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Microscopic section through a small portal vein branch inside the liver (×250 magnified) The portal venous system is responsible for directing blood from parts of the gastrointestinal tract to the liver. Substances absorbed in the small intestine travel first to the liver for processing before continuing to the heart.
The human hepatic portal system delivers about three-fourths of the blood going to the liver.The final common pathway for transport of venous blood from spleen, pancreas, gallbladder and the abdominal portion of the gastrointestinal tract [2] (with the exception of the inferior part of the anal canal and sigmoid colon) is through the hepatic portal vein.
Graphical representation of the electrical conduction system of the heart that maintains the heart rate in the cardiac cycle. Electrical signals arising in the SA node (located in the right atrium) stimulate the atria to contract. Then the signals travel to the atrioventricular node (AV node), which is located in the interatrial septum.
The sinoatrial node is an oval-shaped structure that is approximately 15 mm long, 3 mm wide, and 1 mm thick, located directly below and to the side of the superior vena cava. [1] The size can vary but is usually between 10-30 mm long, 5–7 mm wide, and 1–2 mm deep.
Cardiac arrhythmias can cause heart block, in which the contractions lose their rhythm. In humans, and sometimes in other animals, a mechanical device called an artificial pacemaker (or simply "pacemaker") may be used after damage to the body's intrinsic conduction system to produce these impulses synthetically.
The circulatory system uses the channel of blood vessels to deliver blood to all parts of the body. This is a result of the left and right sides of the heart working together to allow blood to flow continuously to the lungs and other parts of the body. Oxygen-poor blood enters the right side of the heart through two large veins.
The heart functions as a pump and acts as a double pump in the cardiovascular system to provide a continuous circulation of blood throughout the body. This circulation includes the systemic circulation and the pulmonary circulation. Both circuits transport blood but they can also be seen in terms of the gases they carry.
The differing locations of the two bodies ideally position them to take advantage of different information; the carotid bodies, located on one of the main arteries of the neck, monitor partial pressure within arterial vessels while aortic body, located on the aortic arch, monitors oxygen concentration closer to the heart. [3]