Master Deck

What is the mediastinum? How is it split?

The mediastinum is everything between the lungs. Split into the superior and inferior (inferior is then split into anterior, middle, and posterior)

What plane divides the superior from the inferior mediastinum?

The transverse thoracic plane: sternal angle to the T4/5 IV disc

List everything that happens at the sternal-angle (T4/5) plane

Trachea bifurcates (carina); aortic arch begins & ends; azygos arches into SVC; thoracic duct crosses R→L; superior/inferior mediastinum boundary; level of 2nd costal cartilage

What are the normal contents of the ANTERIOR mediastinum? Where is it located?

Fat, lymph nodes, not many things inside. This structure is between the body of the sternum and pericardium

Differential for an ANTERIOR mediastinal mass

Thymoma, Teratoma, Thyroid (retrosternal goiter), Terrible lymphoma

Which mediastinal compartment contains the heart & pericardium?

Middle mediastinum

What are the contents of the POSTERIOR mediastinum? Where is it located?

Thoracic (descending) aorta, esophagus + vagal plexus, thoracic duct, azygos/hemiazygos veins, sympathetic trunk + splanchnic nerves

What is in the middle inferior mediastinum besides the heart and pericardium?

The main bronchi and pulmonary veins

Why is there no trachea in the posterior mediastinum?

The trachea bifurcates at T4/5 (the superior/inferior divider), so below that it's already split into main bronchi (which sit in the MIDDLE compartment)

What is the sternal angle of Louis? Where is it located?

Another name for the sternal angle aka where the manubrium meets the body of the sternum. Located at T4-T5.

Which structures run through BOTH superior and posterior mediastinum?

Esophagus, thoracic duct, vagus nerves (long vertical structures)

The 3 branches of the aortic arch, in order (L to R):

Brachiocephalic trunk, Left common carotid, Left subclavian ADD PIC

Which vein joins the subclavian vein to form the brachiocephalic vein?

Internal jugular vein

How is the SVC formed?

Right + left brachiocephalic veins merge (behind the right 1st costal cartilage) ADD PICTURE

Phrenic nerve: relationship to the lung root

ANTERIOR to the lung root ("phrenic = phront")

Vagus nerve: relationship to the lung root

POSTERIOR to the lung root

Phrenic nerve roots and function

C3, C4, C5 — sole MOTOR to the diaphragm; also sensory to diaphragm/pericardium

Why does diaphragm irritation cause shoulder-tip pain?

Phrenic (C3-5) carries diaphragm sensation; shares roots with shoulder-tip skin dermatome → referred pain

Which branch of the aortic arch goes straight into the neck?

Left common carotid

Which branch of the aortic arch splits? Into what?

Brachiocephalic trunk, splits into right common carotid and right subclavian

What are the structures of the superior mediastinum from anterior to posterior?

From sternum to spine: thymus, veins, arteries, esophagus.

Left recurrent laryngeal nerve: where does it loop?

Under the arch of the aorta (beside ligamentum arteriosum) at T4/5

Where does the azygous vein dump into?

SVC

What does the phrenic nerve do?

Sole motor to diaphragm

Right recurrent laryngeal nerve: where does it loop?

Under the right subclavian artery (in the neck)

Compression of the left RLN would cause?

Hoarseness caused by paralysis of the left vocal cord

If a patient has facial swelling, distended neck veins, and edema of both arms, what are the most likely experiencing? Why? What structure is being compressed?

SVC syndrome. SVC supplied the head, neck, and upper limbs. If blocked/compressed, everything upstream engorges.

Which structure lies immediately posterior to the LEFT ATRIUM? If the left atrium was enlarged, what would occur?

The esophagus is immediately posterior to the left atrium. If the left atrium is enlarged, it will push against the esophagus, causing dysphagia.

Most POSTERIOR chamber of the heart

Left atrium

Most ANTERIOR chamber of the heart

Right ventricle

Swallowing problem vs breathing problem — which tube?

Dysphagia = esophagus; stridor/breathing = trachea/bronchus

What is the course of the thoracic aorta?

Starts at T4/T5/exits via aortic hiatus at T12.

What is the esophagus anterior to? What structure wraps around it?

Anterior to aorta, vagal plexus wraps around it.

What is the course of the thoracic duct? Where does it empty?

Enters at T12 aka the aortic hiatus, ascends on the right, then crosses to the left side of the body at T4/T5. Empties at left venous angle.

What happens if the thoracic duct is torn during esophageal surgery?

Chylothorax aka milky pleural fluid leaks

What is the purpose of the azygos vein?

Caval to caval bypass when the SVC or IVC is blocked.

What is the track of the azygous vein? Where does it drain?

Ascends on the right of vertebral bodies, arches over lung root at T4/T5, then drains into SVC

What are the main 3 esophageal sphincters and their locations?

Cervical (C6), thoracic, and diaphragmatic (T10).

Diaphragm apertures and their levels

T8 caval (IVC + R phrenic); T10 esophageal (esophagus + vagal trunks); T12 aortic (aorta + thoracic duct + azygos)

What does the T8 caval opening do?

Widens on inspiration

What does the T10 esophageal hiatus do?

Pinches on inspiration and resists reflux

Mnemonic for diaphragm openings "I 8 (ate) 10 EGGs AT 12"

IVC T8, Esophagus T10, Aorta T12

What is the origin of the thoracic duct?

Cisterna chyli in the abdomen (~L1-L2)

Thoracic duct drainage site is…

Junction of left subclavian & left internal jugular veins (left venous angle)

What does the thoracic duct drain?

Lymph from the entire body EXCEPT the right upper quadrant

What drains the right upper quadrant lymph?

The right lymphatic duct

Thoracic duct injury (e.g., esophageal surgery) causes what?

Chylothorax (milky chyle in pleural cavity)

Azygos vein: side and course

Ascends on the RIGHT of the vertebral column; arches over the right lung root at T4/5 into the SVC

Azygos vein: clinical importance

Caval-to-caval collateral (bridges IVC and SVC) — critical in SVC syndrome/obstruction

Greater splanchnic nerve: levels and ganglion

T5-T9 → celiac ganglion

Lesser splanchnic nerve: levels and ganglion

T10-T11 → aorticorenal / superior mesenteric ganglion

Least splanchnic nerve: level and ganglion

T12 → renal plexus

Why are splanchnic nerves an exception?

They pass THROUGH the sympathetic chain without synapsing and synapse in PREVERTEBRAL ganglia instead

Which structure increases surface area & creates turbulence to warm/humidify air?

The conchae (turbinates) — NOT the septum or cribriform plate

What forms the roof of the nasal cavity, and what nerve passes there?

Cribriform plate of the ethmoid; transmits the olfactory nerve (CN I)

What forms the nasal septum (medial wall)?

Ethmoid (perpendicular plate) superiorly + vomer inferiorly + septal cartilage (hyaline) anteriorly

Where is Kiesselbach's (Little's) area and why does it matter?

Anterior nasal septum; most common site of epistaxis (nosebleeds)

Which 4 arteries anastomose at Kiesselbach's area?

Anterior ethmoidal, Sphenopalatine, Greater palatine, Superior labial ("LEGS")

Where do the frontal, maxillary, and anterior ethmoid sinuses drain?

Middle meatus

Where does the posterior ethmoid sinus drain?

Superior meatus

Where does the sphenoid sinus drain?

Spheno-ethmoidal recess

Which pharynx region contains the pharyngeal tonsil (adenoids)?

Nasopharynx (above the soft palate)

Which pharynx region contains the palatine tonsils?

Oropharynx

Boundaries of the oropharynx

Soft palate to superior border of the epiglottis

Where does the laryngopharynx become the esophagus?

Inferior border of the cricoid cartilage, at C6

What opens into the nasopharynx (ear connection)?

The Eustachian (auditory) tube — link to otitis media

What nerve innervates the pharyngeal muscles?

Vagus nerve (CN X)

At what vertebral levels is the larynx located?

C3–C6

The 9 laryngeal cartilages: which are unpaired vs paired?

Unpaired: thyroid, cricoid, epiglottis. Paired: arytenoid, corniculate, cuneiform

Which laryngeal cartilage is the ONLY complete ring?

Cricoid cartilage (signet-ring shape, at C6)

Which laryngeal cartilage forms the Adam's apple?

Thyroid cartilage (laryngeal prominence)

Which laryngeal cartilages are elastic (not hyaline)?

Epiglottis, corniculate, cuneiform

True vocal folds vs false (vestibular) folds — function

True (vocal) = voice production; False (vestibular) = protective, minimal voice role

What is the rima glottidis?

The space between the true vocal folds

Recurrent laryngeal nerve: motor supply

All intrinsic laryngeal muscles EXCEPT cricothyroid

Recurrent laryngeal nerve: sensory supply

Sensory BELOW the vocal folds

Superior laryngeal nerve — internal branch

Sensory ABOVE the vocal folds

Superior laryngeal nerve — external branch

Motor to cricothyroid (the RLN exception)