Week 2: CAI Flashcards
Which modalities are used to image the thorax (chest) and its contents?
- CXR
- CT
- MRI
- Ultrasound
What is required when Generating a Radiograph?
- X-ray Source (generator)
- Patient
- Detector (film or more commonly electronic)
- Can be A-P / P-A XR
Why are most thoracic radiographs PA?
- Want heart to appear as close to life-size as possible.
- Commonly used x-ray sources use a divergent light beam, beam outwards so will project larger onto the detector. Thus P-A perspective heart is close to the detector/wall and projection will be shown closer to life-size
What is the Mach Effect?
Edges of darker objects located adjacent to light ones appear darker (and vice versa)
Outline the Systematic Approach to Reading Chest Images
- Demographics
- RIP - Rotation, Inspiration, Penetration
- ABCDE
- Airway - Tracheal position
- Breathing - Hilum, lung fields
- Cardiac - Cardiothoracic ratio
- Diaphragm - Shape & Air underneath
- Everything else - Bones, Peripheries, etc
On a Chest XR, why is posterior part of rib normally more visible than the anterior part of a radiograph?
Anterior part is made from cartilage connecting to sternum. Posterior part is made from bone.
What are the medial ends of the clavicle called?
Sternal ends of the Clavicles
What can Lymphadenopathy of the hilar regions of lungs/ lateral aspects of mediastinum cause?
Oesophageal , tracheal, or superior vena cava compression
What is the costodiaphragmatic recess?
Parietal pleura lined region between thoracic wall and diaphragm - Forms ‘V’ shape
What is the Thorax, what are its openings called? What are the functions of these structures?
- Thorax - Irregular cylindrical cavity with Superior Thoracic Aperture and Inferior Thoracic Aperture openings
- Allow for passageway between abdomen * neck/upper limbs
- Protection, breathing
What may cause injury to the vessels/nerves exiting the Superior Thoracic Aperture?
- Trauma
- Tumour growth compressing vessels/nerves
- An extra cervical rib above rib 1
What are the relations of the Superior Thoracic Aperture
- Body of T1 vertebrae posteriorly
- Medial margins of rib 1 on each side
- Manubrium anteriorly (top of sternum)
What structures exit laterally from the Superior Thoracic Aperture?
- Part of Brachial Plexus
- Subclavian artery
- Subclavian vein
What occurs when there is deflated appearance of the 1st dorsal webspace?
- Compression of C6/C7 nerves exiting at Superior Thoracic Aperture due to tumour or extra rib
- Supplies nervous innervation to muscles in this area
- Resultant muscle atrophy due to loss of nerve supply. Deflated appearance
Why do hiccups occur?
- Due to irritation of diaphragm
- Causes involuntary diaphragmatic contractions
What are the margins of the diaphragm?
- Costal cartilages and bony ribs
- Posteriorly - Ligaments of diaphragmatic crura + lumbar vertebra
Describe the motor and sensory innervation of the diaphragm
- Motor innervation - Solely left and right phrenic nerves
- Sensory Innervation - Left and Right Phrenic Nerves + Additional peripheral innervation from intercostal nerves
What happens if there is unilateral phrenic nerve damage on the right side?
- Right hemidiaphragmatic palsy - Paralysis of side affected
How is Pain felt in the Diaphragm?
- Phrenic nerve + Peripheral Intercostal nerve = Sensory supply
- Inflammation of gallbladder - Tip of Shoulder pain or regional pain in Right Hypochondrium (intercostal Neve)
- Can get inflammation of diaphragm e.g. basal pneumonia, irritation of subphrenic area, malignant disease, pleural effusions
What are pericardial branches?
- Each phrenic nerve supplying the diaphragm (left and right) also give sensory supply to branches of mediastinal pleura + Pericardium of heart
What is meant by Flail Chest?
- Rib fractures can lead to paradoxical movement of the thoracic wall segment affected.
- On inspiration will fall inward as rest of thoracic wall moves outward
What is the Sternum composed of?
- Manubrium
- Body
- Xiphoid Process
- Ossify together with age
What is the Sternum composed of?
- Manubrium
- Body
- Xiphoid Process
- Ossify together with age
What is the significance of the Sternal Angle / Manubiosternal Joint?
- Major Surface Anatomy Landmark
- 2nd Costal cartilage is lateral
- If trace around body = Sternal plane = T4-T5 IV disc
- Divides Mediastinum into Superior & Inferior Parts
What is the Jugular (Suprasternal) Notch
Palpatable region at top of sternum
Describe the Costal Grooves of the Ribs
- On inferior margin of each rib
- Where neurovascular bundle runs
Describe the ribs and its general attachments
- 12 pairs of ribs
- Articulate with thoracic vertebrae posteriorly and costal cartilages anteriorly which attach to the sternum
- Consist of Head, Neck, Angle, and Body regions of bony rib from posterior to anterior aspects.
What is an intercostal nerve block? What is its relevance to the ribs?
- Nerve block delivered around intercostal nerve in space + fascial plane surrounding area.
- Anaesthetists use the angles of the ribs to mark pt and localise most advantageous position for delivery
- Used in cases of trauma - Anaesthesia / Post-operative pain relief
What type of joints are found between ribs and + vertebra?
Synovial joints - Allows for movement
Describe the Articulations of the Ribs
- Head of most ribs articulate with Body + Transverse process of their OWN Vertebra
- AND with vertebral body of the vertebra above
- Joined via synovial joints
State the 3 Rib Classifications
- Vertebrosternal (Ribs 1-7)
- Vertebrocostal (Ribs 8-10)
- Floating (Ribs 11 & 12)
Where do the Neuromuscular bundles that supply the intercostal spaces + tissues sit?
- Main Neuromuscular bundle runs within costal groove Superiorly between internal & innermost intercostal muscles
- Also have Collateral/Accessory Neuromuscular bundle - Less important
- These supply Vein, Artery, and Nerve
Describe a Chest drain
- Performed using Tube Thoracostomy unit/ Chest tube/ Intercostal catheter to drain fluid from pleural or thoracic cavity
- Should be inserted in the inferior part of the intercostal spaces to avoid damaging the main neurovascular bundle
Describe the Sensory and Motor Supply to the Ribs
- Intercostal nerves (Ventral Rami of Spinal Nerves) provide both Sensory + Motor to:
- Intercostal space, Overlying tissues (skin, cartilage, bone, muscle, parietal pleura)
- In a dermatomal arrangement
- Pleuritic pain can refer to a dermatome
- Shingles can distribute to a dermatome
What is the blood supply to the ribs?
- Anterior Intercostal Artery - arises from Internal Thoracic & Musculophrenic Arteries
- Posterior Intercostal Arteries - arises from Descending Aorta
- Form an anastomosis - Collateral circulation for potential bypass if have an Aortic Coarctation (Narrowing)
What Causes Rib Notching (wavy appearance)?
- Increased volume of blood in intercostal arteries that become big, waxy, tortuous.
- Causes bone that it sits in to remodel
- Would be a sign to investigate aorta for possible Aortic Coarctation
Describe the Venous Drainage of the Thoracic Wall
- Via UNPAIRED Azygous System
- Right sided structures - Into Azygous vein –> SVC
- Left sided structures - Into Accessory Azygous Vein / Hemizygous Vein –> Cross midline into Azygous –> SVC
- Upper spaces above this system drain directly into left or right Brachiocephalic veins which join to form Superior Vena Cava.
Along which vertebra do the Sympathetic chain run?
- Posterior thoracic wall T1-L2
Describe Pancoast Tumour and Associated Horner Syndrome
- Pancoast tumour - Apical Lung tumour
- Compression in the apical region can lead to unilateral compression of sympathetic chain at this point which supply head+neck
- Can lead to Horner Syndrome - Ptosis (droopy eyelid) due to paralysis of Superior Tarsal Muscle, Miosis (Constricted Pupil), and Loss of Hemi-fascial sweating
Where does the Respiratory System develop from?
- Develops as an outgrowth of the gut tube
- Appears at 4 weeks as a Diverticulum
- Develops into Lung/Bronchial buds –> Grow into splanchno-pleuric Mesoderm (wk 5)
How does the Oesophagus and Trachea develop into separate structures?
- Via formation of a septum (tissue that grows between oesophagus + trachea
- Wk 4/5
What can occur if Oesophagus and Trachea do not separate correctly?
- Proximal atresia - Oesophagus ends in a blind-ended sac early in tube
- Distal Fistula / Fistula - Communication with the Trachea either with Proximal Atresia or without.
- Must be corrected early in life
Describe the Branching/Development of Lung buds
- 2 lung/bronchial buds develop
- Branch into 3 segmental/secondary bronchi on the right and 2 segmental bronchi on the left
- Segmental bronchi develop to give 3 lung tissue lobes on right and 2 on left + Mesoderm divides with segmental bronchi
- Week 26 - Respiratory epithelia begins developing. Can take up to 10 years to full maturation
- Week 16 - All major lung parts are developed (just not gas exchange)