Identify the correct statement about the human excretory system: MCQ with Answer and Explanation

Explanation:
The Islets of Langerhans are the endocrine (hormone-producing) portions of the pancreas. They are clusters of cells scattered throughout the pancreatic tissue, comprising about 1-2% of the pancreas's mass. They contain several cell types, primarily alpha cells (secreting glucagon), beta cells (secreting insulin), delta cells (secreting somatostatin), and F cells (secreting pancreatic polypeptide). These hormones are crucial for regulating blood glucose levels.

Explanation:
Dengue fever is a mosquito-borne viral infection caused by the Dengue virus (four serotypes). It is primarily transmitted by the bite of an infected female Aedes aegypti mosquito (and Aedes albopictus). These mosquitoes typically bite during the day. Anopheles transmits malaria, and Culex transmits filariasis and Japanese encephalitis.

Explanation:
The placenta acts as a temporary endocrine gland, secreting hCG (which maintains the corpus luteum), hPL (which alters maternal metabolism for fetal growth), and high levels of estrogen and progesterone (which maintain the uterine lining and suppress further ovulation). Prolactin, however, is primarily secreted by the anterior pituitary gland, although its levels rise significantly during pregnancy to prepare the mammary glands for lactation.