Hepatic Portal System Lecture (Test 1) Flashcards
Portacaval Anastomoses Cont
- Caval (Systemic) System: Blood from the rest of the body is transferred by Systemic Veins
- This system directs blood to the HEART though the SVC and IVC
- there are areas in the body where the Portal and Systemic Circulation is CONNECTED
- However, little blood is transferred since the pressures in each are about equal:
A) Esophagus
B) Umbilicus
C) Rectum
Portacaval Anastomoses
- Portal Venous System drained Blood from the Spleen, Pancreas, and all GI Organs between DISTAL ESOPHAGUS and RECTUM
- Then the blood is SHUNTED through the PORTAL VEIN to the LIVER where it is filtered and then returned to the Heart via the IVC
- O2 POOR, NUTRIENT RICH
- Purpose: Do not want TOXINS to enter your Blood Stream directly so after GI Absorption they are put into the LIVER to be filtered
Hepatic Portal System
- Starts as Capillaries in the Digestive System
- Ends as Capillaries in the Liver
- Portal Vein:
a) About 2 inches long
b) VALVELESS - Portal Vein is formed by:
1) Splenic Vein
2) Superior Mesenteric Vein
3) Inferior Mesenteric Vein - Enters either the Superior Mesenteric Vein or the Splenic Vein
***Note: Liver is drained by HEPATIC VEINS
***Note: Portal Vein BRINGS Blood to the Liver
Hepatic Portal System Cont 2
- The HEPATIC PORTAL SYSTEM forms POSTERIOR to the Neck of the Pancreas
- It ends as RIGHT and LEFT Branches in the Liver
- Runs through the HEPATODUODENAL Ligament (Part of the Lesser Omentum) to enter the Liver at the Porta Hepatis
PORTA HEPATIC:
- Deep FISSURE on the Inferior surface of the Liver through which all Neuromuscular structures (Except Hepatic Veins) and Hepatic Ducts enter and leave the Liver
“Typical” Arrangement:
- Proper Hepatic Artery (LEFT)
- Portal Vein (POSTERIOR)
- Bile Duct (RIGHT)
- ** Hepatoduodenal Ligament surrounds it
Hepatic Portal System Cont 3
- Direct tributaries of the Portal Vein:
a) Paraumbiical Veins (Anterior Wall)
b) Cystic Vein
c) Left Gastric Vein
d) Right Gastric Vein
SPLENIC VEIN:
- Splenic Vein (Proper)
- Short Gastric Vein
- Left Gastro-Omental Vein
- Pancreatic Veins
SUPERIOR MESENTERIC:
- Right Gastro-mental Vein
- Pancreaticoduodenal Veins
Superior Mesenteric Vein
- Superior Mesenteric Vein PARALLELS the Superior Mesenteric Artery on the Right
- Tributaries drain the same parts of the Small and Large Intestine supplied by Branches of the Superior Mesenteric Artery
- Joint the Splenic Vein to form the Portal Vein Posterior to the neck of the PANCREAS
Tributaries:
1) Intestinal Veins
a) Ileal Veins
b) Jejunal Veins
2) Ileocolic Veins:
a) Cecal Vein
b) Appendicular Vein
3) Right Colic Vein
4) Middle Colic Vein
Inferior Mesenteric Vein
- Tributaries drain the same parts of the Large Intestine that were supplied by Branches of the Inferior Mesenteric Artery
- The SUPERIOR RECTAL Vein drains SUPERIORLY to join Branches of the LEFT COLIC Veins and form the Inferior Mesenteric Vein
- The Inferior Mesenteric Vein joins the SPLENIC or the Superior Mesenteric Vein to form the PORTAL VEIN
Tributes:
1) Left Colic Vein
2) Sigmoid Vein
3) Superior Rectal Vein
Veins of the Stomach and Esophagus
A) Clinical important overlap between Veins of the Esophagus:
- Blood can drain SUPERIORLY into the AZYGOUS System
- Blood can drain INFERIRLY into the PORTAL System
- Bote the SUBMUCOUS VENOUS PLEXUS in the Esophagus
B) Veins from the Gastrointestinal Tract normally drain into the Portal Vein, either DIRECTLY or INDIRECTLY
C) Veins from Posterior Structures, such as Kidneys, normally drain into the INFERIOR VENA CAVA
Veins Draining the Liver
1) Right Hepatic Vein
2) Middle Hepatic Vein
3) Left Hepatic Vein
***Hepatic Veins are Intersegmental
Inferior Vena Cava
A) Common Iliac veins join to form IVC at L5!!!!!!
- 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 Veterbrae
D) Passes through Liver
E) Pierces the Central Tendon of the Diaphragm at T8!!!!
F) The Inferior Vena Cava also has connections with AZYGOS System of Veins
Inferior Vena Cava Cont 2
A) Drains the POSTERIOR Body Wall
- Posterior Body Wall muscles
- Genitourinary System (Internal Iliac Veins)
- Lower Limbs (External Iliac Veins)
B) Main Tributaries
- Common Iliacs
- Lumbar (Segmental) Veins
- Renal Veins
- Hepatic Veins
Inferiore Vena Cava- Tributaries
- Right and left Common Iliac Veins
- Middle (Median) Sacral Vein
- Lumbar Veins (Paired, Segmental)
- Right and Left Renal Veins
- Right Gonadal Vein
- Right Suprarenal Vein
- Hepatic Veins
- Inferior Phrenic Veins
Note: Left Suprarenal and Gonadal Veins enter Left Renal Vein instead of IVC!!!!!!
Portal Hypertension
- Pressure in the Portal System is unusually HIGH Compared to the Systemic Circulation
- Ex: LIFER FAILURE (Cirrhosis) makes Blood Flow through the Liver more difficult
- VARICIES: Weakened sections of Veins from being stretched and thin from BACKFLOW of Portal Blood into Small Systemic Veins
- Gut, Butt, Caput
Portal-Cabal “Anastomoses” (Collateral Pathways)
- Connections between the Portal Venous System and the Inferior Vena Cava System
- Become important when the Liver is Blocked from Diseases such as Cirrhosis
- Blood Flows back through the Portal System and through the interconnections with the Inferior Vena Cava to return to the Heart
- Possible because the Portal System DOES NOT HAVE VALVES
- The back up o Blood in the Caval System causes VARICOSITIES which are at risk for Hemorrhage
- There are 4 main ways for blood to BYPASS the Liver
1) Esophageal Varicies
2) Caput Medusae
3) Colic Veins to Retroperitoneal Veins
4) Rectla Varicies
Esophageal Varicies
- Esophageal Branches of LEFT GASTRIC Vein connect with Veins on Lower Thoracic Esophagus
- Portal Drainage: Left Gastric Vein —> Portal Vein
- Caval Drainage: Esophageal Vein —> Azygos Vein —> SVC
Clinical Sign: Esophageal Varicose!!!!!!!!!!!!
1) Bleeding
2) Black Tarry Stools
3) Medical Emergency!!!!!!!!
