With reference to the blood in a normal person, which one of the following statements is correct?
(a) Compared to arteries, veins are less numerous and hold less of the body’s blood at any given time.
(b) Blood cells constitute about 70 percent of the total volume of the blood.
(c) White blood cells (WBC) are made by lymph nodes only.
(d) The blood has more platelets than WBC.
(d) The blood has more platelets than WBC.
Explanation:
The number of blood platelets per cubic mm in human blood is 3 lacs while the number of WBCs are 5000/cubic mm of blood. Veins are as complex as the arteries. Veins and arteries both are types of blood vessels. Arteries carry blood from heart to different organs while vein carries blood from different organs to heart. At any given time in a healthy human, the blood amount is same in both, as the circulation of blood never stops.
Blood consists of two parts:
The plasma (water, proteins, inorganic salts and other elements) constitutes 55-60% of blood while cellular part constitutes 40- 45% of total blood. WBCs are produced in red bone marrow, lymph nodes and sometimes even in liver and spleen.