Lecture 8-Hepatic Portal System Flashcards
Portal venous system drains blood from?
- Portal venous system drains blood from the spleen, pancreas, and all GI organs between distal esophagus and rectum
- Then the blood is shunted through the liver where it is filtered and then returned to the heart via the IVC
2 main characteristics of the blood in the hepatic portal vein?
O2 poor, nutrient rich
Why is the blood filtered?
Do not want toxins to enter your blood stream directly so after GI absorption they are put into the liver to be filtered
Caval (systemic) system?
Blood from the rest of the body is transferred by systemic veins
-This system directs blood to the heart through the SVC and IVC
Portacaval anastomoses
-What are they?
Areas in the body where the portal and systemic circulations are connected
-However, little blood is transferred since the pressures in each are equal
Portacaval anastomoses
-Examples?
Esophagus, umbilicus, and rectum
Hepatic portal system
- Starts as?
- Ends as?
- Starts as capillaries in the digestive system
- Ends as capillaries in the liver
Hepatic portal vein-MAIN characteristic?
VALVELESS
Hepatic portal vein-Function?
Brings the blood from GI organs to liver to be filtered (liver is drained by hepatic veins)
Portal vein
-Formed by?
-Splenic vein
-Superior mesenteric vein
-Inferior mesenteric vein
(Enters either the superior mesenteric vein or the splenic vein)
Hepatic portal system
-Where does it form?
Posterior to the neck of the pancreas
Ends as right and left branches in the liver
Portal triad-3 components and their “typical arrangement?
- Proper hepatic a-left
- Portal vein-posterior
- Bile duct-right
The portal triad is surrounded by?
The hepatoduodenal ligament (part of the lesser omentum)
Porta hepatis
-What is it?
Deep fissure on the inferior surface of the liver through which all neurovascular structures (except hepatic veins) and hepatic ducts enter and leave the liver
Direct tributaries of the portal vein?
- Paraumbilical vv (anterior wall)
- Cystic v
- Left gastric
- Right gastric
Direct tributaries of the splenic vein?
- Splenic vein (proper)
- Short gastric vv
- Left gastro-omental v
- Pancreatic vv
Direct tributaries of the superior mesenteric vein?
- Right gastro-omental v
- Pancreaticoduodenal vv
Superior mesenteric vein
-Relationship with SMA?
- Parallels the superior mesenteric a on the right
- Tributaries drain the same parts of the small and large intestines supplied by the branches of the SMA
Superior mesenteric vein
-Joins the splenic vein to form?
Joins the splenic vein to form the portal vein posterior to the neck of the pancreas
Superior mesenteric vein
-Tributes?
- Intestinal vv-jejunal and ileal vv
- Ileocolic v-cecal and appendicular v
- Right colic
- Middle colic
Inferior mesenteric vein
-Tributaries drain?
The same parts of the large intestine that were supplied by branches of the inferior mesenteric artery
Inferior mesenteric vein
-Formed by?
The superior rectal vein drains superiorly to join branches of the left colic veins
Inferior mesenteric vein joins the splenic or SMV to form?
The portal vein
Inferior mesenteric vein
-Tributes?
- Left colic v
- Sigmoid v
- Superior rectal v
Veins of the stomach and esophagus
-Blood drains superiorly into?
The azygous system
Veins of the stomach and esophagus
-Blood drains inferiorly into?
Blood drains inferiorly into the portal system
Veins from GI tract normally drain into?
Portal vein (directly or indirectly)
Veins from posterior structures, such as kidneys, drain into?
IVC
Inferior Vena Cava
- Veins that join to form IVC? Where do they join?
- Location relative to aortic bifurcation?
- Common iliac veins join to form IVC at L5
- Formation is posterior to and inferior the aortic bifurcation
Where is the IVC relative to the aorta?
The IVC lies to the right of the aorta
Inferior vena cava
-Drains the posterior body wall?
- Posterior body wall muscles
- Genitourinary system
- Lower limbs
Inferior vena cava
-Posterior body wall-genitourinary system is drained by?
Internal iliac veins
Inferior vena cava
-Posterior body wall-lower limbs are drained by?
External iliac veins
Inferior vena cava
-Main tributaries?
- Common iliacs
- Lumbar (segmental) veins
- Renal veins
- Hepatic veins
- RIGHT gonadal and suprarenal veins (not left)
Where do the left gonadal and suprarenal veins drain into?
Enter the left renal vein which goes into IVC
Portal hypertension
Pressure in the portal system is unusually high compared to the systemic circulation
Portal hypertension-How is it related to liver failure (cirrhosis)?
Makes blood flow through the liver more difficult
Varicies
- what are they?
- pneumonic?
Weakened sections of veins from being stretched and thin from backflow of portal blood into small systemic veins
-Gut, butt, caput
Portal-caval ‘Anastomoses’
-4 main ways for blood to bypass the liver?
- Esophageal varicies
- Caput medusae
- Colic veins to retroperitoneal veins
- Rectal varicies
Portal-caval ‘anastomoses’
- What happens in liver cirrhosis-Blood can’t get into the liver so?
- How is this possible?
- Blood flows back through the portal system and through the interconnections with the IVC to return to the heart
- Possible because the portal system does not have valves
Portal-caval ‘anastomoses’
-The back up of blood in the systemic system causes?
Varicosities
Esophageal varicies
-Esophageal branches of? Connect with?
-Esophageal branches of left gastric vein connect with veins on lower thoracic esophagus
Esophageal varicies
-Portal drainage?
Left gastric–>portal vein
Esophageal varicies
-Systemic drainage?
Esophageal v.–>Azygos v–>SVC
Esophageal varicies
-Clinical signs?
- Bleeding
- Black tarry stools
- Medical emergency
Caput medusae
-Portal drainage?
-Paraumbilical veins (in falciform ligament)
Caput medusae
-Systemic drainage?
Superficial epigastric veins-inferior epigastric and superficial epigastric veins of the anterior abdominal wall empty into the external iliac and femoral veins
Colic veins to retroperitoneal veins
-Portal drainage?
Veins draining the ascending colon (SMV) and descending colon (IMV)
Colic veins to retroperitoneal veins
-Systemic drainage?
Retroperitoneal veins that drain the posterior body wall
-The veins of Retzius drain into lumbar veins which in turn drain into the IVC
Rectal varicies
-Portal drainage?
Superior rectal veins
Rectal varicies
-Caval drainage?
Middle and inferior rectal veins
Middle/inferior rectal veins–>internal iliac veins–>common iliac veins
Rectal varicies
-Clinical sign?
Hemorrhoids-veins prolapse through rectum
Rectal varicies
-Clinical sign-hemorrhoids-why are they painless?
Happens in upper 2/3 of anal canal-visceral innervation
Pectinate line
- Above pectinate line
- which part of anal canal?
- Innervation?
- Upper 2/3 of anal canal
- Visceral innervation (not painful)
Visceral pain
- Internal organs damaged
- Caused by activation of pain receptors in chest, abdomen, or pelvis
- Pain is vague and not well localized
Pectinate line
- Below pectinate line
- Which part of anal canal?
- Innervation?
- Lower 1/3 of anal canal
- Somatic innervation (painful)
Somatic pain
- Body surface or msk tissues damaged
- Pain is dull or aching
TIPS procedure
- Route to take to get to portal vein?
- What do you do once you get to the portal vein?
Jugular vein–>SVC and IVC–> hepatic vein tributary = liver parenchyma–>portal vein
-Put stent in portal vein to allow blood to flow through the liver normally instead of flowing backward
Review the picture on slide 23!!
SLIDE 23
