The resistance encountered by blood as it flows through the blood vessels is called blood flow resistance. As blood flows, it consumes energy due to friction, which is generally expressed as heat energy. This thermal energy cannot be converted into potential or kinetic energy of the blood, so the pressure of the blood gradually decreases as it flows through the blood vessels. In the case of turbulent flow, each mass in the blood constantly changes the direction of flow, so the energy consumed is more than in laminar flow, and the resistance to blood flow is greater. Reasons for increased resistance to blood flow: Smaller internal diameter of blood vessels, increased blood viscosity. Blood lipid stasis and increased blood viscosity lead to smaller inner diameter of blood vessels and increased resistance! The resistance encountered by the fluid as it flows through the blood vessels is called blood flow resistance. Blood flow resistance is caused by the consumption of energy due to friction during blood flow, which is generally expressed as heat energy. This thermal energy cannot be converted into potential or kinetic energy of the blood, so the pressure of the blood gradually decreases as it flows through the blood vessels. In the case of turbulent flow, each mass in the blood constantly changes its direction of flow, so the energy consumed is more than in laminar flow, and the resistance to blood flow is higher. Portal hypertension: Portal hypertension is a group of syndromes caused by a persistent increase in portal venous pressure, which is caused by cirrhosis in the majority of patients, but in a minority of patients it is secondary to obstruction of the main portal vein or hepatic veins and some unexplained factors. Portal hypertension is divided into three categories according to the anatomical location: prehepatic, intrahepatic and posthepatic. The intrahepatic type is the most common in China, accounting for more than 90% of cases. The intrahepatic type is divided into sinusoidal, pre-sinusoidal and post-sinusoidal types according to the site of hepatic circulation disorder. Among them, sinusoidal type is the main cause of hepatic microcirculation disorder. The increase of portal vein pressure after the obstruction of portal blood return causes: (1) the opening of portal traffic branch, and (2) the increase of hepatic artery blood flow. Clinical manifestations of portal hypertension: (i) splenomegaly and hypersplenism, (ii) establishment of collateral circulation, and (iii) ascites. Hypertensive crisis: Hypertensive crisis is an extremely critical symptom of hypertensive patients, often under the influence of adverse triggers, the blood pressure suddenly rises to 26.6/16 kPa (200/120 mmHg) or more, resulting in acute damage to the heart, brain and kidneys. Patients feel sudden headache, dizziness, blurred vision or blindness, nausea, vomiting, panic, shortness of breath, pale or flushed face; both hands shake, irritability, temporary paralysis, aphasia, angina pectoris, cloudy urine in severe cases, or convulsions and coma in more severe cases.