**Question 48:** What tiny structure is indicated by "A"? **Description:** The image depicts a detailed model of a cell showcasing various cellular organelles. In the top right corner of the image, there is a zoomed-in view with a tiny structure marked as "A". The zoomed-in section highlighted in blue shows a magnified portion of a cellular component, possibly a membrane or vesicle, indicating a specific structure or part of an organelle within the cell. ### Explanation of Figures & Diagrams: 1. **Cell Model Overview**: - The overall diagram presents a cross-section of a cell with multiple colored, detailed structures representing different organelles, such as the nucleus, mitochondria, endoplasmic reticulum, and others. - Various compartments and features are depicted in distinctive colors to differentiate between them easily. 2. **Zoomed-in Section Labeled "A"**: - This part highlights a small, circular or elliptical structure that appears to be part of the cell membrane or a vesicle. - The structural details show a distinct boundary, suggesting a bilayer membrane typical of vesicles or segments of the cell membrane. 3. **Highlighted Feature**: - The significant aspect indicated by "A" is a small, likely lipid-based structure, part of the cell's intricate internal organization. 4. **Possible Identification**: - Given the context and the zoomed-in view, "A" might be a representation of a vesicle, such as a lysosome or secretory vesicle, which plays essential roles in transport and storage within the cell. **Educational Note:** Understanding the structure and function of tiny cellular components like the one indicated by "A" is crucial in cell biology. These structures often participate in critical processes such as transportation of materials, cell signaling, and maintenance of cellular integrity. Through detailed diagrams and zoomed-in views, we can better grasp the complex inner workings of cells. **49) What is the indicated structure?** In the provided slide, a highly detailed microscopical image displays a concentric, multilayered, circular structure that has been highlighted and labeled with the query: "what is this?". This structure is encircled by a yellow boundary, emphasizing its distinctive pattern and arrangement. In the field of histology, such a structure is indicative of a **Pacinian corpuscle**, also known as a lamellar corpuscle. These are mechanoreceptors responsible for sensing pressure and vibration. They are located deep in the dermis and subcutaneous tissue. The layers of concentric lamellae, which resemble an onion cut in cross-section, are characteristic of these corpuscles. The concentric layers are formed by flattened cells, with a fluid-filled space between each layer, which facilitate the detection of mechanical changes in the environment. These structures play crucial roles in the sensory feedback mechanisms of the nervous system, particularly in the detection of vibrations and pressure stimuli.