Body Fluids and Circulation Test - 29

Polycythemia is a condition that results in an increased level of circulating red blood cells in the bloodstream. People with polycythemia have an increased hematocrit, hemoglobin or red blood cell counts. 

Blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the heart's right atrium. As the atrium contracts, blood flows from your right atrium into your right ventricle through the open tricuspid valve. When the ventricle is full, the tricuspid valve shuts. This prevents blood from flowing backward into the atria while the ventricle contracts. As the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery, and to the lungs where it is oxygenated. 

The pulmonary veins are large blood vessels that receive oxygenated blood from the lungs and drain into the left atrium of the heart. There are four pulmonary veins, two from each lung. The pulmonary veins are among the few veins that carry oxygenated blood. The pulmonary artery carries deoxygenated blood from the heart to the lungs. It is one of the only arteries (other than the umbilical arteries in the fetus) that carries deoxygenated blood. 

• Hypertension is caused due to an elevation in the pressure applied during the blood flow in the blood vessels. 
• Normal blood pressure at rest is within the range of 100–140 millimetres mercury (mmHg) systolic and 60–90 mmHg diastolic. 
• Hypertension is present if the blood pressure is persistently at or above 140/90 mmHg for most adults. 

Sodium oxalate (like citrates) can be used to remove calcium ions (Ca$$^{2+}$$) from the blood plasma. The oxalate prevents clotting by forming insoluble calcium salts, thus removing ionic calcium (or cations).
Therefore, the correct answer is option A.

Vitamin K plays an important role in blood clotting. It is required by the body for the synthesis of prothrombin by the liver. Prothrombin is a plasma protein which gets converted into thrombin during the clotting process and thus helps in clotting mechanism. Thus, the correct answer is option B. 

Thrombin is the center of blood clotting process. Blood clotting starts with molecules that sense that something is wrong. For instance, the protein tissue factor is found on the surfaces of cells that are not normally in contact with the blood. If the tissue is cut, the blood flows out of the blood vessels and encounter tissue factor. Then, a cascade of signaling starts, beginning with a few tissue factor molecules and amplifying, like a pyramid scheme, into a response large enough to cure the entire problem. Tissue factor activates a few molecules of Factor VII. These then activate a lot of Factor X. And finally, these activate even more thrombin. Thrombin, when activated, then translates this signal into action. It clips a little piece off of the large protein fibrinogen, causing it to assemble into large stringy networks. These networks then trap lots of blood cells, forming the dark red scab that blocks the damage. Thus, option B is correct.

The RBC count is the total number of red blood cells per cubic millimeter of blood. In response to hypoxia, the hormone erythropoietin, secreted by the kidneys, stimulates the bone marrow to produce red blood cells. The formation of red blood cells is known as erythropoiesis. Normal red blood cells values at various ages are: 

Pulmonary vein carries oxygenated blood from the lungs to the left atrium. It is the only vein in the human body carrying oxygenated blood.