Consider the following statements about the human kidneys: 1. They are located in the abdominal cavity. 2. They produce the hormone renin. 3. They filter approximately 180 liters of blood per day. Which of the above is/are correct? MCQ with Answer and Explanation

Explanation:
The skin and mucous membranes form the first line of defense (innate immunity), acting as physical barriers that prevent pathogens from entering the body. White blood cells (leukocytes), including phagocytes and lymphocytes, are the cellular components of the immune system that identify, attack, and destroy pathogens. Antibiotics are drugs designed to kill or inhibit the growth of bacteria; they are completely ineffective against viruses, which lack the cellular machinery targeted by antibiotics. Thus, statements 1 and 2 are correct.

Explanation:
Synovial fluid is a viscous, egg-white-like fluid secreted by the synovial membrane in synovial joints (e.g., knee, hip). It lubricates articular cartilage, reducing friction and wear, and also nourishes cartilage. CSF cushions CNS, pleural fluid reduces lung friction, aqueous humor is in the eye.

Explanation:
Pleiotropy occurs when one gene influences several distinct phenotypic traits. Example: phenylketonuria (PKU) caused by a single gene defect leads to mental retardation, light skin color, and musty odor. Polygenic inheritance is many genes affecting one trait, epistasis is gene interaction, multiple alleles are more than two alleles for a gene.