Editing Vascular system (section)

= '''Venous system''' =

== '''Jugular veins''' ==

* See 'neck'

== '''Brachiocephalic veins''' ==

* Begin behind the sternal ends     of the clavicles
* Right: 2-3cm long, descends     to finish behind the right first costal cartilage
* Left: crosses obliquely     behind upper manubrium, to end behind the right first costal cartilage     where it joins the right vein to form SVC

== '''Superior vena cava (SVC)''' ==

* Path
** Commences at the lower      border of the first costal cartilage by confluence of the two      brachiocephalic veins
** Vertically downwards behind      the right border of the sternum
** Enters upper border of right      atrium
* Tributaries
** Both brachiocephalic veins      (at its beginning)
** Azygos vein



== '''Inferior vena cava''' ==

* Course
** Formed by the confluence of      right and left common iliac veins, in front of L5
** Ascends retroperitoneally to      the right of the aorta, and passes in a groove on the liver
*** There is a tributary-free       plane anterior to the retrohepatic cava - can use finger to bluntly       dissect here, below the major veins
** Perforates the tendinous      part of the diaphragm
** Enters the inferoposterior      part of the right atrium
* Features
** No valves in the IVC distal      to a somewhat vestigial valve at its entry into RA
* Relations
** Crossed at its origin by      right CIA
** IVC crossed by root of      mesentery and right gonadal artery
** Lies behind duodenal C/head      of pancreas
** Posterior to epiploic      foramen - covered only by peritoneum
*** Therefore posterior to PV -       this is where a portocaval shunt would be performed - not always       straightforward due to limited mobility of PV
** Two lowermost lumbar      arteries cross behind it lower down
** Right renal artery crosses      behind
** Inferior phrenic and adrenal      arteries cross behind it
** Right adrenal gland lies to      its right
** Right sympathetic chain is      overlain by abdominal IVC
* Tributaries
** Lumbar veins
*** Usually four pairs in       total, but only the caudal 3rd and 4th pairs drain into IVC
*** 1st and 2nd veins drain       into azygos system
*** Major significance is that       the left lumbar veins can get damaged as they pass behind the aorta       during mobilisation
*** Right veins can be damaged       when the IVC is retracted anteriorly during lumbar sympathectomy
** Right gonadal vein (L2)
*** Just below right renal vein
** Renal veins
*** Left vein usually higher       than right by 1-2cm
*** Both veins usually enter at       45 degree angle
*** Right vein 2cm, left vein       longer and draped across front of aorta
** Supra-renal veins
*** Right - very short and       enters IVC just below liver
*** Left - joins left renal       veins
** Inferior phrenic vein
*** Drains the under-surface of       the diaphragm
*** Right vein drains into IVC       usually above the entrance of the right hepatic vein
*** Left vein often double,       with a posterior branch draining into the left adrenal or left renal       vein, but the anterior branch passes in front of the oesophageal hiatus       to drain into IVC or left hepatic vein
** Hepatic veins
*** See 'liver'
* Exposure
** See 'vascular exposures'
* Variants
** IVC duplication (up to renal      veins)
** Left sided IVC
** Left renal vein behind      aorta, or paired sandwich
** Azygos continuation of the      IVC
** Circumcaval ureter

== '''Portal venous system''' ==

* See 'liver'

== '''Azygos system''' ==

* '''Azygos     system'''
** The thoracic wall and upper      lumbar region are drained by the posterior intercostal and lumbar veins      into the azygos veins.
** '''Azygos'''
*** Embryology
**** See above
**** Essentially from the left        and right supracardinal veins of the embryo
*** Course
**** In adults, the functional        commencement is at the union of the ascending lumbar vein with the        subcostal vein of the right side (T12)
**** Passes through the aortic        opening of the diaphragm under the right crus
**** Lies posterolateral to        oesophagus, on the vertebral bodies, with thoracic duct medial to it
**** Arches over the right main        bronchus at about T4 and passes forward to enter the SVC
*** Tributaries
**** Lower eight right        posterior intercostal veins
**** Superior intercostal vein        at its convexity
**** Bronchial veins from the        right lung
**** Some veins from the middle        third of the oesophagus
**** Hemiazygos - two        connections at levels T8 and T9
*** Highly variable
** '''Hemiazygos'''
*** Lies longitudinally on the       left side of the bodies of the thoracic vertebrae
*** Highly variable combination       of hemiazygos and accessory hemiazygos
*** Tributaries
**** Accessory hemiazygos -        left posterior intercostal veins 5-8
**** Hemiazygos - left        posterior intercostal veins 9-12
*** Ends with drainage into       azygos at T8 (accessory hemiazygos) and T9 (hemiazygos)


[[Category:Anatomy]]