Hepatic portal vein
Encyclopedia
- This page is the redirect for portal vein. For a vein that connects two systems of capillary beds see portal venous systemPortal venous systemIn human anatomy, the hepatic portal system is the system of veins comprising the hepatic portal vein and its tributaries. It is also called the portal venous system, although it is not the only example of a portal venous system, and splanchnic veins, which is not synonymous with hepatic portal...
.
The hepatic portal vein is not a true vein
Vein
In the circulatory system, veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart...
, because it does not conduct blood directly to the heart. It is a vessel in the abdominal cavity
Abdominal cavity
The abdominal cavity is the body cavity of the human body that holds the bulk of the viscera. It is located below the thoracic cavity, and above the pelvic cavity. Its dome-shaped roof is the thoracic diaphragm , and its oblique floor is the pelvic inlet...
that drains blood from the gastrointestinal tract
Gastrointestinal tract
The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....
and spleen
Spleen
The spleen is an organ found in virtually all vertebrate animals with important roles in regard to red blood cells and the immune system. In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells and holds a reserve of blood in case of hemorrhagic shock...
to capillary beds in the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
. It is usually formed by the confluence of the superior mesenteric
Superior mesenteric vein
In anatomy, the superior mesenteric vein is a blood vessel that drains blood from the small intestine . At its termination behind the neck of the pancreas, the SMV combines with the splenic vein to form the hepatic portal vein...
and splenic vein
Splenic vein
In anatomy, the splenic vein is the blood vessel that drains blood from the spleen.It joins with the superior mesenteric vein, to form the hepatic portal vein and follows a course superior to the pancreas, alongside of the similarly named artery, the splenic artery.It collects branches from the...
s and also receives blood from the inferior mesenteric
Inferior mesenteric vein
In human anatomy, the inferior mesenteric vein is a blood vessel that drains blood from the large intestine. It usually terminates when reaching the splenic vein, which goes on to form the portal vein with the superior mesenteric vein...
, gastric, and cystic vein
Cystic vein
The cystic vein drains the blood from the gall-bladder, and, accompanying the cystic duct, usually ends in the right branch of the portal vein....
s. The hepatic portal vein is a major component of the hepatic portal system, and it is one of only two portal venous system
Portal venous system
In human anatomy, the hepatic portal system is the system of veins comprising the hepatic portal vein and its tributaries. It is also called the portal venous system, although it is not the only example of a portal venous system, and splanchnic veins, which is not synonymous with hepatic portal...
s in the body. The other is the hypophyseal portal system
Hypophyseal portal system
The hypophyseal portal system is the system of blood vessels that link the hypothalamus and the anterior pituitary in the brain.It allows endocrine communication between the two structures. It is part of the hypothalamic-pituitary-adrenal axis. The anterior pituitary receives releasing and...
.
Conditions involving the hepatic portal vein cause considerable illness and death. An important example of such a condition is elevated blood pressure
Blood pressure
Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...
in the hepatic portal vein. This condition, called portal hypertension
Portal hypertension
In medicine, portal hypertension is hypertension in the portal vein and its tributaries.It is often defined as a portal pressure gradient of 10 mmHg or greater.-Causes:Causes can be divided into prehepatic, intrahepatic, and posthepatic...
, is a major complication of cirrhosis
Cirrhosis
Cirrhosis is a consequence of chronic liver disease characterized by replacement of liver tissue by fibrosis, scar tissue and regenerative nodules , leading to loss of liver function...
.
Anatomy
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Measuring approximately 8 cm (3 inches) in adults, the hepatic portal vein is located in the right upper quadrant of the abdomen, originating behind the neck of the pancreas
Pancreas
The pancreas is a gland organ in the digestive and endocrine system of vertebrates. It is both an endocrine gland producing several important hormones, including insulin, glucagon, and somatostatin, as well as a digestive organ, secreting pancreatic juice containing digestive enzymes that assist...
.
In most individuals, the hepatic portal vein is formed by the union of the superior mesenteric vein
Superior mesenteric vein
In anatomy, the superior mesenteric vein is a blood vessel that drains blood from the small intestine . At its termination behind the neck of the pancreas, the SMV combines with the splenic vein to form the hepatic portal vein...
and the splenic vein
Splenic vein
In anatomy, the splenic vein is the blood vessel that drains blood from the spleen.It joins with the superior mesenteric vein, to form the hepatic portal vein and follows a course superior to the pancreas, alongside of the similarly named artery, the splenic artery.It collects branches from the...
. For this reason, the hepatic portal vein is occasionally called the splenic-mesenteric confluence. Occasionally, the hepatic portal vein also directly communicates with the inferior mesenteric vein
Inferior mesenteric vein
In human anatomy, the inferior mesenteric vein is a blood vessel that drains blood from the large intestine. It usually terminates when reaching the splenic vein, which goes on to form the portal vein with the superior mesenteric vein...
, although this is highly variable. Other tributaries of the hepatic portal vein include the cystic
Cystic vein
The cystic vein drains the blood from the gall-bladder, and, accompanying the cystic duct, usually ends in the right branch of the portal vein....
and gastric veins.
Immediately before reaching the liver, the portal vein divides into right and left. It ramifies further, forming smaller venous branches and ultimately portal venules. Each portal venule courses alongside a hepatic arteriole and the two vessels form the vascular components of the portal triad
Portal triad
A portal triad is a distinctive arrangement in the liver. It is a component of the hepatic lobule. It consists of the following five structures:* hepatic artery* hepatic portal vein* bile duct*lymphatic vessels...
. These vessels ultimately empty into the hepatic sinusoids to supply blood to the liver.
Portacaval anastomoses
The portal venous systemPortal venous system
In human anatomy, the hepatic portal system is the system of veins comprising the hepatic portal vein and its tributaries. It is also called the portal venous system, although it is not the only example of a portal venous system, and splanchnic veins, which is not synonymous with hepatic portal...
has several anastomoses with the systemic venous system
Systemic venous system
In human anatomy, the systemic venous system refers to veins that drain into the right atrium without passing through two vascular beds In human anatomy, the systemic venous system refers to veins that drain into the right atrium without passing through two vascular beds In human anatomy, the...
. In cases of portal hypertension
Portal hypertension
In medicine, portal hypertension is hypertension in the portal vein and its tributaries.It is often defined as a portal pressure gradient of 10 mmHg or greater.-Causes:Causes can be divided into prehepatic, intrahepatic, and posthepatic...
these anastamoses may become engorged, dilated, or varicosed and subsequently rupture.
Accessory hepatic portal veins
Accessory hepatic portal veins are those veins that drain directly into the liver without joining the hepatic portal vein. These include the paraumbilical veins as well as veins of the lesser omentumLesser omentum
The lesser omentum is the double layer of peritoneum that extends from the liver to the lesser curvature of the stomach and the start of the duodenum.- Structure :...
, falciform ligament
Falciform ligament
The falciform ligament is a ligament that attaches the liver to the anterior body wall.It is a broad and thin antero-posterior peritoneal fold, falciform in shape, its base being directed downward and backward and its apex upward and backward...
, and those draining the gallbladder
Gallbladder
In vertebrates the gallbladder is a small organ that aids mainly in fat digestion and concentrates bile produced by the liver. In humans the loss of the gallbladder is usually easily tolerated....
wall.
Physiology
The hepatic portal vein and hepatic arteries form the liver's dual blood supply. Approximately 75% of hepatic blood flow is derived from the hepatic portal vein, while the remainder is from the hepatic arteries.Unlike most veins, the hepatic portal vein does not drain into the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
. Rather, it is part of a portal venous system
Portal venous system
In human anatomy, the hepatic portal system is the system of veins comprising the hepatic portal vein and its tributaries. It is also called the portal venous system, although it is not the only example of a portal venous system, and splanchnic veins, which is not synonymous with hepatic portal...
that delivers venous blood into another capillary system, namely the hepatic sinusoids of the liver. In carrying venous blood from the gastrointestinal tract to the liver, the hepatic portal vein accomplishes two tasks; namely, it supplies the liver with metabolic substrates and it ensures that substances ingested are first processed by the liver before reaching the systemic circulation
Systemic circulation
Systemic circulation is the part of the cardiovascular system which carries oxygenated blood away from the heart to the body, and returns deoxygenated blood back to the heart. This physiologic theory of circulation was first described by William Harvey...
. After draining into the liver sinusoids, blood from the liver is drained by the hepatic vein
Hepatic vein
In human anatomy, the hepatic veins are the blood vessels that drain de-oxygenated blood from the liver and blood cleaned by the liver into the inferior vena cava....
.
Portal hypertension
Increased blood pressureBlood pressure
Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...
in the portal vein, called portal hypertension
Portal hypertension
In medicine, portal hypertension is hypertension in the portal vein and its tributaries.It is often defined as a portal pressure gradient of 10 mmHg or greater.-Causes:Causes can be divided into prehepatic, intrahepatic, and posthepatic...
, is a major complication of liver disease, most commonly cirrhosis
Cirrhosis
Cirrhosis is a consequence of chronic liver disease characterized by replacement of liver tissue by fibrosis, scar tissue and regenerative nodules , leading to loss of liver function...
. Stigmata of portal hypertension include those of chronic liver disease: ascites
Ascites
Ascites is a gastroenterological term for an accumulation of fluid in the peritoneal cavity.The medical condition is also known as peritoneal cavity fluid, peritoneal fluid excess, hydroperitoneum or more archaically as abdominal dropsy. Although most commonly due to cirrhosis and severe liver...
, esophageal varices
Esophageal varices
In medicine , esophageal varices are extremely dilated sub-mucosal veins in the lower esophagus...
, spider nevi, caput medusae
Caput medusae
Caput medusae is the appearance of distended and engorged paraumbilical veins, which are seen radiating from the umbilicus across the abdomen to join systemic veins...
, and palmar erythema
Palmar erythema
Palmar erythema is reddening of the palms at the thenar and hypothenar eminences.-Causes:It is associated with various physiological as well as pathological changes, the principal one of which is portal hypertension. It is also seen in patients with liver dysfunction, such as chronic liver disease...
.
Pylephlebitis
PylephlebitisPylephlebitis
Pylephlebitis is an inflammation of the portal vein or any of its branches. It is usually a complication of intraabdominal sepsis, most often following diverticulitis or appendicitis. It has a poor prognosis...
is infection of the hepatic portal vein, usually arising from an infectious intraabdominal process such as diverticulosis
Diverticulosis
Diverticulosis also known as "diverticular disease" is the condition of having diverticula in the colon, which are outpocketings of the colonic mucosa and submucosa through weaknesses of muscle layers in the colon wall. These are more common in the sigmoid colon, which is a common place for...
.