Anatomy And Pattern Recognition Of Lower Respiratory System And Mediastinum Flashcards
What is the trachea?
The trachea is a tubular passageway connecting the upper respiratory tract to the lungs enabling gas exchange
What are anatomical landmarks for the trachea?
• Inferior margin of the cricoid cartilage (C6)
• Braches into the left and right main bronchi at the carina (T4) - the plane of Ludwig.
• Is in a midline position but can be slightly displaced to the right by the arch of the aorta.
• 10-1cm with a width of 1.5 - 2 cm (wider in men).
What does the trachea consist of?
• The fibro-elastic tissue is flexible and expands and contains “C” shaped cartilage rings which gives it rigidity. These are bridged by annular ligaments.
• Histology
Outer layer – connective tissue
Middle layer – tracheal cartilage, annular ligaments, connective tissue, trachealis muscle
Inner layer – respiratory mucous membrane
What is the carina?
The carina is a ridge of cartilage at the base of the trachea.
• It separates the openings of the right and left main bronchi
• Level of T4 / T5 but moves with breathing
• Lies to left of midline
Why is the carina important?
Important marker for tube position
-ET tubes should be 5cm above the carina to supply air to both lungs
-NG tubes should go straight through the carina
- SVC is to the right side of the carina for CVC (central venous catheter) position.
- Marker for CTPA scans
What can happen if the carina widened?
If widened (more than 100 degrees) can be a sign of:
o Left atrial enlargement
o Cardiomegaly
o Pericardial effusion
o A mass around the area
What is the bronchi?
respiratory epithelium (shorter than trachea) – lamina propria (denser than trachea) –
separated by a discontinuous layer of smooth muscle from the submucosa (cartilage are flat plates)
What are bronchioles?
no cartilage, airways must be kept open by radial traction. Prominent smooth muscle layer. Adjusting the tone of the muscle layer alters airway diameter so air flow can be controlled.
What are respiratory bronchioles?
no goblet cells, alveoli for gaseous exchange. Have alveolar ducts (rings of smooth muscle, collagen and elastic fibres) – leading to alveolar sacs – leading to alveoli - Provide the majority of the lung volume and surface area.
Can communicate between adjacent alveoli through pores of Kohn. Lined with pneumocytes
(provide structure and surfactant)
Fun fact of right main bronchus
Right main bronchus straighter so inhaled objects more likely to end up there
What are the lung lobes?
- superior lobe
- middle lobe
- inferior lobe
What are lung fissures?
• Lung fissures are a double fold of visceral pleura that either completely or incompletely invaginate (turned inside out) the lung parenchyma to form the lung lobes
• You will often see the horizontal fissure on a PA or AP CXR, and sometimes the oblique fissure on a lateral CXR.
What is the left lung fissure?
• Oblique fissure separating the upper lobe from the lower lobe
• T4/T5 posterior to the hemidiaphragm anteriorly
What is the right lung fissure?
• Oblique fissure separating the upper lobe from the lower lobe
• Horizontal fissure separates the upper lobe from the middle lobe
• 4th costal cartilage from the hilum to the anterior and lateral surfaces of the right lung.
Why are the fissures important for us?
For CT lung biopsy
• They help protect infections affecting nearby lobes – good way to differentiate between infection and possible malignancy
What do the lungs look like on CT?
Lung window’
• lungs W:1500 L:-600
Width is contrast and level is brightness - manipulate the grayscale in CT
• Axial slice
What is the pleura?
Covers the lung, chest wall and mediastinum with 2 continuous layers of epithelium
• Visceral – covers the lungs inner layer
• Parietal – covers the chest wall and is the outer later. Nerve supply is the phrenic nerve so inflamed pleura can cause ipsilateral shoulder tip pain
• Separated by a thin layer of liquid.
What is the pleura like on a X-ray?
You can only see the pleura and pleural spaces on plain film when they are abnormal.
• Lung markings should reach the thoracic wall on a CXR
• There should be no space between the pleura
What is the mediastinum?
It is the space in the midline of the chest between the pleura of each lung and extends from the sternum to the vertebral column.
• Contains all the thoracic viscera except the lungs
• Which are Heart
• Great vessels
• Oesophagus
• Trachea
• Phrenic nerve
• Cardiac nerve
• Thoracic duct
• Thymus
• Mediastinal lymph nodes
What is the mediastinum divided into?
Can be divided into parts based on their relationship to the pericardium.
• Superior mediastinum – above the level of the pericardium and plane of Ludwig
• Inferior mediastinum – below the plane of Ludwig:
• Anterior mediastinum – anterior to pericardium
• Middle mediastinum – within the pericardium
• Posterior mediastinum – posterior to the pericardium
What is the hila/hilum?
May be at the same level but commonly the left is higher than the right
• Should look similar in appearance
• Anatomical landmark – anteriorly 3-4th costal cartilage, posteriorly T5-T7
Hila = 2 and hilum = 1
Why do we have the sternum?
- Protect your heart and mediastinum
What is the diaphragm?
C shape structure
Separates chest from abdomen
Main muscle of respiration - how we breathe
What is chilaiditi sign?
It is a condition in which a segment of the intestine is interposed between the liver and diaphragm
. Is the anterior interposition of the colon to the liver reaching the under surface of the right hemi- diaphragm
• One of the cause of pseudopneumoperitonuem
• Can have Chilaiditi syndrome where patients experience pain
What is dextrocardia
Dextrocardia means the heart is on the right side
What is hiatus hernia
Occurs when there is herniation of the abdominal contents through the oesophageal hiatus of the diaphragm
Where the causes and symptoms of hiatus hernia
Causes = increases with age and slight female predilection
Symptoms = chest/abdominal pain
Nausea and vomitting
Sometimes GORD gastro-oesophageal reflux disease
What is the diagnosis of hiatus hernia
Plain film – retrocardiac opacity with air fluid level
CT – fat collection in middle mediastinum, may see hernia or widened oesophageal hiatus
What treatments are used for hiatus hernia
Surgery in severe cases
What is pulmonary embolic disease
Most commonly a blood clot (which often starts in the leg), which travels through the circulatory system and then causes a blockage in the pulmonary artery – can be partial or complete
What are the causes and symptoms of pulmonary embolic disease
Causes
o Recent surgery
o Immobility
o Diseases with a risk of thrombus formation e.g. lupus, HIV, Covid
o Drugs such as the contraceptive pill,
o Pregnancy
o Malignancy
Symptoms
o History fitting any of the causes above
o Tachycardia, dyspnea (breathing difficulty), chest pain, hemoptysis
o Signs of a DVT