Thorax Flashcards
What forms the sternal angle and at what vertebral level is it?
Manubrium articulating with body of the sternum (Level of the 2nd rib) is the sternal angle.
This occurs at T4/5 vertebral level
Describe the costovertebral and costotransverse joints in the rib cage.
Costovertebral - Head of rib articulates with articular facets its own vertebrae and the vertebrae superior to it. Reinforced by the radiate ligament.
Costotransverse - Between the tubercle of the rib and the transverse process of its own vertebrae.
- Medial faces articulates with the transverse process (synovial joint)
- Lateral facet gives rise to lateral costotransverse ligament to the transverse process
Which ribs attach to the sternum, costal cartilages above and which are floating?
Ribs 1-7 attach to the sternum
Ribs 8-10 attach to costal cartilage above
Ribs 11-12 are floating ribs
How does the 12th rib differ from the other ribs
Has no neck, tubercle or costal groove
Only contains one facet which articulates with corresponding vertebra
Describe the Outer, Middle and Inner Layer of thoracic muscles (Including innervation and action)
All innervated by intercostal nerves (Anterior rami of spinal nerves)
Outer Layer
- External Intercostal (Pass obliquely forwards, action to elevate ribs)
- Serratus posterior Superior (Spinous Process C6-T2 to ribs 2-5, elevates ribs)
- Serratus posterior inferior (SP T11-L2 to ribs 9-12, depresses ribs)
Middle Layer
- Internal Intercostal (Pass obliquely backwards, depress ribs)
Inner Layer
- Transversus thoracic (Continuous with transverses abdominis, from inferior sternum to costal cartilages 2-6, weak depressor)
- Innermost intercostal
- Subcostals (inner surface lower ribs then arch to superior border of rib 2 or 3)
Between what muscle layers does the intercostal space lie and what are its contents
Between middle and innermost muscular layers.
Consists of intercostal vein, artery and nerve (Superior to Inferior)
Located on the lower border of the rib.
What are the two branches of the intercostal nerves
Intercostal nerves arise from anterior rami of spinal nerves T1-11.
Give off:
i. Lateral cutaneous branch
ii. Anterior cutaneous branch
What is special regarding the lower 5 intercostal nerves, and especially the 12th intercostal nerve?
The lower 5 intercostal nerves slope downward before exiting their intercostal rib space to supply anterior abdominal wall.
The 12th intercostal nerve is referred to as the subcostal nerve and it passes into the abdominal cavity behind the lateral arcuate ligament and lies behind the kidney
Describe the Posterior and Anterior intercostal arteries that supply the thoracic wall
Posterior intercostal arteries
- Intercostal Space 1&2 from costocervical trunk (subclavian)
- Intercostal spaces 3-11 from Thoracic Aorta
Anterior intercostal arteries
- Intercostal spaces 1-6 from Internal thoracic artery (subclavian)
- Intercostal spaces 7-9 my musculophrenic artery (Branch of internal thoracic a.)
Diaphragm - What Levels do the crura anchor the diaphragm to the vertebrae?
Both are very strong tendons
- Right Crura form L1-3
- Left Crura from L1-2
Diaphragm - Describe the 2 major ligaments of the diaphragm
Median arcuate ligament
- Between both crura and in front of the aorta
- It is a thickening of the psoas fascia
- Sympathetic trunks pass behind the medial arcuate ligament
Lateral arcuate ligament
- Anterior thickening of the lumbar fascia
- Subcostal nerve and vessels pass behind the lateral arcuate ligament
Diaphragm - What is its nerve supply
Phrenic Nerve (C3-5) to each side
Motor supply mainly C4
Diaphragm - What is the blood supply
Right and left inferior phrenic arteries
Lower 5 intercostal arteries and subcostal arteries
Diaphragm - Describe the Major Openings of the diaphragms, what passes through them and the respective vertebral levels
T12 - Aortic Hiatus (Aorta, Azygos vein, thoracic duct)
T10 - Oesophageal Opening (Oesophagus, vagus nerves)
T8 - Vena Caval Opening (IVC, right phrenic nerve)
Others:
*Left phrenic pierces muscular dome
*Hemiazygos vein passes through left crus
*Splanchnic nerves pieces the crura
* Subcostal nerve and vessels pass behind lateral arcuate ligament
Describe the main muscles involved in inspiration and expiration
Inspiration
- Mainly due to diaphragm
- External intercostals also active
- Accessory muscles can also be used including scalenes, sternocleidomastoid, erector spine
Expiration
(largely passive)
- Internal intercostals most active
- Assisted by external oblique, internal oblique and transverses abdomens muscles, latissimus doors
List some of the anatomical landmarks that occur at the sternal angle (T4/5) [Division of superior mediastinum to inferior mediastinum]
- Bifurcation of the trachea
- Beginning and end of the aortic arch
- Just above the bifurcation of the pulmonary trunk
- Azygos vein enters SVC
- Thoracic duct moves from left to right of the oesophagus
- Ligamentum arteriosum attaches from left pulmonary artery to aortic arch
Superior Mediastinum: What two structures does the aortic arch pass over and what are the major branches of the aortic arch?
Passes over:
- Left bronchus
- Pulmonary trunk
Major Branches
- Brachiocephalic a.
- Left common carotid a.
- Left subclavian a.
SM: At what anatomical landmark doe the brachiocephalic a. divide into the right common carotid a. and rich subclavian a.?
behind the right sternoclavicular joint
SM: What is the ligament arteriosum the remnant of? And what structures does it pass between?
Remnant of the doctor arteriosus
Passes between left pulmonary a. and the aortic arch.
SM: What veins are the brachiocephalic vein formed by?
Internal jugular vein and subclavian veins.
SM: At what level does the SVC begin and what level foes it pierce the pericardium?
Brachiocephalic veins join at the lower border of the 1st right costal cartilage
Pierces the pericardium at the 3rd right costal cartilage and receives the azygos vein just prior to this at the 2nd costal cartilage
Describe the nerves that make up the cardiac plexus and where it is located
Superficial
(Left vagus nerve and left cervical sympathetic ganglion)
Lies in front of the ligament arteriosum
Deep
(Left and right vagus nerves, and the right and left recurrent laryngeal nerves, as well as cervical ganglion of sympathetic trunk)
Lies to right of ligament arteriosum and infant of left bronchus
At what level for the trachea commence in the neck and and what level does it bifurcate?
Commences below the cricoid cartilage at the level of C6
Bifurcates into bronchi just below sternal angle (T4/5)
What is the blood supply and innervation to the trachea?
Innervation - recurrent laryngeal nerve
Arterial Supply - inferior thyroid artery and bronchial arteries
Describe the pathway of the Right and Left Phrenic nerves from the neck to the diaphragm
Right Phrenic Nerve
- Crosses anterior to anterior scalene and subclavian artery (posterior to subclavian vein and brachiocephalic veins)
- Lateral to right atrium and anterior to the right bronchus
- Crosses diaphragm by passing through vein canal foramen
Left Phrenic Nerve
- Lateral to left common carotid
- Crosses aortic arch superficial to the left superior intercostal vein and then runs laterally down to the pericardium over the left ventricle
- Reaches the diaphragm and pierces the muscular part
Describe the Pathway of the right and left Vagus nerves from the neck to the thorax
Both lie in neck behind the jugular vein and between the internal carotid artery in the carotid sheath
Right Vagus Nerve
- In contact with trachea once inside the superior mediastinum
- At the sternal angle it passes backward behind the lung root to the oesophagus
Left Vagus nerve
- held away from the trachea by the great arteries
- crosses the arch deep to the left superior intercostal vein
- continues behind the lung root and passes into the midline to enter the oesophageal plexus
What does the fibrous pericardium and the central tendon arise from?
the septum transversum
What is the innervation to the pericardium (Hint: Break down to fibrous, serous [parietal and visceral])
Fibrous: Phrenic nerve
Parietal Serous: Phrenic nerve
Visceral Serous: Cardiac Plexus (Myocardial pain is transmitted by sympathetic nerves)
Describe the crista terminals and fossa ovalis of the right atria
Crista terminalis - separates smooth and roughened areas in the interior surface of the RA
Fossa ovalis is the remnant of the foramen ovale. It lies n the posterior wall (Interatrial septum, above the coronary sinus)
Describe the Trabeculae carneae, papillary muscles and chordae tendinae seen in the ventricles of the heart
Trabeculae carneae - muscular ridges on inner surface
Papillary muscles attach to cusps of AV valves via chordae tendinae to prevent prolapse of valves
Describe the conducting System of the Heart
Describe the arterial supply to the heart
Right Coronary Artery
- (Arises from aortic sinus, passes between right auricle and infundibulum of RV then posteriorly in AV groove)
- Supplies SA node in 60% of people
- in 90% of people gives off posterior inter ventricular a.
Left Coronary artery
(Arises from left aortic sinus behind pulmonary trunk)
i. Left Circumflex a. (passes down back of heart)
ii. Left anterior descending a. (runs down anterior inter-ventricular groove). Supplies SA node in 40% cases. Gives off posterior inter ventricular a. in 10% cases)
Describe the venous drainage of the heart
5 veins drain to coronary sinus which opens into the RA
(Great, middle, small cardiac veins and the posterior vein of LV and oblique vein of LA)
The anterior cardiac veins open into RA
Venae cordis minimae are very small veins in the walls of the 4 chambers that drain to RA
What branches does the descending aorta give off?
Commences at level of T4/5. Gives off:
- 9 posterior intercostal arteries
- Bronchial arteries
- Oesophageal arteries
- Superior phrenic arteries
Describe the musculature and blood supply and innervation of the oesophagus
Skeletal (Striated) Muscle first 1/3rd
Smooth (Non-striated) muscle in second 1/3rd
Blood supply
- Upper 1/3rd - inferior thyroid a.
- Middle 1/3rd - oesophageal branches of thoracic aorta
- Lower 1/3rd - oesophageal branches from left gastric a.
Venous Drainage
- Upper 1/3rd - brachiocephalic vein
- Middle 1/3rd - azygos vein
- Lower 1/3rd - left gastric vein
Innervation
- Upper - recurrent laryngeal nerve and sympathetic fibres of middle cervical ganglion
- Lower part - greater splanchnic nerve, parasympathetic from vagus nerve
Describe the sphincters of the oesophagus
Upper sphincter (Anatomical) - C6. Striated muscle sphincter at junction of pharynx and oesophagus. Produced by the cricopharyngeus muscle. Prevents entrance of air into the oesophagus.
Lower Sphincter (Physiological) - T11. Marked by change from oesophageal to gastric mucosa.
Describe the thoracic duct
Longest lymph channel in body
Originates from cisterns chyli at T12 between aorta and azygos vein
Passes upwards to the left and moves behind the oesophagus
Lies anterior to the great arteries of the aortic arch and enters neck between left internal jugular and subclavian veins
*It does not drain lymph from right arm (drains to brachiocephalic vein)
Describe the azygos vein system
Right azygos vein
- (begins from union of lumbar and subcostal veins)
- Travels through aortic opening adjacent to vertebral bodies and arches over main right bronchus
- Enters SVC at T4/5
- Receives right posterior intercostal veins, bronchial veins, veins from middle third of oesophagus
Left side (Lower is hemiazygos vein, Upper is accessory hemiazygos vein)
- Each lies adjacent to vertebra
- Hemiazygos vein receives lowest four intercostal veins
- Accessory hemiazygos receives the middle four posterior intercostal veins, bronchial veins, veins from middle third of oesophagus)
- The two veins join azygos system, crossing the midline at T8/9
The thoracic sympathetic trunk has 12 ganglia, what do they supply
upper 4 ganglia –> cardiac plexus
lower 8 ganglia –> Splanchnic nerve
Innervation of parietal pleura
In general it’s the intercostal nerves.
Pleura over the mediastinum and the diaphragm centrally are supplied the phrenic nerve.
blood supply of visceral and parietal pleura
Parietal - intercostal arteries
Visceral - Bronchial arteries
What is the pleural reflection and where does this occur
(Where the parietal pleura changes direction as it passes from one wall of pleural cavity to another.)
o At the sternoclavicular joint they meet in the midline at the level of the 2nd rib
o Pass vertically down to the 4th costal cartilage, then the right continues vertically and the left descending laterally
o Each turn lateral at the 6th costal cartilage
o They cross the midclavicular line at the 8th rib
o They cross the midaxillary line at the 10th rib
o They cross the 12th rib at the lateral border of the erector spinae
What is contained in the left and right lung roots
What’s the difference between the right and left bronchus
Right is slightly shorter and more vertical and wider. Thus foreign objects more likely to go down it.
Right bronchus also divides outside of the lung (left does not)
Describe pathway from trachea to alveoli
Trachea L+R Bronchi Segmental Bronchi Conducting bronchioles Terminal Bronchioles Respiratory bronchioles Alveoli
