Thoracic Cavity and Mediastinum Flashcards
What are the 3 parts of the sternum
Manubrium, body, xipoid process
What is the sternal angle
junction of the manubium and steral body
most reliable surface landmark of chest
Where is the sternal angle located relatively
2nd costal cartilage
What articulates with the manubrium
clavicle and 1st costal cartilage
Which ribs are true and why
Ribs 1-7
articulate diretly with the sternum
Which ribs are false and why
Ribs 8-10
articulate with costal cartilages just above them
Which are the floating ribs and where do they end
Ribs 11-12
Terminate in abdominal musculature
How do upper thoracic vertebraes transverse processes articulate with ribs
Have cup shamed facets which allow rotational movements
How do lower thoracic vertebraes transverse processes articulate with ribs
Have flat processes allowing gliding of tubercles
What makes up the boundaries of the thoracic inlet
Anteriorly: manubrium
Latteraly: first pair of ribs
Posteriorly: first thoracic vertebra
What makes up the boundaries of the thoracic outlet
Anteriorly: xiphoid process
Laterally: costal arch from costal cartilages 7to 10 and twelfth rib
Posteriorly: 12th vertetbrae
What is the superficial later of the muscles of the thoracic wall and how do they run
External intercostals: run inferiorly and medialy and extend from tubercles to costal cartilage
What is the middle later of the muscles of the thoracic wall and how do they run
Internal intercostals run at right angles to the superficial layers and extend from sternum to angels of the ribs
What is the Deep later of the muscles of the thoracic wall and how do they run
Represented by transversus thoracis and innermost intercostal
Transversus thoracis: 4 or 5 slips of muscle from posterior surface of lower sternum to superior costal cartilages
Innermost: deep to internal and on most lateral portion of intercostal space (those that span 2 or more intercostal spaces are called subcostal
What is the converrgence in the center of the diaphram called
central tendon or aponeurosis
Where do the nerves and vessels of the thoracic wall run and what is their order
Run between middle and deep layers along costal groove (inferior border
Vein superior to artery that is superior to nerve
What innervates the skin and muscles of the thoracic WALL
anterior rami of thoracic spinal nerves
T1-T11: intercostal
t12: Subcostal
What muscle in the thoracic area do the costal nerves not motor innervate
Diaphram (phrenic)
They do give sensory information to peripheral area of diaphram
Where do posterior intercostal arterires arise
first 2 off costocervical
rest off thoracic aorta
Where do the anterior intercostal arteries arise
internal thoracic artery or the musculophrenic terminal branch of the internal thoracic
Where do the anterior and posterior intercostal veins drain
Posterior: azygos venous system
(right side azygous)
(left side top 1/3 superior vena cava middle 1/3 accessory hemizygous lower 1.3 hemizygous)
Anterior: internal thoracic veins
What changes in space cause a change in pressure of thoracic cavity
Superoinferior change: Diaphram contraction (primary means of increasing thoracic capacity)
anteroposterior change: elevation of the upper 6 ribs by the intercostal muscles ( caused by articulation of tubercles sternum pused forward)
lateral change: caused by elevation of lower ribs which swing up and out laterally`
What maintains intercostal spacing
Contraction of intercostal muscles
How is the mediastinum divided
Superior: continuous with retropharyngeal space and ends at sternal angle and disk between t4t5
Inferior: Anterior, Middle, Posterior
What 7 things contained in the Superior Mediastinum
Thymus: (often just fat pad in adults)
Brachiocephalic veins:
Superior vena cava:
Arch of the aorta:
Vagus and Phrenic nerves:
Trachea:
Esophagus:
What is contained in anterior mediastiunum
In front of pericardial cavity
Internal thoracic vessels: descend posterior to costal cartilages and slightly lateral to sterunum
In children: inferior part of thymus
What 4 things are in the middle mediastiunum
Pericardium
Heart
Roots of great vessels
Phrenic nerve and pericardiacophrenic vessels run between pericardium and meiastinal pleurae
What 7 things are in the posterior mediastiunum
Behind pericardial cavity
Descending aorta:initially left then centers
Esophagus: initially middline and shifts left, anterior to descending aorta before passing diaphram (t10)
Azygous vein:
Acessory Hemiazygous veins:
Thoracic duct: acscend through aortic haitus pass between azzygous vein and descending aorta
Vagus nerves: Posterior to root of lungs (reforms clost to diaphram to make anterior and posterior vagal trunks
Splanchnic nerves: Preganglionic sympathetic fibers pass through crura of diahpram
Why arent inferior vena cava and sypathetic trunks part of mediastinum list
Inferior vena cave immediately enters heart and sympathetic trunks are not between mediastinal pleurae
What vertebrae level do the, Aorta, Esophagus, and inferior vena cava pass through the diaphram
Aorta: t12: through aortic Haitus to become abdominal aorta
Esophagus: shifts to left and enters at T10
Inferior vena cava: Enters at T8
What is the most likely fracture site for a rib crushing injury
Sternal angle
What ribs are most commonly fractured
Middle ribs
Where is a needle placed in thoracentesis or anestisia
On superior border of rib (to avoid nerves arteries and veins)
Why is early diagnosis ssentiol in high speed decelerating injuries
likely trauma to superior mediastinum (ie large vessels)
what would provide collateral cirucation in the event of carctation of the descending aorta
Anastomosation of anterior and posterior intercostal arteries
