Breathing

Vital Organ Protection

Conduit

Heart

Lungs

Great Vessels

Abdominal viscera due to domed shape of diaphragm

Liver under right dome of diaphragm

Stomach/Spleen under left

Posterior aspect of superior pole of kidneys anterior to rib 7 on right and anterior to ribs 6/7 on left

***kidneys higher on left**

Esophagus, Vagus nerves, thoracic duct between abdomen and neck

Phrenic nerves from neck to diaphragm

Trachea, Thoracic Aorta, Superior Vena Cava

-Irregularly shaped cylinder with an open narrow opening (superior thoracic aperature) superiorly and a large opening (inferior thoracic aperature) closed by the diaphagm

-Muscoskeletal wall is flexible and consists of segmentally arragned vertebrae/ribs/muscles/sternum

Posteriorly: twelve thoracic vertebrae and intervening intervetbral discs

Laterally: 12 ribs and three layers of flat intercostal muscles

Anteriorly: sternum (manubrium, body, xiphoid process)

The sternal manubrium angled posteriorly on sternal body at the manubriosternal joint

***major surface landmark to physically examine thorax***

All ribs artiulate with thoracic vertebrae posteriorly

Ribs II to IX have three articulations with vertebral column: body of own vertebrae and vertebrae above, transverse process of own vertebrae

Costal cartilages of ribs I to VII articulate with the sternum

Costal cartilage of ribs VIII to X articulate with inferior margins of costal cartilages above them

• Bounded skeletal elements -> vertebra T1 posteriorly, medial margin of rib I laterally, manubrium anteriorly
• Plane is on an oblique angle with the superior margin of manubrium between TII/TIII
• Structures from upper limbs pass over rib I and suprior part of pleural cavity as they enter/leave mediastinum
• Stuctures between neck and head pass vertically through aperature

• Surrounded by bone, cartliage, ligaments -> body of vertebra TXII posteriorly, rib XII and distal end of rib XI posterolaterally, distal cartilaginous ends of ribs VII to X (costal margin) anterolaterally, xiphoid process anteriorly
• Closed by the diaphragm
• Posterior margin inferior to anterior margin
• Structures pierce the diaphgram or pass posteriorly

• Bounded by sternum anteriorly, thoracic vertebra posteriorly, superior thoracic aperture superiorly, inferior thoracic aperture inferiorly
• Inferior and superior mediastinum separated by transverse plan through sternal angle intervetbral disc between TIV/TV
• Inferior mediastinum separated into anterior, middle, and posterior mediastinum
• Pericardium+heart = middle mediastinum

Parietal Pleura: lining of walls of cavity

Visceral Pleura: pleural lining reflected from mediastinum and onto lung surface

• Superior thoracic aperture opens directly into root of neck
• Superior aspect of each pleural cavity extends about 2-3 cm above rib I and costal cartilage

• Gateway to upper limb on each side of superior thoraic aperture
• Bounded by superior margin of the scapula posteriorly, clavicle anteriorly, and lateral margin of rib I medially (base)
• Lateral apex of triangle formed by medial margin of caracoid process (extends anteriorly from superior margin of scapula)

Inferior vena cava: pierces central tendon of diaphgram to enter right side of mediastinum near TVIII

Esophagus: pierces muscular part of diaphragm to enter abdomen just to left of midline at TX

Aorta: passes posteriorly at midline at TXII

Numerous structures pass through or posteriorly through diaphragm

• Branches from internal thoracic arteries perforate anterior chest wall on each side of sternum at second, third, fourth intercostal space to supply anteromedial parts of each breast
• Medial lymphatic vessels accompany perforating arteries and drain to parasternal nodes
• Vessel/lymphatics of lateral parts of breast emerge from/drain into axillary region

• Marks possition of anterior articulation of rib II (sternal angle)
• Separates superior/inferior mediastinum
• Where aortic arch begins and ends
• Where inferior vena cava penetrates pericardium to enter heart
• Where trachea bifurcates to right and left main bronchi
• Superior limit of pulmonary trunk

Left brachiocephalic vein:drains left side of head/neck/upper limb/upper thoracic wall and crosses midline behind manubrium to superior vena cava

Hemiazygos and accessory hemiazygous vein: drain posterior and lateral parts of left thoracic wall and pass anterior to vertebral bodies and flow into azygos evin on right side which empties into superior vena cava

Thoracic aorta: in posterior mediastinum

Internal thoracic arteries: derive from braciocephalic arteries

Posterior and anterior vessels branch and pass laterally around wall mainly along inferior margin

Anterior rami of thoracic spinal nerves that run with vessels along inferior margin of each rib

Innervate wall, related parietal pleura, and associated skin

T1: Upper limbs

T2: Highest thoracic dermatome and also upper limbs

T6: innervates skin over xiphoid process

T7-T12: follow contours of ribs onto anterior abdominal wall

• Rib posterior attachment superior to anterior attachement --> anterior thoracic walls elevates and moves forward since posterior attachment fixed
• Middle part of ribs inferior to two ends --> ribs elevate and expands wall laterally
• Diaphragm expands and expands volume vertically

Two phrenic nerves that branch off the cervical plexus of the neck from anterior rami of cervical nerves C3, C4, and C5

Mainly from C4