7. Anatomy of the respiratory tract Flashcards
State and describe the divisions of the ribs
True ribs (vertebrocostal):
1-7
Attach directly onto the sternum via own costal cartilage
False ribs (vertebrochondral)
8-10
Cartilage joins onto the cartilage of the superior rib
SO indirectly attached to the sternum
Floating
11-12
End in the posterior abdominal wall
Describe intercostal spaces
Each intercostal space is named after the rib just above it
Costal margin is around the 12th rib - this is where the diaphragm attaches
How does the rib attach to the vertebrae?
Vertebrae contains the COSTAL FACET on the transverse process for the attachment of the rib
Describe the muscles within the intercostal space
External intercostal muscle
- Has fibres that come in anteriorly
- Fibres move down and around
Internal intercostal muscle
- Contains the neurovascular bundle with the intercostal vein, intercostal artery and intercostal nerve
- Fibres move down and back - these go in the opposite direction
Innermost intercostal muscle
- Fibres move down and back
- It can be difficult to tell the difference between the internal and innermost - need to look for the neurovascular bundle that runs inbetween the two
These are muscles of expiration
NEED TO BE ABLE TO RECOGNISE THESE - FIND IMAGES
Briefly describe the anatomy of inspiration
Diaphragm flattens and goes down
Scalene muscles of the neck and intercostals are drawn together - ribs are drawn together
Due to the intercostal muscles - the ribs are raised
Give the mechanism for inspiration
Inspiratory muscles contract - diaphragm moves inferiorly
Ribs elevated and sternum flares
Thoracic cavity volume increases
The lungs stretch due to negative intrapleural pressure
Negative intra-pulmonary pressure
Air flows into the lung down a pressure gradient
What are the two forms of inspiration? Describe these
Quiet - administered by diaphragm and intercostal muscles - when sleeping or very relaxed
Deep - administered via the accessory muscles of breathing:
- Scalene muscles that attach on first and second rib
- Sternoclidomastoids - big muscles in the neck
- Pectoralis minor (look at more in loco)
State and describe the two forms of expiration
Quiet - passive, no muscles are active, natural recoil of the muscles and lungs
Forced - Muscle of the abdomen help pull out the sternum
What is meant by ‘Dyspnea’?
This is difficulty breathing
People with respiratory problems e.g. asthma, emphysema, heart failure
These people use the accessory muscles of breathing
Describe the neuronal control of breathing - what nerves are involved and how do they have an effect?
The nerves involved are the intercostal nerves and the phrenic nerve
Intercostal nerves - spinal segment
-Responsible for the segmentation and sensation over the intercostal space
Phrenic nerve - C3, 4, 5
- Descends down each side of the diaphragm
- Motor fibres to the diaphragm
- Sensory fibres to structures it is passing i.e. parietal pleura over the diaphragm and mediastinal pericardium
Briefly state the structure of the pleurae around the lungs
Parietal pleura - around the chest wall, has the nerve supply of the somatic nerve that’s closest to it around the outside
Visceral pleura - autonomic nerve supply
Interpleural space - this is a potential space
What is a ‘pleural reflection’?
Where the parietal pleura is following the shape of the chest wall but the lung does not follow down quite as far
Briefly describe the surface anatomy of the lung compared to the pleura
Superiorly - there is a very similar pattern, lung and pleura both go above the first rib and the clavicle
Inferiorly - there are pleura reflections where the parietal pleura has a greater expanse than the visceral pleura and lung
Approximately two ribs difference between the lung and the pleural reflection - this is important clinically when there may be fluid in the pleural cavity
Describe the markings of the right lung
Starting anteriorly on the inferior surface at the 6th rib, goes back to the 8th rib, then back to the 10th rib, 12th rib is where the pleurae are and follow this pattern around
Give a brief surface anatomy of the lung
Lungs pass the top of the first rib and the clavicle
Horizontal fissure - on the right runs underneath the 4th rib
Oblique fissure - starts at the 6th rib anteriorly in the mid clavicular line and then goes around at the back to the 4th vertebrae - look for the shoulder blades
Describe the pleural fluid of the pleural cavity
Pleura produces a small amount of pleural fluid
This fills the cavity and causes the visceral pleura to stick to the parietal pleura and SO provides a surface tension (microscope slide analogy)
SO when thoracic cavity expands, the lung expands with it
Only a small amount of fluid is produced
Describe what occurs when different components enter the pleural space
If air enters the pleural cavity, the surface tension between the parietal and visceral pleura is broken - the potential space becomes a real space
Pneumothorax - air in the pleural cavity
Hydrothorax - serous fluid in the cavity
Haemothorax - blood in the cavity
What is meant by ‘pleurisy’? Describe this
This is inflammation to the pleura
Causes pleural rub
Involved with the parietal pleura - they rub against each other
Involves the somatic nerve so causes a great deal of pain
Describe the nerve supply to the lungs and how this can relate to lung disease
Visceral nerve supply
Sympathetic nerve supply - bronchodilator, inhibitory to alveolar glands, paravertebral sympathetic ganglia
Parasympathetic nerve supply - from the vagus nerve, plexus along pulmonary tree, motor - bronchoconstriction
The lung itself has just visceral nerve supply and if lung disease occurs, unlikely to result in pain and instead more likely to show as e.g. night sweats
BUT if disease crosses to parietal pleura, can cause pain - somatic nerve supply
Describe the structure of the right lung
Superior lobe Middle lobe Inferior lobe Fatter, shorter lung Azygous vein over the right lung drains into the SVC
Describe the structure of the left lung
Two lobes from one oblique fissure Superior lobe Inferior lobe Arch of aorta marking can be seen Left ventricle/apex of heart sits here (where middle lobe would be)
Describe the structure of the lung root/hilum
Phrenic nerve is anterior
Vagus nerve is posterior
Contains pulmonary arteries, veins and the airways i.e. primary bronchi (don’t have to identify in spotter unless you can see cartilaginous ring - very similar)
Give the structure of the airways
Trachea bifurcates at CARINA - T5 - into left and right main primary bronchi
These divide into lobar bronchi (secondary) - three on right as superior, middle and inferior and two on left as superior and inferior
There are then segmental bronchi because the lungs are divided into bronchopulmonary segments and each semgent has it’s own tertiary bronchus, artery, autonomic nerves and lymph - these are connected by connective tissue
How does the right main bronchus differ to the left? What is the clinical impact of this?
Right main bronchus has an INTERMEDIATE BRONCHUS and is wider and more vertical than the left main bronchus
This means that any foreign objects inhaled are more likely to lodge down the right main bronchus than the left into the intermediate bronchus
Describe the blood supply of the lungs
Lungs have two blood circulations - bronchiole and pulmonary
Bronchiole - these arteries branch from the descending aorta and supply the bronchus and long lung/parenchima lung tissue - most of these anastomose with pulmonary veins and so some deoxygenated blood enters these arteries and the left side of the heart
Pulmonary - lies anterior to the bronchi
Trace the route of blood through the pulmonary circuit
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