M103 T1 L2 Flashcards
What is the division between the superior and inferior mediastinum?
the transverse thoracic plane
What are the boundaries of the superior mediastinum?
superiorly - the superior thoracic aperture / inlet inferiorly - the sternal angle anteriorly - the manubrium posteriorly - T1 to T4/5 laterally - mediastinal pleura
What are the contents of the superior mediastinum?
trachea & oesophagus
part of the thymus gland & the thoracic duct
phrenic and vagus nerves
arteries - branch of the aorta and branches
veins - brachiocephalic veins, superior vena cava
Why don’t we see the thymus gland in an adult corpse in dissection?
after puberty, the thymus gland atrophies and is replaced by fat
After T-lymphocytes are matured in the thymus gland, where do they go?
they drain into the surrounding area, from the parasternal, brachiocephalic and tracheobronchial nodes
What supplies the thymus?
the internal thoracic artery
What are the arteries in the superior mediastinum?
the arch of the aorta and its 3 branches
What are the three branches of the aortic arch? (BCS)
Brachiocephalic trunk
left Common Carotid artery
left Subclavian artery
What are the branches of the aorta?
ascending aorta
descending aorta
arch of aorta
What branches off the descending aorta?
posterior intercostal arteries
bronchial arteries
lumbar arteries
What is the function of the Ductus Arteriosus in embryology and in adults?
Important in fetal circulation allowing blood to bypass the immature lungs.
Closes at birth and remains in the adult as a ligamentous structure
What are the three features of the trachea?
Tube C-shaped cartilage rings
Trachealis muscle runs posteriorly
Runs from Larynx to Bronchi
From where does the phrenic nerve originate?
the anterior rami of spinal nerves C3-C5
What does the phrenic nerve supply?
the diaphragm
posterior phrenic nerve - supplies the back
anterior phrenic nerve - supplies everything else
Where does the phrenic nerve originate from?
the anterior rami of C3-5
Why is it hard to observe the phrenic nerve as it passes along the pericardium in a cadever?
it’s often fused with the pericardium and it’s hard to differentiate
Where does the vagus nerve enter the superior mediastinum in respect to the phrenic nerve?
medial to the phrenic nerve
What is unusual about how the vagus nerve travels and why is it like this?
it’s coming from the brain all the way down the neck into the thorax, then back up all the way up the neck and to the larynx
this happens because of the way the embryo develops with the aorta arches
Where does the vagus nerve supply (parasympathetically) and by which plexi? (COP)
most of the thorax via cardiac, oesophageal and pulmonary plexi
What does the anterior mediastinum contain?
fatty tissue (Thymus gland in children)
Internal thoracic artery
pericardial-sternal ligaments
parasternal lymph nodes and vessels
What are the boundaries of the anterior mediastinum?
anteriorly - the sternum
posteriorly - the pericardial sac
inferiorly - the diaphragm
superiorly - level T4/5
Under what circumstances does the heart begin to develop?
when angiogenic clusters form in the mesoderm
When does the heart start to beat?
day 22 - 23 bc the growing embryo can no longer satisfy its nutritional requirements by diffusion alone, so it needs an efficient method of acquiring oxygen and nutrients from the maternal blood
What regions is the newly formed heart tube divided into?
Sinus venosus
Primordial atrium
Primordial ventricle
Truncus arteriosus
What happens to the heart tube after day 23?
By day 23 its too long for the pericardial cavity and so starts to fold
What are the effects of folding?
the ventricles and outflow tracks positioned anteriorly
the atria and veins are positioned posteriorly
the septa then grow to divide the heart into 4 chambers
What is the lungs relationship with blood in embryology?
most of the blood is diverted away from the lungs, but they do still need a small amount of blood to develop.
How does oxygenated blood make it to the lungs in embryology?
reaches the foetus through the umbilical vein, which will then travel up through the abdomen where it will meet the inferior vena cava
In the heart of a foetus, how is oxy and deoxy blood mixed?
deoxy (body) and oxy (from the umbilical vein) mix in the inferior vena cava
When the mixed blood enters the right atrium, the blood has two possible directions to flow through
Where does mixed blood travel in a foetus heart?
right atrium
through the foramen ovale
into the left ventricle
aorta
Where does mixed blood from the right atrium flows through the ductus arteriosus in a foetus heart?
right atrium
right ventricle
here, almost all of the blood is shunted through the ductus arteriosus
into the arch of the aorta
Where is the mediastinum located?
middle septum, central compartment of the thorax and located between the left and right pleural cavities
How is the mediastinum divided?
Firstly into superior and inferior at level of sternal angle (junction of vertebrae T4//5)
Further divided into anterior, middle and posterior (the middle is the heart and pericardium)
Where does the thymus gland drain lymph from?
Lymph drains through from parasternal, brachiocephalic and tracheobronchial nodes
Which mediastinum areas does the thoracic duct travel through?
superior mediastinum
posterior mediastinum
What is the longest lymphatic vessel?
the thoracic duct
Where does the thoracic duct originate from?
from beneath the diaphragm
Where does the phrenic nerve travel?
travels through the neck
enters into the superior mediastinum
passes anterior to the main bronchi, along the pericardium
Where does the phrenic nerve travel to?
eventually reaches the diaphragm
Where does the thoracic duct travel?
pierces through the diaphragm
up through the thorax (between the vertebral bodies and the oesophagus)
drains into the venous system at the venous angle
Where does the vagus nerve branch as it travels down?
one that loops under the aorta
Where is the right recurrent laryngeal nerve located?
arises from in front of the subclavian artery
ascends alongside the trachea, posterior to the common carotid artery
What nerve is the right recurrent laryngeal nerve a branch of?
the vagus nerve
What is supplied by the vagus nerve?
the larynx and the vocal cord
What happens to angiogenic clusters forming in the mesoderm?
they canalise to form early blood vessels
two large blood vessels known as the heart tubes form in the cardiogenic area
What happens to the paired heart tubes?
they grow and fuse at approximately day 21
What is the difference between the foramen and fossa?
for - a hole through which nerves and blood vessels pass
fos - a shallow depression in the bone surface
What are the motor functions of the phrenic nerve?
innervates the diaphragm
What structures have their sensory functions innervated by the phrenic nerve?
the central part of the diaphragm
pericardium
the mediastinal parietal pleura
the diaphragmatic parietal pleura
