: primary lung condition (pneumonia, COPD, asthma etc)
Causes of reduced perfusion: PE

28
Q

Transport of oxygen in the blood

A

Dissolved in blood (1.5%)

Bound to haemoglobin (98.5%)

29
Q

Haemoglobin

A

Protein. 2 alpha, 2 beta subunits.

Haem + O2 = oxyhaemoglobin

30
Q

Oxygen binding curve

A

When no O2 bound: Tense state (T-state) with low affinity for O2
When 1 O2 bound Hb alters shape: Relaxed state (R-state). Higher affinity for O2.

When Oxyhaemoglobin reaches tissues with Low O2 it will dissociate to O2 + Hb.

31
Q

Factors affecting Oxygen affinity

A

Increase in O2 affinity moves curve to left.
Decrease moved curve to right.

pH/CO2: When pCO2 increases/pH decreases Hb enters T state and its affinity for O2 decreases (Bohr effect). Inversely when pCO2 decreases and pH increases affinity of O2 increases

2,3-diphosphoglycerate (2,3-DPG): chemical found in RBCs from glucose metabolic pathway. 2,3-DPG binds to Hb and decreased affinity for O2.

Temp: at increased temperature decreased affinity of Hb for O2.

32
Q

Lung cancers

A 
Non-small cell carcinoma (80-85%)
 - Squamous cell carcinoma
 - Adenocarcoma
 - Carcinoid
 - Large cell
Small cell carcinoma (15%)
33
Q

Squamous cell carcinoma of the lung

A

Form from square shaped cells that produce keratin.
Develop centrally.
Strong associated with smoking.
Can produce parathyroid hormone-related peptide (PHTrP)

34
Q

Adenocarcinoma of the lung

A

Originate from glandular structures that produce mucin
Develop peripherally in bronchial or alveolar wall.
Strongly associated with smoking
Can cause hypertrophic osteoarthropathy and can present with clubbing, joint pain, bone pain

35
Q

Carcinoid tumours of the lung

A

Rare (1-2%)
Develop from mature neuroendocrine cells.
Can present as carcinoid syndrome

36
Q

Large cell tumours of the lung

A

5-10%
Lack glandular and squamous differentiation
Most common in peripheries.

37
Q

Small cell carcinoma of the lung

A 
Originate from neuroendocrine cells
Develop centrally near main bronchus.
Strong associated with smoking
Rapidly growing and metastasise early.
Strong associated with smoking. 
Paraneoplastic syndromes: SIADH (ADH), Cushing's syndrome (ACTH). Lambert-Eaton Syndrome (Antibodies against presynaptic calcium channel of neuromuscular junction)
38
Q

Investigations for lung cancer

A

Contrast CT chest
Staging PET-CT or CT-AP +/- Head
Biopsy: transbronchial, US guided endoscopic, CT-guided, video-assisted thoracoscopic

39
Q

Management of Lung cancer

A

Medical:
Metastatic: Chemo +/- radio
Small cell: often metastasised to brain (prophylactic radiotherapy)
Non-small cell: immunotherapy agents

Surgical:
Lobectomy
Pneumonectomy
Wedge resection
Sleeve resection
VATS (video-assisted thoracoscopic surgery)
40
Q

Tidal volume

A

Volume that enters and leaves with each breath from normal quiet inspiration to normal quiet expiration
Average: 0.5L
Increased in pregnancy

41
Q

Inspiratory reserve volume

A

Extra volume that can be inspired above tidal volume, from normal quiet inspiration to maximum inspiration
Average: 2.5L
Relies on muscle strength, lung compliance and normal starting point (end of tidal volume)

42
Q

Expiratory reserve volume

A

Extra volume that can be expired below tidal volume, from normal quiet expiration to maximum expiration
Average: 1.5L
Relies on muscle strength and low airway resistance. Reduced in pregnancy, obesity, severe obstruction

43
Q

Residual volume/reserve volume

A

Volume remaining after maximum expiration
Average: 1.5L
Cannot by measured by spirometry

44
Q

Vital capacity/forced vital capacity

A

Volume that can be exhaled after maximum inspiration
Inspiratory reserve volume + tidal volume + expiratory reserve volume
Average: 4.5L
Requires adequate compliance, muscle strength, low airway resistance

45
Q

Inspiratory capacity

A

Volume breathed in from quiet expiration to maximum inspiration
Tidal volume + inspiratory reserve volume
Average: 3L

46
Q

Functional residual capacity

A

Volume remaining after quiet expiration
Expiratory reserve volume + residual volume
Average: 3L
Affected by height, gender, posture, lung compliance

47
Q

Total lung capacity

A

Volume of air in lungs after maximum inspiration
Residual volume + expiratory reserve volume + tidal volume + inspiratory reserve volume
Average: 6L
Restriction <80% predicted
Hyperinflation >120% predicted
Measure by helium dilution

48
Q

Anatomical dead space

A

Volume of air that never reaches alveoli and so never participates in respiration. Includes upper and lower Respiratory tract up to and including terminal bronchioles

49
Q

Alveolar (distributive) dead space

A

Volume of air that reaches alveoli but never participates in respiration. This can reflect alveoli that are ventilated but not perfused
E.g. PE

50
Q

Simple spirometry

A

Measures: tidal volume, inspiratory reserve volume, expiratory reserve volume

51
Q

Helium dilution

A

Measures total lung capacity

52
Q

Nitrogen washout

A

Method for calculating serial/anatomical dead space

53
Q

Forced vital capacity (FVC)

A

Maximal volume of air expelled in one maximal expiration from a point of maximal inspiration
Obstructive: reduced
Restrictive: <80% predicted

54
Q

Forced expiratory volume in 1 second (FEV1)

A

Maximal volume of air that a subject can expel in one second from a point of maximal inspiration
Obstructive: <80% predicted
Restrictive: <80% predicted

55
Q

FEV1/FVC ratio

A

Obstructive: <0.7
Restrictive: >0.7

X. MRCS: Pathophysiology (13 decks)

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