27-10-22 – Trachea, Bronchial Tree, and Lungs Flashcards
Learning outcomes
- Recall the structures that form the conducting and respiratory portions of the respiratory tract
- Describe the structure, and function of the trachea
- State the relations of the trachea
- Describe how the epithelium and structure of the bronchial trees change as they branch into the lungs
- Describe the structure, function, and relationships of each lung
- Describe the relationships of the structures that make up the root of the lung
- Describe the blood supply, the venous and lymphatic drainage and innervation of the lungs
- Explain the concept of, and clinical significance of the bronchopulmonary segments
- Discuss the clinical conditions that may affect the respiratory tract
- Appreciate normal appearance of the trachea and lungs on plain radiographs and cross-sectional images
Where is the trachea in relation to the larynx?
How long and wide is the trachea?
Where does it start and finish?
- The trachea is a continuation of the larynx, and sis underneath the cricoid cartilage of the laryngeal skeleton
- The trachea is 10-11cm long and about 2.5cm wide
- The trachea starts at C6 and ends at T4/T5 (sternal angle) at the carina
What is the trachea composed of?
Why is this?
What is the muscle in the trachea?
What is the role of this muscle?
What would happen if the trachea didn’t consist of cartilage?
- The trachea is composed of C-shaped hyaline cartilages
- This is to ensure the trachea stays open at all times
- The trachealis muscle along with some fibrous tissue is found in the posterior trachea between the ends of the tracheal cartilages
- The trachealis muscle is smooth muscle under the control of the ANS, and is responsible for altering the tracheal diameter
- If the trachea didn’t consist of cartilage, it would collapse on inhalation due to the negative intra-thoracic pressure
What 8 structures is the trachea related to in the cervical region?
- 8 structures the trachea is related to in the cervical region:
1) Sternohyoid muscle
2) Sternothyroid muscle
3) Isthmus of the thyroid gland – the centre that connects the 2 lobes (located between 2nd and 4th tracheal cartilages)
4) Inferior thyroid vessels – at risk during tracheostomy
5) Carotid sheath – contains internal carotid (common carotid further down), internal jugular and vagus nerve)
6) Brachiocephalic trunk
7) Jugular venous arch
8) Recurrent laryngeal nerve
Where does the trachea enter the thoracic cavity?
Where does the left recurrently laryngeal nerve lie in relation to the trachea?
Where does the trachea divide?
- The trachea enters the thoracic cavity through thoracic inlet (rib 1, T1, superior manubrium)
- The left recurrent laryngeal nerve lies in the groove between the trachea and the oesophagus
- At the level of the Sternal angle (T4/5 intervertebral disc) the trachea divides into left and right principal (main) bronchi (at about 2cm below entry into thoracic cavity)
What 4 neurovascular structures are on the right of the trachea in the thoracic cavity?
What 2 neurovascular structures are on the left of the trachea in the thoracic cavity?
- 4 neurovascular structures are on the right of the trachea in the thoracic cavity:
1) Right vagus nerve
2) Azygos vein
3) SVC
4) Right brachiocephalic - 2 neurovascular structures are on the left of the trachea in the thoracic cavity:
1) Left vagus nerve
2) Left brachiocephalic vein
How are cross-section CT scans orientated?
Label these structures in a cross-section scan of T3 (superior mediastinum).
What is used in scans to make structures more prominent?
What prominent structures of the aortic arch can be seen in this scan of T3?
- The CT scans are taken so that we are looking at the feet upwards (inferiorly to superiorly)
- This means right is left, and left is right
- Contrasting agents (iodine based and barium-sulphate compounds) can be used to make arteries/veins/structures more prominent
- In this cross-sectional scan of T3 (superiormediastinum), we can see the 3 branches of the aortic arch:
1) Brachiocephalic trunk
2) Left common carotid artery
3) Left subclavian artery
What 2 important vessels can be seen in a cross-section CT of T4 (superior mediastinum)?
Label these structures on a cross-sectional scab if T4.
- In a cross-section CT of T4, we can see:
1) Cross section of the aortic arch
2) Superior vena cava – right and left brachiocephalic veins have joined to form the superior vena cava
What 4 arteries supply the trachea?
What are the 2 veins that drain the trachea?
What 2 sets of lymph nodes drain the trachea?
Where does ANS innervation of the trachea come from?
- 4 arteries that supply the trachea:
1) Inferior thyroid artery
2) Bronchial arteries
3) Tracheal branches of aorta
4) Mediastinal branches of internal thoracic artery - 2 veins that drain the trachea:
1) Inferior thyroid vein (plexus)
2) Bronchial veins - 2 sets of lymph nodes that drain the trachea:
1) Pretracheal lymph nodes
2) Paratracheal lymph nodes - Parasympathetics of the Trachea come from the vagus nerve
- Sympathetics of the trachea come from the sympathetic trunks
What does the trachea divide into?
How do the right and left main bronchus differ?
Where will aspirated foreign bodies go?
- The trachea divides into the left and right main (principal) bronchi at T4/T5
- The right main bronchus is slightly more vertical, shorter, and wider
- Aspirated foreign bodies are more likely to go down the right main bronchus
What do the main bronchi divide into?
How many lobar bronchi are in each lung?
What do segmental bronchus pass to?
In what pattern to the bronchi divide?
- The main (principal) bronchi divide into lobar (secondary) bronchi, which will then subdivide into segmental (tertiary) bronchi
- There are 2 lobar bronchi in the left lung, and 3 lobar bronchi in the right lung
- Each segmental bronchi pass to a specific pulmonary segment
- The bronchi divide like a tree, decreasing in diameter.
What do segmental bronchi lead to?
What does this then lead to?
Where is the greatest resistance to air flow?
What is diameter of bronchioles reliant on?
What can occur in asthma?
What can be used to treat asthma?
- Segmental bronchi lead onto terminal bronchioles
- Terminal bronchioles are connected to respiratory bronchioles
- Bronchioles cause the greatest resistance to air flow in the conducting passages
- Diameter of bronchioles is entirely reliant on smooth muscle tone
- In asthma, these smooth muscles contract strongly enough to almost completely shut off the air passage ways in the bronchioles
- Salbutamol inhalers can be used to treat asthma by acting as B2 receptor agonists and causing bronchodilation
What does each respiratory bronchiole connect to?
What does each alveolar duct open to?
What is the reason for having so many alveoli?
- Each respiratory bronchiole is connected to about 2-11 alveolar ducts
- Each alveolar duct opens into alveolar sacs, which are clusters of 5-6 alveoli
- A large number of alveoli provides a very large surface area for the diffusion of gases
What are the 3 surfaces of the lungs?
What are the 3 borders/margins of the lungs?
What is the apex of each lung called? Where does the apex of each lung sit?
Where does the base of each lung sit?
How do the shapes/size of each lung differ?
What are the lungs separated by?
- 3 surfaces of the lungs:
1) Costal
2) Diaphragmatic
3) Mediastinal - 3 borders/margins of the lungs:
1) Anterior border
* The anterior border of the lung corresponds to the pleural reflection, and it creates a cardiac notch in the left lung
2) Posterior border
* The posterior border is thick and extends from the C7 to the T10 vertebra, which is also from the apex of the lung to the inferior border.
3) Inferior border
* The inferior border is thin and separates the base of the lung from the costal surface
- The apex of the lung is called the cupula
- The apex of each lung sits above the first rib
- The base of the lungs sit on the diaphragm
- The left lung has the cardiac notch
- The right lung is shorter and wider than the left lung due to the liver
- The lungs are separated by the mediastinum
How many lobes does each lung have?
What is the lingula?
Where is the lingula located?
What are the lobes separated by?
- The right lung has 3 lobes, and the left lobe has 2 lobes
- The lingula represents an analog for the middle lobe of the right lung, which is absent in the left lung due to the position of the heart on the left side of the thoracic cavity.
- The lingula is located on the superior lobe of the left lung
- The superior and middle lobe of the right lung are separated by the horizontal fissure (diagram s wrong way round)
- The middle and inferior lobe of the right lung are separated by the oblique fissure
- The superior and inferior lobes of the left lung are separated by the horizontal fissure
Label these lung impressions.
Why is it difficult for the oesophagus to make an impression?
- It is difficult for the oesophagus to make an impression because it is not open all the time
- When we aren’t swallowing, it is collapsed
Label these structures related to each lung
What is the root of the lung?
What is the root of the lung outlined by?
What is pleural reflection?
What are the 6 different structures that are in the root of the lung?
What are these structures covered by?
What is another role of these structures?
- The root of the lung (aka the hilum) is a collection of structures that attach the lung to structures in the mediastinum
- The root is outlined by pleural reflection on the mediastinal surface of the lung
- Pleural reflection is the lines along which the parietal pleura changes direction as it passes from one wall of the pleural cavity to another.
- 6 different structures that are in the root of the lung:
1) A pulmonary artery
2) Two pulmonary veins – superior and inferior pulmonary vein for each lung
3) A main bronchus
4) Bronchial vessels – how lungs receive and drain blood (arteries and veins)
5) Nerves
6) Lymphatics - These structures are covered by a sleeve of mediastinal pleura that reflects onto the surface of the lung
- These structures also suspend the lung and keep it in place
What is lung parenchyma?
What does it consist of?
How does main bronchi branching differ between each lung?
Where is the pulmonary artery usually located in the root of the lung?
Where are pulmonary veins usually located in the root of the lung?
What is the pulmonary ligament made from?
What does it allow?
- Lung parenchyma is the portion of the lungs involved in gas exchange
- The lung parenchyma consists of a large collection of near spherical gas exchanging units, the alveoli.
- On the right lung, the main bronchi gives off a superior lobar bronchi branch in the root, then when in the lung, splits into middle and inferior lobar bronchi
- On the left lung, the main bronchi branch into the superior and inferior lobar bronchi in the lung
- In the root of the lung, the pulmonary artery is usually anterior and superior to the bronchi and pulmonary veins
- In the root of the lung, the pulmonary veins are usually located anterior and inferior to the bronchi
- The pulmonary ligament is made from a fold of the mediastinal pleura
- The pulmonary ligament allows for the movement of the root of the lung during respiration
What are bronchopulmonary segments?
What 3 things do they each have?
How many bronchopulmonary segments are there?
What is the shape of bronchopulmonary segments?
What direction does their apex move in?
What is each segment separated by?
What passes through the inter-segmental septum of the bronchopulmonary segments?
Is there anastomosis between neighbouring segments?
What are 2 reasons this is useful?
- Bronchopulmonary segments are the smallest functionally and structurally independent unit
- They are sections of the lung with their own:
1) Branch of the pulmonary artery
2) ANS nerves
3) Segmental (tertiary) bronchus (1 segmental bronchus for each bronchopulmonary segment) - There are a total of 10 bronchopulmonary segments, with 10 accompanying segmental bronchi
- The bronchopulmonary segments are pyramid shape
- The apices point towards the hilum
- Each segment is separated by a wall of connective tissue
- There are tributaries (veins that drain into larger vein) of the pulmonary vein and lymphatics tend to pass in the inter-segmental septum of the bronchopulmonary segments
- There is no anastomosis between bronchopulmonary segments
- This is useful because:
1) It allows for safe surgical removal of one segment without damaging the rest
2) Makes the spread of disease more difficult between segments
Where are each of the 10 bronchopulmonary segments found in the right lung?
What lobe are they each found in?
- 10 bronchopulmonary segments found in the right lung:
1) Superior lobe:
* Apical
* Anterior
* Posterior
1) Middle lobe:
* Medial
* Lateral
2) Inferior lobe:
* Superior/Apical
* Anterior
* Posterior
* Medial
* Lateral
Where are each of the 10 bronchopulmonary segments found in the right lung?
What lobe are they each found in?
- 10 bronchopulmonary segments found in the left lung:
1) Superior lobe:
* Apical
* Superior
* Inferior
* Anterior
* Posterior
2) Inferior lobe:
* Superior/apical
* Anterior
* Posterior
* Medial
* Lateral
What are 4 histological features of the bronchioles?
What are the 2 types of alveolar cell?
What is the role of each?
- 4 histological features of the bronchioles:
1) There is little cartilage in the bronchioles, mainly smooth muscle
2) No goblet cells in and distal to respiratory bronchioles
3) The pseudostratified columnar epithelium of the bronchi is replaced by simple cuboidal epithelium of the bronchioles
4) Wall of each pulmonary alveolus is only one cell layer thick, leads to increased diffusion rate - 2 types of alveolar cell:
1) Type I alveolar cell: permit diffusion
2) Type II alveolar cell: produce surfactant that reduces the tendency for pulmonary alveoli to collapse.
What is a bronchoscopy used for?
Where are instruments inserted?
What 2 types of bronchoscopies might a doctor use?
- Bronchoscopy is an endoscopic technique of visualizing the inside of the airways for diagnostic and therapeutic purposes
- An instrument is inserted into the airways, usually through the nose or mouth, or occasionally through a tracheostomy
- Doctors may use a rigid bronchoscopy to in the case of an aspirated (inhalation) foreign body, but will use fibreoptic bronchoscopy most of the time
Where is the apical segment of the inferior lobe located?
What level is it located at?
Why is this lobe prone to pneumonia?
How does the tertiary bronchi of the inferior lobe appear on a bronchogram?
- The apical segment of the inferior lobe is inferolateral to the upper, posterior position of the oblique fissure
- It is at the level of T4
- As its tertiary bronchus drops off the bronchial tree first and posteriorly, it is prone to pneumonia, due to aspiration being most likely to move into this segment, particularly when lying down
What is the arterial supply of the lung tissue?
How many bronchial arteries are there on each side?
What are they branches of?
What might bronchial arteries anastomose with?
Where does this occur?
Where is oxygenated and deoxygenated blood mixing?
What 2 venous systems drain the lungs? Where does blood mixing occur here?
- Lung tissue is supplied by the Bronchial arteries
- x1 on the right, from 3rd posterior intercostal artery or superior posterior intercostal artery
- x2 on the left, from the aorta
- Bronchial arteries may anastomose with pulmonary arteries in the walls of the bronchioles
- This means deoxygenated blood in the pulmonary arteries can contain some oxygenated blood from the bronchial arteries
- Venous blood from the lungs can be drained by:
1) Bronchial veins (goes into the azygos system)
2) Pulmonary veins (small amount of deoxygenated blood in oxygenated pulmonary veins)
What do pulmonary arteries do?
Where do they arise from?
Where do right and left pulmonary arteries pass?
How does each artery compare in length?
How does the branching of right and left pulmonary arteries differ?
- Pulmonary arteries (PA) carry de-oxygenated blood to the lungs at low pressure
- Arise from the pulmonary trunk just below the sternal angle
- Right PA passes anterior to the right primary bronchus and posterior to the ascending aorta and SVC
- Left PA passes anterior to the descending thoracic aorta
- The left PA is shorter than the right PA
- On the right, the upper branch of the PA branches prior to the hilum and goes towards the superior lobe, then the middle and inferior branch of the RA branch off within the lungs and go to the middle and inferior lobes
- On the left, the PA branches within the lungs to the superior and inferior branches that go to the super and inferior lobes
What are the 2 lymphatic plexuses that drain the lungs?
Where do they both drain into?
- 2 lymphatic plexuses that drain the lungs:
1) Deep lymphatic plexus
* Runs alongside the arteries and the dividing bronchial tree
2) Superficial (sub-pleural) lymphatic plexus
- These plexuses drain into the pulmonary lymph nodes buried in the hilum
Where is the mediastinum rich in?
Where are superior and inferior tracheobronchial nodes found?
What do they receive?
What can this cause to spread?
Where can anterior and posterior mediastinal lymph nodes be found?
- The mediastinum is rich in lymph nodes
- Superior and inferior tracheobronchial nodes are found clustered around the trachea and oesophagus
- They receive lymph from the lung
- This can lead to the spread of lung tumours
- Anterior mediastinal lymph nodes are found round the brachiocephallic veins
- Posterior mediastinal lymphd nodes can be found behind the heart and adjacent to the oesophagus
Describe the route in which lymph is drain to the bronchomediastinal lymph trunks.
What is the venous (pirogoffs) angle?
Where does lymph from the bronchomediastinal trunks drain into on each side?
- Pirogoffs angle also known as the venous angle, is the junction where the internal jugular and subclavian veins merge to form the brachiocephalic vein
- This happens on both sides
Lymph node drainage of the thorax diagram
Lymph node drainage of the thorax diagram
What is the role of the thoracic duct?
Where does the thoracic duct start?
Where does the thoracic duct enter the thoracic cavity?
What can the thoracic duct be found between in the thoracic cavity?
How does the aorta aid in the function of the thoracic duct?
What does the thoracic duct do at level T4/T5?
Where does it move up to after this?
What does the thoracic duct open into?
What can happen if the thoracic duct is damage?
- The thoracic duct carries lymph from most of the body, except the thorax, upper limb and head and neck on the right side
- The thoracic duct starts at the cisterna chyli, which is a fusiform sac of lymph that uses the thoracic duct as an output channel
- The thoracic duct enters the thoracic cavity through the diaphragm, where is travels alongside the aorta
- The thoracic duct can be found between the aorta and the azygos vein in the posterior mediastinum
- The pulsation of the aorta promotes lymph flow by compressing the thoracic duct so that lymph can flow superiorly against gravity
- At T4/T5, the thoracic duct crosses behind the oesophagus to ascend on its left side
- The thoracic duct then moves further up and arches over the apex of the left lung and pleura
- The thoracic duct then opens into the left brachiocephalic vein at the junction of the left internal jugular and the left subclavian vein (pirogoffs angle)
- If the thoracic duct is damaged, this can lead to a chylothorax, where lymph can leak into the thoracic cavity.
Label the lymph drainage of the lung diagram
What are the lungs innervated by?
What are the 3 structures that make up the pulmonary plexus?
Where do the ANS fibres of the pulmonary plexus synapse?
What is the action of post-ganglionic ANS fibres?
What is the sensory supply of the visceral pleura?
How does this cause referred pain?
What is the sensory supply to the parietal pleura?
How does this cause referred pain?
- The lungs are innervated by the pulmonary plexuses around the main bronchi at the root of the lung
- Structures that make up the pulmonary plexus (more info post msa):
1) Sympathetics from T2-T4
2) T2-T4 ganglia
3) Parasympathetics from vagus - Parasympathetic fibres from vagus synapse in the plexuses
- Parasympathetic postganglionic fibres are bronchoconstrictors, vasodilators and have secretomotor functions
- Sympathetics fibres from T2-T4 Synapse in the sympathetic ganglia
- Sympathetic postganglionic fibres are bronchodilators, vasoconstrictors
- The visceral pleura has no general sensory supply, so if something injures the visceral pleura, it will be referred and vague
- Parietal pleura has general sensory fibres from the intercostal/phrenic (C3-C5) nerves, so pain will be felt in the dermatome of these nerves
Dermatomes of the skin
Dermatomes of the skin
What is a tracheostomy?
Where is a tube inserted in tracheostomies?
In what 3 situations are they carried out?
- Tracheotomy, or tracheostomy, is a surgical airway management procedure which consists of making an incision on the anterior aspect of the neck and opening a direct airway through an incision in the trachea
- A tube is typically inserted between the 2nd and 3rd tracheal rings
- A tracheostomy may be carried out:
1) To deliver oxygen to the lungs if you’re unable to breathe normally after an injury or accident,
2) Because your muscles are very weak.
3) To allow you to breathe if your throat is blocked – for example, by a swelling, tumour or something stuck in the throat.
Where are incisions for tracheostomies made?
Why are vertical incisions made?
What is a disadvantage of a vertical incision?
What is the alternative to a vertical incision?
Where is the incision made?
- For tracheostomies, a vertical incision is made downwards from the cricoid cartilage
- A vertical skin incision may be required for rapid access to the trachea.
- A vertical skin incision might be under more gravitational pressure from the tracheostomy tube and ventilator circuit, and thus it is more susceptible to pressure ulcers than a transverse skin incision.
- The alternative to a vertical incision is a horizontal (transverse) incision
- An incision is made between the second and third rings, and tracheostomy tube placed
Where do the lungs extend to inferiorly?
- Inferiorly, the lungs extend behind the diaphragm
What is the treatment for a pneumothorax?
Where is the insertion of a needle for treatment of pneumothorax?
What is a hemithorax?
- Treatment for a pneumothorax usually involves inserting a needle or chest tube between the ribs to remove the excess air. However, a small pneumothorax may heal on its own
- The preferred insertion site is the 2nd intercostal space in the mid-clavicular line in the affected hemithorax.
- However, insertion of the needle virtually anywhere in the correct hemithorax will decompress a tension pneumothorax
- Hemithorax: Half of the thorax or, more simply, one side of the chest.
