Thoracic Anatomy, Diaphragm, Trachea, Esophagus, and Nerves Review

Comprehensive practice flashcards covering the anatomy, relations, blood/nerve supply, and clinical correlations of the diaphragm, thoracic nerves, trachea, thoracic duct, and esophagus based on lecture notes.

Why is the right dome (copula) of the diaphragm higher than the left dome?

The right dome is higher due to the underlying larger right lobe of the liver.

What are the sternal and costal origins of the diaphragm?

The sternal origin arises by 2 slips from the back of the xiphoid process, while the costal origin arises by 6 slips from the inner surfaces of the lower 6 costal cartilages and their ribs.

What anatomical structures give origin to the right and left crura of the diaphragm?

The right crus arises from the bodies of the upper 3 lumbar vertebrae, and the left crus arises from the bodies of the upper 2 lumbar vertebrae.

What connections are formed by the median, medial, and lateral arcuate ligaments of the diaphragm?

The median arcuate ligament connects the two crura across the midline in front of the abdominal aorta; the medial arcuate ligament connects each crus to the transverse process of the 1st lumbar vertebra ($L1$); and the lateral arcuate ligament connects the transverse process of $L1$ to the last rib.

What is the motor and sensory nerve supply of the diaphragm?

Motor supply is provided solely by the phrenic nerve ($C3, C4, C5$), which also supplies sensory fibers to its central part. Sensory supply to the peripheral part is provided by the lower 6 thoracic spinal nerves.

What are the anatomical locations and clinical significance of the Foramen of Morgagni and Foramen of Bochdalek?

The Foramen of Morgagni lies between the sternal and costal origins and transmits the superior epigastric vessels. The Foramen of Bochdalek (costo-vertebral triangle) lies between the costal and vertebral origins (mainly on the left side) and is the site where posterior diaphragmatic hernia can occur.

What are the vertebral levels, relative locations, and transmitted structures of the three major diaphragmatic openings?

1. Vena caval opening: level of $T8$, 1 inch to the right of midline in the central tendon; transmits IVC, right phrenic nerve, and lymphatics. 2. Esophageal opening: level of $T10$, 1 inch to the left of midline in the right crus; transmits esophagus, anterior and posterior gastric nerves (left and right vagi), and esophageal branches of left gastric vessels. 3. Aortic opening: level of $T12$, in the midline behind the median arcuate ligament; transmits aorta (to the left), thoracic duct (in-between), and azygos vein (to the right).

What is the thoracic course of the right phrenic nerve?

It descends on the right side of the right innominate vein, superior vena cava (SVC), right atrium (separated by pericardium), and inferior vena cava (IVC), passing in front of the root of the right lung before passing through the IVC opening of the diaphragm.

Which serous membranes receive sensory innervation from the phrenic nerve?

The phrenic nerve provides sensory supply to the 3Ps: pleura (mediastinal and medial half of diaphragmatic), pericardium, and peritoneum.

What are the inferior mediastinal courses and continuations of the left and right vagus nerves?

The left vagus passes behind the hilum of the left lung and continues as the anterior vagal trunk in front of the esophagus. The right vagus passes behind the hilum of the right lung and continues as the posterior vagal trunk behind the esophagus.

What are the dimensions, structure, and vertebral levels for the beginning and bifurcation of the trachea?

The trachea is $10-12\,\text{cm}$ long and $1.5-2\,\text{cm}$ wide, composed of 16–20 C-shaped hyaline cartilage rings. It begins at the lower border of the cricoid cartilage ($C6$) and ends at the sternal angle of Louis (disc between $T4$ and $T5$) by bifurcating into two main bronchi.

Which tracheal rings are covered anteriorly by the isthmus of the thyroid gland?

The 2nd, 3rd, and 4th tracheal rings.

How do the right and left main bronchi compare in terms of length, width, and angle relative to the midline?

The right bronchus is shorter ($1\,\text{inch}$), wider, forms a $25^\circ$ angle with the midline, and divides into 3 lobar bronchi. The left bronchus is longer ($2\,\text{inches}$), narrower, forms a $45^\circ$ angle with the midline, and divides into 2 lobar bronchi.

Why do inhaled foreign bodies more commonly pass into the right main bronchus?

Inhaled foreign material passes more commonly to the right bronchus because it is wider, shorter, and more in line with the trachea.

What is the carina, and what does its dilatation indicate?

The carina is an anteroposterior ridge at the tracheal bifurcation identified during endoscopic examination; it becomes dilated in cases of enlargement of the tracheobronchial lymph nodes.

Where is the recommended incision site for a tracheostomy, and why?

It should be performed in the midline just above the suprasternal notch to avoid injury to large blood vessels.

What are the dimensions, location, and tributaries of the cisterna chyli?

The cisterna chyli is $2\,\text{inches}$ long, located in front of the upper two lumbar vertebrae ($L1-L2$) behind the right crus of the diaphragm between the aorta and azygos vein. It receives one gastrointestinal lymph trunk and two lumbar lymph trunks.

What is the course and termination of the thoracic duct?

It begins at the upper border of $T12$ (upper end of cisterna chyli), enters the thorax via the aortic opening between the azygos vein and aorta, ascends behind the esophagus, inclines to the left at $T5$, and terminates in the left brachiocephalic vein at the root of the neck.

What regions of the body are drained by the thoracic duct versus the right lymphatic duct?

The thoracic duct drains the left side of the head and neck, left upper limb, left half of the thorax, and the entire body below the diaphragm. The right lymphatic duct drains the right side of the head and neck, right upper limb, and right half of the thorax.

What clinical manifestations occur in mediastinal syndrome and what compressive causes produce them?

Mediastinal syndrome causes dyspnea (compression of trachea), dysphagia (compression of esophagus), hoarseness of voice (compression of left recurrent laryngeal nerve), ischemia (compression of aorta), non-pitting edema (compression of thoracic duct), hiccups (compression of phrenic nerve), and Horner Syndrome (compression of sympathetic chain).

What are the length, starting level, diaphragmatic passage level, and termination level of the esophagus?

The esophagus is $25\,\text{cm}$ ($10\,\text{inches}$) long. It begins at $C6$ as a continuation of the pharynx, passes through the esophageal opening of the diaphragm at $T10$ (1 inch left of midline), and terminates at $T11$ (1 inch left of midline) at the gastro-esophageal junction.

At what distances from the upper incisor teeth are normal esophageal constrictions located during esophagoscopy?

Constrictions are located at $7\,\text{inches}$ (pharyngoesophageal junction), $9\,\text{inches}$ (arch of aorta), $11\,\text{inches}$ (left bronchus), and $17\,\text{inches}$ (gastroesophageal junction).

What forms the functional physiological sphincter at the lower end of the esophagus?

The right crus of the diaphragm.

What anatomical anastomosis leads to esophageal varices in portal hypertension?

Anastomosis between the left gastric vein (portal circulation) and tributaries of the azygos vein (systemic circulation).