In the human digestive system, the 'Villi' of the small intestine are covered with even smaller, microscopic projections on the epithelial cells called: MCQ with Answer and Explanation
In the human digestive system, the 'Villi' of the small intestine are covered with even smaller, microscopic projections on the epithelial cells called:
A. Microvilli
B. Flagella
C. Stereocilia
D. Cilia
Answer: Option A
Solution (By JKSSB Mock Tests)
The inner surface of the small intestine is lined with finger-like projections called villi, which increase the surface area for absorption. The epithelial cells (enterocytes) covering these villi have their own microscopic, finger-like projections on their apical surface, called microvilli. Collectively, these microvilli form a 'brush border'. This further massively increases the surface area, maximizing the efficiency of nutrient absorption. Cilia are motile, and stereocilia are found in the inner ear and epididymis.
Explanation:
Adenosine triphosphate (ATP) stores energy in its high-energy phosphate bonds and releases it for cellular work. Glucose and NADH are fuel molecules, not direct energy carriers.
Explanation:
The sinoatrial (SA) node is a specialized cluster of cells in the right atrium near the opening of the superior vena cava. It generates electrical impulses spontaneously, setting the pace of the heartbeat, hence called the pacemaker. The impulse spreads to the atrioventricular (AV) node, then to bundle of His and Purkinje fibers. Normal SA node firing rate is 60-100/min.
Explanation:
Alfred Russel Wallace independently conceived the theory of natural selection and sent his manuscript to Darwin. In 1858, both presented their papers jointly at the Linnean Society. Darwin's 'On the Origin of Species' (1859) elaborated the theory. Mendel discovered genetics, Lamarck proposed inheritance of acquired traits, Malthus influenced Darwin with his ideas on population growth.
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