Resp Session 2 Flashcards
Is breathing in active or passive?
Active
Why is breathing it passive?
Lungs tend to recoil to reach resting expiratory level where all forces are in balance
What facilitates changing lung volume by movement of the thorax?
Pleural seal
What muscles are used for inhalation in quiet breathing?
Diaphragm
External intercostals
What are the accessory muscles used for inspiration?
Sternocleidomastoid
Scalene
Serratus anterior
Pectoralis major
How does the difference between intrapleural and intrapulmonary pressures change on inspiration?
Becomes ore -ve as ribs pull more
What is found in the pleural cavity?
10-20 ml of pleural fluid which is similar to plasma but with less protein
What happens if the integrity of the pleural seal is broken?
Lungs tend to collapse and large space opens between the visceral and parietal pleura
What muscles are used in forced expiration?
Internal intercostals
External and internal abdominal obliques
Rectus abdominis
What is forced expiration?
When you breathe out beyond the resting expiratory level e.g. in exercise
What is the action of the muscles used in forced expiration?
Contract and flatten abdominal wall and push upper GI organs into diaphragm
Why is inspiration to resting expiratory volume following force expiration passive?
Forces on the lungs are unbalanced
What is lung compliance?
Lung stretchiness/ease of inflation measured as volume changeover unit volume
How is compliance of the lungs affected by emphysema?
Increased due to loss of elasticity so no opposing force to inflation
How does fibrosis affect compliance of the lungs?
Decreases as the lungs become stiff
In quiet breathing, when is most effort used?
To expand lungs unless the diaphragm is obstructed e.g. Pregnancy, obesity or surgical corset
What is the elastic recoil of the lungs due to?
Elastic tissue of airways and surface tension of fluid lining alveoli
How does the fluid lining the alveoli increase surface tension and make them harder to stretch?
Polar water molecules attract and interact with air –> surface resists stretching –> wants to collapse alveoli –> increases surface tension
Why does fluid line the alveoli if it makes them harder to inflate?
Needed to dissolve oxygen so it can move into the blood
How does surfactant decease surface tension?
Disrupts interactions between surface molecules
What produces surfactant in the lungs?
Type II pneumocytes
Why are little breaths easy when surfactant is present?
Surfactant is effective at low volume as there are a finite number of molecules which spread out as lung expands, therefore the less spread out they are the more surface tension is reduced
What does Laplace’s law state?
Pressure = (2xsurface tension)/radius
How is Laplace’s law applied to the lung?
Big bubble = large radius –> low pressure
Small bubble = small radius –> high pressure
If bubbles are connected then air moves from small to big bubble and this would happen in the alveoli if surfactant wasn’t present
Explain how surfactant is effective at keeping pressure stable inside the alveoli.
As radius of alveoli increases surfactant molecules spread apart which allows surface tension to rise thus keeping pressure stable
What is respiratory distress syndrome?
Surfactant levels in the lungs are disrupted impairing breathing and gas exchange
Why can babies born prematurely need respiratory support?
Respiratory system develops late so baby might have too little surfactant, stuff lungs, few and large alveoli and little muscle mass
What is the treatment used for babies at risk of respiratory distress syndrome due to premature birth?
Inject mother before birth with steroids to stimulate surfactant production and give air and surfactant after birth
When is respiratory distress syndrome seen in adults?
Major trauma –> inflammatory lung process disrupting surfactant
What does Poiseulle’s law state?
Small tubes have high flow resistance
Considering Poiseulle’s law, why is flow resistance highest in the trachea and lowest in the small airways?
Despite having narrower lumen the bronchial tree branches providing parallel pathways thus compensating for increased flow resistance with more possible pathways
Is the respiratory systems usually a high or low resistance system in quiet respiration?
Generally low
How does flow resistance change in forced expiration?
Small airways are narrowed by external pressure therefore resistance increases dramatically as there is no cartilage to keep them open
What is the result of pressure changes during forced expiration in the lungs?
Air is trapped in alveoli but in healthy individual there is usually enough resilience to overcome this
Why does obstructive airways disease lead to hyperinflation of the lung?
Small airways are already narrowed so in expiration resistance increases much earlier –> breathing out very difficult and more air is trapped in the lungs –> hyperinflation
What forms the bony thorax?
12 thoracic vertebrae
Sternum
12 ribs and their cartilages
11 intercostal spaces
Where are the thoracic outlet and inlet found?
Thoracic outlet = aperture formed by first ribs and superior surface of sternum
Thoracic inlet = aperture formed by 12th ribs
Lost the parts of the sternum superior to inferior.
Manubrium
Sternal angle (manubrio-sternal joint)
Sternal body
Xiphoid process
Does the xiphoid process remain cartilaginous throughout life?
No, only until mid 30s to 40s when it begins to calcify
Which ribs are ‘typical’ ribs?
3-9
What is the costo-transverse joint made by a typical rib?
Traverse process of vertebra + rib tubercle
What does the crest of a typical rib separate?
Articulating surface with corresponding vertebra above rib level and articulating surface with corresponding vertebra to rib level (e.g. Rib 7 = C7)
What runs in the costal groove of a typical rib?
Vein
Artery
Nerve
Which ribs are atypical?
1, 2, 10, 11 and 12
Describe the structure of rib 1.
Shortest, broadest, most curved and head with one facet. Has a groove for subclavian artery and vein
Why is rib 2 said to be atypical?
Has poorly marked costal groove
Describe the structure of ribs 11 and 12.
‘Floating’ ribs with single facet on head, no tubercle an taper at the anterior end
What forms the axis of rib rotation?
Imaginary line running through 2 costovertebral joints
How do the upper ribs move to alter thoracic volume?
Increase sagittal diameter by pushing sternum forward thus increasing A-P diameter
How do the lower ribs move to alter the thoracic volume?
Increase transverse diameter thus increasing lateral diameter
Where are the intercostal muscles found?
Each intercostal space
List the intercostal muscles from superficial to deep.
External intercostal
Internal intercostal
Innermost intercostal
How are the fibres of each type of intercostal muscle arranged?
External: fibres run inferiorly and anteriorly (hands in pockets)
Internal: fibres run inferiorly and posteriorly
Innermost: fibres run inferiorly and posteriorly
How are the intercostal muscles attached to the sternum?
By a membrane as fibres do not reach
What is the result of external intercostal muscle contraction?
Ribs move superiorly
When are internal and innermost intercostal muscles used?
Forced expiration to decrease A-P and lateral diameters of eh chest by moving ribs inferiorly
Between internal and innermost intercostals at lower border of rib therefore insert a needle at the upper border of the rib below to avoid damage
Where does the neurovascular bundle run in relation to the intercostal muscles and what is its clinical relevance?
Describe the neural supply of the muscles in the corresponding intercostal space, parietal pleura and overlying skin of each rib.
Anterior rami of thoracic spinal nerves T1-12 run in neurovascular bundle giving rise to collateral branches where needed
Why is pain from an inflamed parietal pleura felt on the skin directly above?
Due to intercostal nerve supply
How does varicella zoster give rise to a dermatomal rash that does not cross the midline?
Remains dormant in the dorsal root ganglion but on reactivation gives characteristic rash due to intercostal nerve supply
What do the intercostal arteries anastomose with to provide and alternative route for bloodflow to the legs?
Superior epigastric artery
Describe the arterial supply of intercostal muscles, parietal pleura and overlying skin for each rib.
Anterior and posterior intercostal arteries follow path of intercostal nerve in each intercostal space. Posterior comes from thoracic aorta, anterior from internal thoracic aorta
What can anastomose with the anterior and posterior intercostal arteries in the intercostal space?
Each other
Mammary branches
Where do the superior two ribs receive their arterial blood supply from?
Superior intercostal artery, a branch of the subclavian
Where does the venous drainage of each intercostal space go?
Anterior and posterior intercostal veins in neurovascular bundles drain into the Azygos and hemiazygos veins –> SVC
Some drain into the internal thoracic vein
Which muscle accounts for 70% of inspiration?
Diaphragm
Where does the peripheral muscular part of the diaphragm arise from?
Lower ribs
Arcuate ligaments
R and L crus of diaphragm
Where do the muscle fibres of the diaphragm all insert?
Central tendon where the pericardium attaches
What are the arcuate ligaments?
Thickening of posterior abdominal muscles
What are the openings of the diaphragm for?
T8= vena cava T10= oesophagus T12= aorta (aortic hiatus)
Where is the diaphragm positioned during expiration?
R dome reaches behind 5th rib
Left dome in the 5th ICS MCL
Why are dullness sounds from percussion of the liver in hyperinflation lower?
Diaphragm is pushed down
What gives nervous supply to the diaphragm?
Phrenic nerve (C3,4,5 keep you alive)
What gives neural supply to the margins of the diaphragm?
Intercostal nerves
What is the motor function of the phrenic nerve?
Diaphragm
What is the sensory function of the phrenic nerve?
Pericardium
Mediastinal part of parietal pleura
Diaphragmatic parietal pleura
Both surfaces of the diaphragm
Why is pain felt in the shoulder following chest surgery which affected the diaphragm?
Referred pain due to dermatomal distribution of C3,4,5
Where is the median arcuate ligament found in the diaphragm?
Around aortic aperture
Describe the structure of the costodaiphragmatic recess.
Lung doesn’t reach but pleura does and overlaps liver as it reaches down to 6th ICS
Which three arcuate ligaments are found in the diaphragm?
Median
Medial
Lateral
What would a stab wound in the 7th ICS damage?
Skin Intercostal muscles Parietal pleura Visceral pleura Lung Liver
What does the thoracic cavity consist of?
2 lateral pulmonary cavities and the central mediastinum compartment
Describe the visceral pleura.
Covers and adheres to lungs including horizontal and oblique fissures
What 4 parts does the parietal pleura consist of?
Cervical
Mediastinal
Costal
Diaphragmatic
Describe the distribution of each of the four parts of the parietal pleura.
Cervical extends into the root of the neck
Mediastinal covers lateral mediastinum
Costal covers internal surfaces of thoracic wall
Diaphragmatic covers superior diaphragm
Where are the visceral and parietal pleura continuous?
Hilum
What is the function of the film of fluid between the pleura of the lungs?
Allow them to slide over each other and prevents surfaces being pulled apart due to forces between the fluid molecules
What divides the URT and LRT?
Lower border of cricoid cartilage
Where do the L and R bronchi divide?
At the carina behind the sternal angle at T4/5 level
What can be seen on bronchoscopy or bronchogram which indicates enlargement of tracheo-bronchial lymph nodes?
Widening of the carina
Compare the R and L main bronchi.
R= shorter, wider and more vertical L= longer, more horizontal
How many lobar bronchi are in the L and R lung?
R = 3-upper, middle and lower L = 2-upper and lower
What is a bronchopulmonary segment?
A segment of lung with its own segmental bronchi, segmental branch of pulmonary artery and vein supply
What is the clinical relevance of bronchopulmonary segments?
In surgery one segment can be removed with little damage to others and limited bleeding
Where does the horizontal fissure run?
In the R lung from oblique fissure along 4th rib and cartilage border
Where does the oblique fissure of the lung run?
In R lung from the spinous process of T2 to the 6th costal cartilage
What corresponds to the R middle lobe in the L lung?
Lingula
Which lobe is the lingula found in?
L superior
What are the 3 surfaces of each lung?
Diaphragmatic
Mediastinal
Costal
Why can subclavian vein cannulation lead to pneumothorax?
Apex of the lung extends into the root of the neck
What can apical lung tumours compress?
Brachial plexus (esp median cord)
Subclavian vessels
Sympathetic trunk
Describe the blood supply by the bronchial arteries.
From aorta bring oxygenated blood to bronchial tree up to terminal bronchioles
What blood supply do the pulmonary arteries give?
Bring deoxygenated blood from the R heart to alveoli for oxygenation
What prevents ischaemia in PE?
Anastomoses of the bronchial arteries
What are the borders of the four compartments of the mediastinum?
Superior = thoracic inlet --> sternal angle and lower T4 border Anterior = body of sternum --> fibrous pericardium Posterior = vertebral bodies --> fibrous pericardium Middle = between anterior and posterior
What are the contents of the superior mediastinum?
Thymus
Brachiocephalic veins, SVC, brachiocephalic trunk, left common carotid and left subclavian arteries
Vagus, phrenic nerves, R+LRN and cardiac plexus
Trachea
Oesophagus
Thoracic duct and lymphatic ducts
What forms the borders of the posterior mediastinum?
Lateral: mediastinal pleura Anterior: pericardium Posterior: T5-12 Roof: imaginary line between sternal angle and T4 Floor: diaphragm
What is the contents of the posterior mediastinum?
Thoracic aorta Oesophagus Thoracic duct Azygos system of veins Sympathetic trunks
What forms the borders of the anterior mediastinum?
Roof: superior mediastinum Anterior: body of sternum and transversus thoracic muscle Posterior: pericardium Lateral: mediastinal pleura Floor: diaphragm
What are the contents of the anterior mediastinum?
Loose CT which tethers pericardium to sternum Fat Lymphatic vessels and nodes Branches of internal thoracic vessels Thymus only in children
What forms the borders of the middle mediastinum?
Superior: imaginary line between sternal angle and T4
Anterior: anterior margin of pericardium
Posterior: posterior border of pericardium
Lateral: mediastinal pleura of lungs
Inferior: diaphragm
What are the contents of the middle mediastinum?
Heart and pericardium Tracheal bifurcation with L and R main bronchi Great vessels of heart Cardiac plexus L and R phrenic nerves Tracheobronchial lymph nodes
