7. Anatomy of the respiratory tract

Question 1

State and describe the divisions of the ribs

Answer 1

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

Question 2

Describe intercostal spaces

Answer 2

Each intercostal space is named after the rib just above it

Costal margin is around the 12th rib - this is where the diaphragm attaches

Question 3

How does the rib attach to the vertebrae?

Answer 3

Vertebrae contains the COSTAL FACET on the transverse process for the attachment of the rib

Question 4

Describe the muscles within the intercostal space

Answer 4

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

Question 5

Briefly describe the anatomy of inspiration

Answer 5

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

Question 6

Give the mechanism for inspiration

Answer 6

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

Question 7

What are the two forms of inspiration? Describe these

Answer 7

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)

Question 8

State and describe the two forms of expiration

Answer 8

Quiet - passive, no muscles are active, natural recoil of the muscles and lungs

Forced - Muscle of the abdomen help pull out the sternum

Question 9

What is meant by ‘Dyspnea’?

Answer 9

This is difficulty breathing
People with respiratory problems e.g. asthma, emphysema, heart failure
These people use the accessory muscles of breathing

Question 10

Describe the neuronal control of breathing - what nerves are involved and how do they have an effect?

Answer 10

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

Question 11

Briefly state the structure of the pleurae around the lungs

Answer 11

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

Question 12

What is a ‘pleural reflection’?

Answer 12

Where the parietal pleura is following the shape of the chest wall but the lung does not follow down quite as far

Question 13

Briefly describe the surface anatomy of the lung compared to the pleura

Answer 13

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

Question 14

Describe the markings of the right lung

Answer 14

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

Question 15

Give a brief surface anatomy of the lung

Answer 15

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

Question 16

Describe the pleural fluid of the pleural cavity

Answer 16

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

Question 17

Describe what occurs when different components enter the pleural space

Answer 17

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

Question 18

What is meant by ‘pleurisy’? Describe this

Answer 18

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

Question 19

Describe the nerve supply to the lungs and how this can relate to lung disease

Answer 19

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

Question 20

Describe the structure of the right lung

Answer 20

Superior lobe
Middle lobe
Inferior lobe
Fatter, shorter lung
Azygous vein over the right lung drains into the SVC

Question 21

Describe the structure of the left lung

Answer 21

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)

Question 22

Describe the structure of the lung root/hilum

Answer 22

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)

Question 23

Give the structure of the airways

Answer 23

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

Question 24

How does the right main bronchus differ to the left? What is the clinical impact of this?

Answer 24

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

Question 25

Describe the blood supply of the lungs

Answer 25

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

Question 26

Trace the route of blood through the pulmonary circuit

Answer 26

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