Superior, Posterior, Anterior Mediastinum Flashcards
what space is the superior mediastinum?
between thoracic inlet and level of sternal angle (T4-5)
what are the subspaces of the inferior mediastinum?
anterior, posterior
what space is the anterior mediastinum?
between sternum/transversus thoracis muscles and pericardial sac
what occupies the anterior mediastinum in early childhood?
thymus gland
the anterior mediastinum is filled with what structures?
loose connective tissue, fat
what vessels branch from the arch of the aorta?
brachiocephalic trunk, left common carotid artery, left subclavian artery
the superior mediastinum is filled with what structures?
thymus, great vessels, nerves, trachea, esophagus, thoracic duct, prevertebral muscles
what two vessels drain blood into the superior vena cava?
left brachiocephalic vein, right brachiocephalic vein
what nerves are found in the superior mediastinum?
phrenic nerve, left vagus nerve, right vagus nerve, cardiac plexus
what are the branches of the right and left vagus nerve in the superior mediastinum?
right and left recurrent laryngeal nerves
what structures are in the posterior mediastinum?
thoracic aorta, thoracic duct, lymph nodes, esophagus, esophageal plexus, trachea
what level does the trachea bifurcate at?
sternal angle
what are branches of the thoracic aorta?
costocervical trunk, coronary artery, bronchial artery, esophageal artery, posterior intercostal artery, subcostal artery, pericardial artery, mediastinal artery
what are two branches of the costocervical trunk?
deep cervical artery, superior intercostal artery
what nerves are found in the posterior mediastinum?
thoracic sympathetic trunk, lower thoracic splanchnic nerves
what is unique about the lower thoracic splanchnic nerves?
all are sympathetic preganglionic fibers to abdomen
what are the three components of the thoracic sympathetic trunk?
sympathetic ganglion, white ramus communicans, gray ramus communicans
what component of the nerve fiber is in the sympathetic ganglion?
postganglionic (postsynaptic) neuron cell bodies
what nerve fibers are in the white ramus communicans?
preganglionic fibers entering the chain/trunk
what nerve fibers are in the gray ramus communicans?
postganglionic fibers exiting the chain/trunk
what vein handles venous drainage for the posterior mediastinum?
azygos vein
what are the veins that drain into the azygos vein
posterior intercostal vein, mediastinal vein esophageal vein, bronchial vein, hemiazygos vein, accessory hemiazygos vein (can accept blood from left superior intercostal vein)
what do tissues need for perfusion?
oxygen, carbon dioxide removal, substrates (lipids, glucose, amino acids), ions, hormones
acute blood flow control occurs through which processes?
vasodilation, vasoconstriction
long term blood flow control occurs through what structures and processes?
change in vessel size, anastomosis, angiogenesis
what system causes vasoconstriction of arterioles and large veins?
sympathetic nervous system
what effects does the sympathetic nervous system have on the heart?
increase heart rate, increase contractility
resting rate of sympathetic nervous system stimulation causes what?
vasomotor “tone”
what is the transmitter substance of the sympathetic nervous system?
norepinephrine
sympathetic nervous system is more effective in which organs? it is less effective in which organs?
more - kidney, intestines, spleen, skin
less - skeletal muscle, brain
how many liters of fluid is in the intracellular compartment?
28 L
how many liters of fluid is in the extracellular compartment?
14 L
what is another name for the extracellular compartment?
interstitium (cells depend on substances here)
how many liters of fluid is in blood plasma?
3 L
how many liters of fluid is in interstitial fluid?
11 L
what fluid makes up the extracellular compartment?
blood plasma, interstitial fluid, transcellular fluid
where is transcellular fluid found?
synovial, pericardial, peritoneal, and intraocular spaces
what makes up blood?
hematocrit, blood plasma
where is interstitial fluid found? it is the same composition as what other substance, just with less proteins?
in the space between cells
plasma
what is the interstitium filled with?
fluid, fine web/net-like filaments
how does ‘free’ fluid pass through interstitium?
small channels
what does most extracellular fluid diffuse through in the interstituium?
‘gel’
lymph vessels attach to tissues via what?
anchoring filaments
lymph vessels have valves - what vessel does this mirror?
veins
what causes fluid from the interstitial space to enter lymph vessels?
anchoring filaments pull on endothelial cells
body fluid compartments are separated by cell membranes that have what feature?
semi-permeable
equilibrium of fluid and substances is maintained by what processes and mechanical factors?
diffusion, osmosis, capillary filtration, negative pressure in most interstitial spaces
the body is ‘held together’ by what, especially in the superficial fascia layer?
negative pressures
what substances easily pass through membranes because they are lipid soluble?
oxygen, carbon dioxide
what substances easily pass through pores/gated channels in membranes because they are water soluble?
water, electrolytes, glucose
what substances do not easily pass through membranes because they are large molecules?
proteins
what is the transfer of substances across capillary membranes due to thermal motion water molecules and dissolved substances?
diffusion
what is the movement of water across membranes in response to concentration of solutes?
osmosis
what causes water to flow into capillaries?
plasma proteins
what causes negative pressure in most interstitial spaces?
fluid is trapped in ‘gel’ layer of connective tissue, lymph vessels automatically contract to pump fluid out of space
higher pressures/arterial end forces fluid where? lower pressures/venous end forces fluid where?
higher - interstitium
lower- vein
what supports the lymphatic ‘pump?’
low tissue compliance, increased lymphatic flow
“wash out” of proteins with increased lymphatic flow in interstitial space reduces what?
osmosis, capillary filtration rate
what does increased lymphatic flow prevent?
positive pressures in interstitial space (can increase 10-50x normal rate)
what limits the free flow of fluid?
gel-like matrix of tissues (cytoplasm)
why does low tissue compliance support the lymphatic pump?
small changes in extracellular fluid volume associated with large changes in interstitial pressure which limits capillary filtration rate
what is excess fluid in body tissues?
edema
what causes intracellular edema?
ischemia, inflammation, metabolic conditions
what leads to increased intracellular concentrations, change in osmotic pressure, and swelling?
loss of sodium ion pump in cell membrane
what causes extracellular edema?
loss of negative pressure in interstitial space
what causes increased capillary filtration rates, leading to extracellular edema?
kidney disease, heart failure, venous obstruction or failure of venous pump, decreased plasma proteins, inflammation
what can lead to kidney disease?
retention of salt and water
what is the difference between right and left sided heart failure?
right - generalized
left - pulmonary
what is an example of venous obstruction or failure of venous pump that would cause extracellular edema?
paralysis
what is an example of decreased plasma proteins that would cause extracellular edema?
burns, wounds
what is an example of inflammation that would cause extracellular edema?
release of histamines
what causes impaired lymphatic function (lymphedema)?
removal of lymph nodes, cancer, congenital absence of lymph vessels/nodes
edema is largely what type of fluid?
‘free’
‘free fluid’ edema is the basis for what condition?
pitting edema
edema is dependent on what factor, causing fluid to accumulate in inferior spaces like ankles/feet?
gravity
what is edema in the potential spaces?
effusion
where is effusion common in the body?
pericardium, peritoneum, synovial joint
normal interstitial fluid pressures are positive or negative?
negative
what is the normal interstitial fluid pressure in the pleural cavity?
7-8 mg Hg
what is the normal interstitial fluid pressure in the joint spaces?
3-5 mg Hg
what is the normal interstitial fluid pressure in the pericardium?
5-6 mg Hg
what can block lymphatic drainage, leading to positive pressures in the interstitium and causing effusion due to a loss of negative pressure ‘suction?’
injury, infection
