Portal Venous System (EASY Scheme) | Anatomy — Transcript

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1. 0:03What's up. Meditay Here. Now. Now that we've done  the inferior vena cava and the superior vena cava
2. 0:10let's finally cover the Portal Venous System
3. 0:13Now the Portal Venous system is a system of  veins that drain blood from the unpaired organs
4. 0:18of the abdominal cavity. These are the large and  Small intestine, the pancreas, and the stomach.
5. 0:25The gallbladder and the spleen. So blood from these organs will
6. 0:29eventually find its way into the portal vein,  which goes within the hepatoduodenal ligament
7. 0:34into the liver. It bifurcates into the right  and left branches, then divides into smaller
8. 0:40branches to supply the hepatic lobes. And that's why we say all the medications
9. 0:45you take, all the food you eat. Once they're  absorbed from the intestines. They will all go
10. 0:50through the liver within this system to be  processed and filtered before going into
11. 0:54the systemic circulation. And keep in mind this  goes for the exocrine hormones from the pancreas.
12. 1:01So the portal system is an extremely  important system. It makes sure to include
13. 1:07the liver to take part in processing stuff. So let's see how these veins are arranged,
14. 1:17and we'll start with the tributaries  of the superior mesenteric first.
15. 1:31The superior mesenteric vein passes on the  right side of the superior mesenteric artery,
16. 1:37and it goes behind the pancreas. It goes down and terminates as
17. 1:41the Jejunal and ileal veins. They both collect  blood from the loops of the jejunum and ileum.
18. 1:47Then it has the Right colic  vein for the ascending colon,
19. 1:52Ileocoluc Vein which collects blood from the  terminal part of the small intestine and the
20. 1:57caecum, hence the name ileocolic vein. It has a  small tributary vein called the appendicular vein,
21. 2:03which receives blood from the appendix. Other veins that drain into the superior
22. 2:08mesenteric are the middle colic vein, which  collects blood from the transverse colon,
23. 2:14and the Right Gastro-Omental Vein, which collects  blood from the greater curvature of the stomach
24. 2:20and the greater omentum of the peritoneum. So the superior mesenteric receives blood
25. 2:27from all of these veins and  dumps them into the Portal Vein.
26. 2:31Awesome. 1 Down. Let's now do  the Inferior Mesenteric Vein.
27. 2:35The inferior mesenteric vein, as we said, usually  opens into the splenic vein behind the pancreatic
28. 2:42head. But keep in mind veins are very variable.  There are cases where it can open into the
29. 2:48superior mesenteric vein as well, or directly into  the portal vein. But in the majority of cases,
30. 2:54it's going to open into the splenic vein. Alright. So the first tributary is the superior
31. 3:43rectal vein, receiving blood from the superior  part of the rectum, or the rectal ampulla.
32. 3:48Then we have the sigmoid vein, which  collects blood from the sigmoid colon.
33. 3:53And the left colic vein for the descending  colon. So again, the inferior mesenteric
34. 3:59vein collects blood from all of these veins and  dumps the blood primarily into… the Splenic Vein.
35. 4:06So let's now cover the splenic vein. The Splenic Vein originates from the splenic
36. 4:11hilum, as you see here. Then it passes behind  the stomach and the pancreatic body to join the
37. 4:18superior mesenteric vein to form the portal vein. Alright. So first off, it has a vein that
38. 4:23communicates with the Right Gastroomental Vein,
39. 4:26called the Left Gastroomental vein It has the short gastric vein,
40. 4:30which goes up to drain the fundus and the  upper greater curvature of the stomach.
41. 4:36Then it has the pancreatic veins, which arise  along the surface of the pancreatic body
42. 4:42and drain it into the splenic vein. So, just to visualize it a little bit better.
43. 4:47Here we see the Portal vein. Superior Mesenteric
44. 4:51Splenic Vein Inferior Mesenteric,
45. 4:54And here are the pancreatic veins, You see, the Splenic Vein goes
46. 4:59behind the pancreas. And the pancreatic veins  originate from the body and tail of the pancreas
47. 5:06to empty into the splenic vein. After that, the splenic vein
48. 5:10empties into the Portal Vein. So that was the Splenic Vein as well.
49. 5:16Now, let's do some tributary  veins of the Portal Vein.
50. 5:20First, we have the Left Gastric  vein, which collects blood from
51. 5:23the lesser curvature, as you see here And it also receives blood from the abdominal
52. 5:28part of the esophagus, as the esophageal veins. Then the left gastric vein will anastomose
53. 5:34with the right gastric vein to form a  venous arch along the lesser curvature.
54. 5:39So the right gastric vein will collect  blood from the lesser curvature,
55. 5:43and it'll also receive blood from the prepyloric  vein, draining the pyloric part of the stomach.
56. 5:49So that's these two. Then we got the pancreaticoduodenal vein,
57. 5:54which collects blood from the head of  the pancreas and from the duodenum,
58. 5:59and empties into the portal vein. It can also  empty into the superior mesenteric vein sometimes.
59. 6:08Then there's the cystic vein,  collecting blood from the gallbladder
60. 6:11And then we got the paraumbilical veins,  which are two thin veins passing along the
61. 6:17round ligament of the liver, to drain blood  from the anterior part of the abdominal wall
62. 6:23and some parts of the diaphragm as well, directly  into the liver. It does communicate with other
63. 6:30anterior abdominal wall veins as well. So that was all the veins
64. 6:34of the portal venous system. All of these veins unite to form the
65. 6:39portal vein. The portal vein goes into the liver  and branches off to various lobes. Then the right,
66. 6:48intermediate, and left hepatic veins drain  blood from the liver into the inferior vena
67. 6:53cava. So that is how blood goes from the  portal system into the systemic circulation.
68. 7:00Alright. Now there's a concept that you  need to be familiar with because it's very,
69. 7:05very clinically important. And that concept  is called the portocaval anastomoses
70. 7:11This is an anastomosis or a connection  between the tributaries of the portal
71. 7:16vein and the superior or inferior vena cava.  Hence the name Porto-Caval anastomoses.
72. 7:23Now, here I've combined all  of the portal tributaries.
73. 7:27Under physiological conditions, blood flows  from the portal vein to the liver, right?
74. 7:34Under any circumstances that make the blood  pressure in the portal system increase, there's
75. 7:39going to be a problem, right? This condition is  called portal hypertension. So just to throw in a
76. 7:45couple of examples. If there's chronic damage to  the liver due to excessive alcohol consumption,
77. 7:51non-alcoholic fatty liver disease, hepatitis C  infection, or, you know, other metabolic causes.
78. 7:58The body is going to replace damaged cells  with fibrotic tissue. Right? Liver cirrhosis.
79. 8:05It could also be prehepatic causes like portal  vein thrombosis or any external compression of
80. 8:12the portal vein by masses like a tumor. Or post hepatic causes like right-sided
81. 8:17heart failure. Because remember, if  the right side of the heart is failing,
82. 8:21the blood starts building up in the  superior and inferior vena cava,
83. 8:26which in terms also congests  the blood in the portal system.
84. 8:30So, whatever the cause will  lead to portal hypertension.
85. 8:34Now, the blood needs to escape the portal  system, you know? And since it's not flowing
86. 8:40through the liver as efficiently as you want  it to, it has to escape through other places,
87. 8:45through the portocaval anastomoses. So blood flows  through these veins normally, but if there's an
88. 8:52increase in portal pressure, the anastomotic veins  will also start to congest, leading to varices and
89. 8:59ascites. But let's go through them a little bit. Through the esophageal veins, blood will go up to
90. 9:07the esophagus and anastomose with esophageal  veins of the azygos and the hemiazygos veins
91. 9:14and then flow into the superior vena  cava. So, in other words, there's an
92. 9:19anastomosis between the oesophageal veins. Now, suppose there's an increase pressure
93. 9:25in the portal system. In that case, these  veins will start to get congested with blood,
94. 9:31leading to esophageal varices, which  can be seen during an upper endoscopy.
95. 9:36Then there's an anastomosis in the rectum.  And this anastomosis happens through the
96. 9:42superior rectal vein that drains  into the inferior mesenteric vein,
97. 9:46the middle rectal vein that drains into the  internal iliac vein, and the inferior rectal vein,
98. 9:53which drains into the internal pudendal vein. If there's an increase in portal pressure, blood
99. 9:59will get congested in the hemorrhoidal plexus,  forming internal hemorrhoids. Now, keep in mind
100. 10:06that increased portal pressure is an infrequent  cause of hemorrhoids. So if you see a patient
101. 10:11with hemorrhoids, the chances of it being because  of increased portal pressure are low. Alright.
102. 10:20Then there's an anastomosis  between the paraumbilical
103. 10:24and subcutaneous veins around the umbilicus. When  these veins enlarge, they've termed Caput Medusae
104. 10:32or head of medusa. The name originates from  the apparent similarity to Medusa's head,
105. 10:37which had venomous snakes as hair. So, they  ended up calling this condition after her.
106. 10:45These anastomoses happen between  the thoraco-epigastric veins,
107. 10:49which open into the axillary vein,  and the superficial epigastric veins.
108. 10:54This condition is very characteristic  of portal hypertension.
109. 10:58Other signs are, you know,  when you have congested blood,
110. 11:02water starts to go out from the veins filling  up the peritoneal space, leading to ascites.
111. 11:09So that was all I had for the Portal  Venous System and its anastomoses.
112. 11:14I really hope you found this video  helpful. If you did, please put a like.
113. 11:18Comment and subscribe. See you next time.