L2, L3, L5: Anatomy Of Mediastinum Flashcards
Division of mediastinum
- Superior (Divided at angle of Louis T4, T5)
- Inferior
- Anterior (sternum - pericardium)
- Middle
- Posterior (pericardium - vertebral column)
Components of ribs
- Head (2 facets)
- Neck
- Tubercle (prominence between head and facet)
- Shaft (Costal groove for intercostal VAN)
- Angle (downward and anterior)
True ribs and false ribs
True: 1-7th
False: 8-10th
Floating: 11-12th
Components of thoracic vertebrae
- Body
- Transverse process
- Lamina
- Pedicle
- Spine
Components of sternum
Manubrium (manubriosternal joint) Body Xiphoid process (xiphisternal joint)
Sternal angle / Manubriosternal joint / Angle of Louis
Attachment of 2nd rib
T4-T5
Level of carina
Cartilaginous joints and synovial joints
Cartilaginous: 1st rib
Synovial: 2nd - 7th rib
What is in costal groove
Intercostal artery, vein and nerve (VAN)
Where is rib attached to?
Posterior: Body (costovertebral joint, intra-articular ligament) + transverse process (costotransverse joint, costotransverse ) of thoracic vertebrae
Anterior: costal cartilage —> sternum
Both costovertebral and costotransverse joints are synovial joints
Contents of the intercostal space
- External IM (hands in pocket, only present in lateral side)
- Internal IM (surgeon hand gesture)
- Innermost IM (surgeon hand gesture)
- Transversus thoracic muscle / Sternocostalis (2-6th rib to posterior of sternum)
- Subcostalis
- Intercostal VAN (between IM and INM)
Arterial blood flow in thoracic cavity
All starts from aorta
Posterior:
Thoracic aorta —> Posterior intercostal artery (only 1) —> 3-11th posterior ICS
Subclavian artery —> Costocervical trunk —> Superior intercostal artery —> 1-2nd posterior ICS
Anterior:
Subclavian artery —> Internal thoracic artery —> Anterior intercostal artery (1-6th anterior ICS) + Musculophrenic artery (7-9th anterior ICS + diaphragm) + Superior epigastric artery (Rectus abdominis)
Subcostal artery and nerve = below 12th rib (T12)
Venous blood flow in thoracic cavity
Posterior:
Right: 1-2nd ICS —> Right superior intercostal vein —> Azygos —> SVC
Left: 1-2nd ICS —> Left superior intercostal vein —> Accessory hemiazygos —> Azygos —> SVC
Right: 3-11th ICS —> Posterior intercostal vein —> Azygos —> SVC
Left: 3-11th ICS —> Hemiazygos —> Azygos —> SVC
Anterior:
Anterior chest wall —> Anterior intercostal vein —> Internal thoracic vein —> Left brachiocephalic vein
Nerve supply of intercostal space
Anterior rami of 1-11th spinal nerves (Intercostal nerves within costal groove)
Nerve supply of parietal and visceral pleura
Parietal:
Costal pleura + peripheral diaphragmatic pleura: Intercostal nerve
Central diaphragmatic pleura: Phrenic nerve (C3-C5)
Mediastinal pleura: Phrenic nerve (C3-C5)
Visceral: Pulmonary plexus (T2-T5; Vagus nerve)
Left vs Right bronchus
Left: narrower, horizontal, longer
Right: wider, vertical, shorter (短小精悍)
Level of trachea
C6 - T4
Contents of hilum
- Pulmonary artery and pulmonary vein
- Bronchial artery and bronchial vein (supply bronchi, CT, visceral pleura)
- Pulmonary plexus
- Bronchus
- Lymph nodes
Blood supply of pericardium and diaphragm
Pericardicophrenic A+V
Drainage of lymph vessels
Superficial LN (subpleural lymphatic plexus)
—> Deep LN (pulmonary —> bronchopulmonary —> tracheobronchial —> paratracheal)
—> Bronchomediastinal lymphatic trunk
—> Thoracic duct (left) + Right lymphatic duct (right)
—> Brachiocephalic vein
—> SVC
Intersection of MAL, MCL, PPL with visceral and parietal pleura respectively
MAL + parietal: 10th rib MAL + visceral: 8th rib MCL + parietal: 8th rib MCL + visceral: 6th rib PPL + parietal: 12th rib PPL + visceral: 10th rib
Location of apex of lung
2.5cm above thoracic inlet
Two parts of diaphragm
- Muscular part (peripheral)
2. Central tendon
3 openings of diaphragm
ACO:
- Aortic (T12): Aorta, thoracic duct, Azygous vein
- Caval (T8): IVC, phrenic nerve
- Oesophageal (T10): Oesphagus, vagus nerve, blood vessels
Blood supply of diaphragm
- Musculophrenic A/V
2. Inferior phrenic A/V
Nerve supply of diaphragm
Phrenic nerve (C3-C5)
Phrenic nerve: does not belong to ANS but contain somatic, motor and sympathetic (ANS) neurone
Diaphragm arises from:
- Medial arcuate ligament
2. Lateral arcuate ligament
Muscle contraction in: Passive inspiration Active inspiration Passive expiration Active expiration
Passive inspiration:
Diaphragm + External IM
Active inspiration:
Diaphragm + External IM + Scalene (fix 1st rib) + Pectoralis (major&minor) + Serratus
Passive expiration:
Diaphragm (relaxation) + Internal IM + Inn IM + Lung recoil
Active expiration:
Diaphragm (relaxation) + Internal IM + Inn IM + Abdominal + Latissimus dorsi + Quadratus lumborum (fix 12th rib)
Components of thoracic cavity
- Mediastinum
- Lungs
- Pleura
What is mediastinum
- Space located between the lung
- extending to the root of the neck
- below to the diaphragm
Actions of diaphragm
- Respiration (increase vertical diameter)
2. Valsalva’s maneuver
Contents of mediastinum
Superior: Great vessels, Phrenic nerve, Vagus nerve, Sympathetic trunks, Plexus, Trachea, Oesophagus
Anterior: Lymph nodes, remnants of thymus gland, Sternopericardial ligament
Middle: Pericardium, Heart, Trachea
Posterior: Aorta, Azygous, Sympathetic trunks, Splanchnic nerve, Vagus nerve, Thoracic duct, Oesophagus
Classification of nervous system
Anatomically: Central vs Peripheral
- Central: Brain + Spinal cord
- Peripheral: Cranial nerve (12 pairs) + Spinal nerve (31 pairs)
Functionally: Somatic vs Autonomic
- Somatic: Sensory + Motor
- Autonomic: Sympathetic + Parasympathetic
Sympathetic vs Parasympathetic NS
- Function
SNS: Flight or fight, prepare for emergency
PNS: Conserves and restores energy - Anatomical outflow
SNS: T1-L2
PNS: CN3,7,9,10 + S2-S4 - Preganglionic fibre
Both: myelinated + ACh as transmitter - Ganglia
SNS: paravertebral + prevertebral
PNS: small ganglia close to viscera - Postganglionic fibre
SNS: Long, non-myelinated (NE most, ACh very few)
PNS: Short, non-myelinated (ACh) - Activity
SNS: widespread + NE&E from adrenal medulla
PNS: discrete due to few postganglionic fibre - Higher control
Both: hypothalamus
5 plexus and their nerve supply
- Cardiac plexus
Vagus (CN10) + T2-T5 - Pulmonary plexus
Vagus + T2-T5 - Aortic plexus
Vagus + T5-T11 - Renal plexus
Vagus + T12 - Hypogastric plexus
S2-S4 (pelvic splanchnic nerve) + L1-L2
Nerve supply of eye, lacrimal gland, submandibular + sublingual, parotid gland (less important)
Eye:
CN3 + T1-T2
Lacrimal gland:
CN7 + T1-T2
Submandibular + sublingual:
CN7 + T1-T2
Parotid gland:
CN9 + T1-T2
Sympathetic afferent and efferent pathway
Afferent:
Myelinated fibres from viscera through sympathetic ganglion (without synapsing) —> white rami communicantes —> Posterior ganglionic root —> Higher centre / reflex arc
Efferent: Lateral column (anterior horn) —> white rami communicantes —> paravertebral ganglion —> sympathetic trunk
Parasympathetic afferent and efferent pathway
Afferent:
From target organ (without synapsing) —> white rami communicantes —> Posterior ganglionic root / CNS —> Higher centre / reflex arc
Efferent:
Anterior horn —> Plexuses —> Post-ganglionic neurone
Lymphatic drainage of trunk
Left:
Left side: bronchomediastinal, jugular, subclavian trunk (left) —> Thoracic duct
Below diaphragm: Intestinal + lumbar trunk —> Cisterna chyli —> Thoracic duct
Right:
Right upper side (head, thorax, limb) —> bronchomediastinal, jugular, subclavian trunk (right) —> Right lymphatic duct
Thoracic duct + Right lymphatic duct —> Brachiocephalic vein —> SVC
