The myelin sheath around axons in the CNS is formed by: MCQ with Answer and Explanation

Explanation:
Pericardium is outer sac, endocardium inner lining. Myocardium is the middle muscular layer; the outermost is epicardium (visceral pericardium). So 3 is incorrect.

Explanation:
Tuberculosis is a bacterial disease caused by Mycobacterium tuberculosis, primarily affecting the lungs. Polio is a viral disease caused by the poliovirus, attacking the nervous system. Tetanus is caused by the bacterium Clostridium tetani, which produces a neurotoxin that causes severe muscle spasms and affects the nervous system. Thus, only statement 3 is correct.

Explanation:
The hepatic portal vein is a unique blood vessel in the circulatory system that carries nutrient-rich, but potentially toxin-laden, blood from the gastrointestinal tract (stomach, intestines), spleen, and pancreas directly to the liver, rather than to the heart. This allows the liver to process absorbed nutrients, store glycogen, detoxify harmful substances, and regulate blood composition before the blood enters the systemic circulation via the hepatic veins to the inferior vena cava.