Interval 4 Flashcards
Parts of the mediastinum:
- superior (above sternal angle)
- anterior
- inferior
- posterior
superior mediastinum:
- between 1st vertebrate and first rib
- horizontal plane between sternal angle and the intervertebral disc (T4 - 5)
- trachea, brachiocephalic vein, thymus, aortic arch, esophagus, thoracic duct
posterior mediastinum contents:
- esophagus with vagus nerve
- descending aorta
- thoracic duct
- sympathetic trunk
- inferior to horizontal T4-5 plane
- between the pericardium, vertebral column, and diaphragm
middle mediastinum contents:
- heart
- ascending aorta
- pulmonary trunk
- pulmonary veins
- phrenic nerves
anterior mediastinum:
- smaller vessels and nerves
- fat
CT
-thymus in children
Layers of the superior mediastinum:
- endocrine layer: thymus (extends into anterior)
- venous layer: SVC, left/right brachiocephalic veins
- arterial layer: arch of aorta & 3 branches: brachiocephalic artery, left common carotid, and left subclavian
- respiratory layer: trachea, arch of aorta, azygos vein
- digestive layer: contains esophagus
brachiocephalic veins:
- posterior to the sternoclavicular joint
- form by the union of the internal jugular vein and a subclavin vein
- left brachiocephalic vein crosses behind thymus
division of the brachiocephalic artery:
- right common carotid and right subclavian
* common carotids in the middle
ligamentum arteriosum:
- fetal remnant of ductus arteriosus (shunted blood from PT directly to aorta)
- between left pulmonary artery and arch of aorta
Presence of trachea in cross sectional imaging means what?
–you are in the neck or superior mediastinum
indentations on the esophagus:
- two: one from the arch of the aorta (on the left) and one from the left main bronchus anteriorly
- causes constriction site
- two other constriction sites: origin of the esophagus in the neck and at the esophageal hiatus of the diaphragm
thoracic duct:
- contains lymph from the entire abdominal region
- courses posterior to the esophagus
- deviates left, empties into the left subclavian and left internal jugular veins
Vagus Nerve:
- left and right
- through superior mediastinum to the posterior and pass posterior to the root of the lung
- form esophageal plexus on esophagus
- cardiac and pulmonary branches enter the cardiac plexus
left recurrent laryngeal nerve:
- in superior mediastinum
- comes off the vagus nerve after it passes the arch of the aorta
right recurrent laryngeal nerve:
- NOT in superior mediastinum
- hooks around the right subclavian
phrenic nerves:
-pass anterior to the root of the lung
Where to hear mitral valve?
- most commonly diseased
- 5th intercostal space, few cm from the sternum
- problems cause enlarged left ventricle and hypertrophy of right
pulmonary hypertension:
- mitral valve problem (mitral stenosis) causes left ventricle to swell and blood get backed up in left atrium/lungs
- right ventricle hypertrophies as it tries to compensate to the increased resistance
Thrombus in left atrium:
- due to back up from mitral stenosus
- blood clot, can travel into left ventricle -> circulation -> brain -> stroke
posterior mediastinum
- inferior to horizontal T4-5 plane
- between the pericardium, vertebral column, and diaphragm
esophagus muscle:
- skeletal muscle in upper 1/3
- smooth muscle in lower 1/3
- mix in the middle
esophagus innervation:
-esophageal plexus (formed by left/right vagus)
hemiazygos veins:
- drain into the azygos after crossing midline at T8 (azygos drains into SVC at sternal angle)
- receive blood from posterior intercostal veins
organs of the posterior abdominal wall:
kidneys, ureters and adrenal glands
left kidney location:
- superior to the right
- anterior to 11/12 rib
right kidney location:
-anterior to 12th rib
muscles that the kidneys are in contact with
- psoas major
- diaphragm
- transversus abdominis
- quadratus lumborum
renal hilus:
anterior -> posterior: vein, artery, pelvis
cortex of the kidney:
proximal parts of the uriniferous tubules
renal corpuscles
proximal/distal convoluted tubules
medulla of kidney:
renal pyramids: contain distal parts of the collecting ducts
apex of pyramid: open into minor calyx
Loops of Henle:
straight part of the uriniferous tubules
extend into the renal columns between the pyramids
renal pelvis:
- upper part of the ureter
- formed by 3-4 major calyces
- 2-4 minor calyces form a major
Where do renal artery/vein originate?
- aorta at L2
- right artery passes posterior to IVC,
- veins empty into IVC at L2
- left vein passes anterior to aorta (just inferior to SMA)
branches of renal arteries:
- interlobar arteries branch into arcuate arteries between medulla and cortex which go back to interlobar which give rise to afferent arterioles of glomerulus
- blood leave glom via efferent arteries
kidney innervation:
-preganglionic sympathetic axons from the lower thoracic/lumbar splanchnic nerves from T11 and 12 spinal cord segments
these synapse in the aorticorenal ganglia, postganglionic sympathetic axons go to the arteries in the kidney and control arterial blood flow to glomeruli
What kind of organ are kidneys?
retroperitoneal
left renal vein connections:
- left suprarenal
- left gonadal
ureters
- tubes containing smooth muscle, arise around L2
- descend anterior to psoas major
- at the pelvic brim lies between external and internal iliac arteries
blood supply to the ureters:
- upper 1/3: renal
- middle 1/3: common iliac
- lower 1/3: superior vesical artery
adrenal glands:
- endocrine organs that are primarily retroperitoneal
- contain cortex and 3 zones
3 zones of the adrenal glands:
- zona glomerulosa: aldosterone
- zona fasciculate: glucocorticoids
- zona reticularis: reproductive steroids
medulla of adrenal glands:
- contain chromafin cells (derived from NCC) and secrete epi/n-epi
- innervated by preganglionic sympathetic axons (reach through lower thoracic splanchnic nerves)
adrenal blood supply:
- adrenal arteries (branch from renal arteries, aorta, and the inferior phrenic arteries)
- drained by single vein: right adrenal directly to IVC, left to the renal vein
abdominal aorta:
- begins at the aortic hiatus (T12)
- descends to the left of the midline
- bifurcates into the common iliac arteries at L4
location of the renal arteries:
L2
location of the gonadal arteries:
L2/3
inferior phrenic arteries:
supply the diaphragm
IVC location:
L5
-ascends to the right of the midline
Right: renal, adrenal, gonadal veins drain
Left: only renal
Collateral routes for venous blood to pass if IVC obstructed:
- bypass the IVC through anastomoses in the abdomen/pelvis that allow blood to reach the superficial epigastric and inferior epigastric veins which drain into the axillary and subclavian veins
- bypass via lateral thoracic vein which connects the circumflex iliac to axillary
- bypass through anastomoses between the epidural venous plexus and azygos/hemiazygos
- allows for passes if occlusion below L2 but also serve to metastasize tumors
Nerves of the posterior abdominal wall:
- lumbar plexus forms by ventral rami of L1-4 (some from T12)
- ventral rami branch into anterior and posterior regions which form 2 main nerves: femoral and obturator
femoral nerve:
- posterior ventral rami branch from L2, 3, 4
- innervates muscles of the thigh and skin
obturator nerve:
- anterior L2, 3,4 ventral rami
- medial thigh muscles
subcostal nerve:
- inferior to the 12th rib
- innervates abdominal muscles and skin
iliohypogastric nerve
- inferior to subcostal nerve
- innervates abdominal muscles, skin of inguinal/hypogastric regions of anterior abdominal wall
ilioinguinal nerve:
- inferior to the iliohypogastric
- innervates abdominal muscles and skin of inguinal/hypogastric regions of abdominal wall
- passes through the inguinal canal
- innervates skin of the medial thigh, labium majus, and scrotum
genitofemoral nerve:
anterior to the psoas
- femoral branch posterior to inguinal ligament, innervates skin of thigh
- genital branch enter inguinal canal and innervates cremasteric muscle
lateral femoral cutaneous nerve:
-goes into ASIS
three vascular fetal shunts:
- ductus venosus: oxygenated blood in the umbilical vein bypasses the liver - straight to IVC
- foramen ovale: goes straight from right atrium to the left atrium (pulmonary bypass)
- ductus arteriosus: shunts deoxy blood from pulmonary trunk into aorta
**unlike left (high) - right pressure gradient in adults, fetal circulation has a right - left pressure gradient
closure of the fetal shunts:
-due to changes in the pressure gradient/oxygen tensions
remnants of fetal circulation:
- fossa ovalis (foramen ovale)
- ligamentum arteriosum (ductus arteriosus)
- ligamentum teres (umbilical vein - oxygenated)
- ligamentum venosum (ductus venosus)
- medial umbilical ligaments (umbilical artery)
diaphragm:
- controls intrathoracic and intra abdominal pressures
- IVC (T8), esophagus (T10), aorta (T12)
