CR2.3 Vascular anatomy of the thorax

Question 1

Describe the boundaries of the thoracic and abdominal aorta.

Answer 1

Thoracic aorta:

Begins at the level of T4/5 (i.e. tranverse thoracic plane) and traverses the posterior mediastinum. Ends at the aortic hiatus (N.B. the azygos vein and thoracic duct also pass through this) at the level of T12.

Abdominal aorta:

Begins at the aortic hitus and travels slightly to the left of the lumbar vertebrae (i.e. retroperitoneal space). Bifurcates at the level of L4 into right and left common iliac arteries. Splenic vessels and intestines pass anterior to the abdominal aorta.

Question 2

List the three vascular planes.

Answer 2

1. Paired, parietal (i.e. potero-lateral)
2. Paired, viceral (i.e. lateral)
3. Un-paired, visceral (i.e. anterior, midline)

N.B. the vascular planes are the same for the thoracic and abdominal aorta.

Question 3

Describe the paired, parietal branches (postero-lateral) of the aorta.

Answer 3

3rd to 11th posterior intercostal arteries come from the thoracic aorta. The subcostal artery comes from the abdominal aorta and is inferior to the 12th rib. The 1st to 4th lumbar arteries come from the abdominal aorta. The diaphragm is supplied by superior and inferior phrenic arteries from the thoracic and abdominal aorta respectively. The median sacral artery is unpaired but supplies parietal structures.

Question 4

Describe the paired, visceral branches of the aorta.

Answer 4

Thorax: lungs (bronchial arteries; two left direct branch and one right indirect branch)

Abdomen: suprarenal glands (superior and middle suprarenal –> L1), kidneys (renal –> L1), ureters (renal upper), gonads (gonadal ovarian or testicular –> L2)

N.B. middle suprarenal recieves branches from renal and phrenic arteries.

Question 5

Describe the unpaired, visceral branches of the aorta.

Answer 5

Thorax: oesophagus (4-5 oesophageal branches)

Abdomen: foregut (celiac trunk –> T12), midgut (superior mesenteric artery –> L1), hindgut (inferior mesenteric artery –> L3)

N.B. celiac trunk divides into the left gastric, splenic and common hepatic arteries immediately. The mediastinal, pericardial artery is an exception.

Question 6

Complete this table.

Answer 6

Question 7

Describe the posterior intercostals that drain the azygos, accesory and hemiazygos veins.

Answer 7

Azygos: posterior intercostal (2-11)

Accessory: Posterior intercostals (5-8)

Hemiazygos: Posterior intercostals (9-11)

N.B. The arteries the arise from the thoracic aorta drain into the azygos vein (e.g. bronchial, superior phrenic, oesophageal, mediastinal, pericardial).

Question 8

List the two methods of venous drainage of the abdomen.

Answer 8

Systemic –> IVC / SVC –> paired parietal and paired viceral (+ unpaired parietal)

• subcostal
• lumbar
• inferor phrenic
• supraenal (on the left, drain into renal vein)
• renal (on the left, drain into renal vein)
• gonadal
• *median sacral

AND hepatic veins (right, middle, left)

Portal –> hepatic portal vein –> unpaired viceral

• celiac trunk
• superior mesenteric
• inferior mesenteric

Question 9

Define porto-systemic anatomoses and list where this occurs.

Answer 9

Venous communication between the systemic and portal systems.

1. Lower oesophagus
2. Upper anal canal
3. Bare area of liver
4. Periumbilical region
5. Retroperitoneal regions

The portal system is valveless –> shunting of up to 80% of portal blood into collateral channels –> collateral veins will dilate (i.e. varicose) and potentially rupture.