Which of the following blood cells is responsible for humoral immunity?
A. Neutrophils
B. Macrophages
C. B lymphocytes
D. T lymphocytes
Answer: Option C
Solution (By JKExamLibrary)
B lymphocytes differentiate into plasma cells that produce antibodies (immunoglobulins) against specific antigens, providing humoral immunity. T cells mediate cellular immunity, macrophages and neutrophils are phagocytes.
Explanation:
Mature mammalian red blood cells (erythrocytes) lose their nucleus and other organelles during development to maximize space for hemoglobin. Thus they are anucleate. They cannot divide or repair themselves and have a lifespan of about 120 days. Neurons, leukocytes, and hepatocytes are nucleated. RBCs obtain energy through anaerobic glycolysis.
Explanation:
The pineal gland is a small endocrine gland in the brain that secretes melatonin, a hormone that regulates circadian rhythms and sleep-wake cycles. Melatonin production is influenced by light exposure: it increases in darkness and decreases in light. The pituitary is the master gland, thyroid regulates metabolism, adrenal secretes adrenaline.
Explanation:
Porifera (sponges) are characterized by the presence of a complex water canal system (canal system) used for food gathering, respiratory exchange, and waste removal. Water enters through numerous small pores called ostia and exits through a large opening called the osculum. They are mostly marine and asymmetrical.
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