What plane divides the mediastinum into superior / inferior parts?
<span style="text-decoration:underline;">Transverse thoracic plane</span> (T4/5 IV disc)<span style="text-decoration:underline;">
</span>
Inferior mediastinum subdivided 
(anterior / middle / posterior)

Supine position of mediastinum
aortic arch superior to TTP (T4/5 IV disc)
tracheal bifurcation transected by TTP 
central tendon lies at xiphisternal junction (T9)

Standing position of mediastinum
aortic arch transected by TTP (T4/5 IV disc)
central tendon may fall to xiphoid process (T9/10 IV disc)

Contents of superior mediastinum (anterior to posterior)
Thymus
SVC
Brachiocephalic vv.
Aortic arch (BCT / LCC / LScl)
Vagus / Phrenic nn.
Cardiac nerve plexus
L. Recurrent Laryngeal n.
Trachea
Esophagus
Thoracic duct
Prevertebral mm.

Contents of anterior mediastinum
Remnants of thymus
Lymph nodes
Fat &amp; CT

Contents of middle mediastinum
Pericardium
Phrenic nn.
Heart / cardiac plexus
Roots of great vessels
Azygos arch
Main bronchi
Tracheobronchial lymph nodes

Contents of posterior mediastinum
Thoracic aorta
Thoracic duct
Tracheobronchal LN
Azygos / Hemiazygos vv.
Esophagus
Esophageal plexus
Sympathetic trunks
Splanchnic nn.
Vagus nn.

What structures pass w/in space between pericardial sac and visceral pleura?
Pericardiacophrenic aa.
Pericardiacophrenic nn.
Phrenic n.

Organization of Pericardium
<answer>
Outer layer =  fibrous pericardium 

Inner layers = serous pericardium (double layer visceral &amp; parietal)
</answer>

Where does the transverse pericardial sinus lie?
<answer>
Anterior to SVC
Posterior to Aorta &amp; Pulmonary Trunk

Continuous from left to right sides of heart
(oblique pericardial sinus = blind pouch)
</answer>

Pericardial Vasculature
<answer>
Pericardiacophrenic a. 
(branch of int. thoracic a.)

Pericardiacophrenic vv.
(dumps into brachiocephalic vv.)
</answer>

Innervation of Pericardium
<answer>
Phrenic n. (C3-C5)

Somatic only
</answer>

Relationship of structures in middle mediastinum
<answer>
<strong>phrenic n.</strong> passes anterior to root of lung

<strong>vagus n.</strong> passes posterior to root of lung

<strong>pericardiacophrenic vessels</strong> &amp; <strong>phrenic n.</strong> superficial to fibrous pericardium
</answer>

Fibrous skeleton of heart
<answer>
4 annuli fibrosi (fibrous rings) fuse together

CT skeleton separates musculature of atria from ventricles 
(attachment for valves / myocardial fiber bundles)
</answer>

Innervation of Heart
<answer>
<strong>Sympathetics</strong>
 - postganglionic fibers (cervical ganglia) -&gt; cardiac plexus
 - adrenergic (norepinephrine; increase HR / force)
 - visceral afferents carry pain 

<strong>Parasympathetics </strong>
 - vagus n.
 - cholinergic (ACh; decrease HR / force / constrict BV)
</answer>

Where is the SA node located?
junction of SVC &amp; superior crista terminalis

Where is the AV node located?
posteroinferior region of interatrial septum
(near orifice of coronary sinus)

Where do the branches of the AV node divide?
junction of membranous / muscular parts of interatrial septum

CORONARIES
CORONARIES

Venous drainage of Heart
VENOUS

Lymphatic drainage of Heart
<answer>
lymphatics form network adjacent to endo/epicardium

efferent vessels drain along coronary aa. empty into tracheobronchial nodes (lower end of trachea)
</answer>

What is the function of the thymus?
<strong><span style="text-decoration:underline;">Produces lymphocytes</span></strong>
Gradually degrades post-puberty (replaced by fat)

Blood supply to the thymus
Internal thoracic aa.
Superior thyroid aa.

Lymphatic drainage of the body
3/4 = thoracic duct (left)
1/4 = r. lymphatic duct

Brachiocephalic veins
Formed by subclavian / internal jugular vv.
L. BCV is 2x longer than R. BCV
R/L BCV unite to form SVC (1<sup>st</sup> costal cartilage)

R. Brachiocephalic v. receives lymph from...
R. Lymphatic Duct (1/4)

L. Brachiocephalic v. receives lymph from...
Thoracic Duct (3/4)

Brachiocephalic Trunk
<answer>
Most anterior branch of aortic arch
- Posterior to L. BCV
- Anterior to trachea

Divides into RCC / RScl
</answer>

Left Common Carotid Artery
Middle branch of aortic arch
Ascends post. to left sternoclavicular joint (into neck)

Left Subclavian Artery
Most posterior branch of aortic arch
Ascends lateral to trachea

Where do the phrenic nn. lie as they run into thorax?
Lie on anterior surface of anterior scalene mm.

Where do the vagus nn. lie as they run into thorax?
Lies <strong>deep to carotid sheath b/w common carotid aa. &amp; internal jugular vv.</strong> in neck

Path of R. recurrent laryngeal n.
branches from r. vagus n. (anteromedial to RScl a.)
wraps posteriorly around RScl a. 
ascends in tracheoesophageal groove
innervates all intrinsic muscles of larynx except cricothyroid m.

Path of L. recurrent laryngeal n.
branches from l. vagus n. (anteromedial to aortic arch)
wraps around aortic arch (posterolateral to ligamentum arteriosum)
ascends similar to r. recurrent laryngeal

Origin of superior phrenic aa.
Inferior part of thoracic aorta

Esophageal nerve plexus
<answer>
Anterior vagal trunk arises from L. vagus n.
Posterior vagal trunk arises form R. vagus n.

"hang a right"
</answer>

Innervation to esophagus
<answer>
Vagus n. (motor / secretomotor / sensory)
Sympathetics (vasomotor)

<strong>Superior esophagus</strong>
- recurrent laryngeal nn.
- sympathetics (middle cervical ganglion)

<strong>Inferior esophagus </strong>
- esophageal plexus
- parasympathetics (vagus nn.)
- sympathetics (gray rami upper 4 thoracic ganglion)
</answer>

Main blood supply to esophagus
Esophageal branches of thoracic aorta

Thoracic duct
<answer>
Begins at <em><strong>cisterna chili

</strong></em>Empties on left side at junction of internal jugular / L. subclavian vv.
</answer>