A L4 Flashcards
Thoracic wall skeletal elements
Anteriorly:
sternum
rib cage
Posteriorly:
vertebral column
Thoracic inlet - what? boundaries? structures passing thru?
Its an opening from the thorax into the root of the neck
Boundaries:
- 1st rib and its costal cartilage
- upper boundary of manubrium
- T1 vertebrae
Structures:
- Esophagus
- Trachea
- Nerves and blood vessels that supply and drain the neck and head as well as the upper limb (Subclavian artery and vein, brachioceph V and A. and brachial plexus)
What is the thoracic outlet syndrome? How many ppl affected? What can it result in?
-when there is a cervical rib (an extra rib) originating from the transverse process of the C7 vertebra
- It affects about 0.5% of the population
- It can result in the compression of:
–> The lower trunk of the brachial plexus (C8 and T1 nerves) This can result in pain in the medial side of the forearm and hand - can also result in wasting of the small intrinsic muscles of hand)
–> Compression of the subclavian A which can interfere with blood supply to the UL
What formms the boundaries of the thoracic outlet?
- T12 vertebrae
- 11th and 12th ribs
- Costal cartilages of ribs 7-10
- xiphisternal joint of sternum
- This aperture is closed by the diaphragm –> the diaphragm thus separates the thoracic and abdominal cavities
Where is the angle of Louis located? Why is it important?
Sternal angle
- articulation between the manubrium of the sternum and the body of the sternum
- Easily palpable landmark felt as the ridge below the jugular notch
- It’s at the level of rib 2 thus can be used to determine where the remaining ribs and intercostal spaces are
- It’s where the aortic arch begins and ends
- It’s where the trachea bifurcates
Transthoracic plane drawn from sternal angle to level of the T4 to T5 vertebra – separates the superior and inferior mediastinum
Where can bone marrow biopsy be performed in the upper body? why is it done here? and for what reason? type of anaesthetic used?
- In the sternum
- It has a subcutaneous position (right below the skin)
- Contains red marrow throughout life
- Done to aspirate marrow
- To check for any blood diseases such as anemia or leukaemia
- bone marrow transplant
Done under local anaesthetic
What are the 4 areas of a typical rib
a head, a neck, a tubercle and a body
How many ribs are there?
What are the typical articulations of them? What type of joints do they form?
Which ribs are exceptions?
There are 12 ribs
When they articulate with the vertebral column they form synovial joints. They articulate with the column at 2 places:
- Their head articulates with the vertebra of the same number and the one superior to it except for rib 1 that doesn’t articulate with C7.
- Their tubercle articulates with the transverse process of the vertebra of the same number at the synovial COSTOTRANSVERSE JOINT.
** Ribs 11 and 12 dont articulate with the transverse process of the vertebra
What grooves/tubercles does rib 1 possess
- It possesses a tubercle for the attachment of the anterior scalene muscle
- It possesses 2 grooves in which the subclavian A and the Vein lie.
What are the 3 types of ribs?
True ribs: 1-7 –> their costal cartilages articulate directly with the body of the sternum at the sternocostal joint – all of these are synovial except for the joint formed by rib 1 which is cartilaginous.
False ribs: 8-12 –> Their costal cartilage articulates with that of the rib directly above – thus it indirectly articulates with the sternum
Floating ribs: 11+12 –> they dont articulate with the sternum.
What forms the lower costal margin? what is the most inferior point of the thoracic cage?
extends from the xiphisternum
formed by the border of the costal cartilages of ribs 7-10
most inferior point is the 10th costal cartilage
Scoliosis
- Its an s-shaped lateral curvature of the vertebral column
- It could develop to compensate for shortening of one LL
- Mostly idiopathic
- May interfere with the movement of ribs during inspiration if severe - resulting in respiratory incapacity.
What strictires could a fracture of the ribs affect?
Lungs
Kidneys
Liver (right)
Spleen (left)
What is a flail chest?
Occurs when multiple ribs are fractured at 2 points – causes formation of flail segments
This segment will move opposite to the ribs during respiration
If inspiration - ribs moves out but flail segment will move inwards
Can result in problems breathing as lungs cant expand fully. - Patient may need ventilation
What muscles lie in the intercostal spaces? What is their nerve supply? What direction do their fibres run in?
- Intercostal muscles – Have 3 layers:
—> External intercostal muscles (Run antero-inferiorly)
—> Internal intercostal muscles (Run postero-inferiorly)
—> Innermost intercostal muscles (Run postero-inferiorly) - Intercostal nerves
What does the intercostal neurovascular bundle comprise of? What is the order? Which muscles does it lie between? Where is it situated?
What structure is the most likely to get injured and why?
Comprises of:
Intercostal veins (V)
Intercostal Arteries (A)
Intercostal Nerves (N)
The bundle passes between the internal and innermost intercostal muscles
Situated in the subcostal groove of the upper rib of the intercostals space
The nerve lies the lowermost and is thus the most likely to get injured during an injury to the upper part of the intercostal space
Where do the intercostal arteries, veins and nerves arise from/drain into?
Arteries:
Posterior intercostal arteries:
They arise from the descending aorta except for the first 2 which arise from the subclavian A indirectly
Anterior intercostal arteries:
They are branches of the internal thoracic A. which is a branch of the subclavian A.
Veins:
Drain into the azygous vein
—-> The azygos vein on the right
—–> The hemiazygos vein on the left which then drains into the azygos vein.
Nerves:
Arise from the anterior rami of the T1-11 spinal nerves
The nerve passing below the last rib 12 is known as the subcostal nerve and arises from the T12 spinous process.
What is thoracostomy? why is it done? give an example of a disease it might be done in? What area is the tube inserted in? what layers does the tube pierce?
Insertion of a tube thru the layers of the intercostal tissues and and parietal pleura
Done to remove excess fluid or air in the pleural cavity
Example: pneumothorax or pleural effusion
Its inserted in the lower part of the intercostal space to avoid damage to the neurovascular bundle
Layers the tube pierces (8):
- Skin
- Superficial fascia
- Serratus anterior muscle
- External intercostal
- Internal intercostal
- Innermost intercostal
- Endothoracic fascia
- Parietal pleura
What type of muscle fibres does the diaphragm have?
Origin and insertion?
Nerve supply?
Action?
It has radial fibres that run from the periphery of the muscle in towards the central tendon
origin: The lower margin of the rib cage and the upper lumber vertebra (crura)
Insertion: Central tendon of diaphragm (aponeurosis)
Nerve supp;ly:
Motor:
—> Phrenic nerve (C3, 4, 5)
Sensory:
–> Phrenic nerve (central part)
–> Lower intercostal nerves (peripheral part)
Action: It increases the thoracic cavity volume vertically
when it contracts it flattens thus increasing volume.
What structure of the heart is attached to the central tendon of the diaphragm?
The pericardium
Openings in the diaphragm and the stirctures that pass thru?
T8 - Vena cava opening in central tendon
T10 - Esophageal opening + vagus nerves
T12 - Aortic hiatus opening + thoracic duct + usually azygos and hemiazygos vein
Describe referred pain due to diseases involving the diaphragm
Diseases involving the CENTRAL TENDON of the diaphragm:
– Supplied by the phrenic nerve (C3-5)
– Pain can be felt over the C4 dermatome over the shoulder tip
Diseases involving the PERIPHERY of the diaphragm (thoracic/abdominal diseases):
– Supplied by the intercostal nerves
– May be referred to the lower thoracic dermatomes
Describe the pathway of the phrenic nerve
- Leave the cervical plexus at C3-5
- They enter the superior mediastinum
—> The R phrenic nerve descends on the right side of the SVC
—> The L phrenic n. descends on the left side of the aortic arch - They enter the middle mediastinum
- Each one then descends within the pericardial sac anterior to the root of the lung to reach diaphragm.
— Provide motor to diaphragm and sensory to central aspects of diaphragm.
What are the movements of the rib cage during inspiration and what muscles cause them?
What are the inspiratory muscles? What are the accessory muscles of inspiration? Does expiration require any muscles? What are the muscles involved in forced expiration?
