Lecture 19

Question 1

Mediastinum

Answer 1

Space between lungs; consists of superior mediastinum (subdivided into retrosternal and prevertebral) and inferior mediastinum (subdivided into anterior, middle, posterior)

Question 2

Retrosternal Subdivision of Superior Mediastinum

Answer 2

Contains great vessels and branches and the thymus

Question 3

Prevertebral Subdivision of Superior Mediastinum

Answer 3

Contains trachea, esophagus, thoracic duct, sympathetic trunks, and Vagus Nerves

Question 4

Anterior Subdivision of Inferior Mediastinum

Answer 4

Contains thymus, fat, and lymph nodes

Question 5

Middle Subdivision of Inferior Mediastinum

Answer 5

Contains pericardium, phrenic Nerves, pericardiacophrenic artery, and heart and great vessels

Question 6

Posterior Subdivision of Inferior Mediastinum

Answer 6

Contains esophagus, thoracic duct, aorta and branches, vagus nerves, sympathetic trunks, and azygos system of veins

Question 7

Thymus

Answer 7

Located behind manubrium, covered by pleura of the lungs; blood supply by anterior mediastinal arteries from internal thoracic artery and Inferior thyroid arteries from subclavian artery; venous drainage into left brachiocephalic vein; innervated by parasympathetic vagus nerves and sympathetic cardiac sympathetic plexus

Question 8

Pericardium

Answer 8

Encloses heart, consists of arterial and venous mesocardium; also has transverse sinus, which is the space between arterial and venous mesocardium, and the oblique sinus, which is the space between right and left pulmonary veins; blood supply by pericardial and pericardiacophrenic arteries and musculophrenic arteries; innervated by CN X, phrenic nerve, sympathetic trunk

Question 9

Parietal (Serous) Pericardium

Answer 9

Fused to fibrous pericardium

Question 10

Fibrous Pericardium

Answer 10

Fused with central tendon of diaphragm

Question 11

Pericardiacophrenic Ligament

Answer 11

Fused with sternum

Question 12

Esophagus

Answer 12

Runs from base of neck to left of the midline to midline at the level of the aortic arch to left of the midline as it passes through the diaphragm; located behind the trachea, in front of vertebral column, to the right of the thoracic aorta and passes through diaphragm at T10 level; blood supply by bronchial, left gastric, left Inferior phrenic arteries and the thoracic aorta; innervated by esophageal plexus (continuation of posterior pulmonary plexus and formed by left and right vagus nerves)

Question 13

What innervates upper third of esophagus?

Answer 13

This is voluntary muscle and is innervated by recurrent laryngeal nerve

Question 14

What innervates the lower two-thirds of the esophagus?

Answer 14

This is involuntary muscle and is innervated by vagus sympathetic chain

Question 15

Thoracic Aorta

Answer 15

Continuation of aortic arch, begins at lower border of T4 (stern also angle) and lies left of midline; ends at diaphragm T12 and pierces diaphragm and continues as abdominal aorta

Question 16

Branches of Thoracic Aorta

Answer 16

Pericardial branches to posterior pericardium, two bronchial branches to left of bronchus, small superior (10%) and large Inferior (90%) esophageal branches, branch to posterior mediastinum, nine pairs of intercostal arteries, one pair subcostal arteries, and superior phrenic arteries to superior surface of diaphragm

Question 17

Azygos Vein

Answer 17

Formed below level of diaphragm by union of right ascending lumbar vein and right subcostal vein; ascends along right side of thoracic vertebral column, arches over root of right lung and enters superior vena cava; tributaries from right intercostal veins (5-11), superior intercostal vein (drains intercostal spaces 2-4), hemiazygos vein, and accessory hemiazygos vein

Question 18

Hemiazygos Vein

Answer 18

Formed below level of diaphragm by union of left ascending lumbar vein and left subcostal vein; pierces diaphragm, ascends along left side of vertebral bodies to level of T9 and crosses vertebral body and empties into azygos vein

Question 19

Accessory Hemiazygos Vein

Answer 19

Runs left side of upper thoracic vertebral bodies, receives blood from superior intercostal vein and from left intercostal veins 4-8, crosses vertebral body and empties into azygos vein

Question 20

Parasternal Nodes

Answer 20

Lie behind sternum along course of internal thoracic artery, receives lymph from thoracic wall, upper anterior abdominal wall, and diaphragm; also receives significant amount of lymph from mammary gland and dumps into parasternal lymph channel

Question 21

Posterior Intercostal Nodes

Answer 21

Lie behind posterior intercostal space between heads of ribs, receives lymph from thoracic wall and paravertebral regions; drains into thoracic duct from left and lower right and drains into right lymphatic duct from upper right

Question 22

Diaphragmatic Nodes

Answer 22

Lie on upper surface of diaphragm, receives lymph from diaphragm, pericardium, and upper surface of liver; drains to parasternal and posterior mediastinal nodes

Question 23

Posterior Mediastinal Nodes

Answer 23

Lie along esophagus and descending thoracic aorta

Question 24

Brachiocephalic Nodes

Answer 24

Lie along brachiocephalic veins

Question 25

Lymph Trunks

Answer 25

Bronchiomediastinal lymph trunks: receive lymph from posterior mediastinal nodes, brachiocephalic nodes, tracheobronchial nodes, parasternal nodes

Question 26

Left Thoracic Duct

Answer 26

Arises from cisterns chili at union of right and left lumbar trunks; begins on the front of vertebral body T12 or L1, runs up through the thorax along the front of the vertebral column; at first it lies to the right of midline, but moved over to the left side when it reaches level of T5; receives most of lymph from body below diaphragm, drains left side of thoracic cavity and part of right, receives lymph from left internal jugular lymph trunk, left subclavian lymph trunk, and empties into venous system at junction of left internal jugular vein and left subclavian vein

Question 27

Right Thoracic Duct

Answer 27

Drains upper right thoracic cavity, igniting upper extremity, and right side of head and neck; empties into venous system at junction of right jugular vein and right subclavian vein

Question 28

50 Tracheobronchial Lymph Nodes

Answer 28

Some of the largest lymph nodes in the body; include paratracheal, superior tracheobronchial, inferior tracheobronchial, bronchopulmonary, and pulmonary

Question 29

Thoracic Sympathetic Chain

Answer 29

Lies against neck of ribs and costovertebral junctions; 12 Thoracic Ganglia pairs: first one often fused with inferior cervical ganglia (referred to as stellate ganglion collectively); cervical ganglia divided into superior, middle, and inferior

Question 30

Which spinal cord levels are responsible for the preganglionic sympathetic supply to the thoracic viscera?

Answer 30

T1-5

Question 31

Where do the postganglionics of the thoracic cavity come from?

Answer 31

Superior, middle, and inferior cervical ganglia; T1-5 are paravertebral ganglia; exit the chain as direct fibers and travel downwards to enter the thorax as cardiopulmonary splanchnic nerves

Question 32

Splanchnic Nerves

Answer 32

Composed of pregnaglionic fibers and visceral sensory fibers and supply abdominal viscera; synapse in prevertebral ganglia; greater is T5-9 and synapses in celiac ganglion; lesser is T10-11 and synapses in the superior mesenteric ganglion; least is T12 and synapses in the aorticorenal ganglion

Question 33

Vagus Nerve

Answer 33

CN X; major parasympathetic supply to thoracic and abdominal viscera; runs parallel to esophagus (innervates esophagus), passes posterior to root of lung on each side, pierces diaphragm with esophagus and becomes gastric nerve, supplies viscera in thoracic cavity; right vagus nerve becomes posterior vagus trunk and left vagus nerve becomes anterior vagus trunk

Question 34

Branches of Vagi

Answer 34

Cardiac branches to cardiac plexus, pulmonary branches to pulmonary plexus, esophageal branches to esophageal plexus, left recurrent laryngeal nerve from left vagus and right recurrent laryngeal from right vagus

Question 35

Phrenic Nerve

Answer 35

Arises in neck from ventral rami of C3-5 with C4 being major contributor; passes anterior to pulmonary root on each side (only nerve to do so); sole motor innervation to diaphragm; sensory fibers to pericardium, mediastinal pleura, and pleura and peritoneal coverings of diaphragm; pain via phrenic nerves usually referred to base of neck and tip of shoulder; accompanied by pericardiacophrenic arteries (branches of internal thoracic arteries)

Question 36

Respiratory Diaphragm

Answer 36

Muscular sheet with an inferior and a superior fascia; superior fascia = parietal thoracic fascia and the inferior fascia = transversalis fascia; seperates thorax and abdomen and in moderate expiration, reaches level of 5th rib on right side and 5th IC space on left

Question 37

Origins and Attachments of Respiratory Diaphragm

Answer 37

Origins: Sternal = Xiphoid Process Costal = Lower 6 ribs and cartilages Lumbar = Lumbar vertebrae and crura Attachments: Ribs, TV12, distal end of sternum, central tendon (Y shaped attached to lumbar vertebrae via crura, pulls radiating fibers of the diaphragm together to form a dome-shaped muscle; right side is largest part, left is smallest part)

Question 38

Functions of Respiratory Diaphragm

Answer 38

Contraction flattens the muscle and increases the thoracic volume, creates a negative pressure in the thoracic cavity and a positive pressure in the abdominal cavity; floating ribs help to counteract the action of the diaphragm; if the abdominal cavity were surrounded by a bony cage, it would NOT be able to compensate for the increase in pressure

Question 39

Openings in the Diaphragm and Structures that run through them

Answer 39

T8 Caval Foramen: inferior vena cava, accompanied by right phrenic nerve T10 Esophageal Hiatus: esophagus, accompanied by vagus nerve T12 Aortic Hiatus: aorta, accompanied by greater splanchnic nerve

Question 40

Nerve and Arterial Supply to Diaphragm

Answer 40

``` Nerve: Phrenic nerve (C3-5) ``` Arterial: Superior Aspect - pericardiacophrenic artery from internal thoracic, musculophrenic artery from internal thoracic, and superior phrenic artery from aorta Inferior Aspect - inferior phrenic artery from aorta

Question 41

Crura of Diaphragm

Answer 41

Forms muscular pillars, originate from lumbar vertebrae; right from L3, swings left and forms a weak sphincter around the esophagus; left from L2

Question 42

Arcuate of Diaphragm

Answer 42

Median, around aortic opening, bridges proximal ends of crura; medial (lumbocostal arches) from deep fascia of psoas major muscle from transverse process to body of L1; lateral (lumbocostal arches) from deep fascia of quadratus lumborum muscle from transverse processes of L1 to rib 12