Lung/Thorax Flashcards
Parts of the lung
Apex Base Lobes Surfaces Borders
Lobes of the lungs
Right: superior, middle, inferior. Divided by oblique and horizontal fissure.
Left: Superior, inferior. Divided by oblique.
Surfaces of the lung
Mediastinal surface
Daiphragmatic surface
Costal surface
Borders of the lung
Anterior border
Inferior border
posterior border
Lung root
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
Bronchial tree
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.
Sternal angle (Angle of Lois)
T4/5 2nd rib articulation Aortic arch Azygous vein Ligamentum arteriosus Bifurcation of pulmonary trunk Bifurcation of trachea L recurrent laryngeal nerve
Blood supply to the lung
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)
Venous drainage from the lung
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)
Nerve supply to the lung
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
Lymphatic drainage of lung
Superficial (sub pleural): drains lung parenchyma
Deep: drains structures of lung root
Trachea structure
C-shaped cartilaginous rings
Lined with ciliated pseudo stratified columnar epithelium, interspersed with goblet cells. (forms functional mucociliary escalator)
Bronchi structure
Main: Cartilage rings completely encircle wall
Smaller lobar/segmental: crescent shaped cartilage
Bronchioles structure
No cartilage/mucus secreting goblet cells
Club cells produce surfactant lipoprotein.
Conducting bronchioles –>
terminal bronchioles –>
respiratory bronchioles –> alveoli
Alveoli structure
Thin wall of simple squamous epithelium
Muscles of inspiration
Inspiratory muscles: diaphragm, external intercostal muscles
Accessory muscles: scalene, sternocleidomastoid, pec major/minor, serratus anterior. lat doors
Muscles of expiration
Passive expiration requires only relaxation
Forced expiration: anterolateral abdominal wall, internal intercostal, innermost intercostal
Pressure changes in inspiration/expiration
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
Determinants of airway resistance
Ohm’s law: flow = pressure gradient/resistance
Poiseuille’s law: resistance = resistance is inversely proportional to radius to power of 4.
Airway diameter
Determinants of airway resistance
Ohm’s law: flow = pressure gradient/resistance
Poiseuille’s law: resistance = resistance is inversely proportional to radius to power of 4.
Airway diameter
Control of airway diameter
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.
Surfactant and lung function
Produced by Type II alveolar cells
Hydrophilic & hydrophobic component
Disrupt hydrogen bonds between water molecules on surface overcoming surface tension.
Factors affecting gas exchange
Fick’s law: factors affecting diffusion of gas through a liquid:
- Partial pressure difference across barrier
- solubility of gas
- cross-sectional area of fluid
- distance molecules need to travel
- Molecular weight of gas
- Temperature of fluid
Diffusion barrier for gas exchange
Alveolar epithelium Tissue fluid Capillary endothelium Plasma Red cell membrane
Factors affecting rate of diffusion in the lung
Membrane thickness (Fluid: pulmonary oedema. Thickening of alveolar membrane: Pulmonary fibrosis).
Membrane surface area (Destruction go alveolar architecture: emphysema)
V-Q (ventilation perfusion ratio)
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
V-Q mismatch
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
Transport of oxygen in the blood
Dissolved in blood (1.5%)
Bound to haemoglobin (98.5%)
Haemoglobin
Protein. 2 alpha, 2 beta subunits.
Haem + O2 = oxyhaemoglobin
Oxygen binding curve
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.
Factors affecting Oxygen affinity
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.
Lung cancers
Non-small cell carcinoma (80-85%) - Squamous cell carcinoma - Adenocarcoma - Carcinoid - Large cell Small cell carcinoma (15%)
Squamous cell carcinoma of the lung
Form from square shaped cells that produce keratin.
Develop centrally.
Strong associated with smoking.
Can produce parathyroid hormone-related peptide (PHTrP)
Adenocarcinoma of the lung
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
Carcinoid tumours of the lung
Rare (1-2%)
Develop from mature neuroendocrine cells.
Can present as carcinoid syndrome
Large cell tumours of the lung
5-10%
Lack glandular and squamous differentiation
Most common in peripheries.
Small cell carcinoma of the lung
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)
Investigations for lung cancer
Contrast CT chest
Staging PET-CT or CT-AP +/- Head
Biopsy: transbronchial, US guided endoscopic, CT-guided, video-assisted thoracoscopic
Management of Lung cancer
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)
Tidal volume
Volume that enters and leaves with each breath from normal quiet inspiration to normal quiet expiration
Average: 0.5L
Increased in pregnancy
Inspiratory reserve volume
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)
Expiratory reserve volume
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
Residual volume/reserve volume
Volume remaining after maximum expiration
Average: 1.5L
Cannot by measured by spirometry
Vital capacity/forced vital capacity
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
Inspiratory capacity
Volume breathed in from quiet expiration to maximum inspiration
Tidal volume + inspiratory reserve volume
Average: 3L
Functional residual capacity
Volume remaining after quiet expiration
Expiratory reserve volume + residual volume
Average: 3L
Affected by height, gender, posture, lung compliance
Total lung capacity
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
Anatomical dead space
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
Alveolar (distributive) dead space
Volume of air that reaches alveoli but never participates in respiration. This can reflect alveoli that are ventilated but not perfused
E.g. PE
Simple spirometry
Measures: tidal volume, inspiratory reserve volume, expiratory reserve volume
Helium dilution
Measures total lung capacity
Nitrogen washout
Method for calculating serial/anatomical dead space
Forced vital capacity (FVC)
Maximal volume of air expelled in one maximal expiration from a point of maximal inspiration
Obstructive: reduced
Restrictive: <80% predicted
Forced expiratory volume in 1 second (FEV1)
Maximal volume of air that a subject can expel in one second from a point of maximal inspiration
Obstructive: <80% predicted
Restrictive: <80% predicted
FEV1/FVC ratio
Obstructive: <0.7
Restrictive: >0.7
