mediastinum Flashcards
how is the mediastinum divided up?
superior and inferior (to an imaginary line through the sternal angle)
Inferior divided into anterior, middle and posterior
what are the borders of the superior mediastinum?
superior - superior thoracic aperture lateral - pleura of the lungs anterior - sternum posterior - vertebral bodies T1-T4 inferior - continuous with inferior mediastinum
What is in the superior mediastinum?
SVC, left and right brachiocephalic veins Pulmonary artery aorta, brachiocephalic trunk, left common carotid and left subclavian trachea oesophagus thoracic duct vagus and phrenic nerve infrahyoid muscles sympathetic trunk
what are the borders of the middle mediastinum?
Anterior: Anterior margin of the pericardium.
Posterior: Posterior border of the pericardium.
Laterally: Mediastinal pleura of the lungs.
Superiorly: Imaginary line extending between the sternal angle (the angle formed by the junction of the sternal body and manubrium) and the T4 vertebrae.
Inferiorly: Superior surface of the diaphragm.
what are the contents of the middle mediastinum?
heart ascendign aorta SVC Pulmonary trunk phrenic nerve cardiac plexus hilar lymph nodes
what nerves contribute to the cardiac plexus?
vagus nerve - parasympathetics
T1-T4 spinal cord - sympathetics
what are the borders of the posterior mediastinum?
Lateral: Mediastinal pleura (part of the parietal pleural membrane).
Anterior: Pericardium.
Posterior: T5-T12 vertebrae.
Roof: Imaginary line extending between the sternal angle (the angle formed by the junction of the sternal body and manubrium) and the T4 vertebrae.
Floor: Diaphragm.
what are the contents of the posterior mediastinum?
oesophagus thoracic duct thoracic aorta IVC sympathetic trunk azygous system
what are the borders of the anterior mediastinum?
Lateral borders: Mediastinal pleura (part of the parietal pleural membrane).
Anterior border: Body of the sternum and the transversus thoracis muscles.
Posterior border: Pericardium.
Roof: Continuous with the superior mediastinum at the level of the sternal angle.
Floor: Diaphragm.
what are the contents of the anterior mediastinum?
sternopericardial ligaments and thymus (in children)
where is the fibrous pericardium attached to?
diaphragm
sternum
tunica adventitia of great vessels
what is the transverse pericardial sinus?
between arteries and veins entering/leaving the superior heart
anterior: pulmonary artery and aorta
posterior: SVC
what are the layers of the pericardium?
fibrous
parietal and visceral pericardium known as serous pericardium
what are aortic sinuses are where are they?
where the coronary arteries branch from the aorta
just distal to aortic valve behind the valve leaflets - when the heart enters diastole and the aortic valve closes, the backflow of blood into the leaflets is sucked into the coronary arteries as the pressure is lower in them during diastole
describe the path of the left coronary artery
branches from the left of the aorta and travels posterior to the pulmonary trunk, emerging in the left coronary sulcus
what are the branches of the LCA
LAD
Left marginal
left circumflex
may contribute to PIV artery if left dominant
what are the branches of the RCA
Right marginal, PIV artery
describe the path of the right coronary artery
travels in the right coronary sulcus inferiorly between the right atria and rigth ventricle on the anterior surface of the heart before giving off its marginal branch which travels medially along the inferior surface of the right ventricle.
the RCA then travels posteriorly to usually give off the posterior interventricular artery which descends in the posterior interventricular groove
where do diagonal coronary artery branches branch from?
LAD - descend diagonally over the left ventricle
what does the LAD supply?
what does the LCx supply?
what does the left marginal supply?
what does the right coronary artery supply
what does the right marginal artery supply?
what does the posterior interventricular artery supply?
where does the venous drainage of the heart drain into?
coronary sinus in right atrium
where does the coronary sinus run?
continuation of great cardiac vein - runs along inferior border of left atrium towards right atrium
what artery does the middle cardiac vein run with?
PIV artery in posterior interventricular groove ascending from the apex
what artery does the great cardiac vein run with?
LAD in anterior interventricular groove
what artery does the small cardiac vein run with?
some sources say: right marginal branch along inferior anterior surface then travels posteriorly via the right coronary sulcus with the RCA to the coronary sinus
some say just travels with the RCA in the coronary sulcus
where are the anterior cardiac veins and what is special about them?
They run from the right av groove inferior-medially over the anterior wall of the right ventricle
drain directly into the right atrium
where does the left marginal artery usually arise from?
LCx
what is the cristae terminalis? where is it?
in the wall of the right atria, anterior lateral
it is a muscular ridge that runs in the vertical plane
it is the boundary between the:
Sinus venarum – located posterior to the crista terminalis. This part receives blood from the superior and inferior vena cavae. It has smooth walls and is derived from the embryonic sinus venosus.
Atrium proper – located anterior to the crista terminalis, and includes the right auricle. It is derived from the primitive atrium, and has rough, muscular walls formed by pectinate muscles.
where is the sinus venarum?
part of the right atria posterior to the cristae terminalis
originates from the sinus venosus embryologically
what is the atrium proper?
area of right atrium anterior to the cristae terminalis - derived from the primitive atrium
compare the sinus venarum and artrium proper of the right atrium
atrium proper has trabeculated wall - pectinate muscle
sinus venarum has smooth walls
what is the ‘eustation valve’
ridge on the floor of the right atria - embryological remenant - sometimes considered as a IVC valve
where does the coronary sinus drain
right atrium - medial inferior aspect
where is the fossa ovalis and its limbus (border)
inter-atrial septum
what is the thesbian valve
valve of the coronary sinus
what is the tendon of torado
tendon linking the thesbian and eustation ridges
label the diagram
where is the av node?
interatrial spetum superior to the coronary sinus
where is the SA node
superior aspect of cristae terminalis
junction of atria and SVC
what are trabeculae carne? what are the types?
irregular muscular elevations
Ridges – attached along their entire length on one side to form ridges along the interior surface of the ventricle.
Bridges – attached to the ventricle at both ends, but free in the middle. The most important example of this type is the moderator band, which spans between the interventricular septum and the anterior wall of the right ventricle. It has an important conductive function, containing the right bundle branches.
Pillars (papillary muscles) – anchored by their base to the ventricles. Their apices are attached to fibrous cords (chordae tendineae), which are in turn attached to the three tricuspid valve cusps in the RV. By contracting, the papillary muscles ‘pull’ on the chordae tendineae to prevent prolapse of the valve leaflets during ventricular systole.
where is the moderator band (aka septomarginal trabeculae)?
RV - IV septum to anterior RV wall - contains bundle of His
what is the function of chordae tendinae?
papillary muscles contract during systole
chordae tendinae attached to AV valve leaflets
pull on the leaflets preventing regurge
where is the conus arteriosus?
superior RV around pulmonary valve
what veins join to form the azygous vein?
right lumbar and right subcostal vein at level of T12
where is the azygous vein?
runs up right side of vertebral bodies in posterior mediastinum
drains into SVC at level of T4
what tributaries are there to the azygous vein?
hemiazygous - T8
accessory hemiazygous - T7
intercostal veins
what are the 3 structures of the circulatory system left from fetal circulation?
ligamentum arteriosum
ligamentum venosum
fossa ovalis
where is the ductus arteriosus?
between the aorta and left pulmonary artery
describe the path of the umbilical vein
drains from placenta via umbilical cord to the abdomen, travels along the inner surface of the anterior abdominal wall within the falciform ligament to drain into the portal vein and ductus venosus
what is the name of the remnant of the umbillical vein
ligamentum teres (withing falciform ligament)
describe the flow of blood through a fetus
blood is oxygenated at the placenta
travels via the umbilical vein to the portal vein then vis ductus venosus to the IVC
enters RA then shunted across to LA via foramen ovale
passes into LV (bypassing the lungs) then into aorta
any blood that did pass through RV to PA will be shunted back across to the aorta via the ductus arteriosus
systemic circulation
deoxygenated blood leaves the fetus via the umbillical arteries from the internal iliac arteries
what are the medial umbilical ligaments remnants of?
umbilical arteries
where does the thoracic duct arise
cisterna chyli
what diaphragmatic hiatus does the thoracic duct pass through?
aortic
where does the thoracic duct run?
left of oesophagus, ascend thorax to superior thoracic apeture where it arches over the subclavian artery to drain into the subclavian vein (as it joins the internal jugular vein)
where does the external jugular vein drain into?
subclavian vein
what forms the braceocephalic vein?
internbal jugular and subclavian
which side is the bracheocephalic artery on ?
right
what is the function of the splanchnic nerves?
autonomic innervation of the gut and pelvis
what are the roots of the greater splanchnic nerve and what does it supply?
T5-T9
foregut and adrenal medulla
what are the roots of the lesser splanchnic nerve and its function?
T10-11 sympathetic chain
midgut
what are the roots and function of the least splanchnic nerve?
T12 (and sometimes T11) sympathetic chain
kidneys
what splanchnics supply the hindgut?
lumbar splanchnics
