The vitamin essential for the absorption of calcium from the intestine is: MCQ with Answer and Explanation

Explanation:
Vitamin B₁ (thiamine) is water-soluble and functions as a coenzyme (thiamine pyrophosphate) in carbohydrate metabolism, particularly in decarboxylation reactions. Vitamins A, D, E, and K are fat-soluble. B₁ deficiency causes beriberi and Wernicke-Korsakoff syndrome. Being water-soluble, excess is excreted in urine and toxicity is rare.

Explanation:
Down syndrome (trisomy 21) is an autosomal aneuploidy caused by nondisjunction resulting in three copies of chromosome 21. It is characterized by intellectual disability, flat facial profile, protruding tongue, and simian crease. Turner's syndrome is monosomy X (45, X). Klinefelter's is 47, XXY. Phenylketonuria is an inborn error of metabolism (autosomal recessive) due to deficiency of phenylalanine hydroxylase.

Explanation:
The spleen is the largest lymphoid organ in the body. It is located in the abdominal cavity, specifically in the upper left quadrant, tucked between the stomach and the diaphragm, protected by the rib cage (ribs 9-11). It functions primarily in filtering blood, removing old or damaged red blood cells, storing platelets, and mounting immune responses against blood-borne pathogens. It is not located in the thoracic, pelvic, or cranial cavities.