The part of the nephron that creates a concentration gradient in the kidney medulla is: MCQ with Answer and Explanation

Explanation:
The skin and mucous membranes act as primary physical barriers in innate immunity, preventing pathogen entry. Phagocytosis by macrophages and neutrophils is a non-specific (innate) cellular defense mechanism, not a specific immune response. Memory B and T cells are produced during the primary specific immune response and provide rapid, long-lasting immunity upon re-exposure. Thus, statements 1 and 3 are correct.

Explanation:
ADH (vasopressin), released from the posterior pituitary, increases water permeability of the collecting duct and distal tubule, promoting water reabsorption and producing concentrated urine. Its secretion is stimulated by increased plasma osmolarity or decreased blood volume. Aldosterone regulates sodium reabsorption. Parathyroid hormone and calcitonin regulate calcium.

Explanation:
Xanthophylls, oxygenated carotenoids, are responsible for the yellow color of egg yolk, autumn leaves, and corn. Beta-carotene is orange, lycopene red.