What Are Venules?
Small veins have a diameter of more than 200 m, and a layer of smooth muscle is gradually formed outside the endothelium. The median membrane of the larger small vein has one to several layers of smooth muscle. The outer membrane is also gradually thickened. The blood in the small veins flows back. Capillaries are connected between arterioles and veins, most of them are like this.
- Chinese name
- Small vein
- Pipe diameter
- Pipe diameter
- Features
- A more complete layer of smooth muscle
- Blood flow
- Flow back
- Small veins have a diameter of more than 200 m, and a layer of smooth muscle is gradually formed outside the endothelium. The median membrane of the larger small vein has one to several layers of smooth muscle. The outer membrane is also gradually thickened. The blood in the small veins flows back. Capillaries are connected between arterioles and veins, most of them are like this.
1 Vein 1, Anatomy of Vein:
- Capillaries gradually become veins, and initially only a thin layer of connective tissue is added around the endothelium. When the tube diameter reaches 50 m, sparsely arranged smooth muscles appear between the endothelium and connective tissue. When the tube diameter is larger, the smooth muscle becomes a complete layer, and those with a tube diameter of less than 500 m are microvenous. A vein with a diameter of 0.2 to 1 mm is called a small vein. The inner membrane of the small vein has only the endothelium, the middle membrane has 2 to 4 layers of smooth muscles, a few elastic fibers and collagen fibers, and the outer membrane is thin and consists of connective tissue.
2 Classification of small vein 2, hepatic vein occlusion:
- This is a special form of liver damage. It is an obstructive disease of the small veins of the liver caused by some causes. Features acute onset, abdominal pain, hepatomegaly, ascites, etc. There are many reasons for VOD, and there are 4 types now: (1) Plants are known to have ragwort, also known as Senecio Jamaicans have a high incidence of tea drinking. It is similar to Crotalaria, Heliotropium, and some Chinese herbs such as chrysanthemum notoginseng (ie, notoginseng). The plant contains a type of double-pyrrolidine (pyrropinum) that causes small static liver damage and hepatocyte necrosis. (2) Chemicals, certain anti-tumor and immunosuppressive agents such as uratan, azathioprine, thioguanine, cytarabine, and nitrogen mustard, etc .; (3) radiation irradiation, liver tumor irradiation. (4) Allogeneic transplantation is the same as allogeneic bone marrow transplantation. The main pathologies include: thickening and narrowing of the intima of hepatic small veins (central vein and sublobular vein); hepatic sinus congestion; hepatocyte necrosis; fibrosis of central lobular vein and non-portal area. In the acute phase, there are abdominal pain, bloating, rapid hepatomegaly, and rapid ascites. Healed or died of liver failure within 6 weeks, or entered the subacute phase, continued liver enlargement, ascites, and finally entered cirrhosis. Most died of liver coma or portal hypertension with upper gastrointestinal bleeding.