Thorax

Internal thoracic artery descends into thorax 1 Internal thoracic artery descends into thorax 1.2cm lateral to edge of sternum, and ends at the sixth costal cartilage by dividing musculophrenic and superior epigastric arteries

Azygos vein Begins as continuation of right ascending lumbar vein Ascending along the right side of vertebral column Joins superior vena cava by aching above right lung root at level of T4 to T5 Receives right posterior intercostals and subcostal veins plus some of bronchial, esophageal and pericardial veins, and hemiazygos vein Tributaries – hemiazygos v. and accessory hemiazygos v., which receive most left posterior intercostals vein and left bronchial veins

The lymphatic drainage of thorax The lymphatic drainage of thoracic wall To axillary lymph nodes To parasternal lymph nodes (along internal thoracic vessels) To intercostals lymph nodes from deeper structures

lymph nodes of the thoracic contents lymph nodes of trachea, bronchi and lungs Pulmonary lymph nodes lie in the angles of bifurcation of branching lobar bronchi Bronchopulmonary hilar lymph nodes －lie in the hilus of the lung Tracheobronchial lymph nodes －situated above or below the bifurcation of trachea Paratracheal lymph nodes －along each side of the trachea

Anterior mediastinal lymph node lies anterior to the large blood vessels of thoracic cavity and pericardium; the efferents unite with those of paratracheal lymph nodes, to form the right and left bronchomediastinal trunks. The left bronchomediastinal trunk terminates in thoracic duct, and right in the right lymphtic duct Posterior mediastinal lymph nodes lie along the esophagus and thoracic aorta

Anterior branches of thoracic nerves Intercostal nerves - (anterior rami of T1- T11): runs forward inferiorly to intercostals vessels in costal groove of corresponding rib, between intercostals externi and intercostals interni; first six nerves are distributed within their intercostals space, lower five intercostals nerves leave anterior ends of their intercostals spaces to enter abdominal wall Subcostal nerve - (anterior ramus of T12): follows inferior border of T12 rib and passes into abdominal wall Distribution: distributed to intercostales and anterolateral abdominal muscles, skin of thoracic and abdominal wall, parietal pleura and peritoneum

The segmental innervation of anterior surface of trunk T2－sternal angle T4－ nipple T6－xiphoid process T8－costal arch T10－umbilicus T12－midpoint between umbilicus and symphysis pubis

Phrenic nerve Descends over scalenus anterior to enter thorax Accompanied by pericardiophrenic vessels and passes anterior to lung roots between mediastinal pleura and pericardium to supply motor and sensory innervation to diaphragm Sensory fibers supply to pleurae, pericardium and peritoneum of diaphragm; usually right phrenic nerve may be distributed on live, gallbladder and biliary system.

Left vagus nerve Enter thoracic inlet between left common carotid and left subclavian arteries, posterior to left brachiocephalic vein Crosses aortic arch where left recurrent laryngeal nerve branches off Passes posterior to left lung root Forms anterior esophageal plexus Forms anterior vagal trunk at esophageal hiatus where it leaves thorax and passes into abdominal cavity , then divides into anterior gastric and hepatic branches

Right vagus nerve Enter thoracic inlet on right side of trachea Travels downward posterior to right brachiocephalic vein and superior vena cava Passes posterior to right lung root Forms posterior esophageal plexus Forms posterior vagal trunk at esophageal hiatus where it leaves thorax and passes into abdominal cavity, then divides into posterior gastric and celiac branches

Recurrent laryngeal nerves Right one hooks around right subclavian artery, left one hooks aortic arch Both ascend in tracheo-esophageal groove Nerves enter larynx posterior to cricothyroid joint, the nerve is now called inferior laryngeal nerve Innervations: laryngeal mucosa below fissure of glottis , all laryngeal laryngeal muscles except cricothyroid Bronchial and esophageal branches

Thoracic sympathetic trunk Branches of sympathetic trunk to thoracic plexuses Greater splanchnic nerve - formed by preganglionic fibers from T5~T9 ganglia, and relay in celiac ganglion. Lesser splanchnic nerve - formed by preganglionic fibers from T10~T12 ganglia, and relay in aorticorenal ganglion. The postganglionic fibers supply the liver, spleen, kidney and alimentary tract as far as the left colic flexure.

Regional anatomy of thorax

Parts and regions of the thorax Boundaries Superior - jugular notch, sternoclavicular joint, superior border of clavicle, acromion, spinous processes of C7 Inferior - xiphoid process, costal arch, 12th and 11th ribs, vertebra T12 Regions Thoracic wall Thoracic cavity

Landmarks Jugular notch corresponds with The 2th thoracic vertebra in male, the 3th thoracic vertebra in female Sternal angle connects 2nd costal cartilage laterally corresponds with The lower border of 4th thoracic vertebra The bifurcation of trachea in the adult The beginning of aortic arch which ends posteriorly at the same level The esophagus is crossed by the left main bronchus

Ribs and intercostal spaces Costal arch Xiphoid process - xiphisternal junction lies opposite the body of the 9th thoracic vertebra Clavicle Inferior fossa of clavicle Coracoid process Ribs and intercostal spaces Costal arch Infrasternal angle Xiphocostal angle Papillae

Thoracic wall Skin Superficial fascia Deep fascia Thoracoepigastric v. Supraclavicular n. Anterior and lateral cutaneous branches of intercostal n. Deep fascia

Lymphatic drainage of breast Into pectoral ln. from lateral and central parts of breast Into apical and supraclavicular ln. from superior part of breast Into parasternal ln. from medial part of breast Into interpectoral ln. from deep part of breast The lymphatic capillaries of breast form an anastomosing network which is continuous across the midline with that of the opposite side and with that of the abdominal wall

Internal thoracic vessels Internal thoracic a.&v. Parasternal ln. Endothoracic fascia

The muscles of thorax Extrinsic muscles Intrinsic muscles Pectoralis major Pectoralis minor Serratus anterior Intrinsic muscles Intercostales externi Intercostales interni Intercostales intimi Transverses thoracis

Intercostales externi Origin: lower border of riⅡ) Insertion: upper border of rib below origin Action: elevate ribs adding in forced inspiration Replaced anteriorly by external intercostals membrane. Intercostales interni Origin: upper border of rib Insertion: lower border of rib above origin Action: depress ribs for forced expiration Replaced posteriorly by internal intercostals membrane.

Intercostal space Posterior intercostal v. Posterior intercostal a. Intercostal n.

Diaphragm Shape and position: dome-shaped between thorax and abdomen, consists of a peripheral muscular part and a central tendon Origin Sternal part: xiphoid process Costal part: lower six and costal cartilages Lumbar part: arises by two crura from upper 2-3 lumbar vertebrae Insertion: central tendon Weak areas: triangular spaces without muscular tissue Lumbocostal triangle: between costal and lumbar parts. Sternocostal triangle: between costal and sternal parts.

Openings in the diaphragm Aortic hiatus - lies anterior to the body of the 12th thoracic vertebra between the crura. It transmits the aorta, thoracic duct Esophageal hiatus - for esophagus and vagus nerves at level of T10. Vena cava foramen - for inferior vena cava, through central tendon at T8 level T8 T10 T12

Action: Contraction: the dome moving downward, increases the volume of thoracic cavity which results in inspiration, at the same time the intra-abdominal pressure is increased assists in defecation, vomiting or child birth. Relaxation: the dome returns to the former position, reduces the volume to the thoracic cavity, resulting in expiration.

The Mediastinum Concept all of organs between the left and right mediastinal pleurae is called mediastinum. It extends from the sternum in front to the vertebral column behind, and from the thoracic inlet above to the diaphragm below.

Subdivisions of mediastinum Superior mediastinum Inferior mediastinum Anterior mediastinum Middle mediastinum Posterior mediastinum

Left side of mediastnum Left subclavian a. Thoracic duct Left vagus n. Aortic arch Left recurrent n. Thoracic aorta Phrenic n. & pericardiacophrenic a. Sympathetic trunk Root of lung Pericardium Esophagus Greater splanchnic n

Right side of mediastnum Trachea Left vagus n. Superior vena cava Arch of azygos v. Phrenic n. & pericardiacophrenic a. Azygos v. Root of lung Sympathetic trunk Esophagus Pericardium Inferior vena cava

Superior mediastinum Locating - from inlet of thorax to plane extending from level of sternal angle anteriorly to lower border of T4 vertebra posterioly Contents Superficial layer Thymus Three veins Left brachiocephelic v. Right brachiocephelic v. Superior vena cava

Middle layer Aotic arch and its three branches Phrenic n. Vagus n.

Posterior layer Trachea Esophagus Thoracic duct

Relations of aortic arch Anteriorly and to the left - pleura, lung phrenic n., pericardiacophrenic vessels and vagus n. Posteriorly and to the right -trachea, esophagus, left recurrent n., thoracic duct, deep cardiac plexus Superiorly - its three branches, left brachiocephalic v. and thymus Inferiorly - pulmonary a., arterial ligament, left recurrent n., left principal bronchus and superficial cardiac plexus

Triangule of ductus arteriosus Bounded by phrenic n., left vagus n. and left pulmonary a. Contents－ arterial ligament , left recurrent n. and superficial cardiac plexuses

Inferior mediastinum Anterior mediastinum Location - posterior to body of sternum and attached costal cartilages, anterior to heart and pericardium Contents - fat, remnants of thymus gland, anterior mediastinal lymph nodes

Middle mediastinum Location - between anterior mediastinum and posterior mediastinum Contents: hart and pericardium, beginning or termination of great vessels, phrenic nerves, pericardiacophrenic vessels , lymph nodes,

Posterior mediastinum Location - posterior to heart and pericardium, anterior to vertebrae T5 - T12 Contents: esophagus, vagus n., thoracic aorta, azygos system of veins, thoracic duct, thoracic sympathetic trunk, posterior mediastinal lymph nodes

Relations of esophagus Anteriorly - trachea, bifurcation of trachea, left principal branchus, left recurrent n., right pulmonary a., anterior esophageal plexus, pericardium, left atrium, diaphragm

Posteriorly - posterior esophageal plexus, thoracic aorta, thoracic duct, azygos v., hemiazygos v.,accessory hemiazygos v., right posterior intercostal v.

Left - left common carotid a. , left subclavian a Left - left common carotid a., left subclavian a., aortic arch, thoracic aorta, superior part of thoracic duct Right - arch of azygos v.

Relations of thoracic aorta Anteriorly - left root of lung, pericardium and esophagus Posterior - hemiazygos v., accessory hemiazygos v., Right - azygos v. and thoracic duct Left - mediastinal pleura

Thoracic duct Begins in front of L1 as a dilated sac, the cisterna chyli, which formed by joining of left and right lumbar trunks and intestinal trunk Enter thoracic cavity by passing through the aortic hiatus of the diaphragm and ascends along on the front of the vertebral column, between thoracic aorta and azygos vein Travels upward, veering to the left at the level of T5 At the roof of the neck, it turns laterally and arches forwards and descends to enter the left venous angle

Just before termination, it receives the left jugular, subclavian and bronchomediastinal trunks Drains lymph from lower limbs, pelvic cavity, abdominal cavity, left side of thorax, and left side of the head, neck and left upper limb Right lymphatic duct Formed by union of right jugular, subclavian, and bronchomediastinal trunks Ends by entering the right venous angle Receives lymph from right half of head, neck, thorax and right upper limb

Mediastinal spaces Retrosternal space - lies beween sternum and endothoracic fascia Pretracheal space - lies within superior mediastinum, between trachea, bifurcation of trachea and aortic arch Retroesophagus space - lies within superior mediastinum, beween esophagus and endothoracic fascia

Thoracic aorta Continuation of aortic arch at lower border of T4 Courses downward on left side of, then in front of vertebral column Passes through aortic hiatus of diaphragm at level of T12 vertebra to enter abdominal cavity Main branches Parietal branches Nine pairs posterior intercostals arteries One pair subcostal artery For lower nine intercostals spaces and upper part of abdominal wall; superior phrenic arteries supply the superior surface of the diaphragm. Visceral branches Bronchial branches: one or two for each lung Esophageal branches Pericardial branches