Postcaval System

Question 1

what is the portal venous system?

Answer 1

a. drains blood from the spleen, pancreas, and all GI organs b/w distal esophagus and rectum
i. Then blood is shunted through the portal vein to the liver where it is filtered and then returned to the heart via the IVC
ii. Blood here is O2 poor and nutrient rich

Question 2

what is the purpose of the portal venous system?

Answer 2

do not want toxins to enter your blood stream directly so after GI absorption they are put into the liver to be filtered

Question 3

what is the caval system?

Answer 3

• systemic system
  i. Blood from the rest of the body is transferred by systemic veins
  ii. This system directs blood to the heart thru the IVC and the SVC
  iii. There are areas in the body where the portal and systemic circulation is connected
  
  1. However, little blood is transferred since the pressures in each are about equal
     a. Esophagus
     b. Umbilicus
     c. Rectum

Question 4

start and end of hepatic portal system

Answer 4

a. START as capillaries in the digestive system

b. END as capillaries in the liver

Question 5

describe the portal V

Answer 5

i. ~2 inches long
ii. valveless
iii. formed by:
1. splenic vein
2. superior mesenteric vein
3. inferior mesenteric vein
a. enters enter the superior mesenteric vein or the splenic vein

Question 6

where is the hepatic portal system located?

Answer 6

a. The hepatic portal system forms posterior to the neck of the pancreas
i. It ends at left and right branches in the liver
b. Runs thru the heptoduodenal ligament (part of the lesser omentum) to enter the liver at the porta hepatis

Question 7

what is porta hepatis?

Answer 7

deep fissure on the inferior surface of the liver thru which all neurovascular structures (except hepatic vein) and hepatic ducts enter and leave the liver

Question 8

what makes up the portal triad and where are the parts arranged?

Answer 8

i. Proper hepatic A.—LEFT
ii. Portal vein—posterior
iii. Bile duct—right
1. Hepatoduodenal ligament surrounds it

Question 9

superior mesenteric V

Answer 9

a. parallels the superior mesenteric A on the right
i. Tributaries drain the same parts of the small and large intestine supplied by branches of the superior mesenteric A
ii. Joins the splenic V to form the portal V posterior to the neck of the pancreas

Question 10

inferior mesenteric V

Answer 10

i. Tributaries drain the same parts of the large intestine that were supplied by branches of the inferior mesenteric A
ii. Superior rectal V drains superiorly to join branches of the left colic V and form the inferior mesenteric V
iii. The inferior mesenteric V joins the splenic or superior mesenteric V to form the portal V

Question 11

blood draining thru the veins of the esophagus

Answer 11

i. Blood can drain superiorly into the azygous system
ii. Blood can drain inferiorly into the portal system
iii. Not the submucous venous plexus in the esophagus is a connection b/w the 2 systems

Question 12

what veins drain the liver?

Answer 12

-right, middle, and left hepatic veins

Question 13

where does the IVC lie?

Answer 13

a. Formation is posterior to and inferior to the aortic bifurcation
b. Lies to the right and parallel to the aorta
c. Lies to the right of the lumbar and thoracic vertebrae

Question 14

where does the common iliac join to form the IVC?

Answer 14

L5

Question 15

where does the IVC pierce the diaphragm?

Answer 15

T8

Question 16

where does the esophagus pierce the diaphragm?

Answer 16

T10

Question 17

where does the aorta pierce the diaphragm?

Answer 17

T12

Question 18

what does the IVC drain?

Answer 18

i. Posterior body wall muscles
ii. Genitourinary system—by the internal iliac V
iii. Lower limbs—by the external iliac V

Question 19

what are the main tributaries to the IVC?

Answer 19

i. Common iliac V
ii. Lumbar (segmental) V
iii. Renal V
iv. Hepatic V

Question 20

explain portal hypertension

Answer 20

a. Pressure in the portal system is unusually high compared to the systemic circulation
i. Ie. Occurs during liver failure/cirrhosis which makes blood flow thru the liver more difficult
b. Portal V is valveless and blood will flow backwards so Vs dilate and get thin and stretched
i. This causes varicies
1. These are weakened sections of veins from being stretched and thin from backflow of portal blood into small systemic Vs
2. Mnemonic—gut, butt, caput

Question 21

portal caval anastomoses

Answer 21

i. Connections b/w the portal venous system and the IVC
ii. Become important when the liver is blocked from diseases like cirrhosis
iii. Blood flows back thru the portal system and thru the interconnections with the IVC to return to the heart
iv. Possible b/c the portal system does not have valves
v. The back up of blood in the caval system causes varicosities which are at risk for hemorrhage

Question 22

4 main ways for blood to bypass the liver

Answer 22

• esophageal varicies
• caput medusae
• colic Vs to retroperitoneal Vs
• rectal varicose

Question 23

what are the clinical signs of esophageal varicies?

Answer 23

bleeding, black tarry stools, medical emergency

Question 24

what are the clinical signs rectal varicies?

Answer 24

• hemorrhoids–veins prolapse thru rectum

- painless

Question 25

why are rectal varicies painless?

Answer 25

pectinate line splits the anal canal into an upper 2/3 and a lower 2/3

• above the pectinate line there is visceral innervation which is not painful
  
  • internal organs damaged
  • caused by activation of pain receptors inches, abdomen, pelvis
• below pectinate line
  
  • somatic innervation and is painful

Question 26

TIPS procedure

Answer 26

i. TIPS—transjugular intrahepatic portosystemic shunting
ii. You can fix hemorrhaging in esophagus but have ot fix the drainage problem first
1. Most popular stent placed is the TIPS procedure—so connect portal V to comething else in the liver so blood doesn’t go back thru portal V
a. Basically, connect to IVC from portal V to keep blood there
i. Place stent b/w portal V and hepatic C to send it to IVC and then to the heart where it is supposed to